Nelson Vergel
Founder, ExcelMale.com
Curated by Nelson Vergel | B.S. Chemical Engineering, MBA | Founder, ExcelMale.com | 34+ years on TRT | NIH and FDA advisory panel service | Author: Testosterone: A Man's Guide, Beyond Testosterone, The Peptide Consensus
| ExcelMale.com | Updated July 2026
Testosterone builds bone. Older men on TRT gain roughly 7 to 7.5% in lumbar spine bone density in a single year, so you would expect a spine on TRT to fuse better after surgery. The data points the other way. A propensity-matched study of lumbar fusion patients found that men on testosterone replacement therapy had a higher rate of pseudarthrosis, the term for a fusion that fails to knit into solid bone. That gap between what the scan shows and what the bone actually does is the whole story of TRT and orthopedic surgery outcomes, and it changes how you should prepare for any elective bone or tendon procedure.
The pseudarthrosis numbers were consistent at both time points.
Put plainly, TRT users failed to fuse about half again as often at one year. That effect size is larger than what you see from smoking or advanced age, which is saying something, because both are well-known enemies of a good fusion.
Reoperation rates told a softer story. They ran higher in the TRT group but did not reach statistical significance. There are two likely reasons. A nonunion that does not hurt often gets watched rather than cut on again. And some TRT patients carry enough underlying frailty that surgeons hesitate to put them through a revision. So the true burden of failed fusion may be undercounted by looking at reoperations alone.
One reassuring finding: in these spine patients, TRT was not tied to more 90-day blood clots, pulmonary embolism, sepsis, or pneumonia. That runs against some total joint replacement data, where TRT has been flagged for higher clot and revision risk. The likely explanation is baseline risk. Spine surgery carries a lower baseline clot rate than joint replacement, often under 1% versus about 2%, so the blood-thickening effect of testosterone has less room to show up. The TRAVERSE trial did report a 1.8-fold higher pulmonary embolism risk in testosterone users overall, so this is context-dependent, not a green light to ignore clotting.
Two explanations fit the data. The first is confounding by indication. Men who get prescribed TRT often started from a worse place: longer duration of low testosterone, poorer baseline bone quality, more frailty. A 7% density bump sounds good, but if you begin deep in the osteopenic range, that gain may not carry you to a bone that fuses well. The therapy improves the number without normalizing the underlying biology.
The second is the vigor effect. TRT gives men more energy and drive. Some return to heavy activity sooner than a healing fusion can tolerate, which loads the surgical site before it is ready. More movement also means more chances to fall. This may help explain a separate and striking finding: despite denser bone, TRT users in some analyses show markedly higher vertebral fracture rates. Denser bone that gets loaded harder and falls more often can still break.
The honest answer is that we cannot yet separate these fully. Both probably contribute. What matters for you is the conclusion they share: a good DXA score is not proof that your spine is ready to fuse.
The injury rate ran 377.8 per 100,000 person-years in TRT users versus 245.8 in controls. The adjusted odds of an Achilles injury rose 24%. More telling, once injured, TRT users were 54% more likely to need surgery rather than heal in a boot, which suggests these were more complete, more severe ruptures.
The mechanism is a mismatch between muscle and cable. Testosterone grows muscle fast. Tendon adapts slowly. When a stronger muscle pulls on a tendon that has not caught up, the tendon is the weak link. On top of that, androgens appear to stiffen tendon tissue, blunt the relaxin response that keeps tissue pliable, and inhibit matrix metalloproteinases, the enzymes that let a tendon remodel and repair micro-damage. A stiffer tendon that cannot remodel well, pulled by a muscle that got strong quickly, is a setup for rupture.
What the data supports is planning, not panic. If you are heading into a spinal fusion, your surgeon may lower the threshold for osteoinductive materials such as BMP-2 or bone graft adjuncts to overcome weaker fusion biology. If you are having a tendon repair or any procedure where you will be tempted to load early, the plan should include a more conservative return-to-activity schedule. The point is to match the surgical strategy to the real risk, not to yank a hormone you may need.
Bring your recent labs and bone density if you have them, but say out loud that you understand a good density score does not guarantee good fusion. That single sentence tells a surgeon you get the paradox and moves the conversation toward biology instead of just the scan. Nail down the modifiable risks you can still control before the date: keep nicotine at zero, get your HbA1c in range, and sort out nutrition. Those levers matter more in a TRT patient, because they stack on top of an already higher baseline risk.
Does testosterone decrease collagen? digs into how androgens affect collagen synthesis and tendon structure, which is the mechanism behind the injury data.
My experience repairing my torn biceps tendon is a firsthand recovery account from a member on TRT, useful if you are facing a tendon repair yourself.
Albright JA, et al. Testosterone replacement therapy is associated with increased odds of Achilles tendon injury and subsequent surgery: a matched retrospective analysis. Journal of Foot and Ankle Research. 2023;16:76. https://doi.org/10.1186/s13047-023-00678-0
Lincoff AM, Bhasin S, Flevaris P, et al. Cardiovascular Safety of Testosterone-Replacement Therapy (TRAVERSE). New England Journal of Medicine. 2023;389:107-117. https://doi.org/10.1056/NEJMoa2215025
Snyder PJ, Kopperdahl DL, Stephens-Shields AJ, et al. Effect of Testosterone Treatment on Volumetric Bone Density and Strength in Older Men With Low Testosterone. JAMA Internal Medicine. 2017;177(4):471-479. https://doi.org/10.1001/jamainternmed.2016.9539
Cancienne JM, Brockmeier SF, Rodeo SA, Werner BC. The Effect of Sex Hormone Deficiency on the Incidence of Rotator Cuff Repair: Analysis of a Large Insurance Database. Journal of Bone and Joint Surgery. 2022. The Effect of Sex Hormone Deficiency on the Incidence of Rotator Cuff Repair: Analysis of a Large Insurance Database - PubMed
Bhasin S, Brito JP, Cunningham GR, et al. Testosterone Therapy in Men With Hypogonadism: An Endocrine Society Clinical Practice Guideline. Journal of Clinical Endocrinology and Metabolism. 2018;103(5):1715-1744. https://doi.org/10.1210/jc.2018-00229
Vigen R, O'Donnell CI, Baron AE, et al. Association of testosterone therapy with mortality, myocardial infarction, and stroke in men with low testosterone levels. JAMA. 2013;310(17):1829-1836. https://doi.org/10.1001/jama.2013.280386
Corona G, Rastrelli G, Di Pasquale G, et al. Testosterone and Cardiovascular Risk: Meta-Analysis of Interventional Studies. Journal of Sexual Medicine. 2018;15(6):820-838. https://doi.org/10.1016/j.jsxm.2018.04.641
| ExcelMale.com | Updated July 2026
Testosterone builds bone. Older men on TRT gain roughly 7 to 7.5% in lumbar spine bone density in a single year, so you would expect a spine on TRT to fuse better after surgery. The data points the other way. A propensity-matched study of lumbar fusion patients found that men on testosterone replacement therapy had a higher rate of pseudarthrosis, the term for a fusion that fails to knit into solid bone. That gap between what the scan shows and what the bone actually does is the whole story of TRT and orthopedic surgery outcomes, and it changes how you should prepare for any elective bone or tendon procedure.
Does TRT Increase the Risk of Failed Spinal Fusion?
Yes, based on the best data we have. Researchers used a large insurance database to match men on TRT against nearly identical men who were not, then tracked what happened after single-level lumbar fusion. They matched for the things that usually wreck a fusion, including smoking, diabetes, age, and BMI, so the comparison was as fair as claims data allows.The pseudarthrosis numbers were consistent at both time points.
| Interval | TRT users | Non-users | Relative risk |
|---|---|---|---|
| Pseudarthrosis at 1 year | 14.9% | 10.0% | 1.50 |
| Pseudarthrosis at 2 years | 16.7% | 11.9% | 1.41 |
Put plainly, TRT users failed to fuse about half again as often at one year. That effect size is larger than what you see from smoking or advanced age, which is saying something, because both are well-known enemies of a good fusion.
Reoperation rates told a softer story. They ran higher in the TRT group but did not reach statistical significance. There are two likely reasons. A nonunion that does not hurt often gets watched rather than cut on again. And some TRT patients carry enough underlying frailty that surgeons hesitate to put them through a revision. So the true burden of failed fusion may be undercounted by looking at reoperations alone.
One reassuring finding: in these spine patients, TRT was not tied to more 90-day blood clots, pulmonary embolism, sepsis, or pneumonia. That runs against some total joint replacement data, where TRT has been flagged for higher clot and revision risk. The likely explanation is baseline risk. Spine surgery carries a lower baseline clot rate than joint replacement, often under 1% versus about 2%, so the blood-thickening effect of testosterone has less room to show up. The TRAVERSE trial did report a 1.8-fold higher pulmonary embolism risk in testosterone users overall, so this is context-dependent, not a green light to ignore clotting.
Why Would TRT Raise Nonunion and Fracture Risk If It Builds Bone?
This is the core paradox, and it comes down to a simple distinction. Bone mineral density measures how much mineral is packed into the bone. Fusion biology measures whether living bone can remodel and bridge a gap. Those are not the same thing, and TRT seems to help the first while leaving the second short.Two explanations fit the data. The first is confounding by indication. Men who get prescribed TRT often started from a worse place: longer duration of low testosterone, poorer baseline bone quality, more frailty. A 7% density bump sounds good, but if you begin deep in the osteopenic range, that gain may not carry you to a bone that fuses well. The therapy improves the number without normalizing the underlying biology.
The second is the vigor effect. TRT gives men more energy and drive. Some return to heavy activity sooner than a healing fusion can tolerate, which loads the surgical site before it is ready. More movement also means more chances to fall. This may help explain a separate and striking finding: despite denser bone, TRT users in some analyses show markedly higher vertebral fracture rates. Denser bone that gets loaded harder and falls more often can still break.
The honest answer is that we cannot yet separate these fully. Both probably contribute. What matters for you is the conclusion they share: a good DXA score is not proof that your spine is ready to fuse.
Does TRT Increase Achilles and Other Tendon Injury Risk?
The tendon data is larger and cleaner than the spine data. Albright and colleagues matched hundreds of thousands of TRT users against controls and followed Achilles tendon health for two years. Men and women on TRT for at least three consecutive months were injured more often, and when they were injured, the damage was worse.The injury rate ran 377.8 per 100,000 person-years in TRT users versus 245.8 in controls. The adjusted odds of an Achilles injury rose 24%. More telling, once injured, TRT users were 54% more likely to need surgery rather than heal in a boot, which suggests these were more complete, more severe ruptures.
The mechanism is a mismatch between muscle and cable. Testosterone grows muscle fast. Tendon adapts slowly. When a stronger muscle pulls on a tendon that has not caught up, the tendon is the weak link. On top of that, androgens appear to stiffen tendon tissue, blunt the relaxin response that keeps tissue pliable, and inhibit matrix metalloproteinases, the enzymes that let a tendon remodel and repair micro-damage. A stiffer tendon that cannot remodel well, pulled by a muscle that got strong quickly, is a setup for rupture.
Which Age Groups Are Most at Risk?
Not the young lifters you might expect. The highest odds landed in the 66 to 75 age group, with an adjusted odds ratio of 1.66 for men and 1.82 for women. Aging tendons already have fewer cells and more disorganized collagen. Add the energy and strength surge of TRT and you get older people pushing stiffer, more brittle tendons harder than those tendons can handle. The risk increase was nearly equal between sexes, which tells you this is a tendon biology issue, not a male-specific one.Should You Stop TRT Before Orthopedic Surgery?
Not on your own, and probably not at all in most cases. Current guidance does not require stopping non-estrogen hormone therapy before surgery. Stopping TRT abruptly has its own downsides, including a crash in energy and mood during an already stressful recovery. This is a decision to make with your surgeon and prescriber together, weighing the specific procedure.What the data supports is planning, not panic. If you are heading into a spinal fusion, your surgeon may lower the threshold for osteoinductive materials such as BMP-2 or bone graft adjuncts to overcome weaker fusion biology. If you are having a tendon repair or any procedure where you will be tempted to load early, the plan should include a more conservative return-to-activity schedule. The point is to match the surgical strategy to the real risk, not to yank a hormone you may need.
What Should You Tell Your Surgeon If You're on TRT?
Tell them you are on it, how long you have been on it, and your dose and delivery method. That belongs in your history next to smoking and diabetes, because it carries similar weight for fusion outcomes. Ask directly whether your procedure warrants extra fusion support or a slower loading protocol.Bring your recent labs and bone density if you have them, but say out loud that you understand a good density score does not guarantee good fusion. That single sentence tells a surgeon you get the paradox and moves the conversation toward biology instead of just the scan. Nail down the modifiable risks you can still control before the date: keep nicotine at zero, get your HbA1c in range, and sort out nutrition. Those levers matter more in a TRT patient, because they stack on top of an already higher baseline risk.
Frequently Asked Questions
Does TRT make bones stronger or weaker?
Both, in different senses. TRT reliably increases bone mineral density, so bones look denser on a DXA scan. But denser bone is not the same as bone that heals and fuses well, and TRT users show higher rates of nonunion and, in some data, vertebral fracture. Density up, healing biology not necessarily up.Can I still have spinal fusion surgery if I'm on testosterone?
Yes. TRT is not a reason to deny surgery. It is a reason for your surgeon to plan for a higher chance of nonunion, which may mean using extra fusion-promoting materials and watching your recovery more closely.How long should I wait to return to lifting after a tendon injury on TRT?
Longer than you feel you need to. The whole risk pattern in TRT users comes from strong muscle pulling on a tendon that has not caught up. Follow your surgeon's or physical therapist's loading schedule even when your energy says you are ready sooner.Do these risks mean I should quit TRT?
No, and do not stop on your own. These are association studies, not proof that TRT causes these problems, and TRT treats real symptoms of low testosterone. The right move is to tell your surgical team you are on it and let them adjust the plan.Related ExcelMale Forum Discussions
Patients taking hormones seem to be at a higher risk of tendon injury breaks down the orthopedic review on TRT and tendon rupture, with members debating whether harder training, not the hormone, drives the signal.Does testosterone decrease collagen? digs into how androgens affect collagen synthesis and tendon structure, which is the mechanism behind the injury data.
My experience repairing my torn biceps tendon is a firsthand recovery account from a member on TRT, useful if you are facing a tendon repair yourself.
Key References
Miller M, Delgadillo B, Meade M, et al. Testosterone Replacement Therapy in Posterior Lumbar Fusion Patients: A Propensity Score-Matched Analysis of Long-Term Outcomes. Global Spine Journal. 2026. https://doi.org/10.1177/21925682261467396Albright JA, et al. Testosterone replacement therapy is associated with increased odds of Achilles tendon injury and subsequent surgery: a matched retrospective analysis. Journal of Foot and Ankle Research. 2023;16:76. https://doi.org/10.1186/s13047-023-00678-0
Lincoff AM, Bhasin S, Flevaris P, et al. Cardiovascular Safety of Testosterone-Replacement Therapy (TRAVERSE). New England Journal of Medicine. 2023;389:107-117. https://doi.org/10.1056/NEJMoa2215025
Snyder PJ, Kopperdahl DL, Stephens-Shields AJ, et al. Effect of Testosterone Treatment on Volumetric Bone Density and Strength in Older Men With Low Testosterone. JAMA Internal Medicine. 2017;177(4):471-479. https://doi.org/10.1001/jamainternmed.2016.9539
Cancienne JM, Brockmeier SF, Rodeo SA, Werner BC. The Effect of Sex Hormone Deficiency on the Incidence of Rotator Cuff Repair: Analysis of a Large Insurance Database. Journal of Bone and Joint Surgery. 2022. The Effect of Sex Hormone Deficiency on the Incidence of Rotator Cuff Repair: Analysis of a Large Insurance Database - PubMed
Bhasin S, Brito JP, Cunningham GR, et al. Testosterone Therapy in Men With Hypogonadism: An Endocrine Society Clinical Practice Guideline. Journal of Clinical Endocrinology and Metabolism. 2018;103(5):1715-1744. https://doi.org/10.1210/jc.2018-00229
Vigen R, O'Donnell CI, Baron AE, et al. Association of testosterone therapy with mortality, myocardial infarction, and stroke in men with low testosterone levels. JAMA. 2013;310(17):1829-1836. https://doi.org/10.1001/jama.2013.280386
Corona G, Rastrelli G, Di Pasquale G, et al. Testosterone and Cardiovascular Risk: Meta-Analysis of Interventional Studies. Journal of Sexual Medicine. 2018;15(6):820-838. https://doi.org/10.1016/j.jsxm.2018.04.641
