Effect of continuous versus dichotomous outcome variables on study power when sample sizes of orthopaedic randomized trials are small
Abstract
It is often not feasible to conduct large trials in orthopaedic surgery. Therefore, surgeons must identify strategies to optimize the statistical power of their smaller studies. The aim of this study was to compare study power in randomized trials with continuous versus dichotomous outcome variables. We performed a systematic review of the literature to identify randomized trials in orthopaedic trauma. Of these, we examined only those trials with small sample sizes (50 patients or less). The outcomes in each eligible study were categorized as continuous or dichotomous. Standard power calculations were performed for each study, and comparisons were made between continuous and dichotomous outcome variables. We identified 196 randomized trials in orthopaedic trauma. Of these, 76 trials had a sample size of 50 patients or fewer (29 trials with continuous outcomes, 47 trials with dichotomous outcomes). Studies that reported continuous outcomes had a significantly higher mean power than those that reported dichotomous variables (power 49% vs 38%, p=0.042). Twice as many trials with continuous outcome variables reached acceptable levels of study power (i.e. >80% power) when compared with trials with dichotomous variables (37% vs 18.6%, p=0.04). When orthopaedic surgeons anticipate small sample sizes for their study, they can optimize their study's statistical power by choosing a continuous outcome variable.
Integrity signals
Registry
Cites
Statistics
Claims the paper makes
Claims other papers make about this one
Each is checked against this paper’s own text: does it say what the citing paper says it does?
The use of a dichotomous analysis metric compared with a continuous metric reduces statistical power.
“The use of a dichotomous analysis metric compared with a continuous metric reduces statistical power268 269 270”
From SPIRIT 2025 explanation and elaboration: updated guideline for protocols of randomised trials (2025) · cites this paper as [268]
Cites
Clinical Trials: A Practical Approach.
Hill, I. D., & Pocock, S. (1984) · Biometrics · doi:10.2307/2531186 · Cited by 2,918 · see citing works
Statistical Power, Sample Size, and Their Reporting in Randomized Controlled Trials
Moher, D. (1994) · JAMA: The Journal of the American Medical Association · doi:10.1001/jama.1994.03520020048013 · Cited by 608 · see citing works
Peto, R., & Baigent, C. (1998) · BMJ · doi:10.1136/bmj.317.7167.1170 · Cited by 245 · see citing works
Basic statistics for clinicians: 2. Interpreting study results: confidence intervals.
Guyatt, G. H., Jaeschke, R., Heddle, N. M., Cook, D., Shannon, H. S., & Walter, S. D. (1995) · Europe PMC (PubMed Central) · Cited by 118 · see citing works
Basic statistics for clinicians: 1. Hypothesis testing.
Guyatt, G. H., Jaeschke, R., Heddle, N. M., Cook, D., Shannon, H. S., & Walter, S. D. (1995) · Europe PMC (PubMed Central) · Cited by 118 · see citing works
Flagged first, then by citations
Cited by
Sorted by citations
SPIRIT 2013 explanation and elaboration: guidance for protocols of clinical trials
Chan, A.-W., Tetzlaff, J. M., Gotzsche, P. C., Altman, D. G., Mann, H., Berlin, J. A., Dickersin, K., Hrobjartsson, A., Schulz, K. F., Parulekar, W. R., et al. (2013) · BMJ · doi:10.1136/bmj.e7586 · Cited by 6,251 · see citing works
Wichers, M., Peeters, F., Geschwind, N., Jacobs, N., Simons, C. J. P., Derom, C., Thiery, E., Delespaul, P. H., & van Os, J. (2010) · Journal of Affective Disorders · doi:10.1016/j.jad.2009.11.010 · Cited by 189 · see citing works
SPIRIT 2025 explanation and elaboration: updated guideline for protocols of randomised trials
Hróbjartsson, A., Boutron, I., Hopewell, S., Moher, D., Schulz, K. F., Collins, G. S., Tunn, R., Aggarwal, R., Berkwits, M., Berlin, J. A., et al. (2025) · BMJ · doi:10.1136/bmj-2024-081660 · Cited by 171 · see citing works
Are Treatments More Effective than Placebos? A Systematic Review and Meta-Analysis
Howick, J., Smith, C. F., Tsakok, M., Watson, R. A., Tsakok, T., Thomas, J., Perera, R., Fleming, S., & Heneghan, C. J. (2013) · PLoS ONE · doi:10.1371/journal.pone.0062599 · Cited by 152 · see citing works
Mannion, A. F., Junge, A., Grob, D., Dvořák, J., & Fairbank, J. C. T. (2005) · European Spine Journal · doi:10.1007/s00586-004-0816-z · Cited by 124 · see citing works
Hall, N. C., Chipperfield, J. G., Heckhausen, J., & Perry, R. P. (2010) · Psychology and Aging · doi:10.1037/a0019278 · Cited by 110 · see citing works
Development of performance matrix for generic product equivalence of acyclovir topical creams
Krishnaiah, Y. S. R., Xu, X., Rahman, Z., Yang, Y., Katragadda, U., Lionberger, R. A., Peters, J. R., Uhl, K., & Khan, M. A. (2014) · International Journal of Pharmaceutics · doi:10.1016/j.ijpharm.2014.07.034 · Cited by 93 · see citing works
The National Children's Study of environmental effects on child health and development.
Branum, A. M., Collman, G. W., Correa, A., Keim, S. A., Kessel, W., Kimmel, C. A., Klebanoff, M. A., Longnecker, M. P., Mendola, P., Rigas, M. L., et al. (2003) · Environmental Health Perspectives · doi:10.1289/ehp.111-1241458 · Cited by 89 · see citing works
Xu, X., Al-Ghabeish, M., Rahman, Z., Krishnaiah, Y. S. R., Yerlikaya, F., Yang, Y., Manda, P., Hunt, R. L., & Khan, M. A. (2015) · International Journal of Pharmaceutics · doi:10.1016/j.ijpharm.2015.07.066 · Cited by 77 · see citing works
Lyngbakken, M. N., Berdal, J., Eskesen, A. N., Kvale, D., Olsen, I. C., Rueegg, C. S., Rangberg, A., Jonassen, C. M., Omland, T., Røsjø, H. R., et al. (2020) · Nature Communications · doi:10.1038/s41467-020-19056-6 · Cited by 73 · see citing works
Bioequivalence for Topical Products—An Update
Narkar, Y. (2010) · Pharmaceutical Research · doi:10.1007/s11095-010-0250-3 · Cited by 59 · see citing works
Lipira, L. E., Williams, E. C., Huh, D., Kemp, C. G., Nevin, P. E., Greene, P. A., Unger, J. M., Heagerty, P. J., French, A. L., Cohn, S. E., et al. (2018) · AIDS and Behavior · doi:10.1007/s10461-018-2301-4 · Cited by 57 · see citing works
Lovasi, G., Underhill, L., Jack, D., Richards, C. A., Weiss, C. C., & Rundle, A. (2012) · The Open Epidemiology Journal · doi:10.2174/1874297101205010013 · Cited by 60 · see citing works
End-Tidal Hypocapnia Under Anesthesia Predicts Postoperative Delirium
Mutch, W. A. C., El-Gabalawy, R. M., Girling, L. G., Kilborn, K., & Jacobsohn, E. (2018) · Frontiers in Neurology · doi:10.3389/fneur.2018.00678 · Cited by 44 · see citing works
Clinically relevant outcomes in dental clinical trials: challenges and proposals
Pannuti, C. M., Sendyk, D. I., das Graças, Y. T., TAKAI, S. L., Sabóia, V. D. P. A., Romito, G. A., & Mendes, F. M. (2020) · Brazilian Oral Research · doi:10.1590/1807-3107bor-2020.vol34.0073 · Cited by 41 · see citing works
Moore, R. A., Moore, O. A., Derry, S., & McQuay, H. J. (2008) · Arthritis Research & Therapy · doi:10.1186/ar2394 · Cited by 41 · see citing works
Kooijman, L., Berti, S., Asadi, H., Nahavandi, S., & Keshavarz, B. (2023) · Behavior Research Methods · doi:10.3758/s13428-023-02148-8 · Cited by 37 · see citing works
Al‐Saleh, I., Moncari, L., Jomaa, A., Elkhatib, R., Al-Rouqi, R., Eltabache, C., Al-Rajudi, T., Alnuwaysir, H., Nester, M. J., & Aldhalaan, H. (2020) · International Journal of Hygiene and Environmental Health · doi:10.1016/j.ijheh.2020.113629 · Cited by 34 · see citing works
Ang, S., & Malhotra, R. (2017) · Aging & Mental Health · doi:10.1080/13607863.2017.1317329 · Cited by 31 · see citing works
Formulation characteristics and in vitro release testing of cyclosporine ophthalmic ointments
Dong, Y., Qu, H., Pavurala, N., Wang, J., Sekar, V., Martinez, M. N., Fahmy, R. M., Ashraf, M., Cruz, C. N., & Xu, X. (2018) · International Journal of Pharmaceutics · doi:10.1016/j.ijpharm.2018.04.042 · Cited by 29 · see citing works
Li, X., Zhang, N., & He, X. (2020) · The British Journal of Social Work · doi:10.1093/bjsw/bcaa193 · Cited by 29 · see citing works
Amiri, M., Lamballais, S., Geenjaar, E., Blanken, L. M. E., Marroun, H. E., Tiemeier, H. W., & White, T. J. H. (2020) · Autism Research · doi:10.1002/aur.2372 · Cited by 28 · see citing works
The relative efficiency of time-to-threshold and rate of change in longitudinal data
Donohue, M., Gamst, A. C., Thomas, R. G., Xu, R., Beckett, L. A., Petersen, R. C., Weiner, M. W., & Aisen, P. S. S. (2011) · Contemporary Clinical Trials · doi:10.1016/j.cct.2011.04.007 · Cited by 27 · see citing works
Dunn, K. E., Bergeria, C. L., Huhn, A. S., & Strain, E. C. (2020) · Drug and Alcohol Dependence · doi:10.1016/j.drugalcdep.2020.108212 · Cited by 22 · see citing works
Karonitsch, T., Aletaha, D., Boers, M., Bombardieri, S., Combe, B. G., Dougados, M., Emery, P., Felson, D. T., Gómez-Reino, J. J., Keystone, E., et al. (2008) · Annals of the Rheumatic Diseases · doi:10.1136/ard.2008.092353 · Cited by 22 · see citing works
Evaluating drug distribution and release in ophthalmic emulsions: Impact of release conditions
Dong, Y., Hengst, L., Hunt, R., Feng, X., Kozak, D., Choi, S. H., Ashraf, M., & Xu, X. (2020) · Journal of Controlled Release · doi:10.1016/j.jconrel.2020.08.020 · Cited by 20 · see citing works
Measuring Pelvic Organ Prolapse: An Evolution
Barber, M. D. (2024) · International Urogynecology Journal · doi:10.1007/s00192-024-05798-0 · Cited by 23 · see citing works
Daetz, R., Cunha, F., Bittar, J. H. J., Risco, C. A., Magalhaes, F., Maeda, Y., Santos, J. E. P., Jeong, K. C., Cooke, R. F., & Galvão, K. N. (2016) · Journal of Dairy Science · doi:10.3168/jds.2016-11400 · Cited by 20 · see citing works
Papavasileiou, E., Davoudi, S., Roohipoor, R., Cho, H., Kudrimoti, S., Hancock, H., Wilson, J. G., Andreoli, C. M., Husain, D., James, M., et al. (2016) · Graefe s Archive for Clinical and Experimental Ophthalmology · doi:10.1007/s00417-016-3493-9 · Cited by 20 · see citing works
Vo, A. Q., Feng, X., Patel, D., Mohammad, A., Patel, M. A., Zheng, J., Kozak, D., Choi, S. H., Ashraf, M., & Xu, X. (2020) · International Journal of Pharmaceutics · doi:10.1016/j.ijpharm.2020.119761 · Cited by 17 · see citing works
Dong, Y., Hengst, L., Hunt, R., Patel, D., Vo, A. Q., Choi, S. H., Ashraf, M., Cruz, C. N., & Xu, X. (2019) · Journal of Controlled Release · doi:10.1016/j.jconrel.2019.09.010 · Cited by 17 · see citing works
Paquet, M., Cerasuolo, J. O., Thorburn, V., Fridman, S., Alsubaie, R., Lópes, R. D., Cipriano, L. E., Salamone, P., Melling, C. W. J., KHAN, A. R., et al. (2017) · Journal of Stroke and Cerebrovascular Diseases · doi:10.1016/j.jstrokecerebrovasdis.2017.09.038 · Cited by 16 · see citing works
Beckwée, D., Vaes, P., Raeymaeckers, S., Shahabpour, M., Scheerlinck, T., & Bautmans, I. (2016) · Disability and Rehabilitation · doi:10.1080/09638288.2016.1212110 · Cited by 15 · see citing works
Genome-wide association study of suicidal behaviour severity in mood disorders
Zai, C. C. H., Fabbri, C., Hosang, G. M., Zhang, R. S., Koyama, E., Luca, V. D., Tiwari, A. K., King, N. A., Strauss, J., Jones, I. R., et al. (2021) · The World Journal of Biological Psychiatry · doi:10.1080/15622975.2021.1907711 · Cited by 13 · see citing works
A geometric morphometric approach to the study of variation of shovel‐shaped incisors
Carayon, D., Adhikari, K., Monsarrat, P., Dumoncel, J., Braga, J., Duployer, B., Delgado, M., Fuentes‐Guajardo, M., de Beer, F., Hoffman, J. W., et al. (2018) · American Journal of Physical Anthropology · doi:10.1002/ajpa.23709 · Cited by 12 · see citing works
A Systematic Review of Outcome Measures in Orthopaedic Trauma Trials: What Are We Measuring?
Marcano-Fernández, F. A., Cámara-Cabrera, J., Madden, K., Johal, H. S., Ibrahim, N., Kapoor, R., Shehata, M., & Prada, C. (2022) · Indian Journal of Orthopaedics · doi:10.1007/s43465-022-00667-8 · Cited by 11 · see citing works
Ries, T., Wegscheider, K., Wulff, A., Radelfahr, K., Säring, D., Forkert, N. D., & Fiehler, J. (2010) · Neuroradiology · doi:10.1007/s00234-010-0764-8 · Cited by 11 · see citing works
Overrunning in clinical trials: some thoughts from a methodological review
Baldi, I., Azzolina, D., Soriani, N., Barbetta, B., Vaghi, P., Giacovelli, G., Berchialla, P., & Gregori, D. (2020) · Trials · doi:10.1186/s13063-020-04526-5 · Cited by 11 · see citing works
Al‐Saleh, I., Elkhatib, R., Alnuwaysir, H., Aldhalaan, H., Alismail, E., Binmanee, A., Hawari, A., Al-Hazzani, F., Jabr, M. B., & Mohamed, G. A. (2023) · Scientific Reports · doi:10.1038/s41598-023-33715-w · Cited by 10 · see citing works
Genetic associations with dementia‐related proteinopathy: Application of item response theory
Katsumata, Y., Fardo, D. W., Shade, L. M. P., Wu, X., Karanth, S. D., Hohman, T. J., Schneider, J. A., Bennett, D. A., Farfel, J. M., Gauthreaux, K. M., et al. (2024) · Alzheimer s & Dementia · doi:10.1002/alz.13741 · Cited by 9 · see citing works
Weizman, N. F., Defer, M. K., Montbriand, J., Pasquale, J., Silver, A., & Librach, C. L. (2020) · Reproductive Biology and Endocrinology · doi:10.1186/s12958-020-00602-2 · Cited by 9 · see citing works
Planning a Randomized Clinical Trial
Bhandari, M., & Schemitsch, E. H. (2004) · Techniques in Orthopaedics · doi:10.1097/00013611-200406000-00004 · Cited by 9 · see citing works
Self-citationMorris, S. C., Gowd, A. K., Agarwalla, A., Phipatanakul, W. P., Amin, N. H., & Liu, J. N. (2022) · World Journal of Orthopedics · doi:10.5312/wjo.v13.i9.825 · Cited by 8 · see citing works
Nebulised heparin for patients on ventilation: implications for COVID-19 pneumonia
Ball, L., Schultz, M. J., & Pelosi, P. P. (2021) · The Lancet Respiratory Medicine · doi:10.1016/s2213-2600(20)30513-0 · Cited by 7 · see citing works
The National Children's Study of Environmental Effects on Child Health and Development
The National Children's Study Interagency Coordinating Committee (2002) · Environmental Health Perspectives · doi:10.1289/ehp.5781 · Cited by 7 · see citing works
Légaré, S., Chagnon, M., Palijan, A., Kojok, K., & Bissonnette, R. (2022) · Journal of the European Academy of Dermatology and Venereology · doi:10.1111/jdv.17743 · Cited by 6 · see citing works
Malhotra, R., Chei, C., Østbye, T., Chan, A. W.-M., & Matchar, D. B. (2013) · Archives of Gerontology and Geriatrics · doi:10.1016/j.archger.2013.10.004 · Cited by 6 · see citing works
Aneurysm Recurrence Volumetry Is More Sensitive than Visual Evaluation of Aneurysm Recurrences
Schönfeld, M., Schlotfeldt, V., Forkert, N. D., Goebell, E., Groth, M., Vettorazzi, E., Cho, Y. D., Han, M. H., Kang, H., & Fiehler, J. (2014) · Clinical Neuroradiology · doi:10.1007/s00062-014-0330-6 · Cited by 6 · see citing works
Fang, F., Tamura, R., Braun, T., & Kidwell, K. (2022) · Statistics in Biopharmaceutical Research · doi:10.1080/19466315.2022.2118162 · Cited by 5 · see citing works
Murphy, N. J., Graan, D., Briggs, G. D., & Balogh, Z. J. (2023) · Medical Hypotheses · doi:10.1016/j.mehy.2023.111131 · Cited by 5 · see citing works
Svingos, A. M., Robicsek, S. A., Hayes, R. L., Wang, K., Robertson, C. S., Brophy, G. M., Papa, L., Gabrielli, A., Hannay, H. J., Bauer, R. M., et al. (2022) · Neurocritical Care · doi:10.1007/s12028-022-01461-y · Cited by 4 · see citing works
Lyngbakken, M. N., Berdal, J., Eskesen, A. N., Kvale, D., Olsen, I. C., Rueegg, C. S., Rangberg, A., Jonassen, C. M., Omland, T., Røsjø, H. R., et al. (2020) · Research Square · doi:10.21203/rs.3.rs-44055/v1 · Cited by 4 · see citing works
The Radiogenomics of Late-onset Alzheimer Disease
Bonham, L. W., Sirkis, D. W., Hess, C. P., Sugrue, L. P., & Yokoyama, J. S. (2019) · Topics in Magnetic Resonance Imaging · doi:10.1097/rmr.0000000000000222 · Cited by 3 · see citing works
Development of a psychological intervention for post-stroke fatigue
Wu, S. (2016) · ERA · Cited by 2 · see citing works
Pottayil, F., Wohl, R. B., & Parry, J. A. (2026) · European Journal of Orthopaedic Surgery & Traumatology · doi:10.1007/s00590-026-04848-1 · Cited by 1 · see citing works
Kocadal, O., Aktekin, C. N., Pepe, M., Akşahin, E., TAGRİKULU, B., & Dikmen, A. U. (2015) · Turkiye Klinikleri Journal of Medical Sciences · doi:10.5336/medsci.2015-43953 · Cited by 1 · see citing works
Diagnostic and prognostic models: applications and methods
Zuithoff, N. P. A. (2012) · Utrecht University Repository (Utrecht University)
SuperAging: Current findings yield future challenges—A response to Rogalski and Goldberg
Dang, C., & Maruff, P. T. (2019) · Alzheimer s & Dementia Diagnosis Assessment & Disease Monitoring · doi:10.1016/j.dadm.2019.05.004
Andrades, P. R., Danilla, S., & Prado, A. S. (2009) · Plastic & Reconstructive Surgery · doi:10.1097/prs.0b013e3181a83919
Beard, E., Brown, J., & Shahab, L. (2025) · Addiction · doi:10.1111/add.70220 · Cited by 1 · see citing works
Additional file 1 of Overrunning in clinical trials: some thoughts from a methodological review
Baldi, I., Azzolina, D., Soriani, N., Barbetta, B., Vaghi, P., Giacovelli, G., Berchialla, P., & Gregori, D. (2020) · Figshare · doi:10.6084/m9.figshare.12687029
Do Narcissistic People Have More Dating Success? Evidence From a Speed‐Dating Study
Hall, B. T., Hart, W., & Lambert, J. T. (2026) · Journal of Personality · doi:10.1111/jopy.70059
Dung, H. V., Khanh, N. V., Sơn, N. B. N., Ha, H., Đôn, T. Q., Ngan, T. T., & Phương, N. T. T. (2026) · BMC Musculoskeletal Disorders · doi:10.1186/s12891-026-09773-2
Digital device use and disparities in health literacy among older adults
Chun, H., Kim, C., & Kim, I. (2026) · 보건교육·건강증진학회지 · doi:10.14367/kjhep.2026.43.2.87
Kamalabadi, Y. M., Zou, G., Jafari, A., Klotz, A. G. R., & Roshanov, P. S. (2026) · BMJ Surgery · doi:10.1136/bmjsurg-2026-000011
- Authors
- Bhandari, M., Lochner, H., & Tornetta, P.
- Affiliations
- McMaster University Medical Centre (CA)
- Boston Medical Center (US)
- Corresponding author
- Bhandari, Mohit
- Venue
- Archives of Orthopaedic and Trauma Surgery
- Published
- 2002-02-01
- Volume
- 122
- Issue
- 2
- Pages
- 96-98
- ISSN
- 0936-8051 (ISSN-L)
- 1434-3916
- OpenAlex
- W2027513428
- Cited by
- 67
- References
- 5
- Citations by year
- 2026: 6 · 2025: 2 · 2024: 2 · 2023: 3 · 2022: 4 · 2021: 3 · 2020: 12 · 2019: 3 · 2018: 5 · 2017: 2 · 2016: 4 · 2015: 2 · 2014: 2 · 2013: 3 · 2012: 2
- FWCI
- 1.52
- Type
- journal article
- Language
- en
- Open access
- closed
- Licence
- www.springer.com/tdm (tdm)
- Locations
- Archives of Orthopaedic and Trauma Surgery (publishedVersion)
- PubMed (publishedVersion)
- Topics
- Physical Sciences › Mathematics › Statistics and Probability › Statistical Methods in Clinical Trials
- Physical Sciences › Mathematics › Statistics and Probability › Statistical Methods in Epidemiology
- Social Sciences › Decision Sciences › Statistics, Probability and Uncertainty › Meta-analysis and systematic reviews
- Keywords
- statistical power, small sample size, randomized controlled trials, sample size determination
- MeSH terms
- Data Interpretation, Statistical, Female, Humans, Male, Quality Control, Random Allocation, Sensitivity and Specificity, Cluster Analysis, Randomized Controlled Trials as Topic, Treatment Outcome, Sample Size, Orthopedic Procedures, Fractures, Bone
About these checks
Registry, retraction, Cites and statistics results are computed, not judged, with one exception: a printed reference that no index lists is read once by a model before it counts as a citation error. Claims are extracted by a model and kept only when their quote appears verbatim in the text; each cited source is then checked, with a model’s help, for whether it says what the claim relies on. Those verdicts can be wrong — read the claim’s quote and the cited source before relying on one.
Statistics and arithmetic are recomputed, not judged.
Confidence bands are shown only for fields calibrated on our annotated test set. None is calibrated yet, so no band is shown.
What counts as a claim ›How we measure confidence ›How we check this ›
Are you an author, or do you see a problem with this page? Request a review
