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Sacrum

Anatomy and Physiology · NLM MeSH · updated 2026-10-31 · version 1

Citations verified against PubMedNot yet clinician-reviewed10 referencesApproximately 5 min read

Five fused vertebrae forming a triangle-shaped structure at the back of the pelvis.

Table of Contents

1. Definition2. Research landscape3. Reading the evidence4. Open-access studies5. Key reviews6. References7. About this article

Definition and research guide

This page combines a MeSH definition, publication statistics and selected research abstracts. It is a starting point for reading the literature, not a medical textbook or a systematic evidence review.

Content available: 4 complete abstracts (1,044 words), 10 references. Full article text is not stored or reproduced here; follow the PMID, DOI or PMC links to read the original sources and their access terms.

Definition

Five fused vertebrae forming a triangle-shaped structure at the back of the pelvis. It articulates superiorly with the lumbar vertebrae, inferiorly with the coccyx, and anteriorly with the ilium of the pelvis. The sacrum strengthens and stabilizes the pelvis.

Definition: NLM Medical Subject Headings (MeSH) scope note (Public domain (U.S. National Library of Medicine); attribution requested). View the MeSH record.

Also known as: Sacrums; Sacra; Sacral Vertebrae; Vertebrae, Sacral; Sacral Vertebra; Vertebra, Sacral.

Where it fits in the MeSH classification

Broader topics
Spine

Related concepts

  • Vertebrae
  • Pelvis
  • Lumbar Vertebrae
  • Coccyx
  • Ilium

Research landscape

PubMed indexes 10,964 records tagged with the MeSH heading “Sacrum” (counts retrieved 2026-10-31). 1,911 of them (17.4%) were published from 2020 onward, and the busiest period so far is through 1999 with 3,522 records.

Reviews account for 965 records (8.8%) and meta-analyses for 49. Randomized controlled trials number 150 (1.4%) as a share of all records on the topic. Randomized trials make up only a small share of this literature, so much of what is known comes from laboratory, observational or descriptive work.

PubMed records by publication periodthrough 1999: 3,522 records; 2000-2009: 2,214 records; 2010-2019: 3,317 records; 2020 onward: 1,911 records3,522through 19992,2142000-20093,3172010-20191,9112020 onward
Records in PubMed indexed with this heading, by publication period. Real counts from NCBI E-utilities; the final period covers only part of the current year. Volume reflects how much has been published, not how strong the evidence is.
Show the data
PeriodRecords
through 19993,522
2000-20092,214
2010-20193,317
2020 onward1,911
Share of records by publication typeReviews: 8.8 percent; Meta-analyses: 0.4 percent; Randomized controlled trials: 1.4 percentReviews8.8% (965)Meta-analyses0.4% (49)Randomized controlled trials1.4% (150)
Share of all PubMed records on this heading that carry each publication type. Types overlap with other records, so the shares do not sum to 100%.
Publication-type chart data
Publication types among 10,964 PubMed records
TypeRecordsShare
Reviews9658.8%
Meta-analyses490.4%
Randomized controlled trials1501.4%

Method: PubMed query "Sacrum"[MeSH Terms] with publication-type and date filters, retrieved 2026-10-31.

Reading the evidence in anatomy and physiology

Anatomy describes how body structures are built and physiology describes how they normally work, so most findings here are descriptive or mechanistic rather than evidence about treatment. Much of what is known comes from dissection, imaging, tissue studies and experiments in animals, and measurements in healthy volunteers can differ from those in people with disease or at different ages. Normal ranges vary between individuals and populations. Check whether a result was measured in people or in another species, the age and health of the participants, and the method used.

Evidence from open-access studies

These open-access studies come from PubMed’s best-match results for this heading (papers whose main topic it is), ranked here by citation count, with one recent addition. Each abstract is reproduced in full under its recorded open licence so that you can read the authors’ own words. They illustrate the literature; they are not a systematic summary of it. Citation counts measure attention, not reliability or clinical benefit.

Study comparison — selected abstracts, not a systematic review
Study / authorsYearSource label / designEurope PMC citationsLicence / source
Accuracy of clinical neurological examination in diagnosing lumbo-sacral radiculopathy: a systematic literature review
Tawa N, Rhoda A, Diener I
2017Systematic review
Design not recorded in structured metadata
60cc by
PMID 28231784 · DOI · PMC5324296
Global incidence of spinal perineural Tarlov's cysts and their morphological characteristics: a meta-analysis of 13,266 subjects
Klepinowski T, Orbik W, Sagan L
2021Meta-analysis
Design not recorded in structured metadata
53cc by
PMID 33452905 · DOI · PMC8164596
Sacral neuromodulation in children and adolescents with chronic constipation refractory to conservative treatment
van der Wilt AA, van Wunnik BP, Sturkenboom R, Han-Geurts IJ, Melenhorst J, Benninga MA, et al.
2016Research article
Design not recorded in structured metadata
37cc by
PMID 27294660 · DOI · PMC4947479
Fixation of unstable sacral fractures by transpedicular system: a prospective study
Elmoghany ME, Gharbo NO, Ayoub MA, Farouk OA, Mashal HEY
2026Research article
Design not recorded in structured metadata
0cc by
PMID 41233652 · DOI · PMC12881057

Accuracy of clinical neurological examination in diagnosing lumbo-sacral radiculopathy: a systematic literature review [1]

Systematic review Tawa N, Rhoda A, Diener I · · 2017 · cited 60 times (Europe PMC)

Abstract reading summary — source excerpts
Opening excerpt
BackgroundLumbar radiculopathy remains a clinical challenge among primary care clinicians in both assessment and diagnosis.
Closing excerpt
Whether these tests are able to detect the presence of disc herniation and subsequent nerve root compression or hyper-sensitivity of the sacral and femoral plexus due to mechanical irritation still remains debatable.
Interpretation limits
Verbatim excerpts from the authors’ abstract; the closing excerpt may describe a finding, limitation or recommendation. Design, population, effect size and uncertainty have not been independently extracted or appraised. Read the complete abstract and linked paper before interpreting the findings.
Read complete abstract (359 words)

BackgroundLumbar radiculopathy remains a clinical challenge among primary care clinicians in both assessment and diagnosis. This often leads to misdiagnosis and inappropriate treatment of patients resulting in poor health outcomes, exacerbating this already debilitating condition. This review evaluated 12 primary diagnostic accuracy studies that specifically assessed the performance of various individual and grouped clinical neurological tests in detecting nerve root impingement, as established in the current literature.MethodsEight electronic data bases were searched for relevant articles from inception until July 2016. All primary diagnostic studies which investigated the accuracy of clinical neurological test (s) in diagnosing lumbar radiculopathy among patients with low back and referred leg symptoms were screened for inclusion. Qualifying studies were retrieved and independently assessed for methodological quality using the 'Quality Assessment of Diagnostic tests Accuracy Studies' criteria.ResultsA total of 12 studies which investigated standard components of clinical neurological examination of (sensory, motor, tendon reflex and neuro-dynamics) of the lumbo-sacral spine were included. The mean inter-observer agreement on quality assessment by two independent reviewers was fair (k = 0.3 - 0.7). The diagnostic performance of sensory testing using MR imaging as a reference standard demonstrated a sensitivity (confidence interval 95%) 0.61 (0.47-0.73) and a specificity of 0.63 (0.38-0.84). Motor tests sensitivity was poor to moderate, ranging from 0.13 (0.04-0.31) to 0.61 (0.36-0.83). Generally, the diagnostic performance of reflex testing was notably good with specificity ranging from (confidence interval 95%) 0.60 (0.51-0.69) to 0.93 (0.87-0.97) and sensitivity ranging from 0.14 (0.09-0.21) to 0.67 (0.21-0.94). Femoral nerve stretch test had a high sensitivity of (confidence interval 95%) 1.00 (0.40-1.00) and specificity of 0.83 (0.52-0.98) while SLR test recorded a mean sensitivity of 0.84 (0.72-0.92) and specificity of 0.78 (0.67-0.87).ConclusionsThere is a scarcity of studies on the diagnostic accuracy of clinical neurological examination testing. Furthermore there seem to be a disconnect among researchers regarding the diagnostic utility of lower limb neuro-dynamic tests which include the Straight Leg Raise and Femoral Nerve tests for sciatic and femoral nerve respectively. Whether these tests are able to detect the presence of disc herniation and subsequent nerve root compression or hyper-sensitivity of the sacral and femoral plexus due to mechanical irritation still remains debatable.

Abstract reproduced from the open-access article under the recorded cc by licence; © the authors. PMID 28231784 · DOI · PMC5324296

Global incidence of spinal perineural Tarlov's cysts and their morphological characteristics: a meta-analysis of 13,266 subjects [2]

Meta-analysis Klepinowski T, Orbik W, Sagan L · · 2021 · cited 53 times (Europe PMC)

Abstract reading summary — source excerpts
Opening excerpt
BackgroundSpinal perineural Tarlov's cysts (TCs) are considered incidental findings that occasionally might exert pressure upon nerve roots and correspond with patients' signs and symptoms.
Closing excerpt
The purported high incidence in PGAD requires confirmation in case-control studies for the risk-ratio calculation.
Interpretation limits
Verbatim excerpts from the authors’ abstract; the closing excerpt may describe a finding, limitation or recommendation. Design, population, effect size and uncertainty have not been independently extracted or appraised. Read the complete abstract and linked paper before interpreting the findings.
Read complete abstract (281 words)

BackgroundSpinal perineural Tarlov's cysts (TCs) are considered incidental findings that occasionally might exert pressure upon nerve roots and correspond with patients' signs and symptoms. Purpose of this meta-analysis is to deliver global incidence and characteristics (location, size, and shape) of TCs.MethodsFollowing PRISMA checklist, all major databases were searched by two authors for radiologic studies reporting incidence and morphologic features (location, size, and shape) of TCs. Anatomical Quality Assessment tool was applied for risk of bias evaluation. Meta-analysis of random-effects model was employed. Subgroup analysis for regional distribution, gender, sacral levels, age, correspondence with symptoms, and persistent genital arousal disorder (PGAD) were planned ahead.Results22 radiologic studies of level 3 evidence involving 13,266 subjects were included. Global pooled prevalence of TCs was 4.18% (95% CI 2.47-6.30). Mean pooled sagittal diameter was 11.86 mm (95% CI 10.78-12.93). Sacral cysts strongly prevailed over the other segments. Of the sacral, S2 level was the most common (46.7% [95% CI 29.4-60.5]). Geographically, the highest incidence was found in Europe (6.07% [95% CI 1.49-13.00]), followed by North America (3.82% [95% CI 0.49-9.44]), and Asia (3.33% [95% CI 1.52-5.75]). TCs were more common in women than in men (5.84% vs 3.03%, p 2). Subjects with PGAD had incidence of 37.87% (95% CI 2.45-81.75). TCs in pediatric population are rare-0.53% (95% CI 0.02-1.51). 15.59% of TCs corresponded with symptoms.ConclusionsSpinal perineural (Tarlov) cysts are found in a minority of population. S2 level of the sacral bone is affected most frequently. There is female predominance. Correspondence with symptoms is seen in less than one-fifth of TCs. Studies with stronger evidence level are needed to corroborate the results. The purported high incidence in PGAD requires confirmation in case-control studies for the risk-ratio calculation.

Abstract reproduced from the open-access article under the recorded cc by licence; © the authors. PMID 33452905 · DOI · PMC8164596

Sacral neuromodulation in children and adolescents with chronic constipation refractory to conservative treatment [3]

Research article van der Wilt AA, van Wunnik BP, Sturkenboom R, Han-Geurts IJ, Melenhorst J, Benninga MA, et al. · · 2016 · cited 37 times (Europe PMC)

Abstract reading summary — source excerpts
Opening excerpt
PurposeFunctional constipation in children and adolescents is a common and invalidating condition.
Closing excerpt
6) after 3 weeks of test treatment (p ConclusionSNM is a therapeutic option for children with chronic constipation not responding to intensive oral and/or laxative therapy, providing benefits that appear to be sustained over prolonged period of time.
Interpretation limits
Verbatim excerpts from the authors’ abstract; the closing excerpt may describe a finding, limitation or recommendation. Design, population, effect size and uncertainty have not been independently extracted or appraised. Read the complete abstract and linked paper before interpreting the findings.
Read complete abstract (186 words)

PurposeFunctional constipation in children and adolescents is a common and invalidating condition. In a minority of patients, symptoms persist despite optimal conservative therapy. The aim of this study was to evaluate whether the short-term effects of sacral neuromodulation (SNM) in children and adolescents with constipation are sustained over prolonged period of time.MethodsPatients aged 10-20 years, with refractory constipation, fulfilling the Rome III criteria, were included in our study. If SNM test treatment showed >50 % improvement in defecation frequency, a permanent stimulator was implanted. Primary outcome measure was defecation frequency during 3 weeks. Secondary endpoints were abdominal pain and Wexner score. To assess sustainability of treatment effect, a survival analysis was performed. Cross-sectional quality of life was assessed using the EQ-5D VAS score.ResultsThirty girls, mean age 16 (range 10-20), were included. The mean defecation frequency increased from 5.9 (SD 6.5) in 21 days at baseline to 17.4 (SD 11.6) after 3 weeks of test treatment (p ConclusionSNM is a therapeutic option for children with chronic constipation not responding to intensive oral and/or laxative therapy, providing benefits that appear to be sustained over prolonged period of time.

Abstract reproduced from the open-access article under the recorded cc by licence; © the authors. PMID 27294660 · DOI · PMC4947479

Fixation of unstable sacral fractures by transpedicular system: a prospective study [4]

Research article Elmoghany ME, Gharbo NO, Ayoub MA, Farouk OA, Mashal HEY · · 2026

Abstract reading summary — source excerpts
Opening excerpt
PurposeThis study aimed to assess the functional and radiological outcome of transpedicular fixation system for managing unstable sacral fractures in adults.
Closing excerpt
Trial registration(ID/NCT06888583) retrospectively registered.
Interpretation limits
Verbatim excerpts from the authors’ abstract; the closing excerpt may describe a finding, limitation or recommendation. Design, population, effect size and uncertainty have not been independently extracted or appraised. Read the complete abstract and linked paper before interpreting the findings.
Read complete abstract (218 words)

PurposeThis study aimed to assess the functional and radiological outcome of transpedicular fixation system for managing unstable sacral fractures in adults.MethodsThis prospective case series study included 21 patients with unstable type C sacral fractures according to AO Spine classification of sacral fractures. The patients were treated by a transpedicular fixation system connecting the lower lumbar spine to the ilium, as a vertical element, which was bilateral in seven cases and unilateral in 14 cases. A transverse element connecting both sides of the posterior pelvic ring was added to augment fixation in the transverse plane. The minimum period of follow-up was 12 months.ResultsMean Majeed Score was 84,29 ± 9.97; excellent, good and fair classes were present in 14 (66.7%), five (23.8%) and two (9.5%) patients, respectively. There was a significant reduction of the vertical, anterior posterior and rotational displacement postoperatively in comparison to preoperative measures. There was a significant improvement in neurological deficit postoperatively. Eight (38.1%) patients developed complications postoperatively. Wound Infection was the most common complication.ConclusionThe use of transpedicular fixation as a vertical element combined with a transverse element connecting both sides of the posterior pelvic ring, to treat unstable sacral fractures, offers adequate fixation strength that helps to achieve union in a well reduced position, leads to satisfactory functional outcome and improves neurological deficit.Trial registration(ID/NCT06888583) retrospectively registered.

Abstract reproduced from the open-access article under the recorded cc by licence; © the authors. PMID 41233652 · DOI · PMC12881057

Key reviews and meta-analyses

The most cited review-type papers among PubMed’s best-match results for this heading, listed with bibliographic details only. Follow the links for the full text and access terms.

  • Research article Congenital lumbosacral lipomas [5]
    Pierre-Kahn A, Zerah M, Renier D, Cinalli G, Sainte-Rose C, Lellouch-Tubiana A, et al. · Childs Nerv Syst · 1997 · cited 187 times (Europe PMC)
  • Research article Sacropelvic fixation: techniques and complications [6]
    Kebaish KM · Spine (Phila Pa 1976) · 2010 · cited 178 times (Europe PMC)
  • Research article Incidence and risk factors for proximal junctional kyphosis: a meta-analysis [7]
    Liu FY, Wang T, Yang SD, Wang H, Yang DL, Ding WY · Eur Spine J · 2016 · cited 120 times (Europe PMC)
  • Research article Robot-assisted sacrocolpopexy for pelvic organ prolapse: a systematic review and meta-analysis of comparative studies [8]
    Serati M, Bogani G, Sorice P, Braga A, Torella M, Salvatore S, et al. · Eur Urol · 2014 · cited 116 times (Europe PMC)
  • Research article The controversy surrounding sacral insufficiency fractures: to ambulate or not to ambulate? [9]
    Babayev M, Lachmann E, Nagler W · Am J Phys Med Rehabil · 2000 · cited 114 times (Europe PMC)
  • Research article Fragility fractures of the sacrum: how to identify and when to treat surgically? [10]
    Wagner D, Ossendorf C, Gruszka D, Hofmann A, Rommens PM · Eur J Trauma Emerg Surg · 2015 · cited 111 times (Europe PMC)

References

  1. Tawa N, Rhoda A, Diener I. Accuracy of clinical neurological examination in diagnosing lumbo-sacral radiculopathy: a systematic literature review. . 2017. PMID 28231784 · DOI · PMC5324296
  2. Klepinowski T, Orbik W, Sagan L. Global incidence of spinal perineural Tarlov's cysts and their morphological characteristics: a meta-analysis of 13,266 subjects. . 2021. PMID 33452905 · DOI · PMC8164596
  3. van der Wilt AA, van Wunnik BP, Sturkenboom R, Han-Geurts IJ, Melenhorst J, Benninga MA, et al.. Sacral neuromodulation in children and adolescents with chronic constipation refractory to conservative treatment. . 2016. PMID 27294660 · DOI · PMC4947479
  4. Elmoghany ME, Gharbo NO, Ayoub MA, Farouk OA, Mashal HEY. Fixation of unstable sacral fractures by transpedicular system: a prospective study. . 2026. PMID 41233652 · DOI · PMC12881057
  5. Pierre-Kahn A, Zerah M, Renier D, Cinalli G, Sainte-Rose C, Lellouch-Tubiana A, et al.. Congenital lumbosacral lipomas. Childs Nerv Syst. 1997. PMID 9272285 · DOI
  6. Kebaish KM. Sacropelvic fixation: techniques and complications. Spine (Phila Pa 1976). 2010. PMID 21102300 · DOI
  7. Liu FY, Wang T, Yang SD, Wang H, Yang DL, Ding WY. Incidence and risk factors for proximal junctional kyphosis: a meta-analysis. Eur Spine J. 2016. PMID 26994925 · DOI
  8. Serati M, Bogani G, Sorice P, Braga A, Torella M, Salvatore S, et al.. Robot-assisted sacrocolpopexy for pelvic organ prolapse: a systematic review and meta-analysis of comparative studies. Eur Urol. 2014. PMID 24631406 · DOI
  9. Babayev M, Lachmann E, Nagler W. The controversy surrounding sacral insufficiency fractures: to ambulate or not to ambulate?. Am J Phys Med Rehabil. 2000. PMID 10892628 · DOI
  10. Wagner D, Ossendorf C, Gruszka D, Hofmann A, Rommens PM. Fragility fractures of the sacrum: how to identify and when to treat surgically?. Eur J Trauma Emerg Surg. 2015. PMID 26038048 · DOI · PMC4523697

About this article

Sources
NLM Medical Subject Headings (definition, synonyms); NCBI PubMed (counts, identifiers); Europe PMC (open-access abstracts and citation counts).
Verification
Every reference was resolved against PubMed on 2026-10-31; title, year and DOI matched.
Review state
automated source verified; no human expert review has been recorded yet.
Version
1, last updated 2026-10-31.

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At a glance

10,964
PubMed records on this heading
17%
published since 2020
965
review articles
150
randomized trials
10
verified references below

Counts come from PubMed on 2026-10-31; they show how much has been written, not how strong the evidence is.

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