Library
Lists
Topics
LibraryListsTopics
© 2026 Brad Roepke|About·Privacy·Terms·Disclaimer·Support
© 2026·About·Privacy·Terms·Disclaimer·Support
|

The Subcoracoid Space. an Anatomic Study.

·Clin Orthop Relat Res·1987·138 citations·Shoulder & Elbow
PubMed
SummaryAbstract on PubMed →

Gerber et al. used CT imaging of 47 normal shoulders to define the normal subcoracoid space in two arm positions. The study identified which skeletal variables predict subcoracoid impingement risk and quantified how arm position and surgical changes alter available clearance. This is the foundational anatomic reference for understanding subcoracoid impingement syndrome.

Study Snapshot

Design
Prospective anatomic CT study
Setting: Single academic center, University of Bern
Objective
Whether specific skeletal variables predict subcoracoid space size and impingement risk in normal shoulders.
Outcome(s)
Coracohumeral distance (mm) in adduction and forward flexion/internal rotation
Subjects
47 normal shoulders (34 volunteers; 20 also studied in flexion)
Inclusion
  • No history of shoulder pain, dysfunction, or injury
  • Normal clinical exam including range of motion
  • Negative impingement sign and instability testing
Exclusion
  • Abnormal contralateral shoulder (excluded from bilateral analysis)
  • Missing internal rotation CT cut at coracoid tip level
Statistics
Multiple regression analysisStudent's t-test (implied)

Key Findings

  • The mean coracohumeral distance is 8.7 mm in adduction and 6.8 mm in forward flexion/internal rotation (range 2.5–13 mm across individuals). There is no free anatomic space — soft tissues fill the entire bony interval. This is why even a few millimeters of skeletal change can produce symptomatic impingement.
  • Forward flexion with internal rotation is the high-risk position: clearance decreases in 16 of 20 shoulders (p < 0.001), and any modification of the coracohumeral relationship affects the space ~1.5 times more in flexion than at the side. This explains why patients with subcoracoid impingement are symptomatic with overhead activity but not at rest.
  • Two skeletal variables independently predict subcoracoid space size:
    –Coracoglenoid angle. A 1° increase widens space by 0.37 mm (adduction) or 0.53 mm (flexion)
    –Coracoid overlap. A 1 mm reduction narrows space by 0.32 mm (adduction) or 0.54 mm (flexion)
    –Together they explain 69% of variance in adduction and 71% in flexion (r² = 0.69/0.71).
  • The anatomic risk configuration is a small coracoglenoid angle combined with small coracoid overlap. Not a globally enlarged coracoid. A prominent coracoid that points posteriorly (large coracoglenoid angle) may pose no risk, while a smaller coracoid angled toward the humeral head can be highly symptomatic.
  • Women have 1.4 mm less coracohumeral clearance than men with identical skeletal geometry, representing a sex-based risk factor independent of coracoid morphology. This difference alone can be clinically meaningful given the already tight normal dimensions.
  • Iatrogenic and traumatic changes that reduce subcoracoid space include:
    –Coracoid osteotomy or fracture malunion
    –Glenoid neck fracture or posterior glenoplasty
    –Proximal humerus deformity
    –The 1.5× amplification in flexion means even a 1–2 mm skeletal change has outsized functional consequences.
Board PearlThe subcoracoid space averages 8.7 mm (adduction) and 6.8 mm (flexion/IR) — there is no free space, and small coracoglenoid angle plus small coracoid overlap predict impingement.

Clinical Relevance

Subcoracoid impingement was recognized clinically before this paper, but no anatomic data existed to explain which patients were at risk or why surgical procedures sometimes caused or cured it.

When a patient presents with anterior shoulder pain reproduced by forward flexion to 90–100° with internal rotation, evaluate CT for two specific variables: the coracoglenoid angle and the coracoid overlap. A small angle combined with small overlap is the at-risk combination, not an enlarged coracoid in isolation.

Before any procedure that alters coracohumeral geometry — coracoid osteotomy for instability (Latarjet), posterior glenoplasty, or proximal humerus fixation. Account for the 1.5× amplification effect in flexion. A few millimeters of coracoid medialization or humeral head deformity can convert a borderline space into a symptomatic one.

Women warrant extra scrutiny: 1.4 mm less baseline clearance means their margin for tolerating any additional anatomic change is narrower than men with identical radiographic morphology.

Related Articles

Reference

The Subcoracoid Space. an Anatomic Study.

Gerber, Ganz, et al.·Clin Orthop Relat Res·1987·138 citations·Shoulder & Elbow
Landmark

Radiological Assessment of Osteo-Arthrosis.|

Kellgren, Lawrence·Ann Rheum Dis·1957·12,248 citations·General
Landmark

Mesenchymal Stem Cells.

Caplan·J Orthop Res·1991·6,470 citations·Basic Science
Landmark

Traumatic Arthritis of the Hip after Dislocation and Acetabular Fractures: Treatment by Mold Arthroplasty. an End-Result Study Using a New Method of Result Evaluation.

Harris·J Bone Joint Surg Am·1969·5,899 citations·Hip & Knee
Landmark

Bone: Formation by Autoinduction.

Urist·Science·1965·5,546 citations·Basic Science
Landmark

Treatment of Deep Cartilage Defects in the Knee with Autologous Chondrocyte Transplantation.|

Brittberg, Peterson, et al.·N Engl J Med·1994·5,478 citations·Sports Medicine
Landmark

Interrater Reliability of a Modified Ashworth Scale of Muscle Spasticity

Bohannon·Phys Ther·1987·5,350 citations·General
Landmark

Osteoclast Differentiation Factor Is a Ligand for Osteoprotegerin/osteoclastogenesis-Inhibitory Factor and Is Identical to Trance/rankl.|

Yasuda, Suda, et al.·Proc Natl Acad Sci U S A·1998·4,239 citations·Basic Science
Landmark

Comparison of Upper Gastrointestinal Toxicity of Rofecoxib and Naproxen in Patients with Rheumatoid Arthritis. Vigor Study Group.|

Bombardier, VIGOR Study Group, et al.·N Engl J Med·2000·4,036 citations·General
Landmark

Magnetic Resonance Classification of Lumbar Intervertebral Disc Degeneration.

Pfirrmann, Boos, et al.·Spine·2001·3,960 citations·Spine
Landmark

Novel Regulators of Bone Formation: Molecular Clones and Activities.

Wozney, Wang, et al.·Science·1988·3,906 citations·Basic Science
Landmark

The Diagnosis of Osteoporosis.

Kanis, Khaltaev, et al.·J Bone Miner Res·1994·3,840 citations·General
Landmark

"modes of Failure" of Cemented Stem-Type Femoral Components: a Radiographic Analysis of Loosening.

Gruen, Amstutz, et al.·Clin Orthop Relat Res·1979·3,647 citations·Hip & Knee
Landmark

Biomechanical Measures of Neuromuscular Control and Valgus Loading of the Knee Predict Anterior Cruciate Ligament Injury Risk in Female Athletes: a Prospective Study.

Hewett, Succop, et al.·Am J Sports Med·2005·3,495 citations·Sports Medicine
Landmark

Femoroacetabular Impingement: a Cause for Osteoarthritis of the Hip.

Ganz, Siebenrock, et al.·Clin Orthop Relat Res·2003·3,410 citations·Hip & Knee
Landmark

Prevention of Infection in the Treatment of One Thousand and Twenty-Five Open Fractures of Long Bones: Retrospective and Prospective Analyses.

Gustilo, Anderson·J Bone Joint Surg Am·1976·3,211 citations·Trauma
Landmark

The Variation in Isometric Tension with Sarcomere Length in Vertebrate Muscle Fibres.

Gordon, Julian, et al.·J Physiol·1966·3,135 citations·Basic Science
Landmark

Osteoarthritis: a Disease of the Joint as an Organ.|

Loeser, Goldring, et al.·Arthritis Rheum·2012·2,961 citations·Basic Science
Landmark

Radiological Demarcation of Cemented Sockets in Total Hip Replacement.

DeLee, Charnley·Clin Orthop Relat Res·1976·2,913 citations·Hip & Knee
Landmark

Ectopic Ossification Following Total Hip Replacement. Incidence and a Method of Classification.

Brooker, Riley, et al.·J Bone Joint Surg Am·1973·2,880 citations·Hip & Knee
Landmark

The Operation of the Century: Total Hip Replacement.

Learmonth, Rorabeck, et al.·Lancet·2007·2,788 citations·Hip & Knee
Landmark

Fatty Muscle Degeneration in Cuff Ruptures. Pre- and Postoperative Evaluation by CT Scan.

Goutallier, Voisin, et al.·Clin Orthop Relat Res·1994·2,669 citations·Shoulder & Elbow
Landmark

Osseointegrated Titanium Implants. Requirements for Ensuring a Long-Lasting, Direct Bone-To-Implant Anchorage in Man.

Albrektsson, Lindström, et al.·Acta Orthop Scand·1981·2,662 citations·Basic Science
Landmark

The Etiology of Chondromalacia Patellae.

Outerbridge·J Bone Joint Surg Br·1961·2,659 citations·Sports Medicine
Landmark

Fracture and Dislocation Classification Compendium-2018.

Meinberg, Kellam, et al.·J Orthop Trauma·2018·2,622 citations·Trauma
Landmark

The Three Column Spine and Its Significance in the Classification of Acute Thoracolumbar Spinal Injuries.

Denis·Spine·1983·2,566 citations·Spine
Landmark

Dislocations after Total Hip-Replacement Arthroplasties.

Lewinnek, Zimmerman, et al.·J Bone Joint Surg Am·1978·2,549 citations·Hip & Knee
Landmark

Patient Satisfaction after Total Knee Arthroplasty: Who Is Satisfied and Who Is Not?|

Bourne, Charron, et al.·Clin Orthop Relat Res·2010·2,475 citations·Hip & Knee
Landmark

Problems in the Management of Type III (severe) Open Fractures: a New Classification of Type III Open Fractures.

Gustilo, Williams, et al.·J Trauma·1984·2,361 citations·Trauma
Landmark

The Value of Postural Reduction in the Initial Management of Closed Injuries of the Spine with Paraplegia and Tetraplegia. I.

Frankel, Walsh, et al.·Paraplegia·1969·2,283 citations·Spine
Landmark

Vacuum-Assisted Closure: a New Method for Wound Control and Treatment: Animal Studies and Basic Foundation.

Morykwas, McGuirt, et al.·Ann Plast Surg·1997·2,218 citations·Basic Science
Landmark

A System for the Functional Evaluation of Reconstructive Procedures after Surgical Treatment of Tumors of the Musculoskeletal System.

Enneking, Pritchard, et al.·Clin Orthop Relat Res·1993·2,209 citations·Oncology
Landmark

A Controlled Trial of Arthroscopic Surgery for Osteoarthritis of the Knee|

Moseley, Wray, et al.·N Engl J Med·2002·2,154 citations·Hip & Knee
Landmark

The Stabilizing System of the Spine. Part I. Function, Dysfunction, Adaptation, and Enhancement.

Panjabi·J Spinal Disord·1992·2,145 citations·Spine
Landmark

The Outcome and Repair Integrity of Completely Arthroscopically Repaired Large and Massive Rotator Cuff Tears.

Galatz, Yamaguchi, et al.·J Bone Joint Surg Am·2004·2,135 citations·Shoulder & Elbow
Landmark

The Tension-Stress Effect on the Genesis and Growth of Tissues. Part I. the Influence of Stability of Fixation and Soft-Tissue Preservation.

Ilizarov·Clin Orthop Relat Res·1989·2,120 citations·Basic Science
Landmark

A System for the Surgical Staging of Musculoskeletal Sarcoma.

Enneking, Goodman, et al.·Clin Orthop Relat Res·1980·2,112 citations·Oncology
Landmark

A Comprehensive Classification of Thoracic and Lumbar Injuries|Citation only

Magerl·Eur Spine J·1994·2,067 citations·Spine
Landmark

Effect of the Tyrosine Kinase Inhibitor Sti571 in a Patient with a Metastatic Gastrointestinal Stromal Tumor|Citation only|

Joensuu·N Engl J Med·2001·2,056 citations·Oncology
Landmark

Zoledronic Acid and Clinical Fractures and Mortality after Hip Fracture.|

Lyles, HORIZON Recurrent Fracture Trial, et al.·N Engl J Med·2007·1,995 citations·Trauma
Landmark

Factors of Patellar Instability: an Anatomic Radiographic Study.

Dejour, Guier, et al.·Knee·1994·1,987 citations·Sports Medicine
Landmark

Displaced Proximal Humeral Fractures. I. Classification and Evaluation.

Neer·J Bone Joint Surg Am·1970·1,957 citations·Trauma
Landmark

Hip Morphology Influences the Pattern of Damage to the Acetabular Cartilage: Femoroacetabular Impingement as a Cause of Early Osteoarthritis of the Hip.|

Beck, Ganz, et al.·J Bone Joint Surg Br·2005·1,955 citations·Hip & Knee
Core

Porosity of 3D Biomaterial Scaffolds and Osteogenesis.

Karageorgiou, Kaplan·Biomaterials·2005·6,476 citations·Basic Science
Core

A Report: the Definition and Classification of Cerebral Palsy April 2006.

Rosenbaum, Jacobsson, et al.·Dev Med Child Neurol·2007·4,795 citations·Pediatrics
Core

Clinician's Guide to Prevention and Treatment of Osteoporosis.|

Cosman, National Osteoporosis Foundation, et al.·Osteoporos Int·2014·4,062 citations·General
Core

Prevention of Venous Thromboembolism|Citation only

Geerts·Chest·2008·3,825 citations·Hip & Knee
Core

The Development of Assessment of Spondyloarthritis International Society Classification Criteria for Axial Spondyloarthritis (part II): Validation and Final Selection|Citation only|

Rudwaleit·Ann Rheum Dis·2009·3,656 citations·Spine
Core

Radiation Exposure from CT Scans in Childhood and Subsequent Risk of Leukaemia and Brain Tumours: a Retrospective Cohort Study.|

Pearce, Berrington de González, et al.·Lancet·2012·3,643 citations·Pediatrics
Core

Epidemiology of Adult Fractures: a Review.

Court-Brown, Caesar·Injury·2006·3,607 citations·Trauma
Core

Centers for Disease Control and Prevention Guideline for the Prevention of Surgical Site Infection, 2017.|

Berríos-Torres, Healthcare Infection Control Practices Advisory Committee, et al.·JAMA Surg·2017·3,442 citations·General
Core

Osteoblastic Cells Regulate the Haematopoietic Stem Cell Niche.|

Calvi, Scadden, et al.·Nature·2003·3,391 citations·Basic Science
Core

A Joint Coordinate System for the Clinical Description of Three-Dimensional Motions: Application to the Knee.

Grood, Suntay·J Biomech Eng·1983·3,309 citations·Basic Science
Core

Consensus Statement on Concussion in Sport-The 5th International Conference on Concussion in Sport Held in Berlin, October 2016.|

McCrory, Vos, et al.·Br J Sports Med·2017·3,303 citations·Sports Medicine
Core

Oarsi Guidelines for the Non-Surgical Management of Knee Osteoarthritis.|

McAlindon, Underwood, et al.·Osteoarthritis Cartilage·2014·3,129 citations·Hip & Knee
Core

Estimating the Prevalence of Limb Loss in the United States: 2005 to 2050.

Ziegler-Graham, Brookmeyer, et al.·Arch Phys Med Rehabil·2008·2,780 citations·General
Core

Metastasis to Bone: Causes, Consequences and Therapeutic Opportunities.

Mundy·Nat Rev Cancer·2002·2,765 citations·Oncology
Core

Role of Proinflammatory Cytokines in the Pathophysiology of Osteoarthritis.

Kapoor, Fahmi, et al.·Nat Rev Rheumatol·2011·2,711 citations·Basic Science
Core

The Basic Science of Articular Cartilage: Structure, Composition, and Function.|

Sophia Fox, Rodeo, et al.·Sports Health·2009·2,681 citations·Basic Science
Core

Osteoporosis: Now and the Future.|

Rachner, Hofbauer, et al.·Lancet·2011·2,604 citations·General
Core

Clinical Features of Metastatic Bone Disease and Risk of Skeletal Morbidity.

Coleman·Clin Cancer Res·2006·2,461 citations·Oncology
Core

Transfusion of Plasma, Platelets, and Red Blood Cells in a 1:1:1 vs. a 1:1:2 Ratio and Mortality in Patients with Severe Trauma: the Proppr Randomized Clinical Trial

Holcomb, PROPPR Study Group, et al.·JAMA·2015·2,453 citations·Trauma
Core

Direct Decompressive Surgical Resection in the Treatment of Spinal Cord Compression Caused by Metastatic Cancer: a Randomised Trial.

Patchell, Young, et al.·Lancet·2005·2,356 citations·Spine
Core

Fracture and Dislocation Classification Compendium - 2007: Orthopaedic Trauma Association Classification, Database and Outcomes Committee.

Marsh, Audigé, et al.·J Orthop Trauma·2007·2,343 citations·Trauma
Core

Peek Biomaterials in Trauma, Orthopedic, and Spinal Implants.|

Kurtz, Devine·Biomaterials·2007·2,304 citations·Basic Science
Core

Effect of Calcium and Vitamin D Supplementation on Bone Density in Men and Women 65 Years of Age or Older|Citation only|

Dawson-Hughes·N Engl J Med·1997·2,295 citations·General
Core

The Long-Term Consequence of Anterior Cruciate Ligament and Meniscus Injuries: Osteoarthritis.|

Lohmander, Roos, et al.·Am J Sports Med·2007·2,251 citations·Sports Medicine
Core

Diagnosis and Management of Prosthetic Joint Infection: Clinical Practice Guidelines by the Infectious Diseases Society of America.|

Osmon, Infectious Diseases Society of America, et al.·Clin Infect Dis·2013·2,220 citations·Hip & Knee
Core

The Amazing Osteocyte.|

Bonewald·J Bone Miner Res·2011·2,169 citations·Basic Science
Core

Osteosarcoma Incidence and Survival Rates from 1973 to 2004: Data from the Surveillance, Epidemiology, and End Results Program.|

Mirabello, Savage, et al.·Cancer·2009·2,165 citations·Oncology
Core

Projected Volume of Primary Total Joint Arthroplasty in the U.s., 2014 to 2030.

Sloan, Sheth, et al.·J Bone Joint Surg Am·2018·2,092 citations·Hip & Knee
Core

The 2018 Definition of Periprosthetic Hip and Knee Infection: an Evidence-Based and Validated Criteria.

Parvizi, Shohat, et al.·J Arthroplasty·2018·2,065 citations·Hip & Knee
Core

Bone Quality--The Material and Structural Basis of Bone Strength and Fragility.

Seeman, Delmas·N Engl J Med·2006·2,052 citations·Basic Science
Core

Prevalence of Muscular Dystrophies: a Systematic Literature Review.|

Theadom, Feigin, et al.·Neuroepidemiology·2014·2,050 citations·Pediatrics
Core

Mechanisms of Bone Metastasis.

Roodman·Discov Med·2004·2,028 citations·Oncology
Core

The Compressive Behavior of Bone as a Two-Phase Porous Structure.

Carter, Hayes·J Bone Joint Surg Am·1977·1,998 citations·Basic Science
Core

Metastatic Bone Disease: Clinical Features, Pathophysiology and Treatment Strategies.

Coleman·Cancer Treat Rev·2001·1,927 citations·Oncology
Emerging

Diagnosis and Treatment of Hip and Knee Osteoarthritis|

Katz, Loeser, et al.·JAMA·2021·2,126 citations·Hip & Knee
Supplemental

Denosumab for Prevention of Fractures in Postmenopausal Women with Osteoporosis.|

Cummings, FREEDOM Trial, et al.·N Engl J Med·2009·3,382 citations·General
Supplemental

Opgl Is a Key Regulator of Osteoclastogenesis, Lymphocyte Development and Lymph-Node Organogenesis.

Kong, Penninger, et al.·Nature·1999·3,356 citations·Basic Science
Supplemental

Osteoarthritis: New Insights. Part 1: the Disease and Its Risk Factors.

Felson, Fries, et al.·Ann Intern Med·2000·2,525 citations·Hip & Knee
Supplemental

Morbidity at Bone Graft Donor Sites.

Younger, Chapman·J Orthop Trauma·1989·2,008 citations·General
Supplemental

Articular Cartilage Repair: Basic Science and Clinical Progress. a Review of the Current Status and Prospects.

Hunziker·Osteoarthritis Cartilage·2002·1,954 citations·Basic Science
Reference

Induction of Pluripotent Stem Cells from Adult Human Fibroblasts by Defined Factors.

Takahashi, Yamanaka, et al.·Cell·2007·20,127 citations·Basic Science
Reference

Guidelines for the Process of Cross-Cultural Adaptation of Self-Report Measures|Citation only

Beaton·Spine·2000·14,242 citations·General
Reference

Assessment of Coma and Impaired Consciousness. a Practical Scale.

Teasdale, Jennett·Lancet·1974·13,082 citations·Trauma
Reference

Development and Reliability of a System to Classify Gross Motor Function in Children with Cerebral Palsy

Palisano, Galuppi, et al.·Dev Med Child Neurol·1997·8,546 citations·Pediatrics
Reference

Validation Study of Womac: a Health Status Instrument for Measuring Clinically Important Patient Relevant Outcomes to Antirheumatic Drug Therapy in Patients with Osteoarthritis of the Hip or Knee.

Bellamy, Stitt, et al.·The Journal of rheumatology·1988·7,828 citations·Hip & Knee
Reference

Projections of Primary and Revision Hip and Knee Arthroplasty in the United States from 2005 to 2030.

Kurtz, Halpern, et al.·J Bone Joint Surg Am·2007·7,476 citations·Hip & Knee
Reference

The Oswestry Disability Index.

Fairbank, Pynsent·Spine·2000·5,651 citations·Spine
Reference

A Surgical Safety Checklist to Reduce Morbidity and Mortality in a Global Population.|

Haynes, Safe Surgery Saves Lives Study Group, et al.·N Engl J Med·2009·5,579 citations·General
Reference

A Clinical Method of Functional Assessment of the Shoulder.

Constant, Murley·Clin Orthop Relat Res·1987·5,271 citations·Shoulder & Elbow
Reference

Rating Systems in the Evaluation of Knee Ligament Injuries.

Tegner, Lysholm·Clin Orthop Relat Res·1985·4,572 citations·Sports Medicine
Reference

Sf-36 Health Survey Update|Citation only

Ware·Spine·2000·4,490 citations·General
Reference

Rationale of the Knee Society Clinical Rating System.

Insall, Scott, et al.·Clin Orthop Relat Res·1989·4,195 citations·Hip & Knee
Reference

Knee Injury and Osteoarthritis Outcome Score (koos)--Development of a Self-Administered Outcome Measure.

Roos, Beynnon, et al.·J Orthop Sports Phys Ther·1998·3,837 citations·Sports Medicine
Reference

Evaluation of Knee Ligament Surgery Results with Special Emphasis on Use of a Scoring Scale.

Lysholm, Gillquist·Am J Sports Med·1982·2,762 citations·Sports Medicine
Reference

Development and Validation of the International Knee Documentation Committee Subjective Knee Form.

Irrgang, Shelborne, et al.·Am J Sports Med·2001·2,141 citations·Sports Medicine
Reference

Delirium in Older Persons.|Citation only|

Inouye·N Engl J Med·2006·2,082 citations·General
Reference

Calcium Phosphate Ceramics as Hard Tissue Prosthetics.

Jarcho·Clin Orthop Relat Res·1981·2,003 citations·Basic Science
Reference

The Knee Society Total Knee Arthroplasty Roentgenographic Evaluation and Scoring System.

Ewald·Clin Orthop Relat Res·1989·1,948 citations·Hip & Knee
|

The Subcoracoid Space. an Anatomic Study.

·Clin Orthop Relat Res·1987·138 citations·Shoulder & Elbow
PubMed
SummaryAbstract on PubMed →

Gerber et al. used CT imaging of 47 normal shoulders to define the normal subcoracoid space in two arm positions. The study identified which skeletal variables predict subcoracoid impingement risk and quantified how arm position and surgical changes alter available clearance. This is the foundational anatomic reference for understanding subcoracoid impingement syndrome.

Study Snapshot

Design
Prospective anatomic CT study
Setting: Single academic center, University of Bern
Objective
Whether specific skeletal variables predict subcoracoid space size and impingement risk in normal shoulders.
Outcome(s)
Coracohumeral distance (mm) in adduction and forward flexion/internal rotation
Subjects
47 normal shoulders (34 volunteers; 20 also studied in flexion)
Inclusion
  • No history of shoulder pain, dysfunction, or injury
  • Normal clinical exam including range of motion
  • Negative impingement sign and instability testing
Exclusion
  • Abnormal contralateral shoulder (excluded from bilateral analysis)
  • Missing internal rotation CT cut at coracoid tip level
Statistics
Multiple regression analysisStudent's t-test (implied)

Key Findings

  • The mean coracohumeral distance is 8.7 mm in adduction and 6.8 mm in forward flexion/internal rotation (range 2.5–13 mm across individuals). There is no free anatomic space — soft tissues fill the entire bony interval. This is why even a few millimeters of skeletal change can produce symptomatic impingement.
  • Forward flexion with internal rotation is the high-risk position: clearance decreases in 16 of 20 shoulders (p < 0.001), and any modification of the coracohumeral relationship affects the space ~1.5 times more in flexion than at the side. This explains why patients with subcoracoid impingement are symptomatic with overhead activity but not at rest.
  • Two skeletal variables independently predict subcoracoid space size:
    –Coracoglenoid angle. A 1° increase widens space by 0.37 mm (adduction) or 0.53 mm (flexion)
    –Coracoid overlap. A 1 mm reduction narrows space by 0.32 mm (adduction) or 0.54 mm (flexion)
    –Together they explain 69% of variance in adduction and 71% in flexion (r² = 0.69/0.71).
  • The anatomic risk configuration is a small coracoglenoid angle combined with small coracoid overlap. Not a globally enlarged coracoid. A prominent coracoid that points posteriorly (large coracoglenoid angle) may pose no risk, while a smaller coracoid angled toward the humeral head can be highly symptomatic.
  • Women have 1.4 mm less coracohumeral clearance than men with identical skeletal geometry, representing a sex-based risk factor independent of coracoid morphology. This difference alone can be clinically meaningful given the already tight normal dimensions.
  • Iatrogenic and traumatic changes that reduce subcoracoid space include:
    –Coracoid osteotomy or fracture malunion
    –Glenoid neck fracture or posterior glenoplasty
    –Proximal humerus deformity
    –The 1.5× amplification in flexion means even a 1–2 mm skeletal change has outsized functional consequences.
Board PearlThe subcoracoid space averages 8.7 mm (adduction) and 6.8 mm (flexion/IR) — there is no free space, and small coracoglenoid angle plus small coracoid overlap predict impingement.

Clinical Relevance

Subcoracoid impingement was recognized clinically before this paper, but no anatomic data existed to explain which patients were at risk or why surgical procedures sometimes caused or cured it.

When a patient presents with anterior shoulder pain reproduced by forward flexion to 90–100° with internal rotation, evaluate CT for two specific variables: the coracoglenoid angle and the coracoid overlap. A small angle combined with small overlap is the at-risk combination, not an enlarged coracoid in isolation.

Before any procedure that alters coracohumeral geometry — coracoid osteotomy for instability (Latarjet), posterior glenoplasty, or proximal humerus fixation. Account for the 1.5× amplification effect in flexion. A few millimeters of coracoid medialization or humeral head deformity can convert a borderline space into a symptomatic one.

Women warrant extra scrutiny: 1.4 mm less baseline clearance means their margin for tolerating any additional anatomic change is narrower than men with identical radiographic morphology.

Related Articles