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Posteromedial Rotatory Instability

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Other Names

  • Varus Posteromedial Rotatory Instability (PMRI)
  • VPMRI
  • Valgus Posteromedial Rotatory Instability (VPMRI)
  • Medial Rotatory Instability
  • Posteromedial Elbow Instability
  • Rotatory Instability of the Elbow

Background

  • This page refers to Varus Posteromedial Rotatory Instability (PMRI), a form of instability from varus forces leading to Humeroulnar Joint subluxation

History

  • First described by O'Driscoll in 2003[1]

Epidemiology

  • Rare, incidence is undefined, more rare than other causes of elbow instability[2]
  • One case series found the mean age 43, with 79% male[3]

Introduction

Fig 1. Posterolateral rotatory instability typically occurs as a result of a fall on the outstretched arm with the elbow initially in the extended position. As an axial load is applied to the arm, the elbow sustains a valgus moment and the distal humerus internally rotates against the forearm that is fixed to the ground. This results in relative supination of the forearm relative to the humerus. This combination of axial load, valgus force, and supination results in disruption of the lateral collateral ligament as the radial head and coronoid rotate posterolaterally off the distal humerus. Typically, the radius and ulna rotate together as a unit.[4]
Schematic drawings for the mechanism of elbow varus posteromedial rotatory instability.[5]
Drawing of a normal elbow. (A) View of anterior elbow. (B) View of medial elbow with drawings corresponding to components of the MCL. (C) View of the lateral elbow, drawings depict LCL complex. AL, annular ligament; AMF, anteromedial facet; ALF: anterolateral facet; aUCL, anterior band ulnar collateral ligament complex; CT, coronoid tip; LUCL, lateral ulnar collateral ligament; pUCL, posterior band ulnar collateral ligament complex; RCL, radial collateral ligament; ST, sublime tubercle; TL, transverse ligament[6]

General

  • PMRI occurs secondary to axial loading with varus force and internal rotation of the forearm[7]
  • Characteristic injury pattern includes an anteromedial coronoid fracture and disruption of the lateral collateral ligament complex[7]
  • Surgical fixation of coronoid fractures and ligamentous reconstruction is usually indicated to prevent recurrent instability
  • Patients are at high risk of developing early elbow osteoarthritis

Definition

  • Lesions:
    • Fracture of the anteromedial facet of the coronoid process
    • Injuries to the anterior and posterior bundles of the ulnar collateral ligament
    • Injury to the lateral ligaments
  • Elbow instability from varus forces leading to Humeroulnar Joint subluxation
  • Associated with Anteromedial Coronoid Facet Fracture (AMCF)[8]
  • Overall, this injury pattern is poorly studied and reported in the literature

Mechanism of Injury

  • Typical
    • Fall on outstretched arm
    • Associated with varus and axial forces
    • Forearm is in pronation
  • Cho et al[3]
    • Slip or fall in 43 patients (47.2 %)
    • Sports injury in 22 patients (24.2 %)
    • Bicycle injury in 13 patients (14.3 %)
    • Motor vehicle accident in 8 patients (8.8 %)
    • Fall from a height in 4 patients (4.4 %)
    • Roller injury in 1 patient (1.1 %)

Associated Conditions

Relevant Anatomy

  • Coronoid process of the Ulna
    • Important to the stability of the ulnohumeral articulation
    • Deepens the trochlear notch of the ulna
    • Anchors the humeral trochlea in place, preventing its anterior translation
  • Ulnar Collateral Ligament
    • Also called Elbow Medial Collateral Ligament
    • Opposes varus stress

Risk Factors

  • Unknown

Differential Diagnosis

Differential Diagnosis Elbow Pain

Clinical Features

Elbow Varus Stress Test

History

  • Patient should be able to describe the mechanism of injury
  • Usually involves axial compression with varus stress, internal rotation of the forearm
  • Certain maneuvers should cause them to feel like their elbow will 'buckle'
  • They may describe an assocaited with frank elbow dislocation

Physical: Physical Exam Forearm

  • Can be challenging, gross subluxation may not be apparent unless specific ligamentous structures are disrupted
  • Range of motion testing may reveal pain and apprehension, especially if the forearm is supinated
  • Some patients experience spontaneous reduction of subluxation at approximately 60° of flexion[9]
  • Some physicians recommend examining elbow under general anesthesia in the OR[10]

Special Tests

  • Overall, poorly studied and validated in this clinical entity
  • Elbow Varus Stress Test: apply varus stress to the elbow at 20° flexion
    • Should demonstrate increased laxity, particularly when combined with forearm internal rotation[7]]]
  • Gravity Varus Stress Test: shoulder abducted to 90°, repetitive flexion-extension of elbow
  • Hyperpronation Test: Elbow flexed, forearm hyperpronated; apply a medial rotatory force
  • Chair Test: the patient is asked to pick up a chair with forearm pronated, elbow extended
  • Pushup Apprehension Test: patient is asked to perform a pushup with forearms pronated and then supinated

Evaluation

(A) Simple radiographs show the posteromedial type with an anteromedial coronoid facet fracture. (B) A small coronoid fragment is shown on a 3-dimensionally reconstructed CT. (C) The pure-posterior type with an anteromedial coronoid facet fracture is shown on simple radiographs. (D) A coronoid fragment is shown on a 3-dimensionally reconstructed CT[11]
A anteroposterior elbow radiograph demonstrating an AMCF extending to the sublime tubercle (arrow head). There is subtle increased opening of the radiocapitellar joint (arrow). B Coronal PD fat sat MRI demonstrating complete proximal LCL tear (arrow). The proximal ulna is displaced posteriorly in relation to the distal humerus, and therefore not seen in the same plane as the proximal radius. C Sagittal PD fat sat MRI showing significant posterior displacement of the proximal ulna in relation to the humerus with widening of the ulnotrochlear joint (Asterix). The anteriorly displaced trochlea is seen opposite to the AMCF (hollow arrow)[7]

General

  • Diagnosis requires a combination of history, physical exam and imaging data
  • Many of the imaging features of PMRI lack specificity

Radiographs

  • Standard Radiographs Elbow
    • Abnormalities can be subtle
  • Findings on PA view:
    • Decreased medial ulnohumeral joint space, resultant asymmetry of the ulnohumeral joint
    • Varus alignment
    • Widened radiocapitellar joint space
    • Double crescent sign: may pathognomonic for anteromedial coronoid fractures
  • Findings on lateral view
    • Double subchondral density from displaced anteromedial coronoid fragment
    • Loss of parallelism between the medial aspect of the coronoid and the opposing distal humeral articular surface
  • Oblique view may be useful as well[12]

CT

  • All suspected coronoid fractures should undergo CT
  • 3D recon if possible
  • Useful for surgical planning, recognize type of fracture pattern

MRI

  • Essential for evaluating the soft tissue injury pattern in PMRI[11]
  • Key findings:
    • Lateral collateral ligament complex (LCLC) tears: Complete rupture occurs in approximately 83% of PMRI cases[3]
    • Medial collateral ligament injuries: Complete tears of the MCL are seen in about 34% of cases[11]
    • Bone contusion patterns: Posterolateral olecranon contusions help distinguish PMRI from simple posteromedial dislocations
    • Muscle and tendon injuries: Assessment of the extensor muscle complex, which may show distraction-type (77%) or stripping-type (23%) injury patterns

Ultrasound

  • Benefits
    • Dynamic ultrasound can assess ligamentous laxity
    • Allows comparison with the contralateral elbow
    • Demonstrates increased radiocapitellar and ulnohumeral distances under stress in unstable elbows compared to normal elbows
  • Downside
    • May not reliably distinguish between hypermobile and unstable joints
Classification of coronoid fractures[6]
Classification of coronoid fractures according to O'Driscoll et al[6]

Classification

Regan and Morrey Classification[13]

  • Coronoid fracture classification
  • Type 1: represented tip avulsion fractures
  • Type 2: involved up to 50 % of the coronoid
  • Type 3: involved greater than 50 % of the coronoid

O'Driscoll Classification

  • Subdivides coronoid injuries based on location and number of coronoid fragments
  • Recognizes anteromedial facet fractures caused by varus posteromedial rotatory force

Management

A 52‐year‐old male who had a right elbow varus posteromedial rotatory instability (PMRI) due to a traffic accident. (A) The preoperative lateral X‐ray demonstrated subluxation of elbow joint. (B) The preoperative antero‐posterior X‐ray showed anteromedial facet coronoid fractures and humeral lateral epicondylar avulsion fractures. (C, D, E) The anteromedial facet coronoid fracture and humeral lateral epicondylar avulsion fractures were shown on computed tomography (CT) and 3D reconstruction. (F) The coronoid fractures and humeral lateral epicondylar avulsion fractures were treated with suture anchor fixation and the intraoperative antero‐posterior X‐ray showing equal space between the medial and lateral joint space. (G) The intraoperative lateral X‐ray was taken in the extension‐supination position and showed no subluxation or dislocation in the elbow joint. (H, I) The antero‐posterior and lateral X‐ray of the elbow at postoperative 24 months. (J, K) The appearance of the elbow pronation and supination at postoperative 24 months. (L, M) The appearance of the elbow flexion and extension at postoperative 24 months[5]

Management Goals[14]

  • Restore a stable trochlear notch
  • Maintain proper joint alignment while the collateral ligaments heal

Nonoperative

  • Indications
    • Nonoperative indications are poorly defined
    • Recommend non-operative approach to be made in consultation with orthopedic surgeon
  • Potential Indications from Pollock et al[15]
    • Small (type 1, <5 mm displaced)
    • Minimally displaced
    • Not associated with static elbow subluxation
  • Treatment

Operative

  • Indications
    • Most patients
  • Technique
    • AMCF fracture fixation
    • LCL repair/ reconstruction
    • Combination of these techniques
    • Internal joint stabilizer (IJS)

Rehab and Return to Play

Rehabilitation

  • Early phase (0-6 weeks)[16]
    • Emphasize: joint protection, pain control, and early protected range of motion to prevent stiffness
    • Immobilization duration varies from 1 day to 6 weeks depending on injury severity and surgical approach
  • 7 days Post op[17]
    • Passive ROM exercises and isometric strengthening begin at 7 days postoperatively
    • Bracing with initial limitation to 30° of extension is commonly employed during this period
    • Isotonic strength training begins at 6 weeks, progressing to neuromuscular training at 3 months
  • Advanced Phase[18]
    • Total arm strengthening addressing the entire kinetic chain, not just the elbow
    • Sport-specific skills and interval return-to-play programs are gradually introduced
    • Particular attention to mechanics evaluation in overhead athletes

General Elbow Pain Exercise Programs

Return to Play

  • High-quality evidence for PMRI-specific rehabilitation protocols and return to play criteria remains limited
    • Most recommendations extrapolated from general elbow ligament injury rehabilitation
  • General Requirements[3]
    • Full pain-free ROM
    • Strength within 10% of the contralateral side
    • Absence of instability on examination
    • Satisfactory functional scores
  • Return to play timeline
    • Return to activitiies of daily living starts at about 6 weeks postoperatively
    • Meaningful ROM recovery typically occurs by 3 months
    • Muscle strength restoration by 6 months
    • Return to light recreational sports at 4-8 months

Prognosis and Complications

Elbow Osteoarthritis is commonly encountered following PMRI

Prognosis

  • Ryou et al: If fracture fragment less < 5 mm and there was no instability detected with varus stress testing, then conservative management can be considered[11]
    • They reported good results after a mean follow-up of 37 months with an average DASH score of 6
  • Moon et al: 3 minimally displaced anteromedial coronoid fractures treated nonoperatively[19]
    • Excellent results without complications
  • Surgical Management
    • In one case series, 6/18 non-operatively managed AMCF fractures developed arthrosis with fair or poor clinical outcomes[20]

Complications

  • Elbow Osteoarthritis
    • Most significant complication
    • Occurs secondary to joint incongruity and elevated contact pressures[21]
  • Chronic pain
  • Chronic instability
  • Postoperative[3]
    • 22% overall complication rate
    • 15.4% reoperation rate
    • Specific complications: heterotopic ossification, stiffness, persistent instability
  • Missed diagnosis in pediatrics[22]
    • Cubitus varus deformity, chronic elbow instability, recurrent dislocation, traumatic arthritis, and elbow stiffness
  • Complications of delayed/ missed diagnosis
    • Prone to occur due to insufficient recognition of the injury pattern, particularly when initial radiographs appear relatively benign

See Also

Internal

External

References

  1. ↑ O’Driscoll SW, Jupiter JB, Cohen MS, Ring D, McKee MD. Difficult elbow fractures: pearls and pitfalls. Instr Course Lect of the American Academy of Orthopaedic Surgeons. 2003;52:113-34
  2. ↑ Chan, K., & Athwal, G. S. (2016). Varus Posteromedial Rotatory Instability. The Unstable Elbow, 75–84. doi:10.1007/978-3-319-46019-2_6 
  3. ↑ 3.0 3.1 3.2 3.3 3.4 3.5 Cho, Chul-Hyun, et al. "Pure varus posteromedial rotatory instability of the elbow: Radiographic findings, treatment, and outcomes." Injury (2024): 111628.
  4. ↑ Camp, Christopher L., Jay Smith, and Shawn W. O'Driscoll. "Posterolateral rotatory instability of the elbow: part I. Mechanism of injury and the posterolateral rotatory drawer test." Arthroscopy Techniques 6.2 (2017): e401-e405.
  5. ↑ 5.0 5.1 Zhang, Xinan, Yongqing Wang, and Xiaohui Li. "Surgical Treatment of Coronoid Fracture With Elbow Varus Posteromedial Rotatory Instability: An Instructional Review." Orthopaedic Surgery 17.3 (2025): 694-702.
  6. ↑ 6.0 6.1 6.2 Zeltser, David W., Joanne Y. Zhou, and Lauren P. Joseph. "Coronoid Fractures and Varus Posteromedial Rotatory Instability." Operative Techniques in Orthopaedics 33.1 (2023): 101024.
  7. ↑ 7.0 7.1 7.2 7.3 Al-Ani, Zeid, et al. "Posteromedial rotatory instability of the elbow: what the radiologist needs to know." European Journal of Radiology 141 (2021): 109819.
  8. ↑ McLean J, Kempston MP, Pike JM, Goetz TJ, Daneshvar P. Varus Posteromedial Rotatory Instability of the Elbow: Injury Pattern and Surgical Experience of 27 Acute Consecutive Surgical Patients. J Orthop Trauma. 2018 Dec;32(12):e469-e474. doi: 10.1097/BOT.0000000000001313. PubMed PMID: 30444800.
  9. ↑ Bellato, Enrico, et al. "Articular contact area and pressure in posteromedial rotatory instability of the elbow." JBJS 100.6 (2018): e34.
  10. ↑ Anakwe RE, Middleton SD, Jenkins PJ, McQueen MM, Court-Brown CM. Patient-reported outcomes after simple dislocation of the elbow. J Bone Joint Surg Am. 2011;93(13):1220–6.
  11. ↑ 11.0 11.1 11.2 11.3 Rhyou, In Hyeok, et al. "Soft tissue injury patterns in posteromedial rotatory instability with dislocation compared with posteromedial dislocation of the elbow joint." Journal of Shoulder and Elbow Surgery 29.6 (2020): 1259-1266.
  12. ↑ Ramirez MA, Stein JA, Murthi AM. Varus Posteromedial Instability. Hand Clin. 2015;31(4): 557–63.
  13. ↑ Regan W, Morrey B. Fractures of the coronoid process of the ulna. J Bone Joint Surg Am. 1989;71(9): 1348–54.
  14. ↑ Ring D, Horst TA. Coronoid fractures. J Orthop Trauma. 2015;29(10):437–40.
  15. ↑ Pollock JW, Brownhill J, Ferreira L, McDonald CP, Johnson J, King G. The effect of anteromedial facet fractures of the coronoid and lateral collateral ligament injury on elbow stability and kinematics. J Bone Joint Surg Am. 2009;91(6):1448–58.
  16. ↑ Herring, Stanley A., et al. "Initial assessment and management of select musculoskeletal injuries: a team physician consensus statement." Current Sports Medicine Reports 23.3 (2024): 86-104.
  17. ↑ Reuter, Sven, et al. "Rehabilitation, clinical outcome and return to sporting activities after posterolateral elbow instability: a systematic review." European journal of physical and rehabilitation medicine 57.2 (2016): 265-272.
  18. ↑ Ellenbecker, Todd S., Tad E. Pieczynski, and George J. Davies. "Rehabilitation of the elbow following sports injury." Clinics in sports medicine 29.1 (2010): 33-60.
  19. ↑ Moon JG, Bither N, Jeon YJ, Oh SM. Non surgically managed anteromedial coronoid fractures in posteromedial rotatory instability: three cases with 2 years followup. Arch Orthop Trauma Surg. 2013;133(12):1665–8.
  20. ↑ Doornberg JN, Ring DC. Fracture of the anteromedial facet of the coronoid process. J Bone Joint Surg Am. 2006;88:2216–2224
  21. ↑ Bellato, Enrico, et al. "Articular contact area and pressure in posteromedial rotatory instability of the elbow." JBJS 100.6 (2018): e34.
  22. ↑ You, Haifeng, et al. "Diagnosis and Treatment of Varus Posteromedial Rotational Instability of the Elbow Joint in Children: Re-Understanding of the Injury Mechanism Associated With Coronoid Process Fractures." Journal of Pediatric Orthopaedics 44.8 (2024): e698-e704.
Created by:
John Kiel on 10 January 2020 17:28:08
Authors:
Last edited:
13 January 2026 20:11:45
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