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Posteromedial Rotatory Instability

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Other Names

  • Varus Posteromedial Rotatory Instability



  • Incidence is undefined, but more rare than other causes of elbow instability[2]


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.[3]

Associated Injuries

Risk Factors

  • Unknown

Differential Diagnosis

Clinical Features


  • Radiographs
    • Standard 3 views
    • Abnormalities can be subtle
    • On PA, can see:
      • 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
    • Lateral view, can see:
      • 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[5]
  • CT
    • All suspected coronoid fractures should undergo CT
    • 3D recon if possible
    • Useful for surgical planning, recognize type of fracture pattern
  • MRI
    • Generally not required


Regan and Morrey Classification

  • Coronoid fracture classification[6]
  • 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


  • Goal[7]
    • Restore a stable trochlear notch
    • Maintain proper joint alignment while the collateral ligaments heal


  • Recommend non-operative approach to be made in consultation with orthopedic surgeon
  • Nonoperative indications are poorly defined
  • Potential Indications from Pollock et al[8]
    • Small (type 1, <5 mm displaced)
    • Minimally displaced
    • Not associated with static elbow subluxation
  • 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[9]
    • 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[10]
    • Excellent results without complications


  • Important to stabilize displaced AMCF fractures
    • In one case series, 6/18 non-operatively managed AMCF fractures developed arthrosis with fair or poor clinical outcomes[11]

Rehab and Return to Play


  • Unknown

Return to Play

  • Unknown


  • Chronic pain
  • Chronic instability

See Also



  1. 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.
  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. 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.
  4. 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.
  5. Ramirez MA, Stein JA, Murthi AM. Varus Posteromedial Instability. Hand Clin. 2015;31(4): 557–63.
  6. Regan W, Morrey B. Fractures of the coronoid process of the ulna. J Bone Joint Surg Am. 1989;71(9): 1348–54.
  7. Ring D, Horst TA. Coronoid fractures. J Orthop Trauma. 2015;29(10):437–40.
  8. 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.
  9. Rhyou IH, Kim KC, Lee JH, Kim SY. Strategic approach to O’Driscoll type 2 anteromedial coronoid facet fracture. J Shoulder Elbow Surg. 2014;23(7): 924–32.
  10. 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.
  11. Doornberg JN, Ring DC. Fracture of the anteromedial facet of the coronoid process. J Bone Joint Surg Am. 2006;88:2216–2224
Created by:
John Kiel on 10 January 2020 17:28:08
Last edited:
22 December 2022 19:28:21