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EXTENSOR TENDON SUBLUXATION (FINGER)

Introduction

Extensor tendon subluxation is a rare occurrence in non-rheumatoid patients.1,2 It can be congenital or more commonly, due to trauma to the sagittal band and juncturae tendinum.3 Some refer to sagittal band rupture as Boxer’s knuckle, although others reserve this name for rupture of the metacarpophalangeal (MCP) joint capsule, which does not always involve tendon subluxation.

Pathophysiology

  • During flexion or radial/ulnar deviation of the involved digit, subluxation can occur due to traumatic stretching or rupture of the radial sagittal band (in the case of the common ulnar subluxation) or disruption of the ulnar sagittal band and juncturae tendinum (in the much rarer case of radial subluxation).3 Snapping of the tendon over the MCP joint can provoke pain and discomfort. Once the digit is flexed, the subluxed tendon is poorly aligned and may not be able to actively extend the digit.  In this situation, the patient can push the finger into full extension with the opposite hand and then actively keep the injured MP joint extended.  However, the patient cannot initiate full extension of the joint actively without assistance.

Related Anatomy

  • Extensor digitorum communis
  • Extensor digiti minimi       
  • Extensor indicis
  • MCP joint capsule and collateral ligaments
  • Sagittal bands
  • Juncturae tendinae

Incidence and Related Conditions

  • Absent rheumatoid arthritis, this is a rare condition, albeit more common in pugilists.
  • It most commonly involves the middle finger.

Differential Diagnosis

  • MCP joint arthritis
  • Trigger finger
ICD-10 Codes

  • EXTENSOR TENDON SUBLUXATION (FINGER)

    Diagnostic Guide Name

    EXTENSOR TENDON SUBLUXATION (FINGER)

    ICD 10 Diagnosis, Single Code, Left Code, Right Code and Bilateral Code

    DIAGNOSISSINGLE CODE ONLYLEFTRIGHTBILATERAL (If Available)
    EXTENSOR TENDON STRAIN (WRIST AND HAND LEVEL) (SUBLUXATION)    
    - INDEX S66.311_S66.310_ 
    - MIDDLE S66.313_S66.312_ 
    - RING S66.315_S66.314_ 
    - LITTLE S66.317_S66.316_ 
    - THUMB S66.212_S66.211_ 

    Instructions (ICD 10 CM 2020, U.S. Version)

    THE APPROPRIATE SEVENTH CHARACTER IS TO BE ADDED TO EACH CODE FROM CATEGORY S66
    A - Initial Encounter
    D - Subsequent Routine Healing
    S - Sequela

    ICD-10 Reference

    Reproduced from the International statistical classification of diseases and related health problems, 10th revision, Fifth edition, 2016. Geneva, World Health Organization, 2016 https://apps.who.int/iris/handle/10665/246208

Clinical Presentation Photos and Related Diagrams
Extensor Tendon Subluxation
  • Extensor Tendon Subluxation Right Ring Finger
    Extensor Tendon Subluxation Right Ring Finger
  • Sagittal band acute injury (arrow) with long finger MP joint swelling. "Boxer's Knuckle"
    Sagittal band acute injury (arrow) with long finger MP joint swelling. "Boxer's Knuckle"
Symptoms
Snapping/instability of the tendon on flexion, radial or ulnar deviation
Pain and swelling at the MCP joint
Patient can hold finger straight but has difficulty extending from a flexed position
Typical History

A typical patient has ulnar subluxation or dislocation of the middle finger extensor tendon after a traumatic event or associated with an arthritic condition like rheumatoid arthritis or systemic lupus erythematosus (SLE).

Positive Tests, Exams or Signs
Work-up Options
Treatment Options
Treatment Goals
  • Diagnosis of injury early and successfully treated with splinting
  • If not diagnosed early or fails splinting, reconstruct sagittal band and allow patient to regain active extension.
Conservative
  • Splinting to maintain MCP joint extension4,5
  • Initially, static extension splinting and then dynamic extension splinting
Operative
  • In acute cases, direct repair of the sagittal band may occasionally be possible.
  • In chronic cases, the subluxing extensor tendon can be stabilized at the MCP joint using a variety of procedures. Most use a tendon slip;1,3,6 others utilize a free graft of tendon or fascia of the MP capsule.7,8 Generally these repairs are anchored to soft tissue but a bone tunnel method has also been used.8
Treatment Photos and Diagrams
Surgical Treatment of Chronic Sagittal Band Rupture
  • Note chronic long and ring radial sagittal band ruptures with ulnarly subluxed extensor tendons (arrows).
    Note chronic long and ring radial sagittal band ruptures with ulnarly subluxed extensor tendons (arrows).
  • Note how the ulnar subluxation of the extensor tendons is exacerbated by finger flexion (arrows).
    Note how the ulnar subluxation of the extensor tendons is exacerbated by finger flexion (arrows).
  • Note the surgically expose ulnar subluxed extensor tendon (arrow)
    Note the surgically expose ulnar subluxed extensor tendon (arrow)
  • The contracted ulnar sagittal band has been released (2), the extensor tendon is retracted radially (1) and the intact joint capsule is visible.
    The contracted ulnar sagittal band has been released (2), the extensor tendon is retracted radially (1) and the intact joint capsule is visible.
  • A triangular flap of capsule which is attached to the dorsal base of the proximal phalanx has been pulled through a central slip in the extensor tendon (arrow). The flap is held in place with the clamp until it is securely sutured to the extensor tendon.
    A triangular flap of capsule which is attached to the dorsal base of the proximal phalanx has been pulled through a central slip in the extensor tendon (arrow). The flap is held in place with the clamp until it is securely sutured to the extensor tendon.
  • Both the long and ring extensor tendons have been centralized with the capsular flap technique (arrows). The junctura to the little finger has been repaired without tension on the centralization off the ring extensor.
    Both the long and ring extensor tendons have been centralized with the capsular flap technique (arrows). The junctura to the little finger has been repaired without tension on the centralization off the ring extensor.
Hand Therapy
Hand Therapy Splints For Sagittal Band Rupture
  • Yoke splint
    Yoke splint
  • Yoke Splint palmar view
    Yoke Splint palmar view
  • Yoke Splint allows PIP flexion and extension
    Yoke Splint allows PIP flexion and extension
Complications
  • Stiffness
  • Deficits in range of motion (ROM)
  • Failure of the reconstructed extensor mechanism
Outcomes
  • For non-operative treatment with an MCP extension splint, one study showed that 100% (11/11) digits had full ROM, 45% (5/11) was symptom free, 27% (3/11) had very mild subluxation with no pain; and the remaining 27% (3/11) had mild subluxation and moderate pain after 14 months.5
  • One study of tendon-slip sagittal band repair showed that 100% (21/21) of reconstructions were successful in preventing subluxation and resolving pain.3
Video
The initial video segment shows a female patient with subluxation of the ring extensor tendon. The second segment shows a mild more acute female patient with a mild long finger extensor subluxation.
YouTube Video
Sagittal Band Rupture
Key Educational Points
  • The sagittal bands are the primary stabilizers of extensor tendons and the MP joint.1,6
  • Earlier literature suggests that MP extension occurs through the sagittal band sling; however, recent work by Marshall, et al. shows biomechanical evidence that major extension force is through the attachment of the extensor to the extensor hood and middle phalanx.9
  • Capsular flaps attached to the base of the dorsal proximal phalanx can centralize the extensor tendon, but surgeons should be ready to balance the reconstructed sagittal bands with tendon slips thereby adjusting the tension in the junctura.
References

Cited

  1. Carroll C 4th, Moore JR, Weiland AJ. Posttraumatic ulnar subluxation of the extensor tendons: A reconstructive technique. J Hand Surg Am 1987;12(2):227-31. PMID: 3559075
  2. Rayan GM, Murray D. Classification and treatment of closed sagittal band injuries. J Hand Surg Am 1994;19(4):590-4. PMID: 7963312
  3. Watson HK, Weinzweig J, Guidera PM. Sagittal band reconstruction. J Hand Surg Am 1997;22(3):452-6. PMID: 9195454
  4. Ritts GD, Wood MB, Engber WD. Nonoperative treatment of traumatic dislocations of the extensor digitorum tendons in patients without rheumatoid disorders. J Hand Surg Am 1985;10(5):714-6. PMID: 4045155
  5. Catalano LW 3rd, Gupta S, Ragland R,3rd, Glickel SZ, Johnson C, Barron OA. Closed treatment of nonrheumatoid extensor tendon dislocations at the metacarpophalangeal joint. J Hand Surg Am 2006;31(2):242-5. PMID: 16473685
  6. ElMaraghy AW, Pennings A. Metacarpophalangeal joint extensor tendon subluxation: A reconstructive stabilization technique. J Hand Surg Am 2013;38(3):578-82. PMID: 23391359
  7. Rozmaryn LM. Tendon graft reconstruction of extensor hood deficits with subluxation. J Hand Surg Am 1995;20(5):841-3. PMID: 8522753
  8. Kang L, Carlson MG. Extensor tendon centralization at the metacarpophalangeal joint: Surgical technique. J Hand Surg Am 2010;35(7):1194-7. PMID: 20610064
  9. Marshall TG, Sivakumar B, Smith BJ, Hile MS. Mechanics of Metacarpophalangeal Joint Extension. J Hand Surg Am 2018;43(7):681.e1-e5.

Classic article

  • Kettelkamp DB, Flatt AE, Moulds R. Traumatic dislocation of the long-finger extensor tendon. A clinical, anatomical, and biomechanical study. J Bone Joint Surg Am 1971;53(2):229-40. PMID: 5546697
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