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inferior_oblique_nasal_tranposition [2026/07/07 18:35] – [Stager et al. (2007) — Absent SO Tendons] Scott Larsoninferior_oblique_nasal_tranposition [2026/07/13 17:52] (current) – Scott Larson
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 The **inferior oblique anterior and nasal transposition (ANT)** is a strabismus procedure first described by **David R. Stager Sr.** and colleagues in their landmark 2003 publication in the //Journal of AAPOS//. [[https://pubmed.ncbi.nlm.nih.gov/12825055/|Stager et al., 2003]] The procedure involves detaching the inferior oblique (IO) muscle from its insertion and repositioning it both anteriorly and nasally relative to the inferior rectus (IR) muscle insertion, thereby converting the IO from an extorter and elevator into an **intorter and tonic depressor**. The **inferior oblique anterior and nasal transposition (ANT)** is a strabismus procedure first described by **David R. Stager Sr.** and colleagues in their landmark 2003 publication in the //Journal of AAPOS//. [[https://pubmed.ncbi.nlm.nih.gov/12825055/|Stager et al., 2003]] The procedure involves detaching the inferior oblique (IO) muscle from its insertion and repositioning it both anteriorly and nasally relative to the inferior rectus (IR) muscle insertion, thereby converting the IO from an extorter and elevator into an **intorter and tonic depressor**.
  
-===== Surgical Technique =====+====Expected Effect==== 
 +  * Reduction of over-elevation in adduction 
 +    * some have restriction to elevation in adduction  
 +  * Reduction of XT in upgaze 
 +  * Improved head tilt  
 +  * Intorsion  
 +    * 18 degrees average intorsion effect [[https://pubmed.ncbi.nlm.nih.gov/28713055/|Saxena et al., 2017]] 
 +====Surgical Technique====
  
-The IO muscle is disinserted and reattached at a new position typically **2 mm nasal and 2 mm posterior to the nasal border of the IR muscle insertion**. [[https://pubmed.ncbi.nlm.nih.gov/12825055/|Stager et al., 2003]] This placement is critical — by moving the IO's effective insertion nasal to the IR, the muscle's vector of action is fundamentally altered. The procedure differs from standard anterior transposition (ATIO), which places the IO at or near the temporal border of the IR insertion. Stager et al. recommended the use of **Mersilene (permanent) sutures** rather than absorbable suture materials to prevent postoperative retraction of muscle fibers. [[https://pubmed.ncbi.nlm.nih.gov/12825055/|Stager et al., 2003]]+The IO muscle is disinserted and reattached at a new position typically **2 mm nasal and 2 mm posterior to the nasal border of the IR muscle insertion**. [[https://pubmed.ncbi.nlm.nih.gov/12825055/|Stager et al., 2003]] This placement is critical — by moving the IO's effective insertion nasal to the IR, the muscle's vector of action is fundamentally altered. The procedure differs from standard anterior transposition (ATIO), which places the IO at or near the temporal border of the IR insertion. Stager et al. recommended the use of **Mersilene (permanent) sutures** rather than absorbable suture materials to prevent postoperative retraction of muscle fibers.  
 +{{::nasal_transposition_io.png?direct|}}\\ 
 +[[https://pubmed.ncbi.nlm.nih.gov/12825055/|Stager et al., 2003]]
  
-===== Indications =====+====Indications====
  
 The procedure is particularly useful for: The procedure is particularly useful for:
  
-  * Superior oblique (SO) palsy — especially severe, recurrent, or congenital cases with significant extorsion and abnormal head posture [[https://pubmed.ncbi.nlm.nih.gov/12825055/|Stager et al., 2003]] [[https://pubmed.ncbi.nlm.nih.gov/28713055/|Saxena et al., 2017]] +  * Superior oblique (SO) palsy — especially severe, recurrent, or congenital cases with **significant excyclotorsion** and abnormal head posture [[https://pubmed.ncbi.nlm.nih.gov/12825055/|Stager et al., 2003]] [[https://pubmed.ncbi.nlm.nih.gov/28713055/|Saxena et al., 2017]] 
-  * Absent SO tendons — including patients with [craniosynostosis](https://www.openevidence.com/rare-disease/craniosynostosis) [[https://pubmed.ncbi.nlm.nih.gov/17307680/|Hussein, Stager et al., 2007]]+  * Absent SO tendons — including patients with [[https://www.openevidence.com/rare-disease/craniosynostosis| craniosynostosis]] [[https://pubmed.ncbi.nlm.nih.gov/17307680/|Hussein, Stager et al., 2007]]
   * Antielevation syndrome (AES) — as a secondary procedure after prior IO anterior transposition [[https://pubmed.ncbi.nlm.nih.gov/12825055/|Stager et al., 2003]]*   * Antielevation syndrome (AES) — as a secondary procedure after prior IO anterior transposition [[https://pubmed.ncbi.nlm.nih.gov/12825055/|Stager et al., 2003]]*
   * [[https://www.openevidence.com/rare-disease/duane-retraction-syndrome|Duane Syndrome]] with upshoot (though downshoot may worsen) [[https://pubmed.ncbi.nlm.nih.gov/12825055/|Stager et al., 2003]]   * [[https://www.openevidence.com/rare-disease/duane-retraction-syndrome|Duane Syndrome]] with upshoot (though downshoot may worsen) [[https://pubmed.ncbi.nlm.nih.gov/12825055/|Stager et al., 2003]]
   * Dissociated vertical deviation (DVD) with IO overaction [[https://pubmed.ncbi.nlm.nih.gov/20227620/|Fard, 2010]]   * Dissociated vertical deviation (DVD) with IO overaction [[https://pubmed.ncbi.nlm.nih.gov/20227620/|Fard, 2010]]
  
-===== Stager et al. (2003) — Original Series and Outcomes =====+====Stager et al. (2003) — Original Series and Outcomes====
  
 In the original series by Stager, Beauchamp, Wright, Felius, and Stager, 20 patients with IO overaction, SO palsy, absent SO muscles, AES, or Duane syndrome underwent ANT. [[https://pubmed.ncbi.nlm.nih.gov/12825055/|Stager et al., 2003]] Key findings included: In the original series by Stager, Beauchamp, Wright, Felius, and Stager, 20 patients with IO overaction, SO palsy, absent SO muscles, AES, or Duane syndrome underwent ANT. [[https://pubmed.ncbi.nlm.nih.gov/12825055/|Stager et al., 2003]] Key findings included:
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   * Mersilene permanent sutures were recommended to avoid postoperative retraction of muscle fibers   * Mersilene permanent sutures were recommended to avoid postoperative retraction of muscle fibers
  
-===== Stager et al. (2007) — Absent SO Tendons =====+====Stager et al. (2007) — Absent SO Tendons====
  
 In a subsequent study, Hussein, Stager, Beauchamp, Stager, and Felius reported on 9 children (2 unilateral, 7 bilateral) with absent SO tendons who underwent ANT. [[https://pubmed.ncbi.nlm.nih.gov/17307680/|Hussein, Stager et al., 2007]] In a subsequent study, Hussein, Stager, Beauchamp, Stager, and Felius reported on 9 children (2 unilateral, 7 bilateral) with absent SO tendons who underwent ANT. [[https://pubmed.ncbi.nlm.nih.gov/17307680/|Hussein, Stager et al., 2007]]
  
-  * Both unilateral cases achieved orthotropia with no abnormal head posture* +  * Both unilateral cases achieved orthotropia with no abnormal head posture 
-  * In bilateral cases, vertical deviation in adduction and exotropia in upgaze had largely cleared, though some residual vertical deviation in side gaze (3 patients) and V-pattern esotropia in downgaze (2 patients) persisted* +  * In bilateral cases, vertical deviation in adduction and exotropia in upgaze had largely cleared, though some residual vertical deviation in side gaze (3 patients) and V-pattern esotropia in downgaze (2 patients) persisted 
-  * The procedure was most effective in unilateral SO tendon absence* +  * The procedure was most effective in unilateral SO tendon absence 
-  * It is likely to benefit patients with severe congenital fourth nerve palsy in which standard IO weakening procedures have been ineffective*+  * It is likely to benefit patients with severe congenital fourth nerve palsy in which standard IO weakening procedures have been ineffective
  
-===== Subsequent Validation =====+====Subsequent Validation====
  
 Other groups have confirmed the efficacy of ANT: Other groups have confirmed the efficacy of ANT: