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Arthroscopic Correction of the Critical Shoulder Angle through Lateral Acromioplasty: a Safe Adjunct to Rotator Cuff Repair

Gerber, Ernstbrunner·Arthroscopy·2018·130 citations·Shoulder & Elbow
DOI·PubMed
SummaryAbstract on PubMed →

This is a retrospective case series testing whether adding arthroscopic lateral acromioplasty to rotator cuff repair reliably lowers the critical shoulder angle. It asks two questions: does the procedure correct the CSA into the favorable range, and does resecting the lateral acromion damage the deltoid origin or muscle? Forty-nine patients with degenerative full-thickness tears and a CSA of 34° or greater were followed for a mean of 30 months.

Study Snapshot

Design
Retrospective case series
Blinding: Open-label
Setting: Single academic center, Zurich
Funding: Industry (Storz, Zimmer)
Objective
Whether arthroscopic lateral acromioplasty reliably decreases a large CSA without damaging the deltoid
Outcome(s)
Change in critical shoulder angle and deltoid integrity at minimum 12 months
Subjects
49 patients (degenerative full-thickness cuff tears)
  • Arthroscopic RCR with lateral acromioplasty, no anterior acromioplasty
Inclusion
  • Degenerative full-thickness cuff tear
  • CSA 34° or greater
  • Minimum 12-month follow-up
Exclusion
  • Traumatic or irreparable cuff tears
  • Advanced osteoarthritis or glenoid rim wear
  • Previous surgery or inflammatory disease
Follow-up
Minimum 12 months (mean 30)
Statistics
Paired t testWilcoxon signed rankMann-Whitney UChi-square / Fisher

Key Findings

  • Lateral acromioplasty reliably pulled the CSA into the favorable range, from a mean of 37.5° preoperatively to 33.9° postoperatively (P <.001). This is the target zone associated with neither cuff disease nor osteoarthritis.
  • The deltoid tolerated the resection well. There were no cases of dehiscence, no increase in deltoid fatty infiltration, and no significant atrophy. Zone thickness dropped only 2-4% (all nonsignificant), though scarring at the origin appeared in 18 patients (37%).
  • CSA correction quality tracked with strength. Healed repairs corrected to 33° or less had 25% more abduction strength (12 vs 9 points, P =.04) than healed repairs left at 35° or greater. Correcting the angle fully, not just partially, matters for function.
  • Undercorrection predicted failure: postoperative CSA averaged 36° in failed repairs vs 33° in healed repairs (P =.026). The overall retear rate was 14% (7 of 49).
  • Functional scores improved across the board: absolute Constant 59 to 74 points, relative Constant 66% to 83%, and Subjective Shoulder Value 45% to 80% (all P <.001). Two-thirds of patients rated their result excellent.
  • Tear biology still drove failure. Failed repairs had greater preoperative stump retraction (20 vs 9 mm, P =.002) and shorter tendon stumps (9 vs 17 mm, P <.001), reminding you that acromioplasty does not rescue a poor-quality tendon.
  • Failed repairs did clinically worse: absolute Constant 63 vs 75 points (P =.028), SSV 69% vs 88% (P =.025), and abduction 125° vs 154° (P =.022).
Board PearlArthroscopic lateral acromioplasty safely reduces the critical shoulder angle without harming the deltoid; undercorrection means higher retears and weaker abduction.

Clinical Relevance

The critical shoulder angle is a fixed anatomic predictor of degenerative cuff disease: above 34° drives cuff tears, at or below 30° drives osteoarthritis. This paper tests whether you can actually change that angle surgically and get away with it.

The practical answer is yes on safety. Resecting roughly 6 mm of lateral acromion did not detach or atrophy the deltoid origin on MRI or exam, which was the main fear with this technique.

The useful clinical lesson is on dose. Shoulders corrected to 33° or less had stronger abduction and healed more reliably, while residually large angles (near 36°) retore more often. If you do this, correct fully rather than partially.

Weight the evidence carefully. This is a Level IV case series with no control group and no comparison to standard repair. It proves the procedure is safe and biomechanically rational, not that it beats rotator cuff repair alone.

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|

Arthroscopic Correction of the Critical Shoulder Angle through Lateral Acromioplasty: a Safe Adjunct to Rotator Cuff Repair

Gerber, Ernstbrunner·Arthroscopy·2018·130 citations·Shoulder & Elbow
DOI·PubMed
SummaryAbstract on PubMed →

This is a retrospective case series testing whether adding arthroscopic lateral acromioplasty to rotator cuff repair reliably lowers the critical shoulder angle. It asks two questions: does the procedure correct the CSA into the favorable range, and does resecting the lateral acromion damage the deltoid origin or muscle? Forty-nine patients with degenerative full-thickness tears and a CSA of 34° or greater were followed for a mean of 30 months.

Study Snapshot

Design
Retrospective case series
Blinding: Open-label
Setting: Single academic center, Zurich
Funding: Industry (Storz, Zimmer)
Objective
Whether arthroscopic lateral acromioplasty reliably decreases a large CSA without damaging the deltoid
Outcome(s)
Change in critical shoulder angle and deltoid integrity at minimum 12 months
Subjects
49 patients (degenerative full-thickness cuff tears)
  • Arthroscopic RCR with lateral acromioplasty, no anterior acromioplasty
Inclusion
  • Degenerative full-thickness cuff tear
  • CSA 34° or greater
  • Minimum 12-month follow-up
Exclusion
  • Traumatic or irreparable cuff tears
  • Advanced osteoarthritis or glenoid rim wear
  • Previous surgery or inflammatory disease
Follow-up
Minimum 12 months (mean 30)
Statistics
Paired t testWilcoxon signed rankMann-Whitney UChi-square / Fisher

Key Findings

  • Lateral acromioplasty reliably pulled the CSA into the favorable range, from a mean of 37.5° preoperatively to 33.9° postoperatively (P <.001). This is the target zone associated with neither cuff disease nor osteoarthritis.
  • The deltoid tolerated the resection well. There were no cases of dehiscence, no increase in deltoid fatty infiltration, and no significant atrophy. Zone thickness dropped only 2-4% (all nonsignificant), though scarring at the origin appeared in 18 patients (37%).
  • CSA correction quality tracked with strength. Healed repairs corrected to 33° or less had 25% more abduction strength (12 vs 9 points, P =.04) than healed repairs left at 35° or greater. Correcting the angle fully, not just partially, matters for function.
  • Undercorrection predicted failure: postoperative CSA averaged 36° in failed repairs vs 33° in healed repairs (P =.026). The overall retear rate was 14% (7 of 49).
  • Functional scores improved across the board: absolute Constant 59 to 74 points, relative Constant 66% to 83%, and Subjective Shoulder Value 45% to 80% (all P <.001). Two-thirds of patients rated their result excellent.
  • Tear biology still drove failure. Failed repairs had greater preoperative stump retraction (20 vs 9 mm, P =.002) and shorter tendon stumps (9 vs 17 mm, P <.001), reminding you that acromioplasty does not rescue a poor-quality tendon.
  • Failed repairs did clinically worse: absolute Constant 63 vs 75 points (P =.028), SSV 69% vs 88% (P =.025), and abduction 125° vs 154° (P =.022).
Board PearlArthroscopic lateral acromioplasty safely reduces the critical shoulder angle without harming the deltoid; undercorrection means higher retears and weaker abduction.

Clinical Relevance

The critical shoulder angle is a fixed anatomic predictor of degenerative cuff disease: above 34° drives cuff tears, at or below 30° drives osteoarthritis. This paper tests whether you can actually change that angle surgically and get away with it.

The practical answer is yes on safety. Resecting roughly 6 mm of lateral acromion did not detach or atrophy the deltoid origin on MRI or exam, which was the main fear with this technique.

The useful clinical lesson is on dose. Shoulders corrected to 33° or less had stronger abduction and healed more reliably, while residually large angles (near 36°) retore more often. If you do this, correct fully rather than partially.

Weight the evidence carefully. This is a Level IV case series with no control group and no comparison to standard repair. It proves the procedure is safe and biomechanically rational, not that it beats rotator cuff repair alone.

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