Comparison

AO Surgery Reference vs Multiplier

Price, ratings, monetisation and update history for both apps, side by side — with what reviewers say about each.

Head to head
About

AO Surgery Reference

Access a comprehensive online repository of surgical knowledge for fracture management. It provides detailed guidance on diagnosis, treatment, and aftercare for numerous fracture types, supported by extensive illustrations and expert review.

Highlights
  • 353 fracture types covered
  • 172 surgical approaches
  • 1222 surgical procedures
  • Over 30,000 illustrations
  • Feline, canine, and equine fracture care
  • Powerful search function
Features
Read full description

QUICK ONLINE REFERENCE IN CLINICAL LIFE Gain easy access to the award-winning AO Surgery Reference. AO Surgery Reference is an online repository for surgical knowledge. It describes the complete surgical management process from diagnosis to aftercare for all fractures of a given anatomical region, and also assembles relevant material that the AO has published before. It gives access to:   • aid in surgical decision making for 353 fracture types • 172 approaches • 1222 surgical procedures • all richly illustrated with more than 30'000 Illustrations and much more. To ensure the quality of the content, it is authored, edited, and peer reviewed by experienced AO Faculty from all over the world, some of which are also well-known textbook authors/editors. This is a relaunch of the AO Surgery Reference app utilizing the same responsive user interface that was released February 2020. The highlights are: • Consistent navigational logic and user experience on all screen sizes • Inclusion of feline, canine, and equine fracture care • Combination of Preparation – Approach – Reduction and Fixation – Aftercare into one step called treatment. • Introduction of a powerful search function, allowing simplifications of the user interface as it replaces previous shortcuts.

About

Multiplier

This app automates complex calculations for predicting mature height, bone length, and limb length discrepancies in children. It simplifies manual methods, reducing calculation time and errors for various orthopedic and growth-related assessments.

Highlights
  • Predict mature height
  • Calculate bone length
  • Assess limb length discrepancy
  • Analyze growth remaining
  • Plot height on CDC charts
  • Scanogram calculations
  • Foot length analysis
Features
Read full description

The Multiplier App automates calculations to predict mature height and bone length in children. This method was created originally in Baltimore at the University of Maryland and subsequently developed at the International Center for Limb Lengthening (ICLL), Rubin Institute for Advanced Orthopedics (RIAO), Sinai Hospital of Baltimore. We have taught the Multiplier Method for more than 19 years at our annual Baltimore Limb Deformity Course (http://www.DeformityCourse.com). These calculations are typically performed by hand, using various formulae. Certain calculations are easy, but others involve more complicated formulae. Utilizing this app will reduce the time needed for these routine calculations and decrease errors. You need only input certain data (sex, age, length) and the app will calculate the answer by using the appropriate Multiplier formula. The Multiplier App will allow you to make the following calculations: LOWER EXTREMITY · Limb Length Discrepancy (LLD) (Congenital) · LLD (Developmental) · Growth Remaining · Bone Length · Timing of Angular Correction · Timing of Epiphysiodesis · Comprehensive (Congenital) LLD and Epiphysiodesis · Scanogram Calculations (Calculates femur/tibia lengths, overall limb length discrepancy, and amount/side of femur/tibia discrepancies) UPPER EXTREMITY · LLD (Congenital) · LLD (Developmental) · Growth Remaining · Bone Length Height and CDC Growth Charts (Calculates height at maturity, calculates height at every age, and plots the patient’s height and weight on the CDC growth charts) ACHONDROPLASIA · Height · Sitting Height · Leg Length Fetus (Calculates the length of tibia or femur at birth and maturity) FOOT · Foot Length · Foot Length Discrepancy · Foot Height · Foot Height Discrepancy Spine (Calculates sitting height at maturity) Oblique Plane Deformity (Calculates magnitude, orientation, and direction of an oblique plane deformity) Inclined Osteotomy (Calculates the rotational orientation and the vertical inclination of the osteotomy) This app also provides the following additional resources: · Bone Age: Elbow and Hand (Shows how to determine skeletal age by using radiographs of the elbow or hand) · Figures that show the standard measurements for the lower limb and foot · The multiplier formulae that the app uses to perform the calculations · Tables that show the multiplier values that are used in the formulae · Figures that show the Solomin Foot Analysis (Deformity correction planning for the midfoot, hindfoot, and ankle using reference lines and angles provided by Dr. Leonid Solomin) · Figures that show the development of the apophyses, epiphyses, and bones · Bibliography · User guide DISCLAIMER: No growth prediction method is 100% accurate; this App is not a substitute for sound and careful clinical judgment. PRIVACY POLICY: We respect the privacy of the people who use the International Center for Limb Lengthening apps. The Multiplier app does not collect, use, or distribute any data from the users.

Screenshots

AO Surgery Reference4 screens
Multiplier4 screens

Verdict

The call

The clearest difference is monetization model: AO Surgery Reference at free against Multiplier's paid. On price, rating, review sentiment and ratings volume there is nothing between them.

Scored on Price · Rating · Positive reviews · Number of ratings · Update frequency · Ads · In-app purchases · Monetization · Best chart rank · Devices · Requires iOS

CostPrice · In-app purchases · Ads · Monetization

Both are free to download. Neither carries in-app purchases, so what you see is what you pay.

ReceptionRating · Positive reviews · Number of ratings

Multiplier holds the better App Store score, 4.6 against 4.4. Both are backed by a comparable volume of ratings — 14 and 24 respectively. Written reviews complicate that: 86% of AO Surgery Reference's written reviews are positive against 83% of Multiplier's, so the app with the better star average is not the one people write more warmly about.

UpkeepUpdate frequency

Both ship on a similar rhythm, roughly every 6 months. Both last shipped on October 23, 2026.

Scorecard1 real difference · 9 level
AO Surgery Reference versus Multiplier: the parameters behind the verdict, then further details
ParameterAO Surgery ReferenceMultiplier
PriceFreeFree
Rating4.4 (14 ratings)4.6 (24 ratings) — better
Positive reviews85.8% of reviews — better83.3% of reviews
Number of ratings1424 — better
Update frequencyEvery 6 monthsEvery 6 months
AdsNoNo
In-app purchasesNoNo
MonetizationFree — betterPaid
DevicesiPhone, iPad, iPodiPhone, iPad, iPod
Requires iOS13.013.0
Further details — not scored
Size1 MB62 MB
Age rating17+12+
DeveloperAO FoundationLifeBridge Health

Customer experience

AO Surgery Reference

All ratings14 ratings
Positive85.7%
Neutral0.0%
Negative14.3%
Written reviews113 reviews
Positive85.8%
Neutral3.5%
Negative10.6%

Multiplier

All ratings24 ratings
Positive95.8%
Neutral0.0%
Negative4.2%
Written reviews30 reviews
Positive83.3%
Neutral0.0%
Negative16.7%

In-app purchases

None

AO Surgery Reference

No in-app purchases

None

Multiplier

No in-app purchases

Questions

Is AO Surgery Reference free?
AO Surgery Reference is free to download, with no in-app purchases.
Is Multiplier free?
Multiplier is free to download, with no in-app purchases.
Which has better reviews, AO Surgery Reference or Multiplier?
Multiplier is rated higher. AO Surgery Reference averages 4.4 out of 5 from 14 ratings, while Multiplier averages 4.6 from 24 ratings.
Do AO Surgery Reference or Multiplier have ads?
Neither AO Surgery Reference nor Multiplier shows ads.
Which is updated more often, AO Surgery Reference or Multiplier?
AO Surgery Reference ships an update every 6 months, and Multiplier every 6 months. Most recently, AO Surgery Reference was updated on October 23, 2026 and Multiplier on October 23, 2026.

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