aTSA vs RSA for cuff intact arthritis: what is the evidence that informs the choice for each patient?

Both anatomic total shoulder arthroplasty (aTSA) and reverse shoulder arthroplasty (RSA) are considerations for patients with cuff-intact glenohumeral osteoarthritis. Currently many, if not most shoulder surgeons are trending toward RSA. In fact many surgeons have little working experience in performing aTSA. For example, per the Australian registry, the share of primary total shoulder replacements that is anatomic has collapsed from roughly 57% in 2008 to about 4% by 2024, while stemmed reverse has risen to nearly 90% (see figure below) [1]. In some circles the pro RSA argument is based on the contentions that (1) the RSA is easier to perform by less experienced-as well as experienced-surgeons and (2) the RSA as a lower rate of revision.

A look at the published evidence may inform the choice for patients and surgeons:

1. Patient-reported outcomes

With commonly used scores, the two types of arthroplasty seem similar for cuff-intact arthritis. A 2026 meta-analysis of 1,716 patients aged ≥70 with a competent cuff found no significant differences in ASES, Constant, or SST scores [2]. A meta-analysis of 14 studies (4,819 cases) found similar ASES, Constant, SST, SSV, and VAS pain scores [3], as did an earlier systematic review [4] and a propensity score–matched JBJS analysis [5]. 

However, in the UK National Joint Registry, roughly a quarter of 21,918 RSA patients had an “unsatisfactory” Oxford Shoulder Score (<29) [6]. Single-center series using patient-acceptable-symptom-state (PASS) thresholds put the figure higher — 25–40% of RSA patients failed to reach PASS for ASES or SANE at two years [7], and 34–35% still failed at minimum five years [8], with pain the primary factor in these adverse outcomes. 

With the Shoulder Arthroplasty Smart score, aTSA achieved higher absolute postoperative scores even though the improvement from baseline was similar [9]. Among patients who reached a “new normal” (defined as a SANE score  ≥95), aTSA significantly outperformed RSA on higher-demand tasks, motion, and return to sport and work [10]. 

2. Motion 

Across the comparative meta-analyses, aTSA delivered better external and internal rotation, with differences that exceed the MCID and reached 10–11° of external rotation in pooled estimates [2,3,4] as well as  better overall motion in matched cohorts [5]. Rotation enables the patient to perform basic activities of daily living: dressing, toileting, perineal care, and reaching behind the back.

3. Complications

In pooled comparative data, RSA carried a lower overall complication rate than aTSA in the cuff-intact population [2,3]. But the complications the two implants produced differed in kind. Historically, primary stemmed anatomic shoulders done for osteoarthritis using legacy techniques and implants have been revised chiefly for glenoid component loosening (29.1%), rotator cuff insufficiency (27.6%), and instability/dislocation (23.1%), with loosening being predominant [1]. Stemmed reverse shoulders have been revised chiefly for instability/dislocation, infection, loosening, and fracture [1]. 

4. Revision 

At ten years, cumulative percent revision (all diagnoses, modern prostheses) was 5.5% for stemmed reverse, 5.2% for stemless aTSA, and 7.9% for stemmed aTSA (Figure 2 below) [1]. 

It is worthwhile noting that the 7.9% ten-year revision rate for stemmed aTSA includes decades of older, non-crosslinked polyethylene. When the glenoid is crosslinked, aTSA durability improves markedly: in a dedicated AOANJRR study of 10,102 stemmed aTSAs done for osteoarthritis, non-crosslinked polyethylene had more than double the revision risk of crosslinked polyethylene after 18 months (HR 2.3; 95% CI 1.6–3.1), with 12-year cumulative revision of 9% versus 5% [22]. Considering only crosslinked anatomic glenoids, the revision rate for stemmed aTSAs (5%) was comparable to stemmed RSA (5.5%) and stemless aTSA (5.2%). 

Vitamin E–stabilized polyethylene is a type of crosslinked polyethylene, and registries tend to pool the two.  Vitamin E reduces wear and osteolytic particle debris on the bench [23], but no study has yet demonstrated a vitamin-E–versus–plain-crosslinked revision difference in shoulder arthroplasty.

The revision rates for stemless aTSA match those for the RSA; the reasons for this are not clear - perhaps more experienced surgeons, greater ability to achieve the desired humeral component position,  a higher rate of use of modern glenoid components, and/or preferential selection of healthier shoulders with better quality bone. 

Comparative meta-analyses report RSA revision rates about four-fold lower than aTSA in the cuff-intact analysis, OR 0.43; 95% CI 0.29–0.65; p<0.001) [3], although an earlier meta-analysis found no mid-term difference (OR 0.33; p=0.16) [4]. A 2026 propensity-matched study showed a lower early revision rate for aTSAs, but at midterm followup the revision rate increased [12].

However, it is critical to recognize that revision is a poor proxy for clinical failure in RSA. A National Joint Registry analysis concluded that low RSA revision rates may not signify implant success. Instead, patients with poor outcomes and their surgeons may be reluctant to undertake complex RSA revisions which have unpredictable results.[6]. The point is apparent for the most common mode of RSA failure — a painful, poorly functioning but radiographically satisfactory RSA. Such an outcome is experienced by about a quarter of RSA patients [6,7,8], yet RSAs are rarely revised for this indication. A failure that is not revised never appears in the revision rate.

[Complication frequencies were drawn from indexed systematic reviews [26–29] (e.g., PJI 2.4%, acromial/scapular fracture 2.5%, primary-RSA instability 2.5%); the revisability column reflects their reported management — acromial fractures are predominantly treated non-operatively, instability usually presents within 90 days and is treated by component revision, and infection is nearly always surgical. The registry anchor for pain/PROM failure is O’Malley [6].]

The different failure types are not equally salvageable. If an anatomic shoulder fails, it can usually be converted to a RSA with outcomes that approach those of primary RSA.  Primary stemmed anatomic shoulders done for osteoarthritis are revised to a reverse in 89% of cases, keeping the original humeral stem 58% of the time [1]; 93.8% of failed stemless aTSAs are converted to RSAs. On the other hand, revision of a failed reverse to another reverse often fails to yield the desired improvement in comfort and function.

5. Durability

Durability matters most for the patient with decades of active use ahead. At minimum ten-year follow-up, aTSAs sustain their functional gains for primary osteoarthritis [13], the large concurrent aTSA experience supports this option in the high-demand patient who wishes to avoid a RSA [14]. The Australian registry shows modern stemless anatomic matching reverse on revision out to ten years, and crosslinked stemmed-anatomic glenoids more than halve the revision risk of older non-crosslinked ones [1,22].

6. Return to sport 

Return-to-sport rates are high after both implants and highest after aTSA in pooled data [15]. A recent large weightlifting series reported high self-rated comfort, yet its endpoint is a single ordinal “difficulty” item — capturing neither the amount of load nor performance. [16]. When actual one-repetition-max recovery is measured, returners perform below their presymptomatic level, with the largest decrement in bench press [17]. 

7. Surgeon capability. It is often said that a good aTSA outperforms a good RSA, which outperforms a bad aTSA, which outperforms a bad RSA [18].  Some say it is technically easier to do a good RSA than an aTSA (not my view). However it is for sure that as aTSA volume falls, fewer surgeons will be able to reliably provide a good anatomic to their patients with cuff intact arthritis. While some hold that navigation, patient-specific instrumentation, and robotics may improve component positioning; none has been shown to improve patient-reported outcomes or reduce complications for any type of arthroplasty [19,20,21]. It appears that the surgeon is sill the method.

So, in rough summary

Bottom line: 

The patient and the surgeon considering arthroplasty for cuff intact shoulder arthritis should discuss the available evidence on aTSA and RSA.

An aTSA - when performed by a surgeon who can deliver a reliable aTSA -  may be attractive when function and salvageability matter most —  particularly in the more active patient with a reconstructable glenoid.

A RSA may be more attractive in the less active patient, or one whose glenoid morphology or bone quality makes a durable aTSA less certain or when the shoulder surgeon is not comfortable performing an anatomic shoulder arthroplasty.

Two cautions bear on the consideration: the revision rate understates RSA failure, because its most common failure — a painful but intact shoulder — is rarely revised [6]; and roughly a quarter of RSA patients do not reach a satisfactory outcome at all [6,7,8]. 

A choice

Pileated Woodpeckers

Seattle

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References

[1]Lewis PL, Gill DR, McAuliffe MJ, et al. Hip, Knee and Shoulder Arthroplasty: 2025 Annual Report. Australian Orthopaedic Association National Joint Replacement Registry. AOA: Adelaide; 2025. doi:10.25310/MXFR3061. (Figures ST1, ST2; Tables ST6, ST39, ST46–47, ST76.)

[2]Gupta MS, Krishan A, Rashid A, et al. Reverse versus anatomic total shoulder arthroplasty in patients over 70 with a competent rotator cuff and glenohumeral osteoarthritis: a meta-analysis. J Shoulder Elbow Surg. 2026 (online 2025). PMID: 41276069.

[3]Thamrongskulsiri N, Limskul D, Tanpowpong T, et al. Comparison of revision rates and clinical outcomes between anatomic and reverse total shoulder arthroplasty for rotator cuff-intact osteoarthritis: a systematic review and meta-analysis. Clin Orthop Surg. 2025;17(6):907–921. doi:10.4055/cios25012.

[4]Kim H, Kim CH, Kim M, et al. Is reverse total shoulder arthroplasty more advantageous than anatomic TSA for osteoarthritis with intact cuff tendon? A systematic review and meta-analysis. J Orthop Traumatol. 2022;23(1):3. PMID: 34993646.

[5]Kirsch JM, Puzzitiello RN, Swanson D, et al. Outcomes after anatomic and reverse shoulder arthroplasty for glenohumeral osteoarthritis: a propensity score-matched analysis. J Bone Joint Surg Am. 2022. PMID: 35867705.

[6]O’Malley O, Davies A, Sabharwal S, et al. Is there a difference in thresholds for revision between shoulder arthroplasty types? A National Joint Registry study. PLoS One. 2025. doi:10.1371/journal.pone.0330975.

[7]Werner BC, Lederman E, Gobezie R, et al. Understanding the variables associated with failure to achieve an acceptable symptom state after reverse shoulder arthroplasty. Semin Arthroplasty JSES. 2021.

[8]Ardebol J, et al. Defining the MCID and PASS following reverse shoulder arthroplasty for glenohumeral arthritis or cuff tear arthropathy at minimum 5-year follow-up. JSES Int. 2025.

[9]Marigi EM, Hao KA, Friedman RJ, et al. Exactech Equinoxe anatomic versus reverse total shoulder arthroplasty for primary osteoarthritis: case-controlled comparisons using the machine learning-derived Shoulder Arthroplasty Smart score. J Shoulder Elbow Surg. 2023. PMID: 39292145.

[10]Beleckas CM, Schodlbauer DF, Mousad AD, et al. Evaluation of new normal after shoulder arthroplasty: comparison of anatomic vs. reverse total shoulder arthroplasty. J Shoulder Elbow Surg. 2025;34:S43–S49. doi:10.1016/j.jse.2025.02.010. PMID: 40074195.

[11]Barco R, Savvidou OD, Sperling JW, et al. Complications in reverse shoulder arthroplasty. EFORT Open Rev. 2016;1:72–80. doi:10.1302/2058-5241.1.160003.

[12]Leinweber KA, Bowler AR, Diestel DR, et al. Reverse and anatomic total shoulder arthroplasty for glenohumeral osteoarthritis: a propensity-matched comparison at early and midterm follow-up. J Shoulder Elbow Surg. 2026. PMID: 41564999.

[13]Sharareh B, Whitson AJ, Matsen FA III, et al. Minimum 10-year follow-up of anatomic total shoulder arthroplasty and ream-and-run arthroplasty for primary glenohumeral osteoarthritis. J Shoulder Elbow Surg. 2024;33(6):1276–1284. PMID: 37777045.

[14]Matsen FA III, Whitson A, Jackins SE, et al. Ream and run and total shoulder: patient and shoulder characteristics in five hundred forty-four concurrent cases. Int Orthop. 2019;43(9):2105–2115. PMID: 31240359.

[15]Liu JN, Steinhaus ME, Garcia GH, et al. Return to sport after shoulder arthroplasty: a systematic review and meta-analysis. Knee Surg Sports Traumatol Arthrosc. 2018;26(1):100–112. PMID: 28409200.

[16]Abdelshaheed J, Chatterji R, Levy J, et al. Return to weightlifting following anatomic and reverse shoulder arthroplasty. J Shoulder Elbow Surg. 2026;35:1660–1666. doi:10.1016/j.jse.2026.02.002.

[17]Ames A, Shah SS, Pettit R, et al. Against surgeons’ advice: the return to sport in high-demand weightlifters following anatomic total shoulder arthroplasty at average 3.6 years’ follow-up. J Shoulder Elbow Surg. 2023;32(4):e153–e159. doi:10.1016/j.jse.2022.09.027.

[18]Menendez ME, Garrigues GE, Jawa A. Clinical Faceoff: anatomic versus reverse total shoulder arthroplasty for primary glenohumeral osteoarthritis. Clin Orthop Relat Res. 2022;480(11):2095–2100.

[19]Daher M, Fares MY, Boufadel P, et al. Patient-specific instrumentation in primary total shoulder arthroplasty: a meta-analysis of clinical outcomes. Clin Shoulder Elb. 2025;28(2):129–136. doi:10.5397/cise.2024.01095.

[20]Patient-specific instrumentation in shoulder arthroplasty: high tech, low yield? [editorial]. Clin Shoulder Elb. 2025;28(2). doi:10.5397/cise.2025.00423.

[21]Gaj E, Pagnotta SM, Berlinberg EJ, et al. Intraoperative navigation system use increases accuracy of glenoid component inclination but not functional outcomes in reverse total shoulder arthroplasty. Arch Orthop Trauma Surg. 2024;144(1):91–102. doi:10.1007/s00402-023-05038-y.

[22]Page RS, Alder-Price AC, Rainbird S, et al. Reduced revision rates in total shoulder arthroplasty with crosslinked polyethylene: results from the Australian Orthopaedic Association National Joint Replacement Registry. Clin Orthop Relat Res. 2022;480(10):1940–1949. doi:10.1097/CORR.0000000000002293. PMID: 35901440.

[23]Khan AZ, Maxwell MJ, Parrott RM, et al. Effect of vitamin E–enhanced highly cross-linked polyethylene on wear rate and particle debris in anatomic total shoulder arthroplasty: a biomechanical comparison to ultrahigh-molecular-weight polyethylene. J Shoulder Elbow Surg. 2024. PMID: 38182025.

[24]Gowd AK, Liu JN, Cabarcas BC, et al. Single Assessment Numeric Evaluation and patient acceptable symptom state thresholds following shoulder arthroplasty. J Shoulder Elbow Surg. 2021. (PASS: ASES 81.9, SANE 75.5; n=207, mixed TSA/RSA.)

[25]DeVito P, Damodar D, Berglund DD, et al. Predicting outstanding results after reverse shoulder arthroplasty using percentage of maximal outcome improvement. J Shoulder Elbow Surg. 2019;28(6):1223–1231. PMID: 30910258. (SST threshold 61.3% MPI; n=198.)

[26]Shah SS, Gaal BT, Roche AM, et al. The modern reverse shoulder arthroplasty and an updated systematic review for each complication: part I. JSES Int. 2020;4(4):929–943. (Periprosthetic joint infection 2.4% for primary RSA.)

[27]Shah SS, Roche AM, Sullivan SW, et al. The modern reverse shoulder arthroplasty and an updated systematic review for each complication: part II. JSES Int. 2020;5(1):121–137. doi:10.1016/j.jseint.2020.07.018. PMID: 33554177. (Instability, humerus/glenoid fracture, acromial/scapular-spine fracture.)

[28]Zumstein MA, Pinedo M, Old J, et al. Problems, complications, reoperations, and revisions in reverse total shoulder arthroplasty: a systematic review. J Shoulder Elbow Surg. 2011;20(1):146–157.

[29]Lau SC, Large R. Acromial fracture after reverse total shoulder arthroplasty: a systematic review. Shoulder Elbow. 2020;12(6):375–389. doi:10.1177/1758573219876486. PMID: 33281942.

"RSA has a lower revision rate than aTSA". Why that may not mean what you think it does.

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Disclaimers: I have no relationships with any implant company. I do love anatomic total shoulder arthroplasty. The below is my attempt to analyze the available data, but there is a dearth of high-level evidence. I am not a statistician, but here I share my attempt at a deep dive into an important and hotly discussed issue. It is not a quick read, but the topic deserves the depth.

The relative merits of anatomic and reverse total shoulder arthroplasty for osteoarthritis are—and probably will forever be—hotly debated. Many factors contribute to surgeons' views on this topic, including indications, relative difficulty of the procedure, cost, need for preoperative 3D/CT-based planning, need for transfer technologies (robotics, patient-specific instruments, virtual/augmented reality), and the patient's anticipated postoperative comfort, range of motion, and function. In this post, we take a look at the contention that patients whose osteoarthritis is treated with reverse total shoulder arthroplasty have lower rates of revision than those treated with anatomic total shoulder arthroplasty.

The word on the street is that patients having reverse total shoulder arthroplasty (RSA) are less likely to undergo revision than patients having anatomic total shoulder arthroplasty (aTSA). For example, the Australian Orthopaedic Association National Joint Replacement Registry's 2025 Annual Report puts the 10-year cumulative revision rate at 7.4% for aTSA and 5.4% for RSA [1]. The 14-year figures are 9.5% and 6.4%. These numbers are often cited in support of expanding RSA into indications it was not originally designed for—including osteoarthritis with an intact rotator cuff.

Set against those numbers, a finding from O’Malley and colleagues' 2025 National Joint Registry analysis of 21,918 patients should give us pause. RSA had nearly twice the prevalence of unsatisfactory function—Oxford Shoulder Score below 29—as aTSA: 27.0% versus 15.4%. Yet RSA patients with unsatisfactory function were less than half as likely to undergo revision (4.9% vs. 10.6%, p < 0.001) [6]. The implant with the lower revision rate (RSA) is the implant under which a larger proportion of patients are living with poor function.

That paradox is the subject of this post. Two sampling biases and one structural property of the metric itself combine to make revision rate a misleading proxy for clinical success when comparing aTSA to RSA. The first is a confounding mismatch between the patient populations the two operations are performed on. The second is an attrition mechanism that systematically removes the worst outcomes from any cohort with a minimum time to follow-up. The third—and the most important one is that revision rate measures what the surgeon decides to operate on again, not what the patient is living with. Strip these out and the registry-based case for RSA in osteoarthritis with intact cuff is weak.

Two biases and a metric problem

Bias 1: The patient populations are not the same

Restricting to osteoarthritis controls for the obvious confounders of other indications such as cuff tear arthropathy and fracture; even within that restriction, the AOANJRR shows aTSA at 7.7% revision at 10 years and RSA at 5.0% [1]. But the RSA-for-OA cohort is overwhelmingly older: 87.7% of cases are in patients aged 65 or older [1]. When attention is restricted to the demographic where the operations actually compete—younger patients with osteoarthritis—the favorable RSA signal disappears. Figure 1 shows the actual curves from the registry.

Figure 1.  Cumulative percent revision from the AOANJRR 2025 Annual Report. RSA for OA in patients aged <65 (n=3,439, Table ST85) versus aTSA with a polyethylene glenoid for OA, all ages (n=5,120, Table ST44). Markers at the registry's reported time points (1, 3, 5, 7, 10, 14 years); shaded bands show 95% confidence intervals. The RSA <65 curve runs above the aTSA curve at every reported time point. At 14 years RSA <65 reaches 13.2% (95% CI 9.6–17.9) versus 9.4% (95% CI 7.8–11.1) for aTSA—the ratio of point estimates is 1.40. The wide 14-year RSA confidence interval reflects the small number of patients still under follow-up at that time point (n=53), an example of the cohort attrition discussed under Bias 2.  aTSA n-at-risk approximated from Figure ST2 of the AOANJRR 2025 report (all-diagnosis polyethylene glenoid, n=5,413) scaled to the OA-only cohort. RSA n-at-risk taken directly from Table ST85.

Cautions about this comparison are in order. The under-65 RSA-OA cohort is itself selected: these patients typically have severe pathology not amenable to aTSA, so part of their failure rate may reflect disease severity rather than implant inferiority. And the aTSA comparison group is not age-matched. Thus the registry cannot fully answer the like-for-like question—younger patient with intact cuff, RSA versus aTSA—because surgeons mostly do not choose RSA for that patient, and so the comparison cases barely exist. What the registry can show is that the apparent RSA-OA advantage in the registry headline is overwhelmingly driven by older patients for whom aTSA was never going to be offered.

Bias 2: The cohorts are themselves selectively curated

Every minimum-follow-up cohort is, by construction, a survivor cohort. To be analyzed at minimum 2, minimum 5, or minimum 10 years, a patient must have remained alive, in clinic, and with the original implants in place. Patients are excluded if their shoulder was revised before the minimum follow-up, if they died, if they were lost to follow-up, or if they left the surgeon's practice. This is not random. The mechanism is the immortal time bias formalized by Suissa: when cohort entry depends on a span of time during which the outcome of interest (e.g., survivorship to the minimum follow-up time) could not occur, the estimated event rate is systematically biased toward the experience of survivors [2]. Including only patients with minimum two-year follow-up systematically excludes those revised or deceased before two years; the percentage excluded by this immortal time effect grows for minimum five-year follow-up and grows again for minimum ten-year follow-up. This exclusion leaves a “purified” sample of patients more likely to continue life without revision and does not reflect the overall revision risk of the initial cohort.

Three independent processes drive this attrition. Khan and colleagues used Medicare claims on 108,667 elective shoulder arthroplasty patients aged 65 or older and reported 5-year mortality of 14.9% in elective non-fracture cases [3]. Torrens and colleagues prospectively tracked 251 shoulder arthroplasty patients and reported cumulative loss to follow-up of 18.3% at 2 years, 31.5% at 5 years, and 34.3% at 7 years, with older, sicker, and more obese patients selectively lost (HR 1.05 per year of age, HR 2.44 for severe obesity, HR 1.93 per ASA point) [4]. After adding exclusion for pre-threshold revision, at minimum 10-year follow-up only a minority of the original cohort—roughly a quarter to a third—remains analyzable. The minimum-10-year revision rate commonly quoted from a published series is therefore drawn from the least at-risk fraction of the original patient population.

Figure 2.  Approximate share of an original elective shoulder arthroplasty cohort still available for analysis at minimum 2-, 5-, and 10-year follow-up. Mortality components anchored to Khan 2024 [3] (14.9% at 5 years extrapolated to ~30% at 10 years); loss-to-follow-up components anchored to Torrens 2022 [4] (18.3% at 2 years, 31.5% at 5 years, extrapolated to ~36% at 10 years); pre-threshold revision approximated from registry data.

This compounds asymmetrically with the demographic confounding above. RSA cohorts are older and have higher all-cause mortality, so these cohorts lose more patients to death between landmark thresholds. RSA's particular failure modes—acromial fracture, dissatisfaction with limited internal rotation, persistent pain—are also more likely to lead to patients quietly dropping out of follow-up because there is often no good surgical option for them to consider. A published “minimum 5-year RSA-OA revision rate” of 3.5% is best read as 3.5% of the best segment of the original cohort, not the entire cohort. The same dynamic appears directly in Figure 1: at the 14-year time point the RSA <65 cohort retains only 53 of the original 3,439 patients (1.5%), producing the wide confidence interval that runs from 9.6% to 17.9%.

The metric problem: failure is not the same as revision

This is the largest of the three issues, and the one with the most specific mechanism. Revision rate is commonly used as a surrogate for clinical failure. It is a particularly poor surrogate for RSA. Parada and colleagues reported a 10.7% complication rate and 5.6% revision rate for aTSA, versus 8.9% and 2.5% for RSA, in 1,128 cases at mean follow-up of 23 months [5]. The gap between complication and revision was 3.6-fold for RSA versus 1.9-fold for aTSA. The most common RSA complication—acromial or scapular fracture (2.5%)—had a 0% revision rate [5].

O’Malley and colleagues' finding closes the loop: twice the prevalence of unsatisfactory function after RSA, and less than half the rate at which that unsatisfactory function leads to revision [6]. The lower RSA revision rate does not reflect superior implant performance. It reflects a higher threshold for revision in an older, frailer cohort, combined with failure modes that are difficult to address surgically and that surgeon and patient usually choose to accept rather than trying to fix surgically.

Figure 3.  Cumulative revision rate (light bars) and cumulative clinical failure rate (dark bars) for aTSA and RSA at minimum 2-, 5-, and 10-year follow-up. Revision rates anchored to AOANJRR registry data [1]; clinical failure rates anchored to Parada complication rates [5] and O’Malley OSS<29 prevalence [6]. The clinical-failure-to-revision ratio is approximately 3-fold for aTSA across all time points and 5- to 6-fold for RSA.

The asymmetry has a specific cause: the failure modes that drive each operation's clinical burden carry very different probabilities of leading to revision. Most of the failure modes unique to RSA produce clinical problems that rarely lead to revision.

A mode-by-mode look

Figure 4.  Estimated cumulative incidence of patients clinically affected by each failure mode (light bars) versus the proportion undergoing revision attributable to that mode (dark bars). Constructed from AOANJRR revision-cause distributions [1], Parada complication rates [5], O’Malley OSS<29 prevalence [6], systematic-review data on acromial fracture [7–9], Young secondary cuff dysfunction rates [14], Papadonikolakis glenoid radiolucency rates [10], Olson RSA instability rates [15], and Rojas baseplate loosening rates [16].

Acromial and scapular fracture. This mode is unique to RSA and represents the largest disconnect in the literature. Three independent systematic reviews place the incidence at 2.8% (Mahendraraj 2019) [8], 4.0% (Kim 2019) [9], and 5.0% (Patterson 2020) [7]. Of 208 fractures in Patterson's review, only 9 (4.3%) underwent revision arthroplasty [7]. Function deteriorates after fracture regardless of treatment. The clinical-failure-to-revision ratio is approximately 25:1.

Persistent pain. Pain is a major driver of unsatisfactory function but rarely the documented reason for revision. The OSS<29 prevalence in O’Malley—15.4% for aTSA and 27.0% for RSA—captures pain alongside stiffness, ADL limitation, and overall functional compromise [6]. The cleanest reading is the one O’Malley reports directly: RSA patients with poor function are less than half as likely as aTSA patients with poor function to be revised. Some unknown proportion of persistent pain after shoulder arthroplasty represents occult Cutibacterium infection that goes undiagnosed; Pottinger and colleagues showed that 22% of revisions performed for stiffness, pain, or loosening had positive cultures for Cutibacterium despite being categorized clinically as aseptic [11]. Patients with low-grade unrecognized infection who do not undergo revision are invisible in registry data altogether.

Cuff and subscapularis failure. This mode is aTSA-specific. Cuff insufficiency accounts for roughly a quarter of aTSA-OA revisions in the AOANJRR data [1]. The actual prevalence of post-aTSA cuff failure is substantially higher. Young and colleagues, in a multicenter European study of 518 aTSAs followed for a mean of 8.6 years, reported a 16.8% rate of secondary rotator cuff dysfunction, with Kaplan–Meier survivorship free of secondary cuff dysfunction of 100% at 5 years, 84% at 10 years, and 45% at 15 years [14]. Most of this dysfunction was managed with rehabilitation or accepted as part of the clinical course; only a fraction underwent revision. RSA bypasses the rotator cuff biomechanically, so this mode does not apply to RSA. Importantly, aTSA failure due to cuff or glenoid component issues can be revised to RSA with patient-reported outcome improvements [12,13]—a salvage option that is less successful for some of the major RSA-specific failure modes.

Asymptomatic glenoid radiolucency and loosening. aTSA-specific. Papadonikolakis, Neradilek, and Matsen's 2013 systematic review of 27 articles representing 3,853 aTSAs reported asymptomatic glenoid radiolucent lines accumulating at 7.3% per year, symptomatic loosening at 1.2% per year, and surgical revision for loosening at 0.8% per year [10]. Radiographically apparent loosening occurs approximately nine times more frequently than revision. Most asymptomatic radiolucent lines do not progress to clinical failure within the patient's lifetime, but those that do represent a substantial population not captured in revision rates.

Dislocation and instability. Both operations can fail by this mode, but RSA more often. Olson and colleagues' systematic review of 17 studies including 7,885 RSAs reported a pooled instability rate of 2.5%, ranging from 1–5% in primary RSA cohorts and 1–49% in revision RSA [15]. Across studies, treatment was successful with closed reduction and casting in 28–100% of cases and with revision RSA in 55–100%; recurrent instability often required hemiarthroplasty or resection. The clinical-failure-to-revision ratio for instability is approximately 1.5:1 to 2:1—smaller than for the modes above, but RSA-specific risk factors (subscapularis insufficiency, proximal humerus fracture, fracture sequelae) load this mode disproportionately onto the older RSA-for-fracture population.

Baseplate failure (RSA) and overt infection (both RSA and aTSA). These are the modes with the smallest disconnect. Aseptic glenoid baseplate loosening is rare: Rojas and colleagues' meta-analysis of 103 studies including 6,583 RSAs reported a pooled prevalence of 1.16% (95% CI 0.80–1.69%), with 0.90% in primary RSA and 1.69% in revision RSA [16]. When symptomatic, baseplate loosening almost always progresses to revision. Overt infection is similarly almost always revised. Both modes have clinical-failure-to-revision ratios close to 1:1—but the Pottinger finding indicates that the population of patients with low-grade unrecognized infection may be substantially larger than overt-infection counts suggest, and many of those patients neither receive a revision nor appear in registry infection data [11].

Bottom line

The AOANJRR shows a population-level revision-rate advantage for RSA over aTSA. It does not show a like-for-like advantage. Two sampling biases compound: an age and indication mismatch that places most RSA-for-OA cases in older patients to whom aTSA was never going to be offered, and an immortal time bias that removes most of an original cohort from the analyzed group at the 10-year mark, with the older RSA population hit hardest. The third issue is structural rather than statistical. Revision rate measures the surgeon's and patient's thresholds for re-operation, and does not reflect the patient's clinical outcome. The clinical-failure-to-revision ratio is two to three times larger for RSA than for aTSA.

This is not an artifact. It has a specific mechanism. RSA's distinctive failure modes—acromial fracture, persistent pain, scapular notching, dissatisfaction with internal rotation—are largely uncountable in revision data because there is often no good surgical option to consider. By contrast, aTSA failures from cuff or subscapularis tear and from glenoid component loosening can be revised to RSA with clinically significant outcome improvements [12,13]. Revision rate as a quality metric privileges the operation (RSA) whose failures are less likely to be surgically correctable.

Evidence for restricting RSA to its established indications—cuff arthropathy, irreparable cuff tear, selected fractures—rather than expanding it into osteoarthritis with intact cuff is present in the AOANJRR's data.

avocet

reverse avocet

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References

1. Australian Orthopaedic Association National Joint Replacement Registry. Hip, Knee and Shoulder Arthroplasty: 2025 Annual Report. Adelaide: AOA; 2025. Available from: https://aoanjrr.sahmri.com/annual-reports-2025. Data period 1 September 1999 – 31 December 2024.

2. Suissa S. Immortal time bias in pharmacoepidemiology. Am J Epidemiol. 2008;167(4):492–499. doi:10.1093/aje/kwm324. PMID: 18056625.

3. Khan AZ, Zhang X, Macarayan E, et al. Five-year mortality rates following elective shoulder arthroplasty and shoulder arthroplasty for fracture in patients over age 65. JBJS Open Access. 2024;9(2):e23.00133. doi:10.2106/JBJS.OA.23.00133. PMID: 38685966.

4. Torrens C, Martínez R, Santana F. Patients lost to follow-up in shoulder arthroplasty: descriptive characteristics and reasons. Clin Orthop Surg. 2022;14(1):112–118. doi:10.4055/cios21034. PMID: 35251548.

5. Parada SA, Flurin PH, Wright TW, Zuckerman JD, Elwell JA, Roche CP, Friedman RJ. Comparison of complication types and rates associated with anatomic and reverse total shoulder arthroplasty. J Shoulder Elbow Surg. 2021;30(4):811–818. doi:10.1016/j.jse.2020.07.028. PMID: 32763380.

6. O’Malley O, Davies A, Rangan A, Sabharwal S, Reilly P. Is there a difference in thresholds for revision between shoulder arthroplasty types? A National Joint Registry study. PLoS One. 2025;20(8):e0330975. doi:10.1371/journal.pone.0330975. PMID: 40857270.

7. Patterson DC, Chi D, Parsons BO, Cagle PJ. Acromial spine fracture after reverse total shoulder arthroplasty: a systematic review. J Shoulder Elbow Surg. 2019;28(4):792–801. doi:10.1016/j.jse.2018.08.033. PMID: 30497925.

8. Mahendraraj KA, Abboud J, Armstrong A, et al. How common are acromial and scapular spine fractures after reverse shoulder arthroplasty? A systematic review. Bone Joint J. 2019;101-B(6):627–634. doi:10.1302/0301-620X.101B6.BJJ-2018-1187.R1. PMID: 31154841.

9. Kim HM, Chung J, Jeong CW, Yoon JR. Is acromial fracture after reverse total shoulder arthroplasty a negligible complication? A systematic review. Clin Orthop Surg. 2019;11(4):427–435. doi:10.4055/cios.2019.11.4.427. PMID: 31788166.

10. Papadonikolakis A, Neradilek MB, Matsen FA 3rd. Failure of the glenoid component in anatomic total shoulder arthroplasty: a systematic review of the English-language literature between 2006 and 2012. J Bone Joint Surg Am. 2013;95(24):2205–2212. doi:10.2106/JBJS.L.00552. PMID: 24352774.

11. Pottinger P, Butler-Wu S, Neradilek MB, Merritt A, Bertelsen A, Jette JL, Warme WJ, Matsen FA 3rd. Prognostic factors for bacterial cultures positive for Propionibacterium acnes and other organisms in a large series of revision shoulder arthroplasties performed for stiffness, pain, or loosening. J Bone Joint Surg Am. 2012;94(22):2075–2083. doi:10.2106/JBJS.K.00861. PMID: 23172325.

12. Al-Asadi M, Rajapaksege N, Abdel Khalik H, Abesteh J, Athwal GS, Khan M. Outcomes and complications of failed anatomic shoulder arthroplasty revised with reverse arthroplasty: a systematic review. J Shoulder Elbow Surg. 2025;34(7):1832–1840.

13. Tobin JG, Thomas SK, Elwell JA, Roche CP, Rogalski BL, Eichinger JF, Friedman RJ. Anatomic total shoulder arthroplasty revised to reverse total shoulder arthroplasty: clinical and radiographic outcomes compared to primary reverse total shoulder arthroplasty. J Shoulder Elbow Surg. 2025;34(6):1525–1531. PMID: 39694226.

14. Young AA, Walch G, Pape G, Gohlke F, Favard L. Secondary rotator cuff dysfunction following total shoulder arthroplasty for primary glenohumeral osteoarthritis: results of a multicenter study with more than five years of follow-up. J Bone Joint Surg Am. 2012;94(8):685–693. doi:10.2106/JBJS.J.00727. PMID: 22419408.

15. Olson JJ, Galetta MD, Keller RE, Oh LS, O’Donnell EA. Systematic review of prevalence, risk factors, and management of instability following reverse shoulder arthroplasty. JSES Rev Rep Tech. 2022;2(3):261–268. doi:10.1016/j.xrrt.2022.02.009. PMID: 37588866.

16. Rojas J, Choi K, Joseph J, Srikumaran U, McFarland EG. Aseptic glenoid baseplate loosening after reverse total shoulder arthroplasty: a systematic review and meta-analysis. JBJS Rev. 2019;7(5):e7. doi:10.2106/JBJS.RVW.18.00132. PMID: 31145263.

What Reverse Total Shoulder Geometry Will Give My Patient the Best Function and Lowest Complication Risk?

While we know that many patient (osteoporosis, steroid use, inflammatory arthropathy, female sex) and shoulder factors (cuff status, prior surgery, coracoacromial arch integrity, humeral and glenoid deformity) drive the outcome of reverse shoulder arthroplasty, I was curious to see what the literature has to say about the surgeon-controlled variables related to the geometry of the reconstruction. I've tried to focus on the position, rather than the design, of the components. Here's what I think I learned - as always - your comments are welcome.

Avoiding Complications

Minimizing risk of inferior impingement, scapular notching, and baseplate loosening

Place the baseplate flush with the inferior glenoid rim

  Select and place humeral component to achieve a 135° liner-shaft angle

Target 4–10 mm of lateralization of the glenosphere center of rotation (CO): defined as the distance from the glenosphere center of rotation (COR) to the glenoid bone surface (includes the thickness of the baseplate, bone graft and/or augment). Know your glenospheres and don't rely on the numbers on the box: for example, in one implant system the 3mm baseplate plus a "32-4" glenosphere lateralizes the center of rotation by 9mm.

Place baseplate in 0 - 10 degrees of inferior tilt: central screw parallel to floor of supraspinous fossa so that the humeral force on the glenosphere is perpendicular to the screw fixation.

Minimizing risk of neurologic injury and pain.

Avoid excess humeral distalization: acromiohumeral interval (AHI) <30mm, humeral lengthening (pre to postoperative change in AHI) <20mm.

Minimizing risk of acromial and scapular spine fracture

The distance from the glenosphere center (COR) to the most lateral point on the acromial undersurface (DA) should exceed the distance from the glenosphere center (COR) to the lateral tip of the greater tuberosity (DGT). DA ≥ DGT. 

Minimize humeral-sided contribution to global lateralization. Humeral sided lateralization directly increases the distance from the glenosphere center (COR) to the lateral tip of the greater tuberosity (DGT) while leaving the distance from the glenosphere center (COR) to the most lateral point on the acromial undersurface (DA) unchanged, worsening the DA - DGT difference. By contrast glenoid-sided lateralization (increasing lateralization of the glenosphere center of rotation (CO), changes both the DA and DGT simultaneously, preserving more control over the DA - DGT difference.

 

Minimizing instability risk

Strive for humeral retroversion 0°–20° and glenoid retroversion 0°–20° (Recall that soft tissue tension, humero-scapular impingement, liner geometry, and other factors play major roles in rTSA stability).

Optimizing Function

Deltoid efficiency

Position the glenosphere center of rotation inferiorly and posteriorly to maximize the deltoid's mechanical advantage during abduction and flexion

Motion

4–10 mm glenoid-sided lateralization improves internal rotation by displacing the humeral cup away from the scapular neck, reducing the impingement that limits motion.

Glenoid retroversion 0°–20° optimizes external rotation

A 135° liner-shaft angle increases adduction and rotational range

Avoid excess humeral distalization: Keeping acromiohumeral interval (AHI) <30mm, humeral lengthening (change in AHI) <20mm facilitates flexion and external rotation.

"Glenosphere Lateralization" - Resolving the Nomenclature Confusion

The geometry of reverse shoulder arthroplasty reconstruction is frequently discussed in terms of a single number ("glenoid lateralization” , "metallic offset", "lateralization shoulder angle (LSA)), yet none of these numbers captures the important surgeon-controlled variables and their use results in contradictory results in the rTSA literature. 

Three distinct measurements describe different aspects of glenosphere construct geometry. 

Global Lateralization (GL): distance from the glenoid bone surface to the lateral tip of the greater tuberosity (= GT + humeral component contribution). Includes the baseplate and augments. This is the distance that the tuberosity is lateralized from the native glenoid bone. Increases in GL tighten the shoulder - increasing stability, but may also increase the risk of contact between the tuberosity and the acromion when the arm is elevated.

Effective Glenosphere Thickness (GT): distance from the glenoid bone surface to the lateral edge of the glenosphere (= CO + glenosphere radius). Includes the baseplate and augments. This is the glenosphere contribution to global lateralization

.

Center of Rotation Offset (CO): distance from the glenoid bone surface to the glenosphere center of rotation (COR). Includes the baseplate and augments. The COR is the pivot point around which the tuberosity rotates. The position of the COR defines the moment arm for deltoid action. 

All three are measured from the same landmark (glenoid bone surface) but to different endpoints. Each can vary independently of the others through implant selection and surgical technique. Reporting all three measures on postoperative radiographs would resolve most of the apparent conflicts.

A clear-eyed view

Peregrine Falcon

Union Bay Natural Area

2019

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References

1. Arenas-Miquelez A, Murphy RJ, Rosa A, Caironi D, Zumstein MA. Impact of Humeral and Glenoid Component Variations on Range of Motion in Reverse Geometry Total Shoulder Arthroplasty: A Standardized Computer Model Study. J Shoulder Elbow Surg. 2021.

2. Dean EW, Dean NE, Wright TW, et al. Clinical Outcomes Related to Glenosphere Overhang in Reverse Shoulder Arthroplasty Using a Lateralized Humeral Design. J Shoulder Elbow Surg. 2022. [Note: “overhang” is measured as glenosphere-to-baseplate offset on 2D Grashey radiograph, not glenosphere-to-native-bone.]

3. Pak T, Kilic AI, Ardebol J, et al. Glenoid-Sided Lateralization Decreases Scapular Notching With a 135° Humeral Component Arthrex Reverse Shoulder Arthroplasty. J Shoulder Elbow Surg. 2025.

4. Meisterhans M, Bouaicha S, Meyer DC. Posterior and Inferior Glenosphere Position in Reverse Total Shoulder Arthroplasty Supports Deltoid Efficiency for Shoulder Flexion and Elevation. J Shoulder Elbow Surg. 2019.

5. Rai AA, LeVasseur CM, Kane GE, et al. Glenosphere Tilt and Size Predict Shoulder Kinematics During the Hand-to-Back Motion After Reverse Shoulder Arthroplasty. J Orthop Res. 2025.

6. Berton A, Longo UG, Gulotta LV, et al. Humeral and Glenoid Version in Reverse Total Shoulder Arthroplasty: A Systematic Review. J Clin Med. 2022.

7. Keener JD, Patterson BM, Orvets N, Aleem AW, Chamberlain AM. Optimizing Reverse Shoulder Arthroplasty Component Position in the Setting of Advanced Arthritis With Posterior Glenoid Erosion: A Computer-Enhanced Range of Motion Analysis. J Shoulder Elbow Surg. 2018.

8. Lee HH, Park SE, Ji JH, Jun HS. Mid-Term Comparative Study Between the Glenoid and Humerus Lateralization Designs for Reverse Total Shoulder Arthroplasty. BMC Musculoskelet Disord. 2023.

9. Wright MA, Murthi AM. Offset in Reverse Shoulder Arthroplasty: Where, When, and How Much. J Am Acad Orthop Surg. 2021.

10. Wolf GJ, Reid JJ, Rabinowitz JR, et al. Does Glenohumeral Offset Affect Clinical Outcomes in a Lateralized Reverse Total Shoulder Arthroplasty? J Shoulder Elbow Surg. 2022.

11. Nunes B, Linhares D, Costa F, et al. Lateralized Versus Nonlateralized Glenospheres in Reverse Shoulder Arthroplasty: A Systematic Review With Meta-Analysis. J Shoulder Elbow Surg. 2021.

12. Neyton L, Nigues A, McBride AP, Giovannetti de Sanctis E. Neck Shaft Angle in Reverse Shoulder Arthroplasty: 135 vs. 145 Degrees at Minimum 2-Year Follow-Up. J Shoulder Elbow Surg. 2023.

13. Baumgarten KM, Max C. Reverse Total Shoulder Arthroplasty Using Lateralized Glenoid Baseplates Has Superior Patient-Determined Outcome Scores at Short-Term Follow-Up. J Am Acad Orthop Surg. 2024.

14. Kawashima I, King JJ, Wright JO, et al. Shoulder Geometry After Reverse Total Shoulder Arthroplasty With a Medialized Glenoid and a Lateralized Humerus Predicts Subacromial Notching and Acromial or Scapular Spine Fractures. J Shoulder Elbow Surg. 2025.

15. Burden EG, Batten TJ, Smith CD, Evans JP. Reverse Total Shoulder Arthroplasty. Bone Joint J. 2021.

16. Nelson R, Lowe JT, Lawler SM, et al. Lateralized Center of Rotation and Lower Neck-Shaft Angle Are Associated With Lower Rates of Scapular Notching and Heterotopic Ossification and Improved Pain for Reverse Shoulder Arthroplasty at 1 Year. Orthopedics. 2018.

17. Ameziane Y, Audigé L, Schoch C, et al. Mid-Term Outcomes of a Rectangular Stem Design With Metadiaphyseal Fixation and a 135° Neck-Shaft Angle in Reverse Total Shoulder Arthroplasty. J Clin Med. 2025.

18. Jang YH, Lee JH, Kim SH. Effect of Scapular Notching on Clinical Outcomes After Reverse Total Shoulder Arthroplasty. Bone Joint J. 2020.

19. Mollon B, Mahure SA, Roche CP, Zuckerman JD. Impact of Scapular Notching on Clinical Outcomes After Reverse Total Shoulder Arthroplasty: An Analysis of 476 Shoulders. J Shoulder Elbow Surg. 2017.

20. Simovitch R, Flurin PH, Wright TW, Zuckerman JD, Roche C. Impact of Scapular Notching on Reverse Total Shoulder Arthroplasty Midterm Outcomes: 5-Year Minimum Follow-Up. J Shoulder Elbow Surg. 2019.

21. Spiry C, Berhouet J, Agout C, Bacle G, Favard L. Long-Term Impact of Scapular Notching After Reverse Shoulder Arthroplasty. Int Orthop. 2021.

22. Erickson BJ, Werner BC, Griffin JW, et al. A Comprehensive Evaluation of the Association of Radiographic Measures of Lateralization on Clinical Outcomes Following Reverse Total Shoulder Arthroplasty. J Shoulder Elbow Surg. 2022;31:963–970. [Multiple authors report financial relationships with Arthrex, Inc., manufacturer of the implant system used in this study.]

23. Werner BC, Lederman E, Gobezie R, Denard PJ. Glenoid Lateralization Influences Active Internal Rotation After Reverse Shoulder Arthroplasty. J Shoulder Elbow Surg. 2021;30:2498–2505.

24. Southam BR, Bedeir YH, Johnson BM, et al. Clinical and Radiological Outcomes in Lateralized Versus Nonlateralized and Distalized Glenospheres in Reverse Total Shoulder Arthroplasty: A Randomized Control Trial. J Shoulder Elbow Surg. 2023.

25. Longo UG, Gulotta LV, De Salvatore S, et al. The Role of Humeral Neck-Shaft Angle in Reverse Total Shoulder Arthroplasty: 155° Versus <155° — A Systematic Review. J Clin Med. 2022.