All the failures we cannot see

What is a failure?

We often define failure of an arthroplasty as a revision. It is evident, however, that the lack of a revision does not indicate that the patient has had a successful outcome. The lack of a revision simply indicates that the surgeon was unwilling to do another operation on the patient — or that the patient did not want more surgery, even though they were unhappy about the result.

If we equate revision and failure, many clinical failures go unseen. In the UK National Joint Registry, among 21,918 patients with a recorded postoperative Oxford Shoulder Score, 26.99% of those having a reverse total shoulder arthroplasty (RSA) had an unsatisfactory result, defined as an Oxford Shoulder Score below 29. Fewer than 1 in 20 of them (4.87%) were revised. Among patients with an unsatisfactory score, the proportion revised was 10.58% after anatomic total shoulder arthroplasty (aTSA) and 13.86% after hemiarthroplasty [1]. The authors concluded that the lower revision rate after RSA may not indicate better outcomes than anatomic arthroplasty, but rather a higher threshold for revising an RSA [1]. When an RSA fails, the prospect for improving the patient’s comfort and function is often poor, so the patient keeps the implant and keeps the disability.

Furthermore, achieving the minimal clinically important difference (MCID), the substantial clinical benefit, or the patient acceptable symptom state on the ASES, SANE, SST, or VAS after shoulder arthroplasty — the common indicators of a “successful arthroplasty” — did not correlate with patient satisfaction, with willingness to undergo the operation again, or with willingness to recommend it to a friend or family member [3]. In a prospective cohort of 1,559 RSAs, the 134 patients (8.6%) who rated themselves unchanged or worse had nevertheless improved on every measured outcome [4]. Their scores went up. They were not satisfied.

On one hand, a change in a patient-reported outcome that does not reach the MCID establishes that the patient has not improved. On the other hand, a change that exceeds the MCID does not establish that the patient is satisfied. MCID thresholds give strong evidence of failure and weak evidence of success.

Thus, the usual methods do not identify the patients who find their outcomes unsatisfactory.

Inspired by the wonderful book, “All the Light We Cannot See,” we wondered about “All the Failures We Cannot See”.

We are realizing that failure needs to be defined more broadly: the patient is dissatisfied or in pain, has sustained a complication, has been revised, or is simply not better than before surgery. The 1 in 10 patients who report themselves unchanged or worse after an anatomic total shoulder arthroplasty [5], and the roughly 1 in 5 who are dissatisfied after total knee arthroplasty [6], are where we can look for opportunities to improve our method by asking, as Codman would have us do, what could we have done differently that might have prevented the failure? [2, 8, 9]. Over five years Codman tracked his patients by sending them End Result Cards at a year after surgery, asking whether they were better. For those who were not better, he tried to determine why not [10]. What deserves emphasis is his method: he asked each patient for follow-up, and he did it with a simple card. The modern version of Codman’s card is a text message or an email, sent on the anniversary of the operation. The medium has changed; the method has not. Asking is what makes the failures visible.

When we identify a patient with an unsatisfactory result, we have a unique opportunity to ask questions such as “If I had chosen a different implant, if my implant fixation had been better, might this failure have been avoided? Should I have operated on this patient at all? What is different about my care of this patient in contrast to comparable patients in my practice who did well?” As Pearl has argued, these counterfactual questions are the language of causal reasoning [11].

It is important to avoid naming the mode of failure and calling it the cause. “Glenoid component loosening” is not a cause; it is what happened. The question is what led to it — the bone quality, the deformity, the technique of bone preparation, or the seating of the component.

By analogy, consider a report that the battle was lost because the general did not arrive. The general’s absence was not the cause; it was what happened. The battle was lost because the farrier failed to place the horseshoe nails properly, the shoe came loose, the horse stumbled, the general broke his leg, and he could not lead the charge. Once recognized, the nail placement is the thing that must be fixed before the next battle. So the question for us is: what might we do to reduce the risk of glenoid component failure in the next case?

How can we see our failures?

It starts with a secure log of our own cases.

(1)  For each surgery, enter the following

Name | Medical Record No. | Date of Birth | Mobile | Email

Diagnosis | Procedure | Surgery Date

(2)  Prepare a short message — a text or an email, sent through the institution’s patient portal or another secure channel — to go to the patient at 1 year after surgery.

I am interested in knowing how you are doing after your surgery. Please reply to this message. Are you better than before? Have you had any problems? If so, please let me know about them.

(3)  Trigger the message from the surgery date. A calendar reminder and a delayed send will do it; an automated text service will do it without your having to remember. This trigger is the whole reason the log exists.

(4)  When the patient replies, add the response to the log. When the patient does not reply, consider asking the office to telephone them.

Follow-up Date | Improved? | Additional Surgery?

(5)  For each failure (not improved, additional surgery), compare the case and its treatment with similar cases that did not fail.

(6)  Ask yourself what might have been done differently — patient selection, characterization of anatomy, procedure and implant choice, technique, perioperative management, team and system factors — to avoid the failure. Ask, as Codman did, “why not?” Enter this information into the log.

(7)  Keep the log where you will read it. Before a comparable case, look back at what you wrote about the last failure of that kind.

(8)  Recognize that each patient who finds their outcome unsatisfactory is an opportunity to refine your method. Two failures of the same kind are not two instances of one thing. A dislocation after reverse total shoulder arthroplasty in one patient and a dislocation in another are different events — a different patient, a different anatomy, a different set of decisions, a different day in the operating room — and a unique opportunity to learn.

Final thoughts

The measure of success is the steady refinement of our method across a career. Each of us has the opportunity to see whether our patients are better, and to learn from those who are not. Each patient who reports that they are no better is one case we can learn from.

Some of us might prefer to avoid asking a question that carries the risk of getting a “bad news” response. Others might want to avoid calling the patient’s attention to a suboptimal outcome. However, the opposite may be true — by asking, we show the patient that we care. Furthermore, in seeing the failure we may identify a chance to remedy it.

The opportunity to identify, learn from and care for these patients is there for each of us.

Seeing by looking

Short eared owl

Skagit

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References

[1] 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

[2] Menendez ME, Matsen FA 3rd. Learning from surgical failures. J Bone Joint Surg Am. 2026;108(8):547-548. doi:10.2106/JBJS.25.01110

[3] Khan AZ, Vaughan A, Aman ZS, Lazarus MD, Williams GR, Namdari S. Reaching MCID, SCB, and PASS for ASES, SANE, SST, and VAS following shoulder arthroplasty does not correlate with patient satisfaction. Semin Arthroplasty JSES. 2024;34(4):819-826. doi:10.1053/j.sart.2024.03.017

[4] Parsons M, Routman HD, Roche CP, Friedman RJ. Patient-reported outcomes of reverse total shoulder arthroplasty: a comparative risk factor analysis of improved versus unimproved cases. JSES Open Access. 2019;3(3):174-178. doi:10.1016/j.jses.2019.07.004. PMID:31709358

[5] Hao KA, Hones KM, O’Keefe DS, Elwell J, Simovitch RW, Wright TW, King JJ, Schoch BS. Does the relationship between preoperative function and achievement of clinically important benchmarks of success after total shoulder arthroplasty depend on outcome assessment design? Clin Orthop Relat Res. 2025;483(3):377-395. doi:10.1097/CORR.0000000000003347. PMID:39778205

[6] Bourne RB, Chesworth BM, Davis AM, Mahomed NN, Charron KDJ. Patient satisfaction after total knee arthroplasty: who is satisfied and who is not? Clin Orthop Relat Res. 2010;468(1):57-63. doi:10.1007/s11999-009-1119-9. PMID:19844772

[8] Codman EA. The product of a hospital. Surg Gynecol Obstet. 1914;18:491-496.

[9] Reverby S. Stealing the golden eggs: Ernest Amory Codman and the science and management of medicine. Bull Hist Med. 1981;55(2):156-171. PMID:7020802

[10] Codman EA. A Study in Hospital Efficiency: As Demonstrated by the Case Report of the First Five Years of a Private Hospital. Boston, MA: Thomas Todd Co.; 1918.

[11] Pearl J, Mackenzie D. The Book of Why: The New Science of Cause and Effect. New York, NY: Basic Books; 2018.

"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.

Complications and revisions following reverse total shoulder: doing the math.

Summary: Three takeaway points

(1) The commonly used and easy to measure "revision rate" is an inadequate endpoint for evaluating rTSA outcomes. The 8–20 percentage point gap that exists between the complication rate and the revision rate includes a substantial number of patients with failed but unrevised reverse shoulder arthroplasties. These patients are not considered in determining the failure rate when measured by the percentage having revision. Complication-free survival or patient-reported outcome measures should supplement or replace revision rate or "implant survival" as the primary outcome measure for rTSA.

(2) The most common complications of rTSA, acromial and scapular spine fractures, are unique and difficult to solve problems for patients having reverse arthroplasty. In contrast, the most common complications from aTSA - glenoid component loosening and rotator cuff tear - can be effectively managed by revision to a rTSA

(3) The salvage pathway for patients with rTSA failure is poor. Revision rTSA carries a 31% complication rate and 27% re-revision rate, with outcomes that are significantly worse than those for primary rTSA. This contrasts sharply with aTSA-to-rTSA conversion, the outcome of which approaches the outcomes for primary rTSA. 

The details

Complications vs revisions

Meta-analytic evidence reports that anatomic total shoulder (aTSA) has a higher rate of revision compared to reverse total shoulder (rTSA). This observation may have driven much of the shift toward rTSA for patients with cuff-intact arthritis.  However, it may neglect the fact that surgeons and patients can decide against revision of a failed rTSA because of the low rate of success. Thus, the absence of a revision does not indicate a good outcome.

Consider the references below

Complications and further surgery after reverse total shoulder arthroplasty : report of 854 primary cases reported an overall complication rate of 18–22%, yet a revision rate of only ~10%. That 8–12 percentage point gap likely represents patients who are living with a failing implant — either because revision was technically not feasible, or because expected outcomes were too poor to justify reoperation

Incidence, radiographic predictors, and clinical outcome of acromial stress reaction and acromial fractures in reverse total shoulder arthroplasty found 46 acromial stress fractures (5.4%) in 44 patients and 44 acromial stress reactions (5.2%) in 43 patients. The overall union rate was 55% but was significantly higher following operative treatment compared with nonoperative treatment. However, facture consolidation did not result in better clinical outcomes compared with nonunion; this may question the value of attempted fixation.

Comparison of complication types and rates associated with anatomic and reverse total shoulder arthroplasty found that the top 3 complications for rTSA were acromial/scapular fracture/pain ( complication rate 2.5%, revision rate 0.0%), instability (complication rate 1.4%, revision rate 1.0%), pain (1.2%, revision rate 0.2%). Compare the relationship of complications to revisions for rTSA to that for aTSA in the two charts below constructed from the data in this article. Note that a high percentage of the rTSA complications were not associated with surgical revision. Absence of revision ≠ absence of complication,

The Gap Between Revision-Free and Complication-Free Survival 

Long-Term Outcomes of Reverse Total Shoulder Arthroplasty
A Follow-up of a Previous Study The 93% ten-year revision-free survival rate for rTSA did not capture the 29% of patients who experienced complications.

Long term clinical and radiological outcomes of primary reverse total shoulder arthroplasty at a minimum follow-up of 15 years: Norwegian registry data showed 10-year complication-free rates of only 76–80%, despite revision-free survival of 91–95%. That 15–20 percentage point gap represents patients living with failed implants who are invisible in the revision statistics. Again, this gap exists because many rTSA complications—particularly acromial fractures, low-grade infection, and baseplate loosening with severe bone loss—either cannot be addressed surgically or carry such poor expected revision outcomes that conservative management is chosen.

Revision rates alone remain an inadequate measure of rTSA performance; complication-free survival is the more appropriate endpoint.

Outcomes of Revision rTSA

Revision of reverse total shoulder arthroplasty: a scoping review of indications for revision, and revision outcomes, complications, and rerevisions and Revision of failed shoulder arthroplasty: epidemiology, etiology, and surgical options found the most common indications for revision to be instability/dislocation (28–30%), baseplate or glenoid complications (20–25%), and infection (15–23%). Notably low on the list is revision for the most common complication: acromial/spine fractures.

Outcomes After Revision

Revision reverse total shoulder arthroplasty: clinical and radiographic outcomes compared to primary reverse total shoulder arthroplasty found a 31% complication rate and 27% re-revision rate of a failed rTSA: over five times these rates after primary rTSA. The most common complications after revision are recurrent instability (22%), fractures (18%), and baseplate issues (12%). Patients requiring revision rTSA experience markedly worse comfort and function in comparison to primary rTSA

The Salvage Pathway Asymmetry:  revision for aTSA Failure compared to revision for rTSA Failure

Conversion of failed anatomic total shoulder arthroplasty to reverse shoulder arthroplasty yields similar pain and functional outcomes to primary reverse shoulder arthroplasty but has a higher baseplate failure rate: a matched cohort study. In contrast to the often grim outcomes for revision of a failed rTSA, revision of a failed aTSA to a rTSA yields outcomes approaching those of primary rTSA. 

Summary: Three takeaway points (again)

(1) The commonly used and easy to measure "revision rate" is an inadequate endpoint for evaluating rTSA outcomes. The 8–20 percentage point gap that exists between the complication rate and the revision rate includes a substantial number of patients with failed but unrevised reverse shoulder arthroplasties. These patients are not considered in determining the failure rate when measured by the percentage having revision. Complication-free survival or patient-reported outcome measures should supplement or replace revision rate or "implant survival" as the primary outcome measure for rTSA.

(2) The most common complications of rTSA, acromial and scapular spine fractures, are unique and difficult to solve problems for patients having reverse arthroplasty. In contrast, the most common complications from aTSA - glenoid component loosening and rotator cuff tear - can be effectively managed by revision to a rTSA

(3) The salvage pathway for patients with rTSA failure is poor. Revision rTSA carries a 31% complication rate and 27% re-revision rate, with outcomes that are significantly worse than those for primary rTSA. This contrasts sharply with aTSA-to-rTSA conversion, the outcome of which approaches the outcomes for primary rTSA. 

Swans reversing course

Trumpeter Swans

Union Bay Natural Area

Seattle

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Does component malposition lead to revision of shoulder arthroplasty?

Humeral and glenoid component malposition in patients requiring revision shoulder arthroplasty: a retrospective, cross-sectional study lists instability: 32% (most common in RSA cases (40%). rotator cuff tear: 32% — predominantly in TSA (45%), loosening: 25% (highest in RSA (34%), infection: 11%, periprosthetic fracture: 5%. 

This commercially-funded investigation concluded: "The data from this study suggest that component malposition is frequently present among patients requiring revision arthroplasty." and "Improved component positioning is needed, including the development of more effective intra-operative techniques to ensure proper humeral and glenoid component position to minimize the risk of revision surgery." However, this study did not demonstrate that the rate of malposition was more frequent in revised than in unrevised shoulders. To conclude that malposition causes revision, we need to know how often well-functioning, unrevised shoulders also exceed defined thresholds.

Here are some details: component position was measured on pre-revision radiographs. "Thresholds for Malposition" were based on values found in prior publications.

From the above and the figure below it can be seen that the definition of acceptable component position is quite narrow.

The authors note that using narrower thresholds dramatically increases "malposition" rates. For example, lowering the threshold for the change in humeral center of rotation from >5mm to  >3mm increased the rate of "malpositioned" components from 45% to 58% of TSA cases. It seems likely that there are many unrevised shoulder arthroplasties with a change in humeral center of rotation exceeding the 5mm or the 3mm thresholds.

This is akin to having the distance between field goal uprights being 3 feet (below right) rather than the regulation 18.5 feet (below left).  Narrowing the goal posts does not change the quality of the kicker.

To understand the nature of thresholds, we need scatter plots including both revised and unrevised shoulders that show the relationship between component position and outcomes across the full spectrum of both variables. Such plots would reveal the true clinical significance of positioning variations. These data are not included in this study.

The value of scatter plots is shown by four hypothetical examples illustrating different possible relationships between component positioning and outcomes. Each represents a fundamentally different clinical reality with different implications for the value of precision positioning technology.

Figure 1. Scenario A: Hard Threshold Pattern

This pattern shows a clear inflection point at 5 mm deviation. Below this threshold, outcomes remain excellent with minimal variation. Above it, outcomes deteriorate sharply.  The blue dots represent cases without revision, while red dots indicate cases that required revision surgery.

Figure 2. Scenario B: Soft Threshold Pattern (Gradual Decline)

This pattern demonstrates a linear relationship where each degree of deviation causes proportional outcome deterioration. There is no sharp inflection point. Note the increasing concentration of revisions (red dots) as deviation increases, but many poorly-positioned components still function adequately.

Figure 3. Scenario C: No Clear Relationship (Zone of Indifference)

This pattern shows outcomes scattered across the full range regardless of positioning. The flat trend line suggests that within the measured range, this particular positioning parameter has minimal impact on outcomes. Other factors (soft tissue management, patient selection, surgical technique) dominate. The random distribution of revisions (red dots) across all positioning values supports this interpretation.

Figure 4. Scenario D: Inverted U-Shaped Relationship (Optimal Zone)

This pattern demonstrates that extremes in either direction cause poor outcomes, with an optimal zone in the middle. This could represent parameters like humeral version where both excessive anteversion and retroversion are problematic. The concentration of revisions (red dots) at both extremes supports the concept of an optimal middle zone.

Scatter plots such as these reveal (1) the percentage of "well-positioned" implants failed and (2) the percentage of "malpositioned" implants that function successfully and (3) whether it is likely that deviations caused failure, or whether failures have occurred for other reasons, such as instability from poor soft tissue balancing, poor bone quality, infection, or periprosthetic fracture.

Conclusion

The modes of shoulder arthroplasty failure and revision are well established.

Why do primary anatomic total shoulder arthroplasties fail today? A systematic review and meta-analysis  identified implant loosening (26.1%), particularly of the glenoid component, as the most common cause of contemporary aTSA failure, followed by rotator cuff insufficiency (17.3%), instability (10.4%), and infection (10.2%)

Revision of reverse total shoulder arthroplasty: a scoping review of indications for revision, and revision outcomes, complications, and rerevisions found the primary reasons for revision were dislocation or instability (30%), baseplate complications (25%), infection (23%),  acromial/scapular fractures and humeral component issues (10%).

 Notice that the leading causes of failure — loosening, instability, infection — are not primarily positioning problems. Precision technology addresses none of them.

The critical unanswered question is the dose-response relationship between positioning deviation and clinical outcome - four possible patterns are shown by the hypothetical examples above. 

Each surgeon needs to ask, "are the complications experienced by my patients likely to be addressed by component positioning between tight goal posts or are they more likely to be addressed by better patient selection, better component seating, better soft tissue balancing, better prophylaxis against infection, or different component selection?".

Keeping Cool

Dark Eyed Junco

Matsen Backyard

2020

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Here are some videos that are of shoulder interest
Shoulder arthritis - what you need to know (see this link).
How to x-ray the shoulder (see this link).
The ream and run procedure (see this link)
The total shoulder arthroplasty (see this link)
The cuff tear arthropathy arthroplasty (see this link).
The reverse total shoulder arthroplasty (see this link).
The smooth and move procedure for irreparable rotator cuff tears (see this link)

Shoulder rehabilitation exercises (see this link).