Stemless anatomic shoulder arthroplasty - humeral loosening?

The 2023 Australian Orthopaedic Association's National Joint Replacement Registry (a link to the full 2023 report can be found here) reports that in Australia total stemless anatomic shoulder arthroplasties were performed more frequently than total stemmed anatomic shoulder replacements. Excluding revisions for infection, the 10 year revision rate was 3.7% for stemless anatomic total shoulders in comparison to 11.2% for those with stemmed humeral components. The overall seven year revision rate for total stemless anatomic revision was lower for males (3.9%) than females (5.2%), but was not influenced by other prosthetic factors or age. The percentage of these revisions performed for humeral component loosening is not provided. 

So, do we know whether or how often stemless humeral components in anatomic total shoulders loosen?

A PubMed search for humeral component loosening in anatomic stemless shoulder arthroplasty revealed the following reports

2015 Midterm results of stemless shoulder arthroplasty: a prospective study. None of the stemless implants were revised for loosening.

2016 Clinical and Radiographic Outcomes of the Simpliciti Canal-Sparing Shoulder Arthroplasty System: A Prospective Two-Year Multicenter Study There was no evidence of migration, subsidence, osteolysis, or loosening of the humeral components.

2016 Anatomic stemless shoulder arthroplasty and related outcomes: a systematic review. One case of asymptomatic radiographic loosening,

2021 Long-term survival and failure analysis of anatomical stemmed and stemless shoulder arthroplasties. Radiological evaluation showed no loosening of the humeral implants.

2021 Survival of stemless humeral head replacement in anatomic shoulder arthroplasty: a prospective study Clinically and radiologically, the authors observed no loosening of the stemless humeral head component.

2022 Mid-term results of Eclipse total shoulder arthroplasty No humeral components were loose.

2022 Sex-related differences in stemless total shoulder arthroplasty No humeral components were loose.

2023 Midterm results of stemless impaction shoulder arthroplasty for primary osteoarthritis: a prospective, multicenter study. There were no cases of humeral loosening.

2022 Stemless Hemiarthroplasty of the Shoulder Using the SMR(R) System: Summary of Six-Year Experience and Surgical Technique No cases of failure or loosening of the humeral implant.

2022 Early fixation of the humeral component in stemless total shoulder arthroplasty : a radiostereometric and clinical study with 24-month follow-up 20 out of 24 prostheses stabilized within the first 12 months postoperatively. Four prostheses showed continuous migration between 12 and 24 months postoperatively. There were no revisions for loosening.

2022 Short-term results of a new anatomic stemless shoulder arthroplasty - A prospective multicentre study Postoperative radiographs showed no continuous radiolucent lines, subsidence, aseptic loosening or progressive radiolucency.

2023 Short-term radiographic analysis of a stemless humeral component for anatomic total shoulder arthroplasty No humeral component shift or subsidence was observed

2023 Medium-term results of stemless, short, and conventional stem humeral components in anatomic total shoulder arthroplasty: a New Zealand Joint Registry study No patients having stemless arthroplasty were revised for humeral component loosening.

These minimal reported values for loosening of the anatomic stemless humeral component may be due to a combination of several factors:

(1) lack of sufficiently long-term followup - time will tell

(2) surgeons' decision to avoid stemless components in patients suspected of having insufficient bone quality based on preoperative assessment

Simple preoperative radiographic and computed tomography measurements predict adequate bone quality for stemless total shoulder arthroplasty a deltoid tuberosity index of 1.41 on plain films and proximal humeral Hounsfield value of 14.1 units on CT had good sensitivity and specificity for adequate stemless fixation.

Preoperative metaphyseal cancellous bone density is associated with intraoperative conversion to stemmed total shoulder arthroplasty A threshold of 20 Hounsfield can be used to predict which patients are more likely to receive stemmed rather than stemless components.

Preoperative 3D Computed Tomography Bone Density Measures Provide Objective Bone Quality Classifications for Stemless Anatomic Total Shoulder Arthroplasty Preoperative CT imaging allows accurate evaluation of the bone densities in the proximal humerus. Three-dimensional regions of interest, rescaling using patient-specific calibration, and a machine learning model resulted in good-to-excellent prediction for objective bone quality classification. 

(3) surgeon decision to avoid stemless component in patients with soft bone as determined by intraoperative assessment

Simple preoperative radiographic and computed tomography measurements predict adequate bone quality for stemless total shoulder arthroplasty

"If bone quality was deemed adequate on inspection, the surgeon would use his thumb to compress the cut surface of the bone. Bone that was compressed with minimal force was deemed insufficient for stemless component fixation, and therefore placement of a short metaphyseal-fitting stem was performed. Once the stemless trial was implanted, rotational stability was assessed by applying manual torque to the implant via the implant inserter handle, and if the component rotated, the bone was deemed inadequate for stemless fixation. This was repeated for the final implant, and if the implant rotated within the bone under minimal torque, the stemless humeral component was revised to a short-stem meta- physeal-fitting humeral component intraoperatively. Sixty-one planned stemless TSAs were included, with 56 (91.8%) undergoing stemless TSA and 5 (8.2%) undergoing short, metaphyseal-fitting humeral stemmed TSA after intraoperative assessment determined that the bone quality was insufficient for stemless fixation."

Clinical and Radiographic Outcomes of the Simpliciti Canal-Sparing Shoulder Arthroplasty System: A Prospective Two-Year Multicenter Study

"Next the surgeon attempted to compress the neck cut surface with his/her thumb. Bone that was easily compressed with minimal force was also considered not sufficient for implantation. If the physician subjectively determined that the bone had sufficient strength to support the press fit of the nucleus, the humerus was pre- pared with the standardized surgical technique outlined in the protocol: a guide- pin was placed in the center of the cut surface of the humeral head, and sequential bone preparation was completed with cannulated instrumentation. With the three-finned blazer in place, the surgeon tested for stability. If the blazer rotated within the bone, the bone was considered inadequate for implantation of the canal-sparing device. If the bone was still considered acceptable, a metallic humeral cut protector was secured to the trial Simpliciti nucleus to prevent proximal humeral bone damage during glenoid exposure and preparation."

Preoperative metaphyseal cancellous bone density is associated with intraoperative conversion to stemmed total shoulder arthroplasty "The decision to convert to a stemmed humeral component was made intraoperatively based on a lack of stability of the trial stemless component. After the humeral cut was performed at the anatomic neck, a stemless anatomic humeral trial component was placed, followed by a head protector. The glenoid was prepared, and a final glenoid component was placed. When attention was turned back to the humerus, the head protector was removed. If the trial component was stable, then a final stemless component was inserted. If the trial component was grossly mobile, then the decision was made to convert to a stemmed humeral component."

Bone quality in total shoulder arthroplasty: a prospective study correlating computed tomography Hounsfield units with thumb test and fracture risk assessment tool score. "Surgeons are poor at identifying suboptimal bone quality at the anatomic neck of the proximal humerus based on intraoperative thumb test when referencing against CT Hounsfield Units and fracture risk scores."

 

Comment: With their short and mid-term follow up, the available publications do not indicate that loosening of stemless humeral components in anatomic total shoulder arthroplasty is substantial clinical problem. Appartently, surgeons are making good choices regarding when to use a stemless implant based on their preoperative and interoperative observations.

 

If, after completing the glenoid arthroplasty, the stemless humeral component is discovered to be unstable on trialing, the surgeon has several options:

    (1) autograft the insertion site with bone from the resected humeral head until the nucleus of the implant is stable; this technique is useful if a cyst is encountered during humeral bone preparation

    (2) increase the size of the nucleus to achieve a more secure fit in the available bone

    (3) convert from a stemless to a stemmed implant that is compatible with the glenoid component.

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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).

What if aseptic loosening is not aseptic?

Emperor's new clothes: Is particle disease really infected particle disease?

These authors point out that loosening remains the most significant (70%) long-term complication of total hip replacement and that inflammatory response to wear particles is thought to be its main trigger. The clinical presentation includes pain and osteolysis. The diagnosis of 'aseptic' is based on the absence of evidence of infection. But as the authors state, 'the absence of evidence is not evidence of absence'.

Recently, there have been increasing numbers of positive bacterial isolates and other evidence of bacterial presence reported among patients with clinically absent infection.  Such evidence can be missed for many reasons, including failure to submit multiple specimens for culture, failure to submit tissue specimens of sufficient size, failure to sonicate or vortex retrieved implants, reliance on cultures of joint fluid (that will not reveal sessile bacteria in a biofilm), failure to observe cultures for sufficiently long, failure to culture specimens on aerobic and anaerobic media, bacterial fastidiousness or dormancy, presence of prophylactic antibiotics, attribution of positive culture results to 'contamination',  use of complex and arbitrary definitions for 'infection', failure to use non-culture methods for bacterial identification and others.

These authors also point out that bacterial presence may alter the response to micro particles of cement, polyethylene, and bone as well as the ability of bone to maintain itself and integrate with a prosthesis.

Comment: In the shoulder world, we've learned that while some periprosthetic infections are obvious, it is common for revision surgeries for shoulders presenting as pain, stiffness or loosening to yield multiple positive cultures. 

We suggest that a meaningful way to present the culture results from a revision surgery is to indicate the number and sources of the specimens submitted for culture, the culture protocol, and the number of cultures that are positive for each organism. This approach frees us from trying to decide if the joint is 'aseptic' or not, or if it meets someones definition of 'infection'. With these data we may be able to resolve the role that positive cultures play in the presentation and management of failed arthroplasties.

We all remember the time when ulcers were 'caused by acid' before the importance of H. Pylori was recognized.

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Revision arthroplasties have a higher risk of failure.

Revision Total Knee Arthroplasty in the Young Patient: Is There Trouble on the Horizon?

These authors reviewed perioperative data for all total knee arthroplasty revisions performed from August 1999 to December 2009. They found a cohort of eighty-four patients who were fifty years of age or younger and a matched them to a cohort of eighty-four patients who were sixty to seventy years of age with similar dates of surgery, sex, and body mass indices (BMI).

The most common reason for the initial revision was aseptic loosening (27%; 95% confidence interval [CI] = 19% to 38%) in the younger cohort and infection (30%; 95% CI = 21% to 40%) in the older cohort. 

Of the twenty-five second revisions in younger patients, 32% (95% CI = 17% to 52%) were for infection, whereas 50% (95% CI = 32% to 68%) of the twenty-six second revisions in the older cohort were for infection. 

Infection and a BMI of >40 kg/m2 posed the greatest risk of failure of revision procedures, with risk ratios of 2.731 (p = 0.006) and 2.934 (p = 0.009), respectively.

This study showed a relatively poor six-year cumulative survivorship of revision total knee arthroplasties in the younger (71%) and older (66%) groups.

Comment: This series again emphasizes that arthritis in young individuals is a different matter than arthritis. It also emphasizes that revision arthroplasties have a greater risk of infection than primary arthroplasties and that revision of a previously infected arthroplasty has a higher risk of failure.

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Radiographic survival in total shoulder arthroplasty

Radiographic survival in total shoulder arthroplasty

The authors reviewed 302 total shoulders with a cemented, keeled glenoid component at an average of 8.6 years after surgery. Of these 151 had preoperative, early postoperative, and most recent radiographs at a minimum 4 years. Fifty-two of 151 glenoid components (34%) showed a shift in position or a complete lucent line ≥1.5 mm. Component survival free from radiographic failure was 99% at 5 years but only 67% at 10 years. Among multiple factors, only late subluxation superiorly was associated with increased risk for radiographic failure, presumably via the 'rocking horse' effect. Glenoid component survivals free from revision at 5 and 10 years for the 302 shoulders were 99% and 93%.

Almost one-third of the glenoid components had a shift in component position between early postoperative and final radiographs and approximately one-third of all components were felt to be
radiographically at risk for clinical failure. These "at risk" changes began to appear at five years after surgery or later.

These results are similar to those of Kasten (Mid-term survivorship analysis of a shoulder replacement with a keeled glenoid and a modern cementing technique. J Bone Joint Surg Br 2010;92:387-92.), Young (A multicenter study of the long-term results of using a flat-back polyethylene glenoid component in shoulder replacement for primary osteoarthritis. J Bone Joint Surg Br 2011;93:210-6.), and Walch (Results of a convex-back cemented keeled glenoid component in primary osteoarthritis: multicenter study with a follow-up greater than 5 years. J Shoulder Elbow Surg 2011;20:385-94.) ( Patterns of loosening of polyethylene keeled glenoid components after shoulder arthroplasty for primary osteoarthritis. J Bone Joint Surgery Am 2012;94:145-50.).

Clearly fixation of the glenoid component remains a concern. It is also of interest that the revision rate lags substantially behind the rate of radiographic loosening.

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Keeled glenoid for total shoulder in young adults

Mid- to long-term follow-up of total shoulder arthroplasty using a keeled glenoid in young adults with primary glenohumeral arthritis

This is a multicenter Level IV report of  52 total shoulders using a keeled glenoid to treat primary glenohumeral arthritis in patients aged 55 years or younger. Minimum follow-up of 5 years was available in 50 patients at a mean of 115.5 months postoperatively.

Survivorship of the glenoid component with revision surgery for glenoid loosening as the endpoint was 98%  at 5 years and 62.5% at 10 years. This is very interesting in that it indicates the annualized revision rate was 0.4% per year at year five and 3.8% per year at 10 years. This accelerating annualized loosening rate is especially important considering the mean patient age of 50.5 at the time of surgery.

Complications requiring revision surgery were observed in 17 patients - over one third. Glenoid loosening was the most frequent complication that required revision and was observed in 12 cases. Other complications included 2 subscapularis ruptures, 1 case of humeral component loosening, 1 oversized humeral head component, and 1 case of postoperative stiffness. A total of 21 revision surgeries were performed in these 17 patients. 

For these reasons we continue to explore the role of the ream and run procedure in the management of glenohumeral arthritis in young / active patients.

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Ten year outcomes of total shoulders

Results of Cemented Total Shoulder Replacement with a Minimum Follow-up of Ten Years

This is a report on the clinical and radiographic long-term outcomes of 39 shoulders treated with a third-generation cemented total shoulder replacement with a keeled all polyethylene flat backed cemented glenoid component (Aequalis Total Shoulder) and followed for at least ten years.

On average, the Constant Score increased from  27 points preoperatively to  61 points postoperatively. Shoulder flexion increased from 84° preoperatively to 133° postoperatively. Although no humeral components were loose, 36% of the glenoid components were radiographically loose at the time of follow-up. Kaplan-Meier survivorship of the glenoid component was 100% after thirteen years with revision as the end point, whereas survivorship with radiographic loosening as the end point was only 48% after thirteen years.  Cranial migration of the humerus was seen in 69% of the cases. The migration was mild in ten cases (37%), moderate in twelve (44%), and severe in five (19%).

This is an important study. The patterns of glenoid radiographic loosening included superior rocking horse loosening in cases of superior migration resulting from presumed rotator cuff failure

 and posterior rocking horse loosening.

There was no significant difference in the clinical outcomes between patients with and those without radiographic loosening of the glenoid component. There was a trend toward inferior outcomes in cases with severe migration.

It was of interest to see that the onset of radiographic loosening was often after the 10 year mark.

Only one of these patients has required revision surgery.

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Stability of the reverse total shoulder

Reverse total shoulder arthroplasty for the management of failed shoulder arthroplasty with proximal humeral bone loss: is allograft augmentation necessary?
The demands on the rotational stability of a reverse total shoulder are much greater than in an anatomic shoulder for at least three reasons. First the constrained nature of the reverse total shoulder articulation enables the glenoid to 'grab' the humeral component and exert torque on the prosthesis and its fixation into the humerus much more so than the unconstrained glenoid of an anatomic shoulder. Second, as this illustration from the Practical Evaluation and Management of the Shoulder shows, the center of rotation of the humeral head articular surface lies close to the center of the 'orthopaedic axis' i.e. the center of the meduallary canal; as a result the torque lever arm for rotation of the stem in the bone is small.

By contrast, in a reverse total shoulder, the glenoid applies rotational forces to the humeral cup, which is offset in relation to the orthopaedic axis, as diagrammed below.

Finally, as emphasized in this article, the absence of the tuberosities encountered in many cases of revision reverse total shoulder arthroplasty removes the normal stabilizing effect of the proximal humeral bone structure.

Against this background, the authors of this article ask whether allograft augmentation of the deficient proximal humerus encountered in the management of failed shoulder arthroplasty is of benefit. 

Among 251 patients enrolled in a study of reverse total shoulders,  significant humeral bone loss was found in 15 of 56 shoulders undergoing revision for failed arthroplasty without allograft. The average bone loss measured 38.4 mm (range, 26-72 mm). Allograft was avoid out of their concern for the cost of the allograft, increased risk of infection, increased operative time and complexity, graft resorption, and failure of allograft incorporation. A variety of prostheses were used, two were inserted using a press-fit technique and 13 were inserted with cement.

At a minimum of two years, radiographs demonstrated no humeral subsidence or loosening. One modular prosthetic stem fractured. Seven of 15 patients experienced complications: an intraoperative periprosthetic fracture, a case of recurrent instability, a fracture of the humeral stem,  1 deep venous 

thrombosis, 3 transient nerve palsies, and 1 patient experienced painful cerclage cables that required hardware removal.

Considering the complex nature of the shoulders being treated, these results are remarkable, especially with respect to the lack of humeral component loosening. It would be of interest to know more details of their methods for humeral component fixation.

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Glenoid reimplantation

Aseptic glenoid loosening or failure in total shoulder arthroplasty: revision with glenoid reimplantation

Glenoid component failure is a critical concern in total shoulder arthroplasty.  The major factors associated with glenoid component failure are reviewed here. This article is humbling because it represents the best efforts of highly qualified surgeons to revise cases of glenoid component failure - the most common serious complication of total shoulder arthroplasty.

The authors present a retrospective multicenter study of 42 total shoulders with symptomatic failed glenoids. 32 of the glenoids were metal backed and 10 were cemented polyethylene. The main cause of glenoid failure was component loosening in 19 cases (46%) and PE wear or dissociation in 23 (54%).

These failures were revised by reimplantation of an all–polyethylene cemented glenoid component. In this series complications were very frequent, including rotator cuff tears, subscapularis insufficiency, and prosthesis instability. At last follow-up, 7 patients (17%) had already been re-revised because of symptomatic recurrent glenoid loosening. The overall rate of recurrent glenoid loosening (re-revision
plus radiologic loosening) was 67%. Soft-tissue problems and prosthetic instability were significantly associated with recurrent loosening. Of the 10 associated bone grafts performed during the revision procedure, all were partially or totally lysed.

"Aseptic loosening" is term used to refer to loosening without positive cultures - it does not mean that bacteria were not associated with the loosening (only that their presence was not discovered). The most common organism in failed total shoulders is Propionibacterium and special means are necessary to avoid false negative cultures. Failure to manage deep infections may result in failure of replanted components. The authors report that "several intraperative samples of bone and tissue were obtained for
a systematic bacteriologic analysis." but the culture protocol were not detailed and results not presented.

We reviewed the problem of glenoid component failure in some detail in a recent JBJS article. The problems of polyethylene dissociation and wear in metal backed glenoids are well documented and have been discussed previously.

Bone grafting is often discussed as a solution to managing glenoid bone defects, but we have not seen good results reported with this approach. 

Filling the defect from a prior arthroplasty with cement exposes the glenoid to high levels of heat from the curing PMMA. In this figure from the article, "A" shows the index arthroplasty with a substantial cement volume. The revision in "B" used even more cement with subsequent failure.

Our approach to the failed glenoid component is to obtain cultures for Propionibacterium and hold them for at least 3 weeks, perform vigorous washout, continue antibiotics until culture results are finalized, remove the glenoid component and smooth the residual bone without grafting and implant a large diameter head prosthesis.

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Results of Cemented Total Shoulder Replacement with a Minimum Follow-up of Ten Years JBJS

Results of Cemented Total Shoulder Replacement with a Minimum Follow-up of Ten Years JBJS

While most journals require a minimum of two years of followup for reconstructive procedures, patients are interested in knowing longer term outcomes as well. This study is a Level IV followup of 39 out of 60 arthroplasties performed between June 1995 and October 2000 at a minimum of 10 years after a 'third generation' Tornier total shoulder arthroplasty with keeled flat-back glenoid components.  Glenoid anatomy was characterized by standardized anteroposterior and axillary radiographs of the shoulders obtained preoperatively and postoperatively. The morphology of the glenoid was recorded according to the classification described by Walch. The glenoid was type A2 in eleven cases, type B1 in sixteen, type B2 in ten, and type C in two. Loosening was defined as a radiolucent line score of over 12 (out of a maximum of 18), tilting over 5 degrees or subsidence. The authors observed that some shoulders showed loosening only on the AP view, some only on the axillary and some on both. Over a third of the glenoid components were radiographically loose at the time of followup. The mean radiolucent line score for the B2 and C glenoids was significantly greater than that for the A2 and B1 glenoids.

Superior migration of the humeral component was observed in over two thirds of the cases. None of the glenoid components required revision and the Constant scores showed significant improvement.

The high radiographic loosening rates observed in this study for keeled components are consistent with two previous long term result reports, here and here.

So again, glenoid component fixation, especially when the glenoid is biconcave or retroverted, remains a challenge. While shoulders with loose glenoids may remain functional, this loosening remains a concern that has not been resolved by later generation prostheses.

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Results of anatomic nonconstrained prosthesis in primary osteoarthritis with biconcave glenoid. JSES

Results of anatomic nonconstrained prosthesis in primary osteoarthritis with biconcave glenoid. JSES

This important paper points to the importance of posterior humeral subluxation and glenoid biconcavity in the conduct and outcome of shoulder arthroplasty. 

In this series of 92 such patients, the glenoid bone was reamed asymmetrically to achieve a retroversion between 0 and 10 degrees. Seven shoulders had glenoid bone grafting because the desired glenoid anatomy could not be sufficiently corrected by reaming alone. Nine shoulders had posterior capsular tightening and 18 patients wore a brace in neutral rotation for a month after surgery. Apparently no patients had rotator interval plications or the use of eccentric humeral heads.

Twenty percent of the glenoid components were found to be loose and the occurrence of loosening was associated with the amount of posterior bone loss and humeral subluxation. This is a good example of rocking horse loosening.

Fifteen of these shoulders (16%) required revision for glenoid loosening and/or posterior humeral head dislocation, stiffness or pain. Posterior bone grafts and posterior capsular tightening were usually not successful in preventing revision. 

Recognizing the difficulties of managing the not-uncommon situation of posterior humeral subluxation and glenoid biconcavity with a polyethylene socket, we have applied the ream and run with eccentric humeral head placement for active individuals with this situation. Although the authors suggest that a reverse total shoulder may be indicated in such situations, we are reluctant to use the reverse in patients wishing to be physically active. 

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