Short-term evaluation of humeral stress shielding following reverse shoulder arthroplasty using press-fit fixation compared with cemented fixation

Varus-valgus alignment of humeral short stem in reverse total shoulder arthroplasty: does it really matter?

BACKGROUND

The utilization of short humeral stems in reverse total shoulder arthroplasty has gained attention in recent times. However, concerns regarding the risk of misalignment during implant insertion are associated with their use.

METHODS

Eight fresh-frozen cadaveric shoulders were prepared for dissection and biomechanical testing. A bespoke humeral implant was fabricated to facilitate assessment of neutral, varus, and valgus alignments using a single stem, and 10° was established as the maximum permissible angle for misalignments. Shift in humerus position and changes in deltoid length attributable to misalignments relative to the neutral position were evaluated using a Microscribe 3DLx system. The impingement-free range of motion, encompassing abduction, adduction, internal rotation, and external rotation (ER), was gauged using a digital goniometer. The capacity for abduction was evaluated at maximal abduction angles under successive loading on the middle deltoid. A specialized traction system coupled with a force transducer was employed to measure anterior dislocation forces.

RESULTS

Relative to the neutral alignment, valgus alignment resulted in a more distal (10.5 ± 2.4 mm) and medial (8.3 ± 2.2 mm) translation of the humeral component, whereas the varus alignment resulted in the humerus shifting more superiorly (11.2 ± 1.3 mm) and laterally (9.9 ± 0.9 mm) at 0° abduction. The valgus alignment exhibited the highest abduction angle than neutral alignment (86.2°, P < .001). Conversely, the varus alignment demonstrated significantly higher adduction (18.4 ± 7.4°, P < .001), internal rotation (68.9 ± 15.0°, P = .014), and ER (45.2 ± 10.5°, P = .002) at 0° abduction compared to the neutral alignments. Anterior dislocation forces were considerably lower (23.8 N) in the varus group compared to the neutral group at 0°ER (P = .047). Additionally, abduction capability was markedly higher in varus alignment at low deltoid loads than the neutral alignment (5N, P = .009; 7.5 N, P = .007).

CONCLUSIONS

The varus position enhances rotational range of motion (ROM) but increases instability, while the valgus position does not significantly impact ROM or instability compared to the neutral position.

Do the humeral radiographic changes at 5-year follow-up affect the clinical outcomes of press-fit humeral stems in primary reverse shoulder arthroplasties?

INTRODUCTION

The purposes of this study were to analyze and compare the functional outcomes and radiological changes around the press-fit humeral components in two contemporary medialized reverse total shoulder arthroplasty (RTSA) systems at a minimum of 5-year follow-up.

MATERIALS AND METHODS

Between December 2003 and December 2015, 249 consecutive RTSAs were performed at our hospital. Of these, 68 primary uncemented RTSA met our inclusion criteria. The Constant-Murley score (CMS), the modified Constant score, a visual analog scale (VAS) and active shoulder range of motion (ROM) were measured pre- and postoperatively. Radiological assessment was performed by plain radiographs at a minimum of 5 years postoperatively.

RESULTS

At a mean follow-up of 80.2 months, there was no significant difference (p = .59) between the postoperative functional scores and range of motion of the two groups (Delta Xtend and Lima SMR). Radiological data of stress-shielding were observed in 38 patients (55.9%) being slightly more frequent in the Lima SMR group (21 patients) than in the Delta Xtend group (17 patients) (p = .62).

CONCLUSIONS

Our study shows that the good functional results are similar between the two uncemented RTSA systems used and that they do not depend on the presence of radiological changes (stress-shielding) in the humeral stem at a minimum 5-year follow-up.

Medium-term clinical and radiographic outcomes of a cementless prosthesis with a 140° neck-shaft angle in reverse total shoulder arthroplasty

BACKGROUND

The design of humeral implants has evolved from the initial Grammont design, notably regarding the neck-shaft angle (NSA) and through the use of cementless prostheses. Stress shielding was frequently reported with cementless implants, the 2 main risk factors being humeral stem misalignment and high filling ratios. Our hypothesis was that standard length cementless stems with an NSA of 140° would facilitate good alignment with moderate filling ratios, thereby limiting stress shielding and ensuring good clinical outcomes.

METHODS

A single-center retrospective study was conducted of patients who underwent reverse total shoulder arthroplasty between January 2015 and August 2017, with at least 2 years' follow-up. Clinical evaluations included range of motion measurements and Constant and subjective shoulder values scores. Frontal alignment was assessed in terms of the angle (α) between axes of the stem and of the humerus. Filling ratios were measured in the metaphysis of the humerus, in the diaphysis, and at the distal end of the stem and considered excessive above 0.7. Stress shielding was evidenced radiographically by the observation of medial cortical narrowing, medial metaphysis thinning, lateral metaphysis thinning or under-the-baseplate osteolysis.

RESULTS

Eighty-two shoulders were included and 70 had radiographic follow-up data available. The mean patient age was 78 years and 63/81 patients (78%) were female. The mean follow-up time was 39 ± 7 months. The mean α angle was 1.4° ± 0.9° and was less than 5° in all cases. The mean metaphyseal, diaphyseal, and distal filling ratios were 0.61 ± 0.06, 0.70 ± 0.08, and 0.64 ± 0.09, respectively. The mean Constant score improved from 28 ± 11 preoperatively to 64 ± 14 at last follow-up. The mean subjective shoulder values score at last follow-up was 81 ± 12. Seventy-nine percent of patients (55/70) had at least 1 form of stress-shielding related, which were not associated with clinical outcomes, apart from lateral metaphysis thinning, which was associated with lower active anterior elevation (mean, 106° ± 30° vs. 126° ± 28°; P = .01) and lower Constant scores (mean, 56 ± 17 vs. 65 ± 14; P = .06).

CONCLUSION

The use of cementless reverse shoulder prostheses with a NSA of 140° was associated with good clinical outcomes at 2 years' follow-up. The prosthesis stem was correctly aligned with the humeral axis and the filling ratios were <0.7 in all cases. Stress-shielding was common but, apart from lateral metaphysis thinning, this had no impact on clinical outcomes.

Porous versus solid shoulder implants in humeri of different bone densities: A finite element analysis

Porous metallic prosthesis components can now be manufactured using additive manufacturing techniques, and may prove beneficial for promoting bony ingrowth, for accommodating drug delivery systems, and for reducing stress shielding. Using finite element modeling techniques, 36 scenarios (three porous stems, three bone densities, and four held arm positions) were analysed to assess the viability of porous humeral stems for use in total shoulder arthroplasty, and their resulting mechanobiological impact on the surrounding humerus bone. All three porous stems were predicted to experience stresses below the yield strength of Ti6Al4V (880 MPa) and to be capable of withstanding more than 10 million cycles of each loading scenario before failure. There was an indication that within an 80 mm region of the proximal humerus, there would be a reduction in bone resorption as stem porosity increased. Overall, this study shows promise that these porous structures are mechanically viable for incorporation into permanent shoulder prostheses to combat orthopedic infections.

Stress shielding: short-term radiological results of the reverse shoulder arthroplasty with an anatomic proximal coated stem in proximal humeral fractures

PURPOSE

This study aims to determine the stress shielding and other radiological outcomes of patients who underwent an uncemented reverse shoulder arthroplasty (RSA) with an anatomic proximal coated stem for complex proximal humeral fractures (PHF) with 3 or 4 parts at 2 years postoperatively.

METHODS

37 shoulders underwent an uncemented RSA for PHF from November 2015 to February 2019 and were followed up for 2 years. A radiographic assessment of stress shielding, filling ratio, stem stability (radiolucent lines/subsidence/alignment), tuberosity healing and notch was performed.

RESULTS

The mean age at the time of surgery was 72 years (range, 61-85). Stress shielding was appreciated in 31 shoulders (83.8%). The most important characteristic of stress shielding is cortical resorption: Grade 3 resorption occurred in 3 shoulders (8.1%) and grade 4 in 23 (62.2%) as per the grading system defined by Inoue et al. (Inoue et al. in J Shoulder Elbow Surg 26:1984-1989, 2017). A high occurrence of bone resorption was observed in Gruen zones 2 (Lateral Stress shielding) and 7 (Medial Stress shielding). The mean distal filling ratio in patients without stress shielding was 78,48(SD 14,9), whereas in patients with stress shielding, it was slightly higher with a mean of 81,68% (SD 4,89). Tuberosity healing was found in 94.6% (35/37) of the shoulders. No patient had any radiolucent line. No notch was observed.

CONCLUSION

At short-term follow-up, a high rate of tuberosity healing was achieved (94.6%) even though stress shielding was found in 83.8% (31/37) of the shoulders. Bone resorption was most frequently observed externally at zone 2 (Lateral stress shielding) and internally at zone 7 (Medial stress shielding). A higher filling ratio was associated with an increased occurrence of stress shielding. The uncemented anatomic humeral component did not result in early loosening.

LEVEL OF EVIDENCE

IV; Case Series; Treatment study.

The effects of length and width of the stem on proximal humerus stress shielding in uncemented primary reverse total shoulder arthroplasty

INTRODUCTION

To preserve humeral bone during RTSA, stems have been made shorter and cement avoided whenever possible. However, with the increased use of uncemented RTSA, a phenomenon comparable to the stress shielding of the hip has been described for the proximal humerus. The aim of this study was to investigate the influence of stem length and width on proximal humeral bone resorption after primary uncemented RTSA.

MATERIALS AND METHODS

The prospective shoulder arthroplasty database of our institution was reviewed for all primary uncemented RTSAs from 2017 to 2020 in osteoarthritis and cuff tear arthropathy cases with > 2-year follow-up. We compared the clinical and the radiographic 2-year outcome of the short and standard length stems of the same prosthesis design. This allowed us to assess the effects of stem length and width with regard to stress shielding. Furthermore, we defined a cut-off value for the filling ratios to prevent stress shielding.

RESULTS

Fifty patients were included in the analysis, nineteen were in the short stem group (SHORT) and thirty-one in the standard stem group (STANDARD). After 2 years, SHORT showed a relative Constant Score of 91.8% and STANDARD of 98.3% (p = 0.256). Stress shielding was found in 4 patients (21%) in SHORT and in 16 patients (52%) in STANDARD (p = 0.03); it occurred more frequently in patients with higher humeral filling ratios (p < 0.05). The calculated cut-off to prevent stress shielding was 0.7 (± 0.03) for the metaphyseal and distal filling ratio.

CONCLUSION

While short and standard stems for RTSA have good results after 2 years, we found a significant negative effect of higher length and width of the stem with regard to stress shielding. Even though the clinical effects of stress shielding have to be assessed, short stems should be chosen with a filling ratio at the metaphyseal and distal position below 0.7.

LEVEL OF EVIDENCE (A RETROSPECTIVE CASE-CONTROL STUDY)

III.

Two-year minimum survivorship and radiographic analysis of a pressfit short humeral stem for total shoulder arthroplasty

Background

Newer generation humeral stem designs in total shoulder arthroplasty (TSA) are trending towards shorter lengths and uncemented fixation. The goal of this study is to report a 2-yr minimum clinical and radiographic outcomes of an uncemented short-stem press-fit humeral stem in anatomic total shoulder arthroplasty (ATSA) and reverse total shoulder arthroplasty (RTSA).

Methods

A retrospective multicenter database review was performed of all patients who received an uncemented short-length press-fit humeral stem (Equinoxe Preserve humeral stem, Exactech, Inc., Gainesville, FL, USA) in ATSA and RTSA with a minimum two-year follow-up. The primary outcome was the prevalence of humeral stems at risk of radiographic loosening. Secondary outcomes included evaluation of functional outcome scores and prevalence of revision TSA for humeral stem loosening. Two blinded observers performed radiographic analyses, which included humeral stem alignment, canal filling ratio, radiolucent lines, stress shielding (calcar and greater tuberosity), and changes in component position (subsidence and stem shift). At risk stems were defined by the presence of one or more of the following: humeral stem with shifting or subsidence, scalloping of the humeral cortex, or radiolucent lines measuring 2 mm or greater in 3 or more zones.

Results

287 patients (97 ATSA and 190 RTSA) were included in this study. The mean follow-up was 35.9 (±6.1) months. There were significant improvements for all functional outcome scores (P < .05), range of motion (P < .05), and visual analogue pain scale pain (P < .05). The prevalence of humeral stem at risk of radiographic loosening was 1% in the ATSA group (1/97) and 18.4% in the RTSA group (35/190). Calcar resorption was seen in 34% of ATSA and 19% of RTSA, with severe resorption in 12.4% of ATSA and only 3.2% of RTSA. Greater tuberosity resorption was present in 3.1% of ATSA and 7.9% of RTSA. The mean canal filling ratio was 50.2% (standard deviation 11.2%). Using logistic regression, a significant positive correlation between canal filling ratio and stress shielding (P < .01) was seen for both calcar and tuberosity stress shielding. The revision surgery rate was 0% in ATSA compared to 1.6% in RTSA.

Conclusion

This retrospective study demonstrates a low revision rate and low prevalence of humeral stems at risk of radiographic loosening at two years with a press-fit short-stem humeral design in ATSA. Physiologic subsidence of humeral stems can account for higher prevalence of humeral stems at radiographic risk of loosening in RTSA compared to ATSA.

Short-term radiographic analysis of a stemless humeral component for anatomic total shoulder arthroplasty

Background

Standard stemmed humeral implants have traditionally been utilized for total shoulder arthroplasty (TSA) with a recent trend to implant smaller stems including short and stemless humeral designs. However, the rate of stress shielding after stemless TSA has not been primarily studied. Therefore, the objective of this study is to report the short-term survivorship and radiographic analysis of a stemless humeral implant.

Methods

A retrospective cohort review of a prospectively collected, multicenter database for patients undergoing total shoulder arthroplasty with a stemless humeral design (Equinoxe Stemless; Exactech, Inc., Gainesville, FL, USA) with a minimum of 2 years clinical and radiographic follow-up was performed. The primary outcomes were to report the location and rate of stress shielding from a radiographic analysis of the humeral stem. Additionally, the revision rate of the humeral stem is reported. The secondary outcomes included ASES scores, visual analog scale (VAS) pain scores, and range of motion (ROM). Radiographs (anterior-posterior/Grashey and axillary) were reviewed blindly by two fellowship trained shoulder surgeons. Radiographic analysis included stress shielding (partial or complete cortical resorption) and subsidence or shift in component position.

Results

Fifty four patients were included in this study with an average follow-up of 27 months (range 24-32 months). The average age of this cohort was 65 years (range 57-73 years) with 23 patients (43%) being female. Stress shielding was observed in 4 patients (7%) with the medial calcar being the most common location of stress shielding. Three of the 4 patients (75%) had evidence of partial resorption while 1 patient (25%) had evidence of complete resorption. No humeral component shift or subsidence was observed. There were no revisions due to humeral component complications. There was 1 revision surgery for aseptic glenoid loosening. A significant improvement for all clinical outcome measures was seen including with respect to VAS pain, which improved from 6.2 to 1.8 (P < .05), ASES, which improved from 38.2 to 81.8 (P < .05), and ROM which forward flexion improved from 120 degrees to 153 degrees (P < .05) and external rotation improved from 29 degrees to 49 degrees (P < .05).

Discussion

This ongoing study demonstrates a low rate of stress shielding for a stemless design humeral implant at short-term follow-up without any revision surgery due to humeral component complications. Longer term radiographic and clinical analysis with this cohort will be needed to confirm these findings and theoretical benefits for future revision surgeries.

Single-Stage Revision Reverse Shoulder Arthroplasty: Preoperative Planning, Surgical Technique, and Mixed Reality Execution

Revision shoulder arthroplasty is increasing with the number of primary shoulder replacements rising globally. Complex primary and revisions of shoulder arthroplasties pose specific challenges for the surgeon, which must be addressed preoperatively and intraoperatively. This article aimed to present strategies for the management of revision of shoulder arthroplasties through a single-stage approach. Preoperatively, patient factors, such as age, comorbidities, and bone quality, should be considered. The use of planning software can aid in accurately evaluating implants in situ and predict bony anatomy that will remain after explantation during the revision surgery. The planning from such software can then be executed with the help of mixed reality technology to allow accurate implant placement. Single-stage revision is performed in two steps (debridement as first step, implantation and reconstruction as the second step), guided by the following principles: adequate debridement while preserving key soft tissue attachments (i.e., rotator cuff, pectoralis major, latissimus dorsi, deltoid), restoration of glenoid joint line using bone grafting, restoration of humeral length, reconstruction and/or reattachment of soft tissues, and strict compliance with the postoperative antibiotic regimen. Preliminary results of single-stage revision shoulder arthroplasty show improvement in patient outcomes (mean 1 year), successful treatment of infection for those diagnosed with periprosthetic joint infection, and improved cost-benefit parameters for the healthcare system.

Cemented vs. uncemented reverse total shoulder arthroplasty for the primary treatment of proximal humerus fractures in the elderly-a retrospective case-control study

BACKGROUND

Uncemented reverse total shoulder arthroplasty (RTSA) for the primary treatment of proximal humerus fractures (PHF) in elderly patients was introduced at our institution in 2017. Recent reports have raised concerns about increased rates of early bone resorption at the proximal humerus with uncemented fracture stems. The aim of this study was to find out whether there was any difference in functional or radiographic outcomes between cemented and uncemented RTSA for PHF.

METHODS

Seventeen consecutive patients who underwent uncemented RTSA (group nC) in 2017 and 2018 were age and sex matched (propensity score matching 1:2) to 34 patients with cemented RTSA implanted between 2011 and 2016 (group C) for the primary treatment of PHF. These two groups were compared in terms of clinical and radiographic outcomes at 2 years after the index surgery.

RESULTS

The mean bone quality was low in both groups: in group nC the deltoid tuberosity index (DTI) was 1.43 (1.22-1.72) and in group C 1.42 (1.22-1.67). At the final 2 year follow-up, the relative CS was 98.3% (71-118) in group nC and 97.9% (36-125) in group C (p = 0.927); the absolute CS was 70.2 (49-89) in group nC and 68.0 (30-94) in group C (p = 0.509). Lucent lines at the humeral site were seen in 8 cases (47%) in group nC and in 13 cases (38%) in group C (p = 0.056). Compared to 3% in group C, all patients in group nC showed at least grade 1 and 65% showed grade 3 bone resorption at the proximal humerus (p < 0.001).

CONCLUSION

Compared to cemented RTSA bone resorption at the proximal humerus was significantly more frequent in patients with uncemented RTSA for PHF. So far, this is rather a radiographic than a clinical finding, because both groups showed very satisfying functional outcomes and low revision rates at the 2 year follow-up.

LEVEL OF EVIDENCE III

A retrospective case-control study.

Outcomes and complications of primary reverse shoulder arthroplasty with minimum of 2 years' follow-up: a systematic review and meta-analysis

BACKGROUND

Primary reverse shoulder arthroplasty (rTSA) is an effective treatment option for reducing pain and improving function for patients with rotator cuff tear arthropathy, irreparable rotator cuff tears, glenoid deformity, and other challenging clinical scenarios, including fracture sequelae and revision shoulder arthroplasty. There has been a wide range of reported outcomes and postoperative complication rates reported in the literature. The purpose of this systematic review and meta-analysis is to provide an updated review of the clinical outcomes and complication rates following primary rTSA.

METHODS

A systematic review and meta-analysis was performed to evaluate outcomes and complications following primary rTSA according to the Preferred Reporting Items for Systematic reviews and Meta-Analyses (PRISMA) guidelines. Demographics, range of motion, patient-reported outcome measures (American Shoulder and Elbow Surgeons Standardized Shoulder Assessment Form [ASES] and Constant scores), number of complications, and revisions were extracted, recorded, and analyzed from the included articles.

RESULTS

Of the 1415 studies screened, 52 studies met the inclusion criteria comprising a total of 5824 shoulders. The mean age at the time of surgery was 72 years (range: 34-93), and the mean follow-up was 3.9 years (range: 2-16). Patients demonstrated a mean improvement of 56° in active flexion, 50° in active abduction, and 14° in active external rotation. Regarding functional outcome scores, rTSA patients demonstrated a mean clinically significant improvement of 37 in Constant score (minimal clinically important difference [MCID] = 5.7) and ASES score (42.0; MCID = 13.6). The overall complication rate for rTSA was 9.4% and revision rate of 2.6%. Complications were further subdivided into major medical complications (0.07%), shoulder- or surgical-related complications (5.3%), and infections (1.2%). The most frequently reported shoulder- or surgical-related complications were scapular notching (14.4%), periprosthetic fracture (0.8%), glenoid loosening (0.7%), and prosthetic dislocation (0.7%).

DISCUSSION

Primary rTSA is a safe and reliable procedure with low complication, revision, infection, and scapular notching rates. Additionally, patients demonstrated clinically significant improvements in both range of motion and clinical outcome scores.

Comparative study of 145° onlay curved stem versus 155° inlay straight stem reverse shoulder arthroplasty: clinical and radiographic results with a minimum 2-year follow-up

BACKGROUND

Lateralized onlay reverse shoulder arthroplasty (RSA) is designed to ensure better clinical functional recovery and lower rate of complications compared with Grammont medialized inlay RSA. The purpose of the present study was to compare the clinical and radiographic outcomes between these 2 different designs.

METHODS

Eighty-five consecutive patients who underwent RSA were retrospectively analyzed. Nine patients were lost to follow-up, 34 received a curved onlay with a 145° neck-shaft angle (Ascend Flex group), and 42 received a long straight inlay stem with a 155° neck-shaft angle (Delta Xtend group). Patients were reviewed at an average follow-up of 46.8 ± 13.2 months (Ascend Flex group) and 36 ± 10.8 months (Delta Xtend group). Clinical outcome measures included active range of motion, strength, visual analog scale, Constant-Murley score, and the American Shoulder and Elbow Surgeons score. Radiographic evaluation at the final follow-up was performed to assess scapular notching, stress shielding, acromial or scapular fractures, heterotopic ossification, and radiolucent lines or implant loosening.

RESULTS

No differences emerged between the 2 groups in terms of visual analog scale, American Shoulder and Elbow Surgeons and Constant-Murley scores, pain, function, strength, mobility, active forward elevation, active internal rotation, active external rotation at 0° and 90° of abduction, abduction, forward elevation, and external rotation strength (P = n.s.). Statistically superior active abduction was observed in the Delta Xtend group (P = .0017). Scapular notching was observed in 12 shoulders (35.2%) in the Ascend Flex group (a grade 1) and in 10 shoulders (23.8%) in the Delta Xtend group (P = n.s.). No differences emerged between the 2 groups in terms of humeral or glenoid radiolucency (P = n.s.). Higher rate of humeral stress shielding rate was observed in the Ascend flex cohort (P = n.s.).

CONCLUSIONS

No statistically significant difference emerged between the 145° onlay curved stem vs. the 155° inlay straight stem according to most of the evaluated parameters. Statistically superior active abduction was observed in the 155° group although it did not affect patients' satisfaction.

The Definition of Periprosthetic Osteolysis in Shoulder Arthroplasty: A Systematic Review of Grading Schemes and Criteria

BACKGROUND

Periprosthetic osteolysis is a known complication after shoulder arthroplasty that may lead to implant loosening and revision surgery. To date, there is no consensus in the shoulder arthroplasty literature regarding the definition of osteolysis or the grading criteria, thus making it difficult to quantify and compare outcomes involving this complication. The purpose of this study was to perform a systematic review of the literature to assess how periprosthetic osteolysis in shoulder arthroplasty is defined and evaluated radiographically.

METHODS

A systematic review of MEDLINE, Scopus, Cochrane, and CINAHL was performed in August 2021 for studies that provided a definition and/or grading criteria for osteolysis in shoulder arthroplasty. Only studies with a minimum of 2 years of radiographic follow-up were included.

RESULTS

Thirty-four articles met the inclusion criteria. After consolidating studies by the same primary author that included the same grading criteria, 29 studies were examined for their definition and grading criteria for osteolysis. Of these, 19 (65.5%) evaluated osteolysis surrounding the glenoid and 18 (62.1%) evaluated osteolysis surrounding the humerus. There was considerable heterogeneity in the systems used to grade periprosthetic osteolysis surrounding the glenoid, whereas humeral periprosthetic osteolysis was often categorized via visualization into binary or categorical groups (e.g., presence versus absence; mild, moderate, or severe; partial versus complete). Four studies (13.8%) provided novel measurements for assessing either glenoid or humeral osteolysis.

CONCLUSIONS

Considerable heterogeneity exists in the assessment and grading of periprosthetic osteolysis in shoulder arthroplasty. The most common grading systems were binary and used qualitative visual interpretation, making them relatively subjective and prone to bias. Quantitative measurements of osteolysis were infrequently utilized. A standardized method of assessing osteolysis would be of value to facilitate communication and research efforts.

Humeral stem with low filling ratio reduces stress shielding in primary reverse shoulder arthroplasty

PURPOSE

Some patients show severe humeral bone stress shielding even one year after press-fit humeral stem, which can be a risk factor for implant durability. This study compared humeral stress shielding and clinical outcomes between high and low filling ratio (HFR and LFR) stems in primary reverse shoulder arthroplasty (RSA).

METHODS

From 2015 to 2020, 104 patients who underwent RSA with a non-cemented standard-length humeral stem were examined. The humeral stems included large press-fit stems (HFR group, 53 patients) or small non-press-fit stems with autogenous cancellous bone grafting (LFR group, 51 patients). The radiologic and clinical outcomes were compared between the groups one year post-operatively.

RESULTS

One patient in the LFR group with early infectious dislocation was excluded from the 1-one year evaluation. No stress shielding was observed in 27/50 (54.0%) and 5/53 (9.4%) of patients in the LFR and HFR groups, while 3/50 (6%) and 19/53 (35.8%) patients showed high-stress shielding, respectively. However, the stem alignment change, subsidence, complications and evidence of loosening did not differ between the groups. The final range-of-motion and functional scores were significantly poorer in the LFR group than those in the HFR group, although the difference was minimal.

CONCLUSION

Even at one year follow-up, patients receiving LFR stems with autogenous bone grafting had significantly less humeral stress shielding compared to patients with HFR stem with press-fit in primary RSA, without compromising stem stability.

Reverse shoulder arthroplasty for proximal humeral fracture in the elderly. Cemented or uncemented stem?

OBJECTIVE

The purposes of this study were to compare functional outcomes, radiographic stem changes and complication rate in patients with proximal humeral fractures operated with cemented or uncemented RSA.

METHODS

Retrospective review of 68 primary RSAs in PHF, 45 cemented/23 uncemented. Functional outcomes were evaluated according to constant, ASES scales and the range of motion (ROM). Radiographic assessment was performed at a minimum of two years post-operatively.

RESULTS

The mean follow-up cemented/uncemented was 37.8/26.5 months (p = .04) and the mean age 78/80 years old (p = .09). The functional outcome and range of movement were equivalent in the two groups except for the forward flexion that was significantly higher in the cemented group (p = .03). Stress shielding was seen in 30.4% of uncemented group and none in the cemented. Anatomic tuberosity healing was significantly higher with uncemented components compared with cemented components (64% vs 91%, p = .02). Cemented stems had radiolucent lines with a width of 2 mm or more in three or more Gruen zones in 9% vs 0% in the uncemented group and an evident change in the stem position was present in 4% vs 0% in the non-cemented group.

CONCLUSION

At mid-term follow-up, no differences in functional outcomes were detected depending on the stem fixation technique. Cemented stems, however, have a complication rate (including stem loosening) significantly higher than press-fit stems.

Clinical outcomes of reverse total shoulder arthroplasty for elective indications versus acute 3- and 4-part proximal humeral fractures: a systematic review and meta-analysis

BACKGROUND

Reverse total shoulder arthroplasty (RTSA) has continued to increase in clinical utility and popularity as an effective treatment for cuff tear arthropathy (CTA), irreparable rotator cuff tears (RCTs), osteoarthritis, and acute 3- and 4-part proximal humeral fractures. Performing RTSA for acute proximal humeral fractures presents the unique challenges of tuberosity management, bone loss, and instability compared with elective indications such as CTA or irreparable RCTs. The purpose of this study was to compare the clinical outcomes, active range of motion (ROM), radiographic outcomes, and complications between patients undergoing elective RTSA (RTSA-E) and those undergoing RTSA for fracture (RTSA-F).

METHODS

A systematic review of the literature was conducted in accordance with Preferred Reporting Items for Systematic Reviews and Meta-analyses (PRISMA) guidelines. We queried 3 electronic databases (Embase, Cochrane, and PubMed) using the search term "reverse" AND "shoulder" AND "arthroplasty." Studies investigating the clinical outcomes of RTSA for traumatic and/or elective indications were included. Studies were excluded if they included RTSA performed for fracture sequelae, inflammatory arthritis, post-traumatic osteoarthritis, or avascular necrosis. Data collected included patient demographic characteristics, subjective outcome measurements, ROM, and complications. The pooled means and proportions along with their 95% confidence intervals were generated by a random-effects model that incorporated the between-study variations in weighting.

RESULTS

A total of 134 studies (11,651 shoulders) investigating the clinical outcomes of RTSA-E patients and 66 studies (3117 shoulders) investigating RTSA-F patients were included in this systematic review. Analysis of patient-reported outcomes demonstrated that RTSA-F patients experienced significantly lower Constant scores than RTSA-E patients; however, relative Constant scores, Simple Shoulder Test scores, Disabilities of the Arm, Shoulder and Hand scores, American Shoulder and Elbow Surgeons scores, and visual analog scale pain scores were similar. RTSA-F patients also had significantly lower forward elevation, abduction, and external rotation. RTSA-F patients experienced tuberosity complications at a significantly higher rate than RTSA-E patients (25.9% vs. 4.1%). There was no significant difference between the 2 groups in terms of other complications such as heterotopic ossification, radiographic loosening, revision, nerve injury, postoperative stiffness, infection, dislocation, and component loosening.

DISCUSSION

RTSA performed for acute 3- and 4-part proximal humeral fractures yields overall worse clinical outcomes and active ROM compared with RTSA performed for elective indications including CTA, massive irreparable RCTs, and osteoarthritis with deformity. Tuberosity healing may be a major contributing factor to the difference in clinical outcomes. In the setting of RTSA-F, patient and surgeon expectations may need to be tempered and appropriate measures undertaken to optimize tuberosity healing.

Specific Design of a Press Fit Humeral Stem Provides low Stress Shielding in Reverse Shoulder Arthroplasty at minimum 5 Years FU

Press fit fixation is becoming more popular in RSA to preserve, in theory, bone capital. Several studies report that bone resorption can be very high around humeral stems depending on their size, shape and mode of fixation. The aim of the current study is to mid-term follow-up clinical and radiological result of a press fit ovoid regular stem RSA in non acute trauma cases.

Radiological changes, infections and neurological complications after reverse shoulder arthroplasty related to different design types and their rates: Part II

Early reported complication rates with the Grammont-type reverse shoulder arthroplasty (RSA) were very high, up to 24%.A 'problem' is defined as an intraoperative or postoperative event that is not likely to affect the patient's final outcome, such as intraoperative cement extravasation and radiographic changes. A 'complication' is defined as an intraoperative or postoperative event that is likely to affect the patient's final outcome, including infection, neurologic injury and intrathoracic central glenoid screw placement.Radiographic changes around the glenoid or humeral components of the RSA are very frequently observed and described in the literature.High complication rates related to the Grammont RSA design led to development of non-Grammont designs which led to a dramatic fall in the majority of complications.The percentage of radiological changes after RSA is not negligible and remains unsolved, despite a decrease in its occurrence in the last decade. However, such changes should be now considered as simple problems because they rarely have a negative influence on the patient's final outcome, and their prevalence has dramatically decreased.With further changes in indications and designs for RSA, it is crucial to accurately track the rates and types of complications to justify its new designs and increased indications. Cite this article: EFORT Open Rev 2021;6:1109-1121. DOI: 10.1302/2058-5241.6.210040.

Periprosthetic Stress Shielding of the Humerus after Reconstruction with Modular Shoulder Megaprostheses in Patients with Sarcoma

(1) Background: Modular megaprosthetic reconstruction using a proximal humerus replacement has emerged as a commonly chosen approach after bone tumor resection. However, the long-term risk for revision surgery is relatively high. One factor that might be associated with mechanical failures is periprosthetic osteolysis around the stem, also known as stress shielding. The frequency, potential risk factors, and the effect on implant survival are unknown. (2) Methods: A retrospective single-center study of 65 patients with sarcoma who underwent resection of the proximal humerus and subsequent reconstruction with a modular endoprosthesis. Stress shielding was defined as the development of bone resorption around the prosthesis stem beginning at the bone/prosthesis interface. The extent of stress shielding was measured with a new method quantifying bone resorption in relation to the intramedullary stem length. All patients had a minimum follow-up of 12 months with conventional radiographs available and the median follow-up amounted to 36 months. (3) Results: Stress shielding was observed in 92% of patients (60/65). The median longitudinal extent of stress shielding amounted to 14% at last follow-up. Fifteen percent (10/65) showed bone resorption of greater than 50%. The median time to the first radiographic signs of stress shielding was 6 months (IQR 3–9). Patients who underwent chemotherapy (43/65) showed a greater extent of stress shielding compared to those without chemotherapy. Three percent (2/65) of patients were revised for aseptic loosening, and one patient had a periprosthetic fracture (1/65, 1.5%). All these cases had >20% extent of stress shielding (23–57%). (4) Conclusions: Stress shielding of the proximal humerus after shoulder reconstruction with modular megaprosthesis is common. It occurs within the first year of follow-up and might be self-limiting in many patients; however, about one third of patients shows progression beyond the first year. Still, mechanical complications were rare, but stress shielding might be clinically relevant in individual cases. The extent of stress shielding was increased in patients who underwent perioperative chemotherapy. Stress shielding can be quantified with an easy method using the stem length as a reference.

Humeral osteolysis after reverse shoulder arthroplasty using cemented or cementless stems comparative retrospective study with a mean follow-up of 9 years

INTRODUCTION

The cause of proximal humeral osteolysis after reverse shoulder arthroplasty (RSA) remains controversial. The primary objective of our study was to compare the radiographic outcomes of Grammont-type RSA when a cemented stem is used versus when a cementless stem is used. The secondary objective was to identify the cause of these radiographic changes, especially for the cementless stems.

HYPOTHESIS

More proximal humerus bone loss occurs when a cementless humeral stem is used.

METHODS

With a minimum follow-up of 5 years, two paired cohorts were compared retrospectively: 70 RSA with cemented stem and 70 RSA with cementless stem. Using the radiographs made at the final follow-up visit, we looked for tuberosity resorption, signs of stress shielding, the presence of periprosthetic radiolucent lines and scapular notching.

RESULTS

At a mean follow-up of 9 years (5.0-20.6), the RSA revision rate was 1.8% in the cemented group and 3.6% in the cementless group (p=1). Tuberosity resorption was twice as common in the cementless group: 59% versus 30% (p<0.001). Signs of stress shielding such as osteopenia were only present in the cementless group. In both groups, tuberosity resorption was often associated with scapular notching. In the shoulders with tuberosity resorption, stage≥3 scapular notching was more common in the cementless group (p=0.001).

DISCUSSION

For the cementless stems, proximal humeral osteolysis can in part be attributed to stress shielding. The relationship between notching and tuberosity resorption in the two groups also suggests a secondary biological cause.

LEVEL OF EVIDENCE

III; Comparative retrospective study.

Treating cuff tear arthropathy by reverse total shoulder arthroplasty: do the inclination of the humeral component and the lateral offset of the glenosphere influence the clinical and the radiological outcome?

PURPOSE

Reverse total shoulder arthroplasty is widely used for the treatment of cuff tear arthropathy. Standard implants consist of a humeral component with an inclination angle of 155° and a glenosphere without lateral offset. Recently, lower inclination angles of the humeral component as well as lateralized glenospheres are implanted to provide better rotation of the arm and to decrease the rate of scapular notching. This study investigates the clinical and radiological results of a standard reverse total shoulder in comparison with an implant with an inclination angle of 135° in combination with a 4 mm lateralized glenosphere in context of cuff tear arthropathy.

MATERIAL AND METHODS

For this retrospective comparative analysis 42 patients treated by reverse total shoulder arthroplasty for cuff tear arthropathy were included. Twenty-one patients (m = 11, f = 10; mean age 76 years; mean follow-up 42 months) were treated with a standard 155° humeral component and a standard glenosphere with caudal eccentricity (group A), while twenty-one patients (m = 5, f = 16; mean age 72 years; mean follow-up 34 months) were treated with a 135° humeral component and 4 mm lateral offset of the glenosphere (group B). At follow-up patients of both groups were assessed with plain X-rays (a.p. and axial view), Constant Score, adjusted Constant Score, the subjective shoulder value and the range of motion.

RESULTS

The clinical results were similar in both groups concerning the Constant Score (group A = 56.3 vs. group B = 56.1; p = 0.733), the adjusted CS (group A = 70.4% vs. group B = 68.3%; p = 0.589) and the SSV (group A = 72.0% vs. group B = 75.2%; p = 0.947). The range of motion of the operated shoulders did not differ significantly between group A and group B: Abduction = 98° versus 97.9°, p = 0.655; external rotation with the arm at side = 17.9° versus 18.7°, p = 0.703; external rotation with the arm positioned in 90° of abduction = 22.3° versus 24.7°, p = 0.524; forward flexion = 116.1° versus 116.7°, p = 0.760. The rate of scapular notching was higher (p = 0.013) in group A (overall: 66%, grade 1: 29%, grade 2: 29%, grade 3: 10%, grade 4: 0%) in comparison to group B (overall: 33%, grade 1: 33%, grade 2: 0%, grade 3: 0%, grade 4: 0%). Radiolucency around the humeral component was detected in two patients of group B. Stress shielding at the proximal humerus was observed in six patients of Group A (29%; cortical thinning and osteopenia in zone M1 and L1) and two patients of group B (10%; cortical thinning and osteopenia in zone M1 and L1). Calcifications of the triceps origin were observed in both groups (group A = 48% vs. group B = 38%).

CONCLUSION

Theoretically, a lower inclination angle of the humeral component and an increased lateral offset of the glenosphere lead to improved impingement-free range of motion and a decreased rate of scapular notching, when compared to a standard reverse total shoulder implant. This study compared two different designs of numerous options concerning the humeral component and the glenosphere. In comparison to a standard-fashioned implant with a humeral inclination of 155° and a standard glenosphere, implants with a humeral inclination angle of 135° and a 4 mm lateralized glenosphere lead to comparable clinical results and rotatory function, while the rate of scapular notching is decreased by almost 50%. While the different implant designs did not affect the clinical outcome, our results indicate that a combination of a lower inclination angle of the humeral component and lateralized glenosphere should be favored to reduce scapular notching.

LEVEL OF EVIDENCE

Level III, retrospective comparative study.

Primary reverse shoulder replacement with a short stem: A systematic literature review

Background

Total shoulder arthroplasty implant designs have continued to evolve over the years. One recent change has been the shortening of the humeral component to preserve bone stock and to facilitate revision surgery. Despite promising clinical results, radiographic bone adaptions occur frequently in short-stem total shoulder arthroplasty, and limited data exist on short-stem reverse shoulder arthroplasty (RSA). The purpose of this systematic review was to provide an overview about the functional and radiographic outcomes after an uncemented short-stem RSA, as well as identify areas of clinical importance that are underreported in the current literature.

Methods

A systematic review of the literature was performed in accordance with the PRISMA guidelines using PubMed, Cochrane Central Register of Controlled Trials, and EMBASE. Clinical outcome studies reporting on short-stem RSA outcomes with evidence level I-IV were included. Demographics, clinical and radiological outcomes, as well as complications and revision data were systematically analyzed and described.

Results

Ten studies, published between 2014 and 2019, reporting on 555 shoulders with a mean follow-up of 32 months (range, 20-99.6 months) met the inclusion criteria. For all studies cuff tear arthropathy was the main indication for RSA (36%), followed by primary osteoarthritis (20%). Clinical outcome was reported in nine of ten studies, with range of motion improving in all studies. Six of the seven studies that used the Constant score (CS) demonstrated significant improvement (27.9 points to 69.3 points in weighted means). All studies reported on radiographic changes and bone adaptions. Among these, scapular notching was the most commonly observed (60 out of 327 cases, 18%) but without any described implication on clinical outcomes. No stem loosening was recorded at any final follow-up. A total of 63 complications (12.9%) were reported, with scapula fractures being the most commonly reported complication. Revision surgery was necessary in 24 cases (4.9%).

Conclusion

Good clinical results, comparable with long-stem RSAs, are reported at short-term follow-up for short-stem RSAs. Humeral bone adaptions occur frequently but aseptic stem loosening is not a matter of concern at short-term follow-up. An area of clinical importance that is under-reported is the relation between filling ratio and stem alignment in short-stem RSA.