Short-term clinical outcome of an anatomic short-stem humeral component in total shoulder arthroplasty

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.

Anatomic glenohumeral arthroplasty: State of the art

Anatomical total shoulder arthroplasty in its modern form where it reproduces the normal shoulder has been utilized clinically for more than half a century. As the technology and the designs have changed to recreate the humeral and glenoid sides of the joint, the sophistication of design has resulted in the growing number of cases annually worldwide. This increase is due in part to the increasing number of indications that the prosthesis can treat with successful results. On the humeral side, there have been design changes to better reflect the proximal humeral anatomy, and humeral stems are increasingly placed safely without cement. Platform systems which allow conversion of a failed arthroplasty to a reverse configuration without stem extraction is another design change. Similarly, there has been increasing utilization of short stem and stemless humeral components. Extensive experience with shorter stem and stemless devices, however, has yet to demonstrate the purported advantages of these devices, as recent studies have demonstrated equivalent blood loss, fracture rates, operative times, and outcome scores. Easier revision with these shorter stems remains to be definitively established, with only one study comparing the ease of revision between stem types. On the glenoid side, hybrid cementless glenoids, inlay glenoids, cementless all-polyethylene glenoids, and augmented glenoids have all been investigated; however, the indications for these devices remain unclear. Lastly, innovative surgical approaches to implanting shoulder arthroplasty and the use of patient specific guides and computerized planning, while interesting concepts, still await validation before they are utilized on a widespread basis. While reverse shoulder arthroplasty has been increasingly used to reconstruct the arthritic shoulder, anatomic glenohumeral replacement maintains a significant role in the armamentarium of the shoulder surgeon.

Does humeral fixation technique affect long-term outcomes of total shoulder arthroplasty?

BACKGROUND

For anatomic total arthroscopic repair, cementless humeral fixation has recently gained popularity. However, few studies have compared clinical, radiographic, and patient-reported outcomes between cemented and press-fit humeral fixation, and none have performed follow-up for longer than 5 years. In this study, we compared long-term postoperative outcomes in patients receiving a cemented versus press-fit humeral stem anatomic arthroscopic repair.

METHODS

This study retrospectively analyzed 169 shoulders that required primary anatomic total shoulder arthroplasty (aTSA). Shoulders were stratified by humeral stem fixation technique: cementation or press-fit. Data were collected pre- and postoperatively. Primary outcome measures included range of motion, patient reported outcomes, and radiographic measures.

RESULTS

One hundred thirty-eight cemented humeral stems and 31 press-fit stems were included. Significant improvements in range of motion were seen in all aTSA patients with no significant differences between final cemented and press-fit stems (forward elevation: P=0.12, external rotation: P=0.60, and internal rotation: P=0.77). Patient reported outcome metrics also exhibited sustained improvement through final follow-up. However, at final follow-up, the press-fit stem cohort had significantly better overall scores when compared to the cemented cohort (visual analog score: P=0.04, American Shoulder and Elbow Surgeon Score: P<0.01, Simple Shoulder Test score: P=0.03). Humeral radiolucency was noted in two cemented implants and one press-fit implant. No significant differences in implant survival were observed between the two cohorts (P=0.75).

CONCLUSIONS

In this series, we found that irrespective of humeral fixation technique, aTSA significantly improves shoulder function. However, within this cohort, press-fit stems provided significantly better outcomes than cemented stems in terms of patient reported outcome scores. Level of evidence: III.

Validation of the distal filling ratio in uncemented convertible short-stem shoulder arthroplasty

INTRODUCTION

Radiographic stress shielding is a common finding in uncemented convertible short-stem shoulder arthroplasty (UCSSSA). The distal filling ratio (DFR) has been described as a predictor for the occurrence of stress shielding. A DFR > 70% was mentioned as a risk factor for the occurrence of stress shielding for some UCSSSA. However, measurements were only performed on conventional radiographs and no validation exists for 3D automated planning tools.

METHODS

DFR was manually measured on postoperative true ap radiographs of 76 shoulder arthroplasties using a standardized protocol and were compared to preoperative CT scans with an automated calculation of the DFR after virtual implantation of the stem.

RESULTS

The mean DFR measured on X-rays was 75.9% (SD = 8.7; 95% CI = 74-78) vs. 78.9% (SD = 9.1; 95% CI = 76.8-83) automatically measured on CT scans. This difference was significant (p < 0.001). In 7 out of 76 cases (9%) the difference between manual measurement on radiographs and computerized measurement on CT scans was > 10%.

CONCLUSION

Manual measurement of the DFR is underestimated on conventional radiographs compared to automated calculation on CT scans be a mean of 3%. Therefore, automated measurement of the DFR on CT scans seems to be beneficial, especially in cases with osteopenic cortices. Manual measurement of the DFR on conventional ap radiographs in cases without CT scans, however, is still a viable alternative.

LEVEL OF EVIDENCE

Level IV, retrospective study.

Complications and revisions in anatomic and reverse short stem shoulder arthroplasty

INTRODUCTION

One current trend in the field of shoulder arthroplasty is a design shift to shorter and metaphyseal fixed humeral stem components. The aim of this investigation is to analyze complications resulting in revision surgery after anatomic (ASA) and reverse (RSA) short stem arthroplasty. We hypothesize that complications are influenced by the type of prosthesis and indication for arthroplasty.

MATERIALS AND METHODS

A total of 279 short stem shoulder prostheses were implanted by the same surgeon (162 ASA; 117 RSA), and 223 of these prostheses were implanted as primary procedures; in 54 cases, arthroplasty was performed secondary to prior open surgery. Main indications were osteoarthritis (OA) (n = 134), cuff tear arthropathy (CTA) (n = 74) and posttraumatic deformities (PTr) (n = 59). Patients were evaluated at 6 weeks (follow-up 1; FU1), 2 years (FU2) and the time span of the last follow-up defined as FU3 with a minimum FU of 2 years. Complications were categorized into early complications (within FU1), intermediate complications (within FU2) and late complications (> 2 years; FU3).

RESULTS

In total, 268 prostheses (96.1%) were available for FU1; 267 prostheses (95.7%) were available for FU2 and 218 prostheses (77.8%) were available for FU3. The average time for FU3 was 53.0 months (range 24-95). A complication leading to revision occurred in 21 prostheses (7.8%), 6 (3.7%) in the ASA group and 15 (12.7%) in the RSA group (p < 0.005). The most frequent cause for revision was infection (n = 9; 42.9%). After primary implantation, 3 complications (2.2%) occurred in the ASA and 10 complications (11.0%) in the RSA group (p < 0.005). The complication rate was 2.2% in patients with OA, 13.5% in CTA and 11.9% in PTr.

CONCLUSIONS

Primary reverse shoulder arthroplasty had a significantly higher rate of complications and revisions than primary and secondary anatomic shoulder arthroplasty, respectively. Therefore, indications for reverse shoulder arthroplasty should be critically questioned in each individual case.

The impact of tobacco use on clinical outcomes and long-term survivorship after anatomic total shoulder arthroplasty

Introduction

Postoperative outcomes following total shoulder arthroplasty can be affected by preoperative health factors such as tobacco usage.

Methods

The charts of patients who underwent anatomic total shoulder arthroplasty were retrospectively analyzed and stratified based on smoking status. The primary data included range of motion and patient reported outcomes. Additionally, demographic, radiographic, and survivorship analyses were conducted. All data were analyzed using statistical inference.

Results

There were 78, 49, and 16 non-smoker, former smoker, and current smoker shoulders respectively with no significant differences in sex, American Society of Anesthesiologists status, body mass index, or mean follow-up time (average: 10.7 yrs). Smokers (51.5 ± 10.4 years) were younger than both non-smokers (64.9 ± 8.1 years; p < 0.01) and former smokers (65.1 ± 9.1years; p < 0.01) at the time of surgery. For non-smokers and former smokers, all range of motion and patient reported outcome scores significantly improved. Smokers reported significant improvements in all patient reported outcomes and external and internal rotation. Visual Analog Scale, American Shoulder and Elbow, and Simple Shoulder Test scores were lower for smokers comparatively, but these differences did not reach significance. Forward elevation was higher postoperatively for non-smokers (149.7o ± 17.2o) and former smokers (147.1o ± 26.0o) compared to current smokers (130.9o ± 41.2o; p = 0.017). No differences between the cohorts were found in the radiographic analysis. Revision rates were lower in the non-smoking cohort (7.7%) compared to both former (20.4%; p = 0.036) and current smokers (37.5%; p < 0.01). Survival curves showed that non-smoker implants lasted longer than those of current smokers.

Conclusion

After a decade, patients generally had improved shoulder range of motion, functionality, and pain regardless of smoking status. However, current smokers required shoulder replacements sooner and revision surgery more frequently.

Lesser Tuberosity Osteotomy Healing in Stemmed and Stemless Anatomic Shoulder Arthroplasty Is Higher with a Tensionable Construct and Affected by Body Mass Index and Tobacco Use

BACKGROUND

This study compared the healing rates of lesser tuberosity osteotomy (LTO) for anatomic total shoulder arthroplasty (TSA), repaired with either standard knot tying or a tensionable construct. Second, we evaluated LTO healing in stemmed and stemless prostheses and identified the patient characteristics associated with healing.

METHODS

An analysis of consecutive primary TSAs approached with an LTO performed by a single surgeon between 2016 and 2020 was conducted. In the first two years of the study period, the LTOs were repaired with four #2 polyblend sutures passed through drill tunnels and around a short press-fit stem, followed by manual knot tying. Subsequently, a tensionable construct with suture tapes (TCB) was universally adopted. The radiographic appearance of the LTO was evaluated at a minimum of six months postoperatively.

RESULTS

A total of 340 patients met the study criteria, including 168 with manual knot tying, 84 TCB repairs with a stemmed implant, and 88 TCB repairs with a stemless implant. There was no difference in the baseline demographics between the groups. The LTO healing rate of the manual knot tying group (85%) was lower than that of the stemmed (95%) and stemless (98%) TCB groups (p < 0.001). When directly comparing the LTO healing between the stemmed and stemless TCB groups, the differences were not significant (p = 0.44). Across all constructs, the body mass index (BMI) was higher in the displaced nonunion group (p = 0.04), with a failure rate of 9.4% for a BMI between 30 and 40, 12.5% for a BMI between 40 and 50, and 28.6% for a BMI > 50. The rate of tobacco use was higher in the displaced nonunion group (p = 0.037).

CONCLUSION

A tensionable construct improves LTO healing compared to manual knot tying, irrespective of the implant type. In addition to the surgical technique, the patient factors that influence tuberosity healing include a greater BMI and tobacco use.

LEVEL OF EVIDENCE

Level III, retrospective comparative study.

A Radiographic Analysis of Proximal Humeral Anatomy in Patients with Primary Glenohumeral Arthritis and Implications for Press-Fit Stem Length

While short stems in total shoulder arthroplasty (TSA) preserve bone stock and facilitate revision surgery, they have been associated with higher rates of malalignment and loosening in some cases compared to standard length stems. The purpose of this study was to analyze the intramedullary canal in progressive increments distal to the greater tuberosity to provide anatomic information about the optimal length of press-fit short stems for alignment and stability in TSA. We hypothesized that the humeral canal diameter will remain variable for the first 50 to 75 mm distal to the greater tuberosity and will become consistent thereafter. A retrospective review of 99 consecutive patients undergoing TSA with CT scans was performed. Intramedullary anterior-posterior (AP) and medial-lateral (ML) width as well as diameter were analyzed on two-dimensional computed tomography following multiplanar reconstruction. Measurements were taken at consistent distances distal to the greater tuberosity (GT). The transition point was measured at the proximal level of the humerus where endosteal borders of the medial and lateral cortices became parallel. The mean transition point was 73 mm from the GT (range: 53 to 109 mm). ML and AP widths became consistent 80 mm distal to the GT. IM diameter became consistent after 90 mm distal to the GT and a stem length of 90 mm extended past the transition point in 91.9% of cases. In TSA, a humeral stem length of 90 mm is required to predictably reach points at which the humeral canal becomes cylindrical and consistent in diameter. This information may aid data-driven decisions on humeral stem length during press-fit fixation, assuring consistency of alignment and implant stability, while maintaining ease of revision associated with a short stem implant. Level of evidence: III

Innovations in Shoulder Arthroplasty

Innovations currently available with anatomic total shoulder arthroplasty include shorter stem designs and augmented/inset/inlay glenoid components. Regarding reverse shoulder arthroplasty (RSA), metal augmentation, including custom augments, on both the glenoid and humeral side have expanded indications in cases of bone loss. In the setting of revision arthroplasty, humeral options include convertible stems and newer tools to improve humeral implant removal. New strategies for treatment and surgical techniques have been developed for recalcitrant shoulder instability, acromial fractures, and infections after RSA. Finally, computer planning, navigation, PSI, and augmented reality are imaging options now available that have redefined preoperative planning and indications as well intraoperative component placement. This review covers many of the innovations in the realm of shoulder arthroplasty.

Using standard-length compactors to implant short humeral stems in total shoulder arthroplasty: A cadaver study of humeral stem alignment

Background

Short-stem implants in shoulder arthroplasty were recently developed and reported clinical outcomes are good. However, radiological analysis often reveals humeral stem misalignment in the frontal plane, along with high filling ratios that can lead to proximal bone remodeling under stress shielding. The aim of this cadaveric study was to test whether using compactors for standard-length (> 100 mm) stems to implant short (< 100 mm) stems reduces the risk of stem misalignment without compromising in terms of a higher filling ratio.

Methods

In a cadaveric study, twenty short stems were implanted using instrumentation for standard-length stems. Alignment and filling ratios were evaluated on anteroposterior radiographs for both the compactors and the stems. The angular deviations (α) from the humeral axis of the compactors and the short stems were measured. Misalignment was defined as |α| > 5°. Metaphyseal and diaphyseal filling ratios were calculated and defined as either high (≥ 0.7) or low (< 0.7).

Results

The median angular deviations of the compactors and the short stems were respectively 1.6° (range, 0.03 to 5.9°) and 1.3° (range, 0.3 to 9.6°). Nineteen of the 20 compactors (95%) and 17/20 short stems (85%) were correctly aligned. The proportions of correctly aligned compactors and stems were not significantly different (95% CI, −0.33 to 0.11; Z-test of proportions p = .60), and the respective angular deviations were significantly correlated (Spearman ρ = .60, p = 0.006). The diaphyseal and metaphyseal filling ratios of the compactors and the stems were all low.

Conclusions

In this series of 20 implants in cadavers, the narrow short humeral stems implanted with compactors for standard-length stems were correctly aligned with the humeral axis. This approach may be a way to achieve both correct frontal alignment and low filling ratios.

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.

A comprehensive evaluation of the association of radiographic measures of lateralization on clinical outcomes following reverse total shoulder arthroplasty

BACKGROUND

Although reverse total shoulder arthroplasty (RTSA) has excellent reported outcomes and satisfaction, patients often have postoperative limitations in range of motion (ROM), specifically internal rotation. Increased lateralization is thought to improve ROM following RTSA. The purpose of this study was to evaluate the association between radiographic measurements of lateralization and postoperative ROM and clinical outcome scores following RTSA. The authors hypothesized that increased radiographic lateralization would be associated with improved postoperative ROM, specifically internal rotation, but have no significant association with clinical outcome scores.

METHODS

Patients who underwent RTSA with a 135° neck-shaft angle prosthesis and minimum 2-year clinical and radiographic follow-up were included and retrospectively reviewed. Postoperative radiographs were evaluated for several lateralization measurements including the lateralization shoulder angle (LSA), distance from the lateral border of the acromion to the lateral portion of the glenosphere, distance from the glenoid to the most lateral aspect of the greater tuberosity, and the distance from the lateral aspect of the acromion to the most lateral aspect of the greater tuberosity. Linear regression analyses were used to evaluate the independent association of each radiographic measurement of lateralization on forward flexion, external rotation, internal rotation, and the American Shoulder and Elbow Surgeons Standardized Shoulder Assessment Form (ASES) index score at 2 years postoperation. Receiver operating characteristic (ROC) curves were constructed to identify significant thresholds of each radiographic lateralization measurement.

RESULTS

A total of 203 patients were included. For internal rotation, a greater LSA (P = .007), shorter acromion to glenosphere distance (meaning more glenoid lateralization) (P = .005), and a greater acromion to greater tuberosity distance (with the tuberosity more lateral to the acromion) (P = .021) were associated with improved internal rotation. Overall, ROC analysis demonstrated very little significant data, the most notable of which was the LSA, which had a significant cutoff of 82° (sensitivity 57%, specificity 68%, P = .012).

CONCLUSION

Of the numerous radiographic measures of lateralization after RTSA, the LSA is the most significantly associated with outcomes, including improved internal rotation and a decrease in forward flexion and ASES score. The clinical significance of these statistically significant findings requires further study, as the observed associations were for very small changes that may not represent clinical significance.

Stemless Total Shoulder: A Review of Biomechanical Fixation and Recent Results

Introduction: Anatomic total shoulder arthroplasty is the replacement of the humeral head and glenoid surfaces with the goal of replicating normal anatomy. It is commonly utilized for patients with osteoarthritis, rheumatoid arthritis, and osteonecrosis, who have decreased range of motion (ROM), persistent pain, and loss of strength. Total shoulder Arthroplasty (TSA) is the third most common joint replacement in the United States. The incidence of TSA has been increasing, some data suggest that by the year 2025, TSA incidence may rise to 439,206 operations per year. In recent years, stemless total shoulder implants have become available. Results: These implants preserve bone stock while decreasing complications such as osteolysis, stress shielding and periprosthetic fracture. Stemless implants improve anatomic reconstruction and biomechanical function of the shoulder joint. Conclusion: Increasing amounts of data suggest stemless TSA to be a safe and effective technology that will become more common in the coming year.

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.

Does commercially available shoulder arthroplasty preoperative planning software agree with surgeon measurements of version, inclination, and subluxation?

BACKGROUND

Preoperative planning with commercially available imaging software in shoulder arthroplasty may allow for improved decision-making and more accurate placement of the glenoid component.

METHODS

A total of 81 consecutive shoulder computed tomography scans obtained for preoperative planning purposes for shoulder arthroplasty were analyzed by commercially available software from 4 companies (Blueprint: Wright Medical, Memphis, TN, USA; GPS: Exactech, Gainesville, FL, USA; Materialise: DJO, Vista, CA, USA; and VIP: Arthrex, Naples, FL, USA) and by 5 fellowship-trained sports medicine/shoulder surgeons. Inclination, version, and subluxation of the humerus were measured in a blinded fashion on axial and coronal sequences at the mid-glenoid. Surgeon measurements were analyzed for agreement and were compared with the 4 commercial programs.

RESULTS

Surgeon reliability was acceptable for version (intraclass correlation coefficient [ICC]: 0.876), inclination (ICC: 0.84), and subluxation (ICC: 0.523). Significant differences were found between surgeon and commercial software measurements in version (P = .03), inclination (P = .023), and subluxation (P < .001). Software measurements tended to be more superiorly inclined (average -2° to 2° greater), more retroverted (average 2°-5° greater), and more posteriorly subluxed (average 7°-10° greater) than surgeon measurements. In comparing imaging software measurements, only Blueprint was found to produce significantly different version measurements than surgeon measurements (P = .02).

CONCLUSION

Preoperative planning software for shoulder arthroplasty has limited agreement in measures of version, inclination, and subluxation measurements, whereas surgeons have high inter-reliability. Surgeons should be cautious when using commercial software planning systems and when comparing publications that use different planning systems to determine preoperative glenoid deformity measurements.

Short stem humeral components in reverse shoulder arthroplasty: stem alignment influences the neck-shaft angle

INTRODUCTION

Shorter humeral reverse total shoulder arthroplasty (RTSA) stems may reduce stress shielding, however, potentially carry the risk of varus/valgus malalignment. This radiographic study's purpose was to measure the incidence of stem malalignment and thus the realized neck-shaft angle (NSA). The hypothesis was that malalignment of the stem is a frequent postoperative radiographic finding.

METHODS

Radiographs of an uncemented curved short stem RTSA with a 145° NSA were reviewed. The study group included 124 cases at a mean age of 74 (range 48-91) years. The humeral stem axis was measured and defined as neutral if the value fell within ± 5° of the longitudinal humeral axis. Angular values > 5° were defined as malaligned in valgus or varus. The filling ratio of the implant within the humeral shaft was measured at the level of the metaphysis (FR_met) and diaphysis (FR_dia).

RESULTS

The average humeral stem axis angle was 4 ± 3° valgus, corresponding to a true mean NSA of 149 ± 3°. Stem axis was neutral in 73% (n = 90) of implants. Of the 34 malaligned implants, 82% (n = 28) were in valgus (NSA = 153 ± 2°) and 18% (n = 6) in varus (NSA = 139 ± 1°). The average FR_met and FR_dia were 0.68 ± 0.11 and 0.72 ± 0.11, respectively. A low positive association was found between stem diameter and filling ratios (r = 0.39; p < 0.001); indicating smaller stem sizes were more likely to be misaligned.

CONCLUSION

Uncemented short stem implants may decrease stress shielding; however, approximately one quarter were implanted > 5° malaligned. The majority of malaligned components (86%) were implanted in valgus, corresponding to an NSA of > 150°. As such, surgeons must be aware that shorter and smaller stems may lead to axial malalignment influencing the true SA.

LEVEL OF EVIDENCE

Level IV, retrospective study.

Three-dimensional Volumetric Filling Ratio Predicts Stress Shielding in Short-stem Anatomic Total Shoulder Arthroplasty

INTRODUCTION

Three-dimensional (3-D) CT volumetric filling ratio (VFR) is a better predictor of proximal humerus stress shielding after short-stem anatomic total shoulder arthroplasty (aTSA) than using plain radiographs.

METHODS

Forty-four patients with short-stem aTSAs, preoperative CT scans, and a minimum 3-year radiographic follow-up were included. Patients were divided into group A (stress shielding) and group B (no stress shielding) based on the radiographic analysis. Standard implant filling ratios were measured on plain radiographs. The 3-D VFR of the metaphyseal and diaphyseal segments of the aTSA stem was measured using MIMICS (Materialise). The area under a receiver operator characteristic curve was used to determine the predictive strength of the 3-D VFR method.

RESULTS

The average age and radiographic follow-up was 69 years and 44 months. Group A had 19 patients and statistically higher filling ratios using 3-D VFR method than group B, whereas no notable differences were found between the groups using standard techniques. The 3-D VFR had an area under a receiver operator characteristic curve of 92%, which supports it as a good predictor of stress shielding.

CONCLUSIONS

These methods enable early identification of patients at risk for stress shielding and can also be valuable in improving humeral stem designs.

LEVEL OF EVIDENCE

Level III. Case-control study.

Prospective, Blinded, Randomized Controlled Trial of Stemless Versus Stemmed Humeral Components in Anatomic Total Shoulder Arthroplasty: Results at Short-Term Follow-up

BACKGROUND

Stemless humeral components for anatomic total shoulder arthroplasty (aTSA) have several reported potential benefits compared with stemmed implants. However, we are aware of no Level-I, randomized controlled trials (RCTs) that have compared stemless implants with stemmed implants in patients managed with aTSA. We sought to directly compare the short-term clinical and radiographic outcomes of stemless and stemmed implants to determine if the stemless implant is noninferior to the stemmed implant.

METHODS

We performed a prospective, multicenter, single-blinded RCT comparing stemless and short-stemmed implants in patients managed with aTSA. Range-of-motion measurements and American Shoulder and Elbow Surgeons (ASES), Single Assessment Numeric Evaluation (SANE), and Constant scores were obtained at multiple time points. Device-related complications were recorded. Radiographic evaluation for evidence of loosening, fractures, dislocation, or other component complications was performed. Statistical analysis for noninferiority was performed at 2 years of follow-up for 3 primary end points: ASES score, absence of device-related complications, and radiographic signs of loosening. All other data were compared between cohorts at all time points as secondary measures.

RESULTS

Two hundred and sixty-five shoulders (including 176 shoulders in male patients and 89 shoulders in female patients) were randomized and received the allocated treatment. The mean age of the patients (and standard deviation) was 62.6 ± 9.3 years, and 99% of the shoulders had a primary diagnosis of osteoarthritis. At 2 years, the mean ASES score was 92.5 ± 14.9 for the stemless cohort and 92.2 ± 13.5 for the stemmed cohort (p value for noninferiority test, <0.0001), the proportion of shoulders without device-related complications was 92% (107 of 116) for the stemless cohort and 93% (114 of 123) for the stemmed cohort (p value for noninferiority test, 0.0063), and no shoulder in either cohort had radiographic signs of loosening. Range-of-motion measurements and ASES, SANE, and Constant scores did not differ significantly between cohorts at any time point within the 2-year follow-up.

CONCLUSIONS

At 2 years of follow-up, the safety and effectiveness of the stemless humeral implant were noninferior to those of the stemmed humeral implant in patients managed with aTSA for the treatment of osteoarthritis. These short-term results are promising given the potential benefits of stemless designs over traditional, stemmed humeral components.

LEVEL OF EVIDENCE

Therapeutic Level I. See Instructions for Authors for a complete description of levels of evidence.

Subsidence of Uncemented Short Stems in Reverse Shoulder Arthroplasty-A Multicenter Study

BACKGROUND

The radiological phenomenon of subsidence following the implantation of uncemented short-stem reverse prostheses (USSP) has not yet been described. The purpose of this study was to describe the rate and potential risk factors for subsidence. We hypothesized that subsidence may be a frequent finding and that a subsidence of >5 mm (mm) is associated with an inferior clinical outcome.

METHODS

A total of 139 patients with an average age of 73 ± 9 years were included. The clinical and radiological outcome was evaluated at a minimum follow-up (FU) of 12 months.

RESULTS

No humeral component loosening was present at a mean FU of 18 (range, 12-51) months. Mean Constant Score (CS) and Subjective Shoulder Value (SSV) improved significantly from 34.3 ± 18.0 points and 37.0 ± 19.5% preoperatively to 72.2 ± 13.4 points and 80.3 ± 16.5% at final FU (p < 0.001). The average subsidence of the USSP was 1.4 ± 3.7 mm. Subsidence of >5 mm was present in 15 patients (11%). No association between a subsidence >5 mm and CS or SSV was found (p = 0.456, p = 0.527). However, a subsidence of >5 mm resulted in lower strength at final FU (p = 0.022). Complications occurred in six cases (4.2%), and the revision rate was 3.5% (five cases).

CONCLUSIONS

Although subsidence of USSP is a frequent radiographic finding it is not associated with loosening of the component or a decrease in the clinical outcome at short term FU.

LEVEL OF EVIDENCE

Level 4, retrospective study.

Predicting Postoperative Course After Total Shoulder Arthroplasty Using a Medical-Social Evaluation Model

INTRODUCTION

The ability to predict successful outcomes is important for patient satisfaction and optimal results after shoulder arthroplasty. We hypothesize that a medical-social scoring tool will predict resource requirements in doing total shoulder arthroplasty (TSA).

METHODS

A retrospective analysis of 453 patients undergoing TSA was undertaken. Preoperatively, medical and social surveys were completed by each patient. Demographics, comorbidity scores, hospital course, postdischarge disposition, and readmissions were collected.

RESULTS

The average length of stay was 1.6 days (0 to 7). There was an association with utilization of home care or inpatient rehabilitation and both the medical (7.3 versus 3.9; P = 0.0002) and social (7.1 versus 3.4; P < 0.0001) components of the survey. There was a weak correlation between hospital length of stay and the social component of the survey (R = 0.29; P < 0.001), but not the medical component (R = 0.04; P = 0.38). No variable was predictive of readmission. Social score of eight was found to be predictive of postoperative requirement of home care or rehabilitation.

CONCLUSION

This study found that Medical and Social Survey Scores can stratify patients who are at risk of requiring more advanced postdischarge care and/or a longer hospital stay. With this, we can match patients to the most appropriate level of postoperative care.

Humeral stem lucencies correlate with clinical outcomes in anatomic total shoulder arthroplasty

Background

Humeral stem lucencies are uncommon after uncemented anatomic total shoulder arthroplasty (aTSA), and their clinical significance is unknown. This study compares clinical outcomes of aTSA with and without humeral stem lucencies.

Methods

Two-hundred eighty aTSAs using an uncemented grit-blasted metaphyseal-fit humeral stem between 2005 and 2013 were retrospectively evaluated for radiographic humeral stem lucencies. All shoulders were evaluated at a minimum 5-year follow-up from a multicenter database. Clinical outcomes included range of motion (ROM) and American Shoulder and Elbow Surgeons Standardized Shoulder Assessment Form (ASES) score, Constant score, University of California-Los Angeles Shoulder Score (UCLA), Simple Shoulder Test (SST), and Shoulder Pain and Disability Index (SPADI) scores. Postoperative radiographs were evaluated and complications were recorded.

Results

Two-hundred forty-three humeral stems showed no radiolucent lines. Among the 37 humeral stems with lucent lines, lines were most common in zones 8, 4, 7, and 3. Preoperative ROM and functional outcomes were similar between groups. Postoperative change in outcomes exceeded the minimal clinically important difference (MCID) for all ROM and outcomes in both groups. Postoperative change between groups showed no significant difference in ROM or outcome scores, but improved mean abduction exceeded the MCID in the patients without humeral lines. The complication rate after omitting patients with humeral loosening was higher in patients with humeral lucencies, as was the revision rate. There was also a higher glenoid-loosening rate in patients with humeral lucencies.

Conclusion

Humeral lucent lines after uncemented stemmed aTSA have a small negative effect on ROM and functional outcomes compared with patients without lucent humeral lines, which may not be clinically significant. The complication and revision rates were significantly higher in patients with humeral lucencies.

Proximal humeral osteolysis and glenoid radiolucent lines in an anatomic shoulder arthroplasty: a comparison of a ceramic and a metal humeral head component

BACKGROUND

In vitro wear studies demonstrate decreased polyethylene wear with a ceramic compared with a metal humeral head. In this in vivo study, we analyzed prospectively collected 5-year data, comparing the outcomes of 2 types of humeral implants.

METHODS

Sixty-two anatomic total shoulder arthroplasties (TSAs) (59 patients) were performed using the same glenoid component and 2 types of modular humeral implants (metal-head long-stem prosthesis in group A vs. ceramic-head stemless prosthesis in group B). Radiographic analysis for proximal humeral osteolysis and glenoid component radiolucent lines was performed at an average of 5.5 years. Functional outcomes were prospectively evaluated according to the visual analog scale score for pain; satisfaction level; American Shoulder and Elbow Surgeons score; active elevation; Shoulder Pain and Disability Index score; and Disabilities of the Arm, Shoulder and Hand score.

RESULTS

There were 39 TSAs in group A (mean age, 68.1 years) and 23 TSAs in group B (mean age, 67 years). Clinical improvement was similar for both groups. Some proximal humeral osteolysis occurred in 56% of all TSAs. Group A showed increased osteolysis compared with group B (72% vs. 30%, P = .005). Glenoid radiolucent lines were far more frequent in group A, and group A showed a direct relationship between the extent of humeral osteolysis and the severity of glenoid radiolucent lines (P < .001).

CONCLUSION

The stemless ceramic-head replacements showed fewer glenoid radiolucent lines and less humeral osteolysis than the long-stem metal-head replacements. In the group with metal-head replacements, correlation was shown between glenoid radiolucent lines and humeral osteolysis.

Subscapularis Repair During Reverse Total Shoulder Arthroplasty Using a Stem-Based Double-Row Repair: Sonographic and Clinical Outcomes

Background:

Treatment of the subscapularis in reverse total shoulder arthroplasty (RTSA) is a controversial topic, with conflicting evidence regarding outcomes after repair.

Purpose/Hypothesis:

The purpose of this study was to report clinical and sonographic outcomes of a through-implant double-row suture technique for subscapularis repair in RTSA and to compare clinical outcomes and range of motion (ROM) between patients with an intact subscapularis tendon repair versus those whose tendon repair was not intact. The authors hypothesized that the novel repair technique would find more than 80% of tendons intact on ultrasound, with significant improvement in clinical outcome scores and ROM. The authors also hypothesized that patients with an intact subscapularis tendon repair would have better clinical outcomes compared with those with a nonintact tendon repair.

Study Design:

Case series; Level of evidence, 4.

Methods:

The study included all patients who underwent RTSA by 1 of 2 surgeons between August 2016 and March 2017 with the through-implant double-row suture technique for subscapularis repair. Subscapularis tendon integrity was assessed postoperatively via ultrasound at minimum 1-year follow-up. American Shoulder and Elbow Surgeons (ASES), Single Assessment Numeric Evaluation (SANE), and pain visual analog scale (VAS) scores were recorded at the final follow-up visit in addition to ROM measures.

Results:

A total of 48 patients (31 males, 17 females; mean age, 68.9 ± 7.4 years; mean follow-up, 13.8 ± 2.1 months) were included. On ultrasound, the subscapularis was intact in 83.3% of patients. Regarding preoperative versus postoperative outcome scores, the ASES score (mean ± SD) significantly improved from 38.3 ± 14.7 to 81.9 ± 13.6, the SANE score significantly improved from 29.8 ± 24.2 to 75.5 ± 21.0, and the VAS pain score significantly improved from 5.9 ± 2.1 to 1.2 ± 1.6 (P < .001 for all). Forward flexion and external rotation significantly improved. No significant difference existed in clinical outcome scores or ROM between patients with intact versus torn subscapularis tendons based on ultrasound.

Conclusion:

Subscapularis repair using a stem-based double-row repair technique during RTSA demonstrated an overall healing rate of 83.3%, as evidenced by ultrasound examination at short-term follow-up. Integrity of subscapularis repair did not affect clinical outcome or ROM.

Current state of short-stem implants in total shoulder arthroplasty: a systematic review of the literature

Background

Humeral stem length in anatomic total shoulder arthroplasty (TSA) continues to decrease in an attempt to preserve bone. Outcomes following short-stem TSA are not well documented. The purpose was to systematically review and report the outcomes and revisions following short-stem humeral implants for TSA.

Methods

A systematic review was registered with PROSPERO and performed with PRISMA guidelines using 3 publicly available free databases. Therapeutic clinical outcome investigations reporting TSA outcomes of short-stem implants with levels of evidence I-IV were eligible for inclusion. All study, subject, and surgical technique demographics were analyzed and described.

Results

Thirteen studies were included (average follow-up: 33 months, range 24-84 months; 8 studies [62%] were multicenter and 6 [46%] were from Europe). All studies were published in the last 8 years, and almost all (12/13, 92%) reported results of uncemented components. Most of the studies (9/13, 70%) reported results from the Aequalis Ascend or Ascend Flex Stem (Tornier). Improvements were seen in all measured range of motion planes and patient-reported outcome scores. Complications were infrequent, with a 2% humeral loosening rate, a 3% overall revision rate, and a 1% rate of revision for aseptic humeral loosening. Radiographic results showed a 13% rate of radiolucent lines, a 16% rate of condensation lines, and a 22% rate of calcar osteolysis.

Conclusion

Short-stem TSA humeral implants provide excellent results, with low revision rates in the short term. Long-term follow-up will be necessary to understand the clinical impact of radiographic calcar osteolysis.

Proximal humeral bony adaptations with a short uncemented stem for shoulder arthroplasty: a quantitative analysis

Background

Short uncemented stems have recently been proposed as an alternative to classic long stems for shoulder arthroplasty. The early results are promising, but bony adaptations of the proximal humerus have been reported. The aim of this study was to quantify these phenomena using the Ascend Flex stem and to determine the risk factors.

Materials and methods

In a retrospective, single-center study, 183 shoulder arthroplasties were evaluated at 2-year follow-up. All patients underwent clinical evaluations preoperatively and at last follow-up. Radiographs were obtained preoperatively, postoperatively, and at last follow-up. Four types of bony adaptations were analyzed: medial cortical narrowing (MCN), medial metaphysis thinning (MMT), lateral metaphysis thinning (LMT), and under-the-baseplate osteolysis. The risk factors were analyzed in a multivariate model.

Results

MCN was found in 72.6% of cases and was severe (>50%) in 4.4%. MMT was found in 46.4% of cases and was severe in 3.3%. LMT was found in 9.8% of cases and was severe in 2.8%. The risk factors for MCN were the distal filling ratio, osteoporosis, and female sex, whereas MMT and LMT were only influenced by stem axis deviation. Under-the-baseplate osteolysis was found in 34.4% of cases. No influence of bony adaptations on the clinical outcomes was observed. We found no complications related to the stem or to stem loosening.

Conclusion

The radiographic evolution was satisfactory at mid-term follow-up. Bony adaptations seemed to be limited phenomena, without any observed consequence. Avoiding excessive filling and axis deviation may limit these phenomena.

Radiographic outcomes of impaction-grafted standard-length humeral components in total shoulder and ream-and-run arthroplasty: is stress shielding an issue?

BACKGROUND

The purpose of this study was to evaluate humeral stress shielding in shoulder arthroplasties performed with a smooth, standard-length humeral stem fixed with impaction autografting.

METHODS

Two-year outcomes were evaluated for 48 ream-and-run arthroplasties and 78 total shoulder arthroplasties (TSAs) performed at a single institution. Postoperative radiographs were analyzed for adaptive changes, calcar osteolysis, and component shift or subsidence. Radiographic outcomes were analyzed for associations with patient demographic characteristics, humeral stem filling ratios, and glenoid loosening; clinical outcomes were assessed using the Simple Shoulder Test.

RESULTS

At 2 years after surgery, the ream-and-run procedures showed partial calcar osteolysis in 9 cases (19%). The TSAs showed partial calcar osteolysis in 19 cases (24%) and complete calcar osteolysis in 2 (3%). Humeral component subsidence or component shift was observed in 3 ream-and-run procedures (6%) and in 8 TSAs (10%). These radiographic findings were not significantly associated with patient demographic characteristics, canal-filling ratios, or clinical outcomes.

CONCLUSION

When inserted with impaction autografting, a smooth, standard-length humeral stem offers a secure bone-preserving approach for humeral component fixation in shoulder arthroplasty. These results with a conventional prosthesis can serve as a basis for comparison for new component designs and fixation methods.

Cemented humeral stem versus press-fit humeral stem in total shoulder arthroplasty: a systematic review and meta-analysis

AIMS

The aim of this study was to evaluate the differences in revision and complication rates, functional outcomes, and radiological outcomes between cemented and press-fit humeral stems in primary anatomical total shoulder arthroplasty (TSA).

MATERIALS AND METHODS

A comprehensive systematic review and meta-analysis was conducted searching for studies that included patients who underwent primary anatomical TSA for primary osteoarthritis or rheumatoid arthritis.

RESULTS

There was a total of 36 studies with 927 cemented humeral stems and 1555 press-fit stems. The revision rate was 5.4% (95% confidence interval (CI) 3.9 to 7.4) at a mean of 89 months for cemented stems, and 2.4% (95% CI 1.1 to 4.7) at a mean of 40 months for press-fit stems. A priori subgroup analysis to control for follow-up periods demonstrated similar revision rates: 2.3% (95% CI 1.1 to 4.7) for cemented stems versus 1.8% (95% CI 1.4 to 2.9) for press-fit stems. Exploratory meta-regression found that longer follow-up was a moderating variable for revision (p = 0.003).

CONCLUSION

Cement fixation had similar revision rates when compared to press-fit stems at short- to midterm follow-up. Rotator cuff pathology was a prevalent complication in both groups but is likely not related to fixation type. Overall, with comparable revision rates, possible easier revision, and decreased operative time, humeral press-fit fixation may be an optimal choice for primary anatomical TSA in patients with sufficient bone stock. Cite this article: Bone Joint J 2019;101-B:1107-1114.

Postoperative radiographic findings of an uncemented convertible short stem for anatomic and reverse shoulder arthroplasty

BACKGROUND

Several short-stemmed press-fit humeral components have been developed in recent years for anatomic total shoulder arthroplasty (TSA) as well as reverse shoulder arthroplasty (RSA). Varying radiographic outcomes have been reported, with some studies reporting concerning rates of aseptic loosening. This study analyzed the radiographic findings of a press-fit convertible short-stemmed humeral component in both TSA and RSA.

METHODS

There were 150 anatomic TSAs (group 1) and 77 RSAs (group 2) analyzed radiographically at a minimum follow-up of 2 years postoperatively. Plain radiographs were reviewed for stem loosening, alignment, signs of stress shielding, and the filling ratio.

RESULTS

At final follow-up, 49% of group 1 and 65% of group 2 had no evidence for radiographic changes. In those with radiographic changes, low bone adaptions were found in 83% and high adaptions in 17% in both groups. Larger stem sizes with higher filling ratios were associated with high radiographic adaptions in both groups (P = .02). The overall filling ratios were higher in group 2 (P = .002). Cortical contact of the stem led to higher bone adaptions (P = .014).

CONCLUSIONS

The short humeral component analyzed in this study showed encouraging survival rates without aseptic loosening. Radiographic changes are associated with a higher filling ratio and cortical contact of the stem. Surgeons should aim to achieve fixation with the minimal required canal filling to minimize radiographic changes with the uncemented humeral component used in this study.

Comparison of revision rates and radiographic observations of long and short, uncoated and coated humeral stem designs in total shoulder arthroplasty

There is no consensus on outcomes of long versus short and uncoated versus coated uncemented stems in total shoulder arthroplasty (TSA).

We reviewed the literature to compare revision rates and adverse radiographic observations at ⩾ 2 years of various uncemented humeral stem designs.

We performed an electronic PubMed search for studies on uncemented primary TSA that reported one or more of the following observations at ⩾ 2 years for distinct stem designs: stem revision; subsidence; stress shielding; radiolucent lines; and humeral loosening.

The search returned 258 records, from which 20 articles (22 cohorts) met the inclusion criteria.

The most frequently reported designs were short uncoated stems (7/13 cohorts) at < 3 years and long uncoated stems (8/9 cohorts) at > 3 years.

The incidences of revisions and adverse radiographic observations were lower for short coated designs, compared with short and long uncoated designs, but these findings should be confirmed by prospective studies with a longer follow-up.

Cite this article: EFORT Open Rev 2019;4:70-76. DOI: 10.1302/2058-5241.4.180046.

Short-term results of a second generation anatomic short-stem shoulder prosthesis in primary osteoarthritis

INTRODUCTION

The aim of the study was to evaluate the short-term clinical results of anatomic total shoulder arthroplasty with a short-stem prosthesis in primary osteoarthritis.

MATERIALS AND METHODS

65 shoulders with a mean age of 70 years (range 47-85 years) were available for minimum follow-up of 24 months. Clinical outcome was determined by range of motion, Constant score (CS) age and sex-adjusted Constant score (CS%), and subjective shoulder value (SSV). The influence of six different factors (high bone adaptations, age > 65 years, female gender, dominant side, atrophy of the supraspinatus tendon ≥ grade 2, glenoid type B2/B3) on the clinical outcome was assessed.

RESULTS

At mean follow-up of 37 months (range 24-58 months), the CS improved from 36 ± 8 to 75 ± 12 (p < 0.001). The shoulder flexion (100° ± 21° to 159° ± 19°) as well as the external rotation (3° ± 11° to 43° ± 18°) improved significantly (p < 0.001). Three complications were noted (transient neuropraxia of the radial nerve, subjective instability, hematoma with superficial wound infection) leading to one revision surgery (wound debridement). No stem loosening was observed. High bone adaptation was present in 19 out of 65 shoulders (29%). The clinical outcome was not influenced by high bone adaptations (p ≥ 0.095). Age > 65 years (n = 44) and female gender (n = 38) were associated with worse clinical outcome (p ≤ 0.043).

CONCLUSIONS

In the short term, the clinical results of this anatomical short-stem shoulder prosthesis are encouraging. A low prevalence of high bone adaptations was found without any influence on the clinical outcome and stem loosening was not observed.

Stress shielding of the humerus in press-fit anatomic shoulder arthroplasty: review and recommendations for evaluation

Uncemented press-fit humeral stems were developed with the goal of decreasing operative time, preserving bone stock, and easing revision. In recent years, short stems and stemless humeral implants have also become available. These press-fit humeral implants have varying designs that can lead to changes in stress distribution in the proximal humerus. Such stress shielding manifests as bony adaptations and may affect long-term functional outcome and the ability to perform revision. However, current studies of humeral fixation during total shoulder arthroplasty are complicated because a variety of classification systems have been used to report findings. The purpose of this report is to review the current literature on press-fit fixation of the humeral component during total shoulder arthroplasty and propose minimum requirements for radiographic descriptions of stress shielding.

Mid-term results of anatomical total shoulder arthroplasty for primary osteoarthritis using a short-stemmed cementless humeral component

Aims

The aim of this study was to evaluate the clinical and radiological outcome of using an anatomical short-stem shoulder prosthesis to treat primary osteoarthritis of the glenohumeral joint.

Patients and Methods

A total of 66 patients (67 shoulders) with a mean age of 76 years (63 to 92) were available for clinical and radiological follow-up at two different timepoints (T1, mean 2.6 years, sd 0.5; T2, mean 5.3 years, sd 0.7). Postoperative radiographs were analyzed for stem angle, cortical contact, and filling ratio of the stem. Follow-up radiographs were analyzed for timing and location of bone adaptation (cortical bone narrowing, osteopenia, spot welds, and condensation lines). The bone adaptation was classified as low (between zero and three features of bone remodelling around the humeral stem) or high (four or more features).

Results

The mean Constant score improved significantly from 28.5 (sd 11.6) preoperatively to 75.5 (sd 8.5) at T1 (p < 0.001) and remained stable over time (T2: 76.6, sd 10.2). No stem loosening was seen. High bone adaptation was present in 42% of shoulders at T1, with a slight decrease to 37% at T2. Cortical bone narrowing and osteopenia in the region of the calcar decreased from 76% to 66% between T1 and T2. Patients with high bone adaptation had a significantly higher mean filling ratio of the stem at the metaphysis (0.60, sd 0.05 vs 0.55, sd 0.06; p = 0.003) and at the diaphysis (0.65 sd 0.05 vs 0.60 sd 0.05; p = 0.007). Cortical contact of the stem was also associated with high bone adaptation (14/25 shoulders, p = 0.001). The clinical outcome was not influenced by the radiological changes.

Conclusion

Total shoulder arthroplasty using a short-stem humeral component resulted in good clinical outcomes with no evidence of loosening. However, approximately 40% of the shoulders developed substantial bone loss in the proximal humerus at between four and seven years of follow-up. Cite this article: Bone Joint J 2018;100-B:603–9.