Radiographic evaluation of humeral head reconstruction with stemmed and stemless spherical implants compared with stemless elliptical head implants

Clinical and radiographic outcomes at 5-8 years of the Catalyst CSR stem-free ellipsoid anatomic total shoulder arthroplasty in a series of 206 shoulders

BACKGROUND

Anatomic total shoulder arthroplasty (aTSA) using an ellipsoid-shaped stem-free humeral head implant and a multiplanar osteotomy technique has demonstrated advantages in cadaver, biomechanical, radiographic, and short-term clinical studies in reproducing anatomy, reducing outliers, and demonstrating improved early range of motion and good early outcomes. The purpose of this study was to report the outcomes of this implant and method after a minimum 5-year follow-up and compare them with other mid-term reports of implants in the literature.

METHODS

This retrospective study of prospectively collected data included 239 shoulders in 209 patients who underwent aTSA with an ellipsoid stem-free humerus prosthesis and an all-polyethylene glenoid component from the Catalyst CSR Shoulder System between August 2016 and September 2019. Inclusion criteria were patients with advanced glenohumeral joint arthritis with an intact rotator cuff regardless of patient age. Clinical outcomes including range of motion, patient-reported outcome measures, and radiographs were evaluated at multiple time points postoperatively, with a minimum 5-year follow-up.

RESULTS

Five-year follow-up or more was achieved in 92% of living patients. There were 206 shoulders in 179 patients that were included in the study with mean follow-up of 71 months (range: 60-100). Mean age at surgery was 72 years (range: 56-90). Forward elevation improved from 113° to 146° (P < .001), external rotation improved from 25° to 49° (P < .001), and internal rotation improved from L5 to L2 (P < .001). There were statistically significant improvements in American Shoulder and Elbow Surgeons score (37 to 94, P < .001), Single Assessment Numeric Evaluation (36 to 95, P < .001), and visual analog scale (6.7 to 0.4, P < .001), all exceeding thresholds of minimal clinically important difference and substantial clinical benefit. Seventy seven percent of patients reported a Single Assessment Numeric Evaluation score ≥ 95 at final follow-up. Preoperative glenoid morphology did not appear to have an effect on clinical or functional outcome scores. There were no implant failures of the humerus component in any patients and no radiographic signs of humerus loosening in any of the 140 shoulders that had final radiographs. Implant revision rate for any cause was 3% at nearly 6 years. Low-grade medial calcar stress shielding was observed in 1% of patients.

CONCLUSIONS

At 5-year minimum follow-up, the Catalyst CSR stem-free ellipsoid aTSA reliably restores anatomy, provides excellent patient satisfaction, clinical improvement in all outcome measures studied, low rates of revision, and no radiographic signs of humerus loosening.

Analysis of factors influencing optimal humeral-sided reconstruction in anatomic total shoulder arthroplasty

Background

The introduction of different humeral implants for the treatment of osteoarthritis was intended to improve the ability to anatomically reconstruct the proximal humerus. New technology should ideally lead to improvements in optimal reconstruction. The primary aim of this study was to compare three humeral implant types (long stem, short stem, and stemless) to replicate the proximal humeral anatomy and assess the impact of transitions across each stem type, including initial learning curves.

Methods

This was a retrospective review of 298 patients (175 males and 123 females) who underwent anatomic total shoulder arthroplasty utilizing three following stem types: 145 long stem, 102 short stem, and 51 stemless implants. An AP radiograph which met a criterion of optimal/orthogonal view of the humeral head and stem was selected for every included patient. A best fit circle, an articular surface circle and postoperative measure of neck-shaft angle (NSA) was measured by two independent observers. The distance between the centers of two circles (center of rotation [COR] shift) and NSA were then compared for each stem type. In order to assess transitions in technology, two sets of patients in the stemmed groups were selected: initial year (79 long stem, 62 short stem) and final year (66 long, 40 short) of utilization. A cumulative sum control chart analysis was used to assess the learning curves of each of the stem types by the initial year of utilization according to the radiographic measurement of COR shift.

Results

The stemless implant showed best reconstruction with a mean COR shift of 3.0 ± 1.6 mm and NSA of 137 ± 6° (P < .001). The transition from long stem to short stem utilization showed significantly worse COR shift and NSA, 3.3 ± 2.1 mm to 4.1 ± 1.9 mm and 138.5 ± 4.4° to 141.0 ± 4.4° (max P = .032), respectively. The impact of transitions to newer technology demonstrated an increased operative time (100 to 128 and 135 min). The cumulative sum control char learning curves demonstrated a completion of the learning phases at 12 cases for both the long and short stem designs, but there was no identifiable learning phase for the stemless implant, suggesting an immediate entry to the consolidation phase.

Conclusion

When assessing reconstruction of the premorbid shoulder joint, the stemless implant had the greatest efficacy and shortest learning curve. Stemless anatomic humeral reconstruction is more replicable in recreating the anatomic shape of the humerus and is quicker to master compared to standard or short stemmed implants but did have a greater initial operative time.

Influence of humeral position of the Affinis Short stemless shoulder arthroplasty system on long-term survival and clinical outcome

BACKGROUND

The purpose of this study was to evaluate the influence of humeral position of the Affinis Short implant in stemless anatomic total shoulder arthroplasties (STSAs) on clinical and radiologic results and mid- to long-term survival in the treatment of primary osteoarthritis (OA) of the shoulder.

METHODS

Eighty patients treated with a stemless shoulder arthroplasty for OA of the shoulder were evaluated with a mean follow-up of 92 ± 14 months (range 69-116 months) by the Constant Score (CS), Disabilities of the Arm, Shoulder, and Hand questionnaire (DASH), and active range of motion (ROM). Radiographic assessment for bone adaptations and humeral implant position was performed by plain radiographs. Comparison of the pre- and postoperative centers of rotation (CORs) was used to assess the restoration of the geometry of the humeral head. The appraisal of proper humeral component positioning was correlated with the functional outcomes. A Kaplan-Meier analysis was performed to investigate the influence of humeral implant position compared to survival time. Complications were noted.

RESULTS

The ROM (P < .001), CS (P < .001), and DASH scores (P < .001) showed significant improvements after surgery for the entire series. The COR restoration was anatomic in 75% (n = 60) of all implants and in 25% (n = 20) nonanatomic implants (pre- and postoperative COR deviation of 2.7 ± 1.8 mm vs. 5.1 ± 3.2 mm, P = .0380). The humeral component position did not affect the functional outcome whereas the 10-year unadjusted cumulative survival rate for the anatomic group was significantly higher in comparison with the nonanatomic group (96.7% vs. 75%, P = .002). The radiologic evaluation revealed minor periprosthetic bone adaptions in various forms without clinical significance or further intervention. No revision was necessary because of a failed fixation of the stemless humeral component.

CONCLUSIONS

Regarding the treatment of primary OA of the shoulder, STSA shows excellent long-term survival and clinical outcomes. In particular, STSA implants are able to restore the geometry of the humeral head. Nonanatomic reconstruction may influence the survival over the long term in different pathways. Further studies are necessary to elucidate the effect of humeral component position in STSA on function, pain, and implant survival rates.

Radiographic comparison of eccentric stemmed vs. concentric stemless prosthetic humeral head positioning after anatomic total shoulder arthroplasty

INTRODUCTION

Maintaining premorbid proximal humeral positioning is an essential consideration of anatomic total shoulder arthroplasty (aTSA), as malposition of the prosthetic humeral head can result in poor clinical outcomes. Stemless aTSA prosthetic heads are usually concentric, while stemmed aTSA prosthetic heads are typically eccentric in nature. Therefore, the purpose of this study was to compare the ability to restore native humeral head position between stemmed (eccentric) vs. stemless (concentric) aTSA.

MATERIALS AND METHODS

Postoperative anteroposterior radiographs of 52 stemmed and 46 stemless aTSAs were analyzed. A best-fit circle was created using previously published and validated techniques to represent the premorbid humeral head position and axis of rotation. This circle was juxtaposed with another circle following the arc of the implant head. Next, the offset in center of rotation (COR), radius of curvature (RoC), and humeral head height above the greater tuberosity (HHH) were measured. Additionally, based on prior studies, an offset of >3 mm at any point between the implant head surface and premorbid best-fit circle was considered significant and further classified as overstuffed or understuffed.

RESULTS

RoC deviation was significantly greater in the stemmed cohort than the stemless cohort (1.19 ± 1.37 mm vs. 0.65 ± 1.17 mm, P = .025). There was no statistically significant difference in deviation from premorbid humeral head between the stemmed and stemless cohorts for COR (3.20 ± 2.28 mm vs. 3.23 ± 2.09 mm, P = .800) or HHH (1.12 ± 3.27 mm vs. 0.92 ± 2.70 mm, P = .677). When comparing overstuffed implants to appropriately placed implants, there was a significant difference in overall COR deviation in stemmed implants (3.93 ± 2.51 mm vs. 1.92 ± 1.05 mm, P < .001). Superoinferior COR deviation (stemmed: 2.38 ± 3.01 mm vs. -0.61 ± 1.59 mm, P < .001; stemless: 2.70 ± 1.75 mm vs. -0.16 ± 1.87 mm, P < .001), mediolateral COR deviation (stemmed: 0.79 ± 2.65 mm vs. -0.62 ± 1.27 mm, P = .020; stemless: 0.40 ± 1.41 mm vs. -1.13 ± 1.96 mm, P = .020), and HHH (stemmed: 3.61 ± 2.73 mm vs. 0.50 ± 1.31 mm, P < .001; stemless: 3.98 ± 1.18 mm vs. 0.53 ± 1.41 mm, P < .001) were significantly different between overstuffed implants and appropriate implants in both the stemmed and stemless cohorts.

DISCUSSION

Stemless and stemmed aTSA implants have similar rates of reproducing satisfactory postoperative humeral head COR with both producing COR deviation most commonly in the superomedial direction. Deviation in HHH contributes to overstuffing in both stemmed and stemless implants, COR deviation contributes to overstuffing in stemmed implants, while RoC (humeral head size) is not associated with overstuffing. Based on this study, it appears that neither eccentric nor concentric prosthetic heads are superior in recreating premorbid humeral head position.

Elliptical Humeral Head Implants in Anatomic Total Shoulder Arthroplasty

Humeral implants for anatomic total shoulder arthroplasty and hemiarthroplasty have typically used spherical humeral heads that have a uniform diameter and radius of curvature. However, the native humeral head has a more elliptical morphology, which has spurred interest in nonspherical implant designs. Cadaveric studies indicate that the native humeral head diameter is 10% longer in the superior-inferior plane than the anterior-posterior plane and has a radius of curvature that is approximately 8% greater. An elliptical implant that more closely replicates native anatomy may allow for more accurate coverage of the humeral resection surface with less implant overhang and risk of overstuffing. Biomechanical evidence suggests that an elliptical implant yields glenohumeral kinematics that mimic the native joint, and early clinical results are promising. As clinical research continues to emerge, it will become clearer whether encouraging cadaveric, biomechanical, and early clinical data translates to meaningful sustained improvements in patient outcomes.

Contact Mechanics of Elliptical and Spherical Head Implants during Axial Rotation in Anatomic Total Shoulder Arthroplasty: A Biomechanical Comparison

BACKGROUND

Elliptical humeral head implants have been proposed to result in more anatomic kinematics following total shoulder arthroplasty (aTSA). The purpose of this study was to compare glenohumeral contact mechanics during axial rotation using spherical and elliptical humeral head implants in the setting of aTSA.

METHODS

Seven fresh-frozen cadaveric shoulders were utilized for biomechanical testing in neutral (NR), internal (IR), and external (ER) rotation at various levels of abduction (0°, 15°, 30°, 45°, 60°) with lines of pull along each of the rotator cuff muscles. Each specimen underwent the following three conditions: (1) native, and TSA using (2) an elliptical and (3) spherical humeral head implant. Glenohumeral contact mechanics, including contact pressure (CP; kPa), peak contact pressure (PCP; kPa), and contact area (CA; mm2), were measured in neutral rotation as well as external and internal rotation using a pressure mapping sensor.

RESULTS

Elliptical head implants showed a significantly lower PCP in ER compared to spherical implants at 0° (Δ-712.0 kPa; p = 0.034), 15° (Δ-894.9 kPa; p = 0.004), 30° (Δ-897.7 kPa; p = 0.004), and 45° (Δ-796.9 kPa; p = 0.010) of abduction, while no significant difference was observed in ER at 60° of abduction or at all angles in NR and IR. Both implant designs had similar CA in NR, ER, and IR at all tested angles of abduction (p > 0.05, respectively).

CONCLUSIONS

In the setting of aTSA, elliptical heads showed significantly lower PCP during ER at 0° to 45° of abduction, when compared to spherical head implants. However, in NR and IR, PCP was similar between implant designs. Both designs showed similar CA during NR, ER, and IR at all abduction angles.

LEVEL OF EVIDENCE

basic science; controlled laboratory study.

Stemless total shoulder arthroplasty using a novel multiplanar osteotomy and elliptical humeral head results in both improved early range of motion and radiographic center of rotation compared with standard total shoulder arthroplasty

BACKGROUND

Restoration of the native glenohumeral anatomy is an important consideration in obtaining optimal range of motion (ROM) after anatomic total shoulder arthroplasty (TSA). Recently, a new stemless TSA system has been developed that uses both a multiplanar osteotomy (MPO), to improve the surgeon's ability to restore humeral center of rotation (COR), and an elliptical humeral head to improve ROM. The purpose of our study was to compare the difference in early postoperative ROM and restoration of radiographic COR, between this stemless TSA and standard stemmed TSAs.

METHODS

This was a retrospective review of 50 consecutive primary TSAs performed by a single surgeon for glenohumeral osteoarthritis. The initial cohort underwent TSA with a standard stemmed humeral component with a circular humeral head (n = 25), whereas the subsequent cohort underwent stemless TSA using an MPO and an elliptical humeral head (n = 25). Postoperative data collection included active shoulder ROM as measured by goniometer, complications or revision surgery, and measurements of radiographic COR. Patients were assessed at 6 weeks, 12 weeks, 6 months, and 12 months after surgery. Change in COR was determined on postoperative radiographs by 2 fellowship-trained surgeons on 2 separate occasions. Intra- and interrater reliability were computed using intraclass correlation coefficients.

RESULTS

For both mean forward flexion (FF) and external rotation (ER), there was greater ROM in the MPO-elliptical group at all time points, which was statistically significant. Mean change in FF favored the MPO group at 6 and 12 weeks and was statistically significant and above the minimal clinically important difference (MCID): 6 weeks, standard -15.8° vs. MPO 8.4° (P = .004); 12 weeks, standard 6.4° vs. MPO 29.2° (P = .001). Mean change in ER favored the MPO group at 6 weeks and was statistically significant: standard 5.4° vs. MPO 14.0° (P = .02). There were no revision surgeries in either group. Average change in COR was 2.7 mm in the standard group and 1.8 mm in the MPO-elliptical group, which was statistically significant (P < .001). Number of patients with >3 mm of difference in COR was 10 (40%) in the standard group and 1 (5%) in the MPO-elliptical group, which was statistically significant (P = .002). Average intraclass correlation coefficient was 0.75, indicating good reliability within and between surgeon measurements.

CONCLUSION

The use of a multiplanar osteotomy and elliptical humeral head was associated with improved early range of motion and better reproduction of the radiographic COR compared with standard stemmed TSA.

Stemless components lead to improved radiographic restoration of humeral head anatomy compared with short-stemmed components in total shoulder arthroplasty

BACKGROUND

Restoring the native center of rotation (COR) in total shoulder arthroplasty (TSA) has been shown to improve postsurgical function, subjective outcomes, and implant longevity. The primary purpose of this study was to compare postoperative radiographic restoration of the humeral COR between short-stem and stemless humeral implants by evaluating the mean COR shift between the 2 techniques. Secondary outcomes evaluated were comparisons of COR shift outliers, humeral head implant thickness and diameter, direction of COR shift, and neck-shaft angle (NSA).

METHODS

This study was a multicenter retrospective comparative study using a consecutive series of primary anatomic TSA patients who received either a short-stem or stemless humeral implant. Radiographically, COR and NSA were measured by 2 fellowship-trained surgeons using the best-fit circle technique on immediate postoperative Grashey radiographs.

RESULTS

A total of 229 patients formed the final cohort for analysis that included 89 short stems and 140 stemless components. The mean COR shift for short stems was 2.7 mm (±1.4 mm) compared with 2.1 mm (±0.9 mm) for stemless implants (P < .001). The percentage of short-stem implant patients with a >2 mm COR difference from native was 66.0% (n = 62) compared with 47.4% (n = 64) for stemless (P = .006). The percentage of short-stem patients with a >4 mm COR difference from native was 17.0% (n = 16) compared with 3.0% (n = 4) for stemless (P < .001). The mean humeral implant head thickness for short stems was 18.7 ± 2.2 mm compared with 17.2 ± 1.3 mm for stemless implants (P < .001). The mean humeral head diameter for short stems was 48.7 ± 4.4 mm compared with 45.5 ± 3.5 mm for stemless implants (P < .001). The NSA for the short-stem cohort was 136.7° (±3.6°) compared with 133.5° (±6.0°) for stemless (P < .001).

CONCLUSIONS

Stemless prostheses placed during TSA achieved improved restoration of humeral head COR and were less likely to have significant COR outliers compared with short-stem implants.

Outcomes of different stem sizes in shoulder arthroplasty

Background

The successive refinement in implant design and operative technique alongwith improved understanding has resulted in increased incidence of total shoulder arthroplasty (TSA). Simultaneously, the indications of TSA have widened and include a range of shoulder pathologies.

Methods

Using the keywords and relevant literature, we have described an overview of the different stem sizes used in shoulder arthroplasty. Relevant description of clinical and radiological outcome is done with regards to different stem sizes.

Discussion

There are plethora of shoulder replacement systems, based on unique philosophy and having their own advantages and disadvantages. Additionally, the rise in ageing population had increased the need for revision TSA, thereby necessitating the judicious choice of implant at primary TSA. We further present the role of cemented and uncemented humeral stems and discuss the findings of finite element analysis. The choice of humeral stem size and use of cemented or uncemented stems have been reported to affect the clinical and radiological outcomes.