Does prosthetic humeral articular surface positioning associate with outcome after total shoulder arthroplasty?

The impact of 3-dimensional humeral planning and standard transfer instrumentation on reconstruction of native humeral anatomy for anatomic total shoulder arthroplasty

BACKGROUND

Preoperative 3-dimensional (3D) computed tomography (CT)-based planning for anatomic total shoulder arthroplasty (TSA) has grown in popularity in the past decade with the primary focus on the glenoid. Little research has evaluated if humeral planning has any effect on the surgical execution of the humeral cut or the positioning of the prosthesis.

METHODS

Three surgeons performed a prospective study using 3D-printed humeri printed from CTs of existing patients, which were chosen to be -3, -1, 0, 1, and 3 standard deviations of all patients in a large database. A novel 3D printing process was used to 3D print not only the humerus but also all 4 rotator cuff tendons. For each surgical procedure, the printed humerus was mounted inside a silicone shoulder, with printed musculature and skin, and with tensions similar to human tissue requiring standard retraction and instruments to expose the humerus. Three phases of the study were designed. In phase 1, humeral neck cuts were performed on all specimens without any preoperative humeral planning; in phase 2, 3D planning was performed, and the cuts and implant selection were repeated; in phase 3, a neck-shaft angle (NSA) guide and digital calipers were used to measure humeral osteotomy thickness to aid in the desired humeral cut. All humeri were digitized. The difference between the prosthetic center of rotation (COR) and ideal COR was calculated. The percentage of patients with a varus NSA was calculated for each phase. The difference in planned and actual cut thickness was also compared.

RESULTS

For both 3D change in COR and medial to lateral change in COR, use of preoperative planning alone and with standard transfer instrumentation resulted in a significantly more anatomic restoration of ideal COR. The deviations from planned cut thickness decreased with each phase: phase 1: 2.6 ± 1.9 mm, phase 2: 2.0 ± 1.3 mm, phase 3: 1.4 ± 0.9 mm (P = .041 for phase 3 vs. phase 1). For NSA, in phase 1, 7 of 15 (47%) cases were in varus; in phase 2, 5 of 15 (33%) were in varus; and in phase 3, 1 of 15 (7%) cases was in varus (P = .013 for phase 3 vs. phase 1).

CONCLUSIONS

Use of preoperative 3D humeral planning for stemless anatomic TSA improved prosthetic humeral COR, whether performed with or without standard transfer instrumentation. The use of an NSA cut guide and calipers to measure cut thickness significantly reduced the percentage of varus humeral cuts and deviation from planned cut thickness.

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.

The effect of humeral head positioning and incomplete backside contact on bone stresses following total shoulder arthroplasty with a short humeral stem

BACKGROUND

The use of uncemented humeral stems in total shoulder arthroplasty (TSA) is known to be associated with stress shielding. This may be decreased with smaller stems that are well-aligned and do not fill the intramedullary canal; however, the effect of humeral head positioning and incomplete head backside contact has not yet been investigated. The purpose of this study was to quantify the effect of changes in humeral head position and incomplete head backside contact on bone stresses and expected bone response following reconstruction.

METHODS

Three-dimensional finite element models of 8 cadaveric humeri were generated, which were then virtually reconstructed with a short-stem implant. An optimally sized humeral head was then positioned in both a superolateral and inferomedial position for each specimen that was in full contact with the humeral resection plane. Additionally, for the inferomedial position, 2 incomplete humeral head backside contact conditions were simulated whereby contact was defined between only the superior or inferior half of the backside of the humeral head and the resection plane. Trabecular properties were assigned based on computed tomography attenuation and cortical bone was applied uniform properties. Loads representing 45° and 75° of abduction were then applied, and the resulting differentials in bone stress versus the corresponding intact state and the expected time-zero bone response were determined and compared.

RESULTS

The superolateral position reduced resorbing potential in the lateral cortex and increased resorbing potential in the lateral trabecular bone, while the inferomedial position produced the same effects but in the medial quadrant. For the inferomedial position, full backside contact with the resection plane was best in terms of changes in bone stress and expected bone response, although a small region of the medial cortex did experience no load transfer. The implant-bone load transfer of the inferior contact condition was concentrated at the midline of the backside of the humeral head, leaving the medial aspect largely unloaded as a result of the lack of lateral backside support.

DISCUSSION

This study shows that inferomedial humeral head positioning loads the medial cortex at the cost of unloading the medial trabecular bone, with the same occurring for the superolateral position except that the lateral cortex is loaded at the cost of unloading the lateral trabecular bone. Inferomedial positioned heads also were predisposed to humeral head lift-off from the medial cortex, which may increase the risk of calcar stress shielding. For the inferomedial head position, full contact between the implant and resection plane was preferable.

Patients who have intraoperative deviations in their preoperative plan have inferior clinical and radiographic outcomes after anatomic total shoulder arthroplasty

BACKGROUND

Three-dimensional computed tomography preoperative planning has become adopted among shoulder arthroplasty surgeons. Prior studies have not examined outcomes in patients in whom the surgeon implanted prostheses that deviated from the preoperative plan compared with patients in whom the surgeon followed the preoperative plan. The hypothesis of this study was that clinical and radiographic outcomes would be equivalent between patients undergoing anatomic total shoulder arthroplasty that had a deviation in the components predicted in the preoperative plan and patients who did not have a change in the components predicted in the preoperative plan.

METHODS

A retrospective review of patients who had preoperative planning for anatomic total shoulder arthroplasty from March 2017 through October 2022 was performed. Patients were stratified into 2 groups: patients in whom the surgeon used components that deviated from those anticipated by the preoperative plan (changed group), and patients in whom the surgeon used all of the components anticipated by the preoperative plan (planned group). Patient-determined outcomes including the Western Ontario Osteoarthritis Index, American Shoulder and Elbow Surgeons score, Single Assessment Numeric Evaluation, Simple Shoulder Test (SST), and Shoulder Activity Level were recorded preoperatively, at 1 year, and at 2 years. Preoperative and 1-year postoperative range of motion was recorded. Radiographic parameters to assess restoration of proximal humeral anatomy included humeral head height, humeral neck angle, humeral centering on the glenoid, and postoperative restoration of the anatomic center of rotation.

RESULTS

A total of 159 patients had intraoperative changes to their preoperative plan, and 136 patients underwent arthroplasty without changes to their preoperative plan. The planned group had higher scores than the group that had a deviation in the preoperative plan for every patient-determined outcome metric at every postoperative time point with statistically significant improvements found in the SST and Single Assessment Numeric Evaluation at 1-year and the SST and American Shoulder and Elbow Surgeons score at 2-year follow-up. No differences were found in range of motion metrics between the groups. Patients who did not have a deviation in their preoperative plan had more optimal restoration of their postoperative radiographic center of rotation than patients who did have a deviation in their preoperative plan.

CONCLUSIONS

Patients who have intraoperative changes to their preoperative plan have (1) inferior postoperative patient-determined outcome scores at 1 and 2 years after surgery and (2) a larger deviation in the postoperative radiographic restoration of the humeral center of rotation than patients who did not have intraoperative changes from the initial plan.

Evaluation of the Painful Total Shoulder Arthroplasty

Despite the overall success of anatomic and reverse total shoulder arthroplasties (aTSA and rTSA), some patients continue to have or develop pain postoperatively. As the number of shoulder arthroplasties continues to increase in the United States, it is important that surgeons are able to recognize, diagnose, and treat the various pathologies. Some painful etiologies are specific to either aTSA or rTSA, and others can occur with both implant types. Infections, stiffness, neurologic syndromes, polyethylene wear, aseptic implant loosening, and metal allergies occur, regardless of implant choice. However, after an aTSA, subscapularis repair failure, superior rotator cuff tear, and joint overstuffing can result in shoulder pain. After a rTSA, specific causes of postoperative pain include instability, scapular notching, acromial or scapular spine fractures, subcoracoid pain, and neurologic injury. Regardless of the diagnosis, the surgeon must be methodical in the evaluation and, when appropriate, use blood work, advanced imaging studies, joint aspirations, shoulder arthroscopy, and nerve studies. Once diagnosed, appropriate treatment should be undertaken to resolve the cause of the pain or at least minimize the effect of the pain on the patient's outcome.

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.

Accuracy of free-hand humeral head resection planned on 3D-CT models in shoulder arthroplasty: an in vitro analysis

INTRODUCTION

Three-dimensional planning of humeral head osteotomy in shoulder arthroplasty (SA) is understudied. This study evaluated whether a standard osteotomy technique along the anterosuperior anatomic neck (ASOT) could be surgically reproduced as pre-operatively planned on 3D-CT models.

MATERIAL AND METHODS

Pre-operative planning in 12 cadaver shoulders was performed on a 3D-CT model of the humerus to calculate the planned osteotomy plane (planned OP). The osteotomy was then performed using a free-hand technique, and a post-operative CT scan was obtained for analysis (performed OP). Planes were compared with regards to inclination, retroversion, and resected humeral head thickness so the accuracy could be quantified.

RESULTS

The absolute errors between the performed and planned OP were 2° (0-10°), 5° (0-14°), and 4 mm (1-7 mm) for inclination, retroversion, and resected head thickness, respectively. Deviation < 10° for inclination and retroversion and < 5 mm for resected humeral head thickness between planned and performed OP was achieved in 92%, 83%, 58% of cases, respectively. No differences were found for inclination (p = 0.289), whereas retroversion and resected head thickness were smaller than planned (p ≤ 0.027).

CONCLUSIONS

Pre-operative planning of the ASOT using a 3D-CT model is accurate within a threshold of 10° when using a free-hand technique in 92% of cases for inclination. Retroversion and resected head thickness differed from the pre-operative plan, thereby limiting the unrestricted use of humeral head osteotomy planning from 3D-CT models in SA. These findings are a reference for further studies to develop and quantify the accuracy of pre-operative planning software including cutting guides for SA using 3D-CT models.

LEVEL OF EVIDENCE

Basic science article.

Restoration of the native humeral anatomy during stemless anatomic total shoulder arthroplasty: a radiographic comparison of intramedullary versus freehand resection

BACKGROUND

During anatomic total shoulder arthroplasty (aTSA), the humeral head can be resected with or without the use of an intramedullary cutting guide, the former referred to as intramedullary (IM) resection and the latter referred to as freehand (FH) resection. Outcomes following aTSA are predicated upon the restoration of the native humeral anatomy, which can be more challenging with stemless implants. To date, no studies have determined which method of humeral head resection is superior in restoring native anatomy. Our purpose was to determine whether FH or IM resection was superior in restoring native anatomy during aTSA with stemless implants.

METHODS

A review of all patients who underwent aTSA using the stemless Tornier Simpliciti Shoulder System at two academic institutions by two separate surgeons between January 2017 and June 2020 was performed. One surgeon at one institution performed stemless aTSA using the IM resection technique, while the second surgeon utilized the FH resection technique. Patients were excluded if they underwent surgery for an indication other than glenohumeral osteoarthritis, if they received a short-stem or standard-stem implant, or if they lacked adequate preoperative and postoperative Grashey radiographs. One hundred eleven patients across both institutions (51 IM, 60 FH) were included for the final radiographic assessment. The humeral head height (HH) and neck-shaft angle (NSA) were measured on preoperative and postoperative Grashey radiographs. The centers of rotation (CORs) were measured on postoperative Grashey radiographs. Patients were classified as having acceptable restoration of their native anatomy if the change (Δ) in COR or HH was ≤3 mm and ≤ 5 mm, respectively, or if the postoperative NSA was ≥130°.

RESULTS

IM resection had the greatest acceptable restoration of COR (90.2% IM versus 70% FH, P = .009), HH (96.1% IM vs. 63.3% FH, P < .001), and NSA (96.1% IM vs. 78.3% FH, P = .006) relative to FH resection. The mean postoperative NSAs for the IM and FH cohorts were 134.4° (±2.1°) and 133.8° (±5.4°), respectively (P = .208). The mean ΔCORs for the IM and FH groups were 1.2 (±1.5) and 2.3 (±1.2) mm, respectively (P < .001). Finally, the mean ΔHHs for the IM and FH cohorts were 1.7 (±1.4) and 4.4 (±2.9) mm, respectively (P < .001).

CONCLUSIONS

Restoration of the native humeral anatomy following stemless aTSA occurred at a significantly higher rate when using IM vs. FH resection.

Fixed- vs. variable-angle humeral neck cut in anatomic total shoulder arthroplasty: a randomized controlled trial

BACKGROUND

Variable neck-shaft angle (NSA) stemmed humeral components have been incorporated into certain implant designs to better re-create normal anatomy in total shoulder arthroplasty (TSA). The purpose of this study was to determine if premorbid glenohumeral joint anatomy is better restored with a fixed- vs. variable-NSA prosthesis.

METHODS

A randomized controlled trial was performed including 50 patients with osteoarthritis indicated for primary anatomic TSA. Patients were randomized preoperatively to receive either a variable- (n = 26) or fixed-NSA (n = 24) prosthesis. Humeral neck cut in the variable-NSA group matched the patient's anatomic neck, with prosthetic NSA of 127.5°, 132.5°, and 137.5° available. Fixed-NSA cuts were made with an intramedullary guide of 132.5°. Preoperative and postoperative radiographs were evaluated for specific radiographic anatomic variables: NSA, head thickness, tuberosity-to-head height, head offset, articular arc, greater tuberosity offset, and center of rotation (COR). Postoperative radiographic criteria were compared between groups.

RESULTS

No differences were found between groups in demographics or preoperative radiographic measures. When comparing average difference in preoperative and postoperative measurements in the fixed-NSA group, the humeral head offset from the humeral shaft axis significantly decreased by 1.4 mm (P = .046), and the COR moved superiorly (3.0 mm, P = .002) without significant medialization or lateralization. In the variable angle group, humeral head offset decreased but did not reach significance (1.2 mm, P = .091), and the COR also moved superiorly (2.9 mm, P < .001) without significant medialization or lateralization. All remaining radiographic parameters did not significantly change from pre- to postoperative imaging. In comparing the fixed- and variable-NSA groups' net change from the premorbid measurements, no significant differences were found in tuberosity-to-head height, head offset, or COR position in both the horizontal and vertical planes.

CONCLUSIONS

Both fixed- and variable-NSA anatomic TSA humeral components demonstrate adequate restoration of premorbid anatomy radiographically.

Comparison of Postoperative Anatomy Using Anatomic Total Shoulder Arthroplasty Versus Soft-Tissue Balancing Total Shoulder Arthroplasty

BACKGROUND

The importance of anatomic reconstruction of the proximal humerus on shoulder biomechanics and kinematics after anatomic total shoulder replacement (aTSR) has been highlighted by a number of investigations. The humeral head designs of current-generation shoulder arthroplasty emphasize either anatomic or soft-tissue balancing total shoulder arthroplasty (sbTSR) philosophies. The purpose of this study was to compare the postoperative anatomy of TSR systems used to treat primary glenohumeral osteoarthritis.

METHODS

This was a matched cohort study of 60 patients treated with either press-fit aTSR or sbTSR by two shoulder surgeons. The analysis of postoperative true AP radiographs was performed to calculate multiple representative anatomic parameters of the TSR.

RESULTS

A significant difference was observed in the average measurements between the sbTSR and aTSR designs about the humeral head center offset (5.2 ± 0.4 mm versus 3.9 ± 0.3 mm; P = 0.02), implant-humeral shaft angle (0.3 ± 0.3 varus versus 1.7 ± 0.3 valgus, P < 0.001), and humeral head to tuberosity height (8.8 ± 0.4 mm versus 6.2 ± 0.4, P < 0.001), respectively. No significant difference was observed in the average measurements between the two systems' designs regarding the head-shaft angle (133.4° ± 0.8° versus 135.0° ± 1.0°, P = 0.16) and the relation of humeral head to lateral humeral cortex (0.15 ± 0.6 mm inside the lateral cortex versus 0.19 ± 0.6 outside the lateral cortex; P = 0.69), respectively.

CONCLUSIONS

Despite differing design philosophies of these systems, and some notable differences, the absolute differences between the measured anatomic parameters were small and not likely clinically relevant. Anatomic and soft-tissue balancing humeral arthroplasty implants can both reliably reconstruct proximal humeral anatomy.

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

Background

The purpose of this study was to compare the accuracy of anatomic reconstruction of three different humeral head designs after anatomic total shoulder arthroplasty.

Methods

Postoperative radiographs of 117 patients who underwent anatomic total shoulder arthroplasty with three different implant designs (stemmed spherical, stemless spherical, and stemless elliptical) were analyzed for landmarks that represented the prearthritic state and final implant position. We assessed the change in center of rotati7on and humeral head height on the anteroposterior view and the percentage of prosthesis overhang on the axillary lateral view. A modified anatomic reconstruction index, a compound score that rated each of the 3 parameters from 0 to 2, was created to determine the overall accuracy of the reconstruction.

Results

Excellent modified anatomic reconstruction index scores (5 or 6 points) were achieved by 68.1% of the cases in the stemless elliptical group compared with 33.3% of the cases in the stemless spherical group and by 28.3% of the cases in the stemmed spherical group (P = .001).The mean difference in restoration of humeral head height (P < .001) and percentage of prosthesis overhang (P < .001) was superior for the stemless elliptical group compared with the two other spherical head groups. There was no difference between groups for the shift in center of rotation (P = .060).

Conclusions

In this radiographic investigation comparing three different humeral head designs with respect to anatomic restoration parameters, the stemless elliptical implant more closely restored the geometry of the prearthritic humeral head as assessed by humeral head height, prosthesis overhang, and a compound reconstruction score.

Does computerized CT-based 3D planning of the humeral head cut help to restore the anatomy of the proximal humerus after stemless total shoulder arthroplasty?

BACKGROUND

Restoration of proximal humeral anatomy (RPHA) after total shoulder arthroplasty (TSA) has been shown to result in better clinical outcomes than is the case in nonanatomic humeral reconstruction. Preoperative virtual planning has mainly focused on glenoid component placement. Such planning also has the potential to improve anatomic positioning of the humeral head by more accurately guiding the humeral head cut and aid in the selection of anatomic humeral component sizing. It was hypothesized that the use of preoperative 3-dimensional (3D) planning helps to reliably achieve RPHA after stemless TSA.

METHODS

One hundred consecutive stemless TSA (67 males, 51 right shoulder, mean age of 62 ±9.4 years) were radiographically assessed using pre- and postoperative standardized anteroposterior radiographs. The RPHA was measured with the so-called circle method described by Youderian et al. We measured deviation from the premorbid center of rotation (COR), and more than 3 mm was considered as minimal clinically important difference. Additionally, pre- and postoperative humeral head diameter (HHD), head-neck angle (HNA), and humeral head height (HHH) were measured to assess additional geometrical risk factors for poor RPHA.

RESULTS

The mean distance from of the premorbid to the implanted head COR was 4.3 ± 3.1 mm. Thirty-five shoulders (35%) showed a deviation of less than 3 mm (mean 1.9 ±1.1) and 65 shoulders (65%) a deviation of ≥3 mm (mean 8.0 ± 3.7). Overstuffing was the main reason for poor RPHA (88%). The level of the humeral head cut was responsible for overstuffing in 46 of the 57 overstuffed cases. The preoperative HHD, HHH, and HNA were significantly larger, higher, and more in valgus angulation in the group with accurate RPHA compared with the group with poor RPHA (HHD of 61.1 mm ± 4.4 vs. 55.9 ± 6.6, P < .001; HHH 8.6±2.2 vs. 7.6±2.6, P = .026; and varus angulation of 134.7° ±6.4° vs. 131.0° ±7.91, P = .010).

CONCLUSION

Restoration of proximal humeral anatomy after stemless TSA using computed tomography (CT)-based 3D planning was not precise. A poorly performed humeral head cut was the main reason for overstuffing, which was seen in 88% of the cases with inaccurate RPHA. Preoperative small HHD, low HHH, and varus-angulated HNA are risk factors for poor RPHA after stemless TSA.

Infraspinatus and deltoid length and patient height: implications for lateralization and distalization in reverse total shoulder arthroplasty

BACKGROUND

Restoration of muscular strength is predicated on restoration of muscle length. The purpose of this study was to describe infraspinatus and deltoid length preoperative to reverse total shoulder arthroplasty (RTSA) to guide distalization and lateralization to restore preoperative muscle length.

METHODS

This was a retrospective radiographic study. We measured the infraspinatus length on preoperative computed tomographic images and the deltoid length on preoperative radiographs. For all measurements, reliability was first established by comparing measurements between 2 observers, and intraclass correlation coefficients (ICCs) were calculated. We then calculated descriptive statistics for these muscle lengths and developed a formula to predict these muscle lengths from patient demographics.

RESULTS

We measured infraspinatus length in 97 patients and deltoid length in 108 patients. Inter-rater reliability was excellent, with all ICCs >0.886. The mean infraspinatus length was 15.5 cm (standard deviation 1.3) and ranged from 12.6-18.9 cm, whereas the deltoid length was 16.2±1.7 cm and ranged from 12.5-20.2 cm. Both infraspinatus (r = 0.775, P < .001) and deltoid length (r = 0.717, P < .001) were highly correlated with patient height but did not differ between diagnoses. Formulae developed through linear regression allowed prediction of muscle length to within 1 cm in 78% and within 2 cm in 100% for the infraspinatus and 60% and 88% for the deltoid.

CONCLUSION

Deltoid and infraspinatus length are variable but highly correlated with patient height. To maintain tension, 2 mm of lateralization and distalization should be added for every 6 inches (∼15 cm) of height above average for a Grammont-style RTSA.

Radiographic humeral head restoration after total shoulder arthroplasty: does the stem make a difference?

BACKGROUND

Humeral stem designs for total shoulder arthroplasty have varied over the years, with a recent trend toward shorter stems. The purpose of this study was to examine the impact of humeral component stem length on the ability to restore the native humeral head anatomy.

METHODS

We performed a retrospective review including patients who underwent total shoulder arthroplasty for primary osteoarthritis between 2007 and 2017 with complete operative reports and adequate radiographs. Surgical data including stem design were collected. Preoperative and postoperative radiographic measurements of the center of rotation (COR), humeral head height (HH), and neck-shaft angle were performed. Restoration of the native humeral anatomy was deemed "acceptable" based on postoperative differences in the COR ≤ 3 mm, HH ≤ 5 mm, and neck-shaft angle > 130°. Deviations between preoperative and postoperative measurements were compared across stem types. All available 2-year stemless implant radiographs were also analyzed.

RESULTS

In total, 261 patients were included, with 31 stemless, 43 short-stem, and 187 standard-stem implants. There was no significant difference in COR restoration in the x-axis direction (P = .060) or y-axis direction (P = .579). There was no significant difference in restoration of acceptable HH by stem type (P = .339). Stemless arthroplasty implants were more likely to be placed in varus (22.6%) compared with short-stem (7.0%) and standard-stem (3.7%) designs (P < .001).

CONCLUSION

Restoration of humeral anatomic parameters occurred significantly less with stemless implants than with short- and standard-stem implants. The stem of a shoulder arthroplasty implant aids surgeons in accurately restoring patient-specific anatomy.

Outcomes after a Grammont-style reverse total shoulder arthroplasty?

BACKGROUND

The purpose of this study was to determine the factors associated with outcomes after reverse total shoulder arthroplasty (RTSA).

METHODS

We retrospectively evaluated all RTSAs performed by the senior author between January 1, 2007, and November 1, 2017. We evaluated pain visual analog scale (VAS), Simple Shoulder Test (SST), and American Shoulder and Elbow Surgeons Standardized Shoulder Assessment Form (ASES) scores and complication and reoperation rates at a minimum of 2-year follow-up. We evaluated preoperative and 2-week postoperative radiographs for glenoid inclination (GI), medialization as distance between the center of the humeral head or glenosphere and the line of the deltoid, and distalization via the acromial-greater tuberosity distance. We performed inter- and intrarater reliabilities via intraclass correlation coefficients (ICCs) and conducted a multivariable analysis.

RESULTS

We included 230 RTSAs in the analysis, with 70% follow-up at a median of 3.4 years. Reliability was acceptable with all ICCs >.678. Increased postoperative GI was significantly associated with increased VAS pain postoperatively (P = .008). Increased distalization was associated with an increased rate of complications and reoperations (P = .032). Younger age (P = .008), female gender (P = .009), and lower body mass index (BMI) (P = .006) were associated with worse ASES scores. Female gender (P < .001) and lower BMI (P = .039) were associated with worse SST scores. Female gender (P = .013) and lower BMI (P = .005) were associated with worse VAS-pain scores.

CONCLUSION

Age, gender, and BMI are associated with outcome after RTSA. In this retrospective analysis of a Grammont-style RTSA, superior inclination is associated with increased pain postoperatively, whereas excessive arm lengthening is associated with increased risk for complication or reoperation.

Eclipse stemless shoulder prosthesis vs. Univers II shoulder prosthesis: a multicenter, prospective randomized controlled trial

BACKGROUND

Total shoulder arthroplasty is an accepted treatment for glenohumeral osteoarthritis. The Arthrex Eclipse shoulder prosthesis is a stemless, canal-sparing humeral prosthesis with bone ingrowth capacity on the trunnion, as well as through the fenestrated hollow screw, that provides both diaphyseal and metaphyseal load sharing and fixation.

METHODS

Between 2013 and 2018, 16 sites in the United States enrolled 327 patients (Eclipse in 237 and Arthrex Univers II in 90). All patients had glenohumeral arthritis refractory to nonsurgical care. Strict exclusion criteria were applied to avoid confounding factors such as severe patient comorbidities, arthritis not consistent with osteoarthritis, and medical or prior surgical treatments that may have affected outcomes. Patients were randomized to the Eclipse or Univers II group via block randomization.

RESULTS

In total, 149 Eclipse and 76 Univers II patients reached 2-year follow-up (139 Eclipse patients [93.3%] and 68 Univers II patients [89.5%] had complete data). The success rate using the Composite Clinical Success score was 95% in the Eclipse group vs. 89.7% in the Univers II group. No patient exhibited radiographic evidence of substantial humeral radiolucency, humeral migration, or subsidence at any point. Reoperations were performed in 7 patients (3.2%) in the Eclipse group and 3 (3.8%) in the Univers II group.

CONCLUSION

The Arthrex Eclipse shoulder prosthesis is a safe and effective humeral implant for patients with glenohumeral arthritis at 2-year follow-up, with no differences in outcomes compared with the Univers II shoulder prosthesis.

Does Having a Rotator Cuff Repair Before Total Shoulder Arthroplasty Influence Outcomes?

Background:

The number of rotator cuff repairs (RCRs) is increasing each year. Total shoulder arthroplasty (TSA) is a successful treatment option for patients with glenohumeral osteoarthritis with a functioning rotator cuff.

Purpose/Hypothesis:

The purposes of this study were to report the outcomes of TSA in patients with ipsilateral RCR and determine whether patients with a history of ipsilateral RCR who subsequently underwent TSA had differences in outcomes compared with matched controls who underwent TSA with no history of RCR. We hypothesized that patients with prior RCR will have significant improvements in clinical outcome scores, with no difference in outcomes after TSA compared with those with no prior RCR.

Study Design:

Cohort study; Level of evidence, 3.

Methods:

Patients eligible for inclusion were those with a history of prior RCR who underwent TSA at a single institution with a minimum 2-year follow-up between 2000 and 2015. Outcomes for this group, including American Shoulder and Elbow Surgeons (ASES) scores, were reported and then compared with a matched control group of patients who underwent TSA with no history of prior RCR. Controls were matched based on age, sex, and preoperative ASES score.

Results:

Overall, 14 patients (64% males; mean ± SD age, 65.1 ± 11.1 years) underwent prior ipsilateral RCR before TSA. ASES scores significantly improved from 42.9 to 78.5 at 2 years and to 86.6 at 5 years. When compared with 42 matched control patients (matched 1:3) who underwent TSA with no history of RCR, there was no significant difference in ASES scores at 2 years (78.5 vs 85.3; P = .19) and 5 years (86.6 vs 90.9; P = .72) between the prior RCR and no RCR groups.

Conclusion:

TSA in patients with a history of prior ipsilateral RCR led to significant improvements in clinical outcomes. No difference in clinical outcomes at 2 or 5 years after TSA was found between patients with and without a history of prior ipsilateral RCR.

Overstuffing in resurfacing hemiarthroplasty is a potential risk for failure

PURPOSE

Literature describes the concern of an overstuffed shoulder joint after a resurfacing humeral head implant (RHHI). The purpose of this study was to evaluate inter-observer variability of (1) the critical shoulder angle (CSA), (2) the length of the gleno-humeral offset (LGHO), and (3) the anatomic center of rotation (COR) in a patient population operated with a Global Conservative Anatomic Prosthesis (CAP) RHHI. The measurements were compared between the revision and non-revision groups to find predictive indicators for failure.

METHODS

Pre- and postoperative radiographs were retrieved from 48 patients who underwent RHHI from 2007 to 2009 using a Global CAP hemiarthroplasty for end-stage osteoarthritis. This cohort consisted of 36 females (12 men) with a mean age of 77 years (SD 7.5). Two musculoskeletal radiologist and two specialized shoulder orthopedic surgeons measured the CSA, LGHO, and COR of all patients.

RESULTS

The inter-observer reliability showed excellent reliability for the CSA, LGHO, and the COR, varying between 0.91 and 0.98. The mean COR of the non-revision group was 4.9 mm (SD 2.5) compared to mean COR of the revision group, 8 mm (SD 2.2) (p < 0.01). The COR is the predictor of failure (OR 1.90 (95%Cl 1.19-3.02)) with a cut of point of 5.8 mm. The mean CSA was 29.8° (SD 3.9) There was no significant difference between the revision and non-revision groups (p = 0.34). The mean LGHO was 2.6 mm (SD 3.3) post-surgery. The mean LGHO of the revision group was 3.9 (SD 1.7) (p = 0.04) post-surgery. Despite the difference in mean LGHO, this is not a predictor for failure.

CONCLUSION

The CSA, LGHO, and COR can be used on radiographs and have a high inter-observer agreement. In contrast with the CSA and LGHO, we found a correlation between clinical failure and revision surgery in case of a deviation of the COR greater than 5 mm.

TRIAL REGISTRATION

Institutional review board, number: ACLU 2016.0054, Ethical Committee number: CBP M1330348. Registered 7 November 2006.

Normal and Pathoanatomy of the Arthritic Shoulder: Considerations for Shoulder Arthroplasty

The glenohumeral joint is a highly mobile, complex articulation that relies not only on the bony support between the humeral head and glenoid but also on appropriate balance and tension of the surrounding soft-tissue structures. Recreating the normal anatomic relationships is a basic premise in joint arthroplasty, which can be challenging in shoulder arthroplasty, as the normal glenohumeral anatomy has considerable variation from patient to patient. Also, as the anatomy of the glenohumeral joint becomes distorted with advanced shoulder pathology, it becomes a challenge to return the shoulder to its premorbid anatomic state. Failure to restore normal anatomic parameters after shoulder arthroplasty has been shown to have deleterious effects on postoperative function and implant survival. As the recognition of this has grown, shoulder prostheses have evolved to allow for considerable more variation in an attempt to recreate patient-specific anatomy. However, understanding the progression of shoulder pathology to better predict the patient's premorbid anatomy remains limited. A thorough understanding of the premorbid and pathologic anatomy of the glenohumeral joint will aid in preoperative planning and intraoperative execution and lead to a more predictable reconstruction of the shoulder, which is critical for a successful outcome after shoulder arthroplasty.