Abstract
Background
Aspherical humeral head morphology has previously been shown to be associated with progression of glenohumeral osteoarthritis. Habermeyer et al classified humeral head morphology as either spherical or aspherical. Aspherical head morphology was associated with increased incidence of glenoid deformity (B2) as well as decentering of the humeral head, but the authors did not correlate these findings to clinical outcomes. The purpose of this investigation is to apply these findings to the evaluation of clinical outcomes following anatomic total shoulder arthroplasty (aTSA) and to further define preoperative humeral head pathomorphology.
Methods
We performed a retrospective review of all patients who underwent primary aTSA who had adequate pre- and postoperative radiographs and 2-year follow-up. Preoperative radiographs were analyzed and humeral heads were classified as either spherical, mild aspherical, or major aspherical. Axillary images were evaluated to quantify centering of the humeral head and glenoid morphology. Postoperative radiographs were analyzed to quantify implant center of rotation (COR) utilizing the best fit circle technique. Patient-reported outcomes, range of motion and strength at 2-years postoperatively were recorded. Statistical significance was evaluated using chi-square and paired t-test statistics for both regression analysis and univariate analyses.
Results
A total of 259 patients met inclusion criteria for this study. Of these, 158 patients (61%) were classified as spherical, 64 patients (25%) mild aspherical, and 37 patients (14%) major aspherical. Males were higher represented among patients with mild and major aspherical humeral heads. Aspherical humeral heads had a significantly higher incidence of B2 glenoid morphology, while spherical heads had a significantly higher incidence of A1 glenoids. Patients with aspherical humeral heads were found to have significantly worse external rotation preoperatively compared to those with spherical heads. There were no significant differences in postoperative range of motion. However, postoperative improvements in external rotational strength and belly press strength were significantly higher in patients with aspherical humeral heads. Preoperative humeral head morphology did not have any influence on patient-reported outcomes at 2-year follow-up or on radiographic postoperative implant restoration of COR.
Discussion/Conclusion
Aspherical head morphology was associated with a higher incidence of male gender and B2 glenoid morphology; however, humeral head deformity alone was not shown to lead to diminished outcomes or worse COR restoration following TSA. Patients with aspherical preoperative humeral head morphology were not found to have worse clinical or radiographic outcomes compared to patients with spherical heads; however, patients with aspherical humeral heads did make significant improvements in rotational strength at 2-year follow-up.
Keywords: Shoulder, Arthritis, Humerus, Head, Morphology, Arthroplasty, Outcomes
One of the hallmarks of primary glenohumeral osteoarthritis (GHOA) is progressive joint degeneration, which includes wear of both the humeral and glenoid sides of the glenohumeral articulation. While glenoid wear patterns have traditionally been recognized as important factors in total shoulder arthroplasty (TSA), the morphology of the humeral head has only recently garnered increased clinical attention.2,11,16,18,20 Prior studies from Youderian et al, Knowles et al, and Jacxens et al analyzed humeral head morphology in primary GHOA based on computed tomography scans, but understanding of humeral head shape morphology and posterior translation of the humeral head with respect to the center of the glenoid remains poorly understood.9,13,22
Habermeyer et al performed an investigation of pathomorphologic changes of the humeral head in primary GHOA using radiographic, magnetic resonance imaging, and 3-dimensional photographic analysis of the humeral head.5 Their study included 55 patients with primary GHOA who underwent anatomic total shoulder arthroplasty (aTSA) who were classified as having either spherical or aspherical humeral head preoperatively and evaluated the association between humeral head sphericity and arthritis type. They identified two types of primary GHOA; (1) spherical osteoarthritis where the humeral head does not have substantial coronal or transverse plane deformity, no posterior subluxation, and the cartilage wear is primarily caudal; and (2) aspherical osteoarthritis where the humeral head becomes flattened and is accompanied by deformation in the transverse plane with posterior humeral head decentering, and the cartilage wear typically involves the cranial portions in the sagittal plane.5 Aspherical humeral heads were shown to exhibit altered contour, cartilage erosion, and eccentric osteophyte formation.7,13,15,19 Compared to patients with GHOA with spherical humeral heads, patients with aspherical heads had a higher incidence of B2 glenoid morphology and posterior humeral head subluxation.9,18 Ultimately, these changes can disrupt joint congruity and result in abnormal glenoid loading, which in turn may increase glenoid wear and disease progression. However, the influence on preoperative humeral head morphology on outcomes following aTSA was not investigated.3,5,12,16,19
The purpose of this study was to evaluate the effect of humeral head pathomorphology on clinical and radiographic outcomes following aTSA. We hypothesized that aspherical humeral head morphology would be associated with worse clinical outcomes and higher variation in radiographic center of rotation (COR) restoration following aTSA than patients who had spherical humeral heads preoperatively. We also hypothesized that aspherical humeral head morphology would be associated with a higher proportion of type B and C glenoid morphology preoperatively.
Materials and methods
Patient database and outcome measures
This is a retrospective comparative study utilizing a multi-institution shoulder arthroplasty registry database for patient analysis. Institutional review board approval was obtained at each site prior to enrolling patients in the registry, and the data were retrospectively reviewed according to the approved institutional review board. Inclusion criteria were all patients undergoing primary aTSA who were rotator cuff-intact with adequate preoperative radiographs, 2 years of clinical follow-up, and adequate postoperative radiographs. For patients undergoing aTSA, all patients underwent treatment with all-polyethylene glenoid component. All stem types were included (stemless, short stem, and standard stem length). Exclusion criteria were patients undergoing revision TSA, Those with metal-backed glenoid components, and those with inadequate preoperative or postoperative radiographs. A total of 288 total patients were included in the initial review, and 29 patients were subsequently excluded due to inadequate pre- or postoperative radiographs for a total of 259 patients. Four board-certified shoulder and elbow surgeons served as radiographic reviewers. Preoperative and postoperative radiographs were analyzed, as well as patient-reported outcome scores (PROs), range of motion (ROM), and strength following the 2-year postoperative follow-up. PROs collected included he American Shoulder and Elbow Surgeons, Constant–Murley (CM), visual analog scale, Veterans Rand 12 Item Health Survey , Western Ontario Osteoarthritis of the Shoulder Index, and Single Assessment Numeric Evaluation. Strength was measured in pounds using a dynamometer for CM strength, external rotation (ER) strength, and belly press strength. ROM was measured by the treating surgeons' team with a goniometer for active forward flexion, active ER in adduction, active ER with the arm at 90° (ER90), and internal rotation (IR) with the arm at 90° (IR90). IR was also estimated to the nearest spinal level (IRspine).
Radiographic evaluation
Radiographic evaluation was based on standardized true anterior–posterior (or Grashey view) radiographs and axillary radiographs. Utilizing preoperative Grashey view radiographs, humeral heads were classified as either spherical (Fig. 1), in which humeral head cortical boundaries fit a perfect circle; mild aspherical (Fig. 2), in which cortical boundaries did not fit within confines of best-fit circle in one quadrant; or major aspherical (Figs. 3 and 4), in which cortical boundaries did not within confines of best-fit circle in more than one quadrant. This expands on the original classification by Habermeyer et al by creating a third group and allowing more precise classification of preoperative humeral head morphology. Axillary images were evaluated to quantify decentering of the humeral head and glenoid morphology according to the method and classification described by Walch et al based on the relationship of the center of the humeral head to the scapular axis.18,20 Postoperative radiographs were analyzed to quantify implant COR and neck shaft angle (NSA) of the prothesis. NSA was measured as the angle between the humeral proximal articular surface and the intramedullary axis of the humeral shaft. Ideal implant COR was identified using the best-fit circle method described by Youderian et al.22 Axillary radiographs were used to evaluate the centering of the humeral head postoperatively similarly to how humeral head decentering was measured preoperatively.
Figure 1.
Preoperative AP (A) and axillary (B) radiographs of a patient with a spherical humeral head with humeral head cortical boundaries fitting within a best-fit circle and minimal posterior humeral head decentering. Postoperative AP (C) and axillary (D) radiographs demonstrating restoration of center of rotation and a centered humeral head. AP, anterior–posterior.
Figure 2.
Preoperative AP (A) and axillary (B) radiographs of a patient with a mild aspherical humeral head in which humeral head cortical boundaries did not fit within a perfect circle in one quadrant with central glenoid wear and minimal posterior humeral head decentering. Postoperative AP (C) and axillary (D) radiographs demonstrating restoration of center of rotation and a centered humeral head. AP, anterior–posterior.
Figure 3.
Preoperative AP (A) and axillary (B) radiographs of a patient with a majoraspherical humeral head in which cortical boundaries did not within confines of best-fit circle in more than one quadrant posterior glenoid wear and posterior humeral head subluxation. Postoperative AP (C) and axillary (D) radiographs demonstrating restoration of center of rotation and a centered humeral head. AP, anterior–posterior.
Figure 4.
Intraoperative photographs of a patient demonstrating major aspherical humeral head morphology.
Statistical analysis
Patient demographics, pre- and postoperative functional outcomes, PROs, and radiographic analysis were recorded. Descriptive statistics (mean and standard deviation for continuous variables, frequencies, and percentages for categorical variables) were calculated for the entire cohort and stratified by classification of humeral head type (spherical, mild aspherical, major aspherical). Statistical significance was evaluated using chi-square for univariate analysis of categorical variables and one-way analysis of variance with a Tukey post hoc test for univariate analysis of continuous variables. P < .05 was considered significant. All analyses were performed using SPSS version 29 (IBM Corp., Armonk, NY, USA).
Results
A total of 288 patients were identified who were eligible for inclusion in the study. Twenty-nine patients were excluded due to inadequate pre- or postoperative radiographs, thus 259 patients were available for final review. Mean follow-up was 4.6 ± 1.2 years. Demographic information is presented in Table I. Preoperative classification of humeral head morphology according to our modification of Habermeyer et al's classification system included 158 patients (61%) who met classification as spherical, 64 patients (25%) classified as mild aspherical, and 37 patients (14%) classified as major aspherical. There were no significant differences between the three groups in patient age, body mass index, diabetes, or arm dominance. There was a significantly higher percentage of patients who smoked in the spherical vs. mild aspherical group (8.2% vs. 0%, P = .018) and in the major aspherical group vs. mild aspherical group (10.8% vs. 0%, P = .007) but not in the spherical vs. major aspherical group. There was a higher percentage of male patients in those who had mild aspherical (65.6%) and major aspherical heads (73.0%) compared to those who had spherical heads (53.7%). The difference between the percentage of male patients was statistically significant when comparing patients with spherical vs. major spherical head morphology (P = .029)
Table I.
Patient data.
| Variable | Spherical (N = 158) |
Mild aspherical (N = 64) |
Major aspherical (N = 37) |
ANOVA (P values) |
|||||
|---|---|---|---|---|---|---|---|---|---|
| Mean | Standard deviation | Mean | Standard deviation | Mean | Standard deviation | Sphrical vs. mild | Spherical vs. major | Mild vs. major | |
| Age (yr) | 65.9 | 7.6 | 66.7 | 7.7 | 65.8 | 7.2 | .791 | .996 | .851 |
| BMI (kg/m2) | 31.0 | 6.8 | 29.5 | 6.2 | 30.6 | 4.3 | .233 | .925 | .675 |
| Sex, male (N, %) | 84 | 53.2% | 42 | 65.6% | 27 | 73.0% | .090 | .029 | .444 |
| Smoking (N, %) | 13 | 8.2% | 0 | 0.0% | 4 | 10.8% | .018 | .616 | .007 |
| Diabetes (N, %) | 19 | 12.0% | 6 | 9.4% | 4 | 10.8% | .572 | .837 | .816 |
| Dominant arm (N, %) | 73 | 46.2% | 31 | 48.4% | 19 | 51.4% | .762 | .572 | .778 |
| Glenoid morphology | |||||||||
| A1 | 91 | 57.6% | 18 | 28.1% | 8 | 21.6% | <.001 | <.001 | .471 |
| A2 | 1 | 0.6% | 3 | 4.7% | 0 | 0.0% | .040 | .628 | .181 |
| B1 | 24 | 15.2% | 11 | 17.2% | 3 | 8.1% | .711 | .262 | .203 |
| B2 | 35 | 22.2% | 30 | 46.9% | 22 | 59.5% | <.001 | <.001 | .223 |
| B3 | 4 | 2.5% | 2 | 3.1% | 4 | 10.8% | .805 | .022 | .115 |
| C | 1 | 0.6% | 0 | 0.0% | 0 | 0.0% | .524 | .628 | n.a. |
| D | 2 | 1.3% | 0 | 0.0% | 0 | 0.0% | .366 | .492 | n.a. |
| COR shift from ideal (mm) | 2.6 | 1.8 | 2.7 | 1.6 | 2.8 | 1.8 | .955 | .779 | .920 |
| Prosthetic NSA (degrees) | 134 | 6 | 134 | 5 | 134 | 5 | .864 | .912 | 1.000 |
BMI, body mass index; COR, center of rotation; n.a., not applicable; NSA, neck shaft angle; ANOVA, analysis of variance.
Patient demographic data and preoperative radiographic parameters.
Patients with mild aspherical and major aspherical humeral heads also had a significantly higher incidence of B2 glenoid morphology compared to those with spherical head morphology (46.9% and 59.5% compared to 22.2%, respectively) (P < .001 spherical vs. mild aspherical, P < .001 spherical vs. major aspherical). Major aspherical heads also had a significantly higher association with B3 type glenoid morphology compared to spherical heads (P = .022). Spherical heads had a significantly higher incidence of A1 glenoid morphology (57.6%) compared to patients with mild aspherical and major aspherical heads (28.1% and 21.6%, respectively) (P < .001 spherical vs. mild aspherical, P < .001 spherical vs. major aspherical).
Radiographic analysis
Postoperatively, there were no significant differences in restoration of glenohumeral joint COR or prosthetic NSA (Table I). The postoperative COR shift from ideal was 2.6 mm for patients with spherical head morphology, 2.7 mm for mild aspherical head morphology, and 2.8 mm for patients with major aspherical head morphology, which was not statistically significant. When evaluating COR outliers, the percentage of patients with a >2 mm COR difference from native was 53.8% (n = 85) for spherical heads, 60.9% (n = 39) for mild aspherical heads, and 62.2% (n = 23) for major aspherical heads, which was not statistically significant. The percentage of patients with a >4 mm COR difference from native was 13.9% (n = 22) for spherical heads, 18.8% (n = 12) for mild aspherical heads, and 16.2% (n = 6) for major aspherical heads (P = .366 spherical vs. mild aspherical, P = .720 spherical vs. major aspherical, P = .749 mild vs. major aspherical) (Table II).
Table II.
COR outliers.
| Variable | Spherical (N = 158) |
Mild aspherical (N = 64) |
Major aspherical (N = 37) |
ANOVA (P values) |
|||||
|---|---|---|---|---|---|---|---|---|---|
| Mean | Standard deviation | Mean | Standard deviation | Mean | Standard deviation | Spherical vs. mild | Spherical vs. major | Mild vs. major | |
| Mean COR shift | 2.6 | 1.8 | 2.7 | 1.6 | 2.8 | 1.8 | .955 | .779 | .920 |
| N | % | N | % | N | % | Spherical vs. mild | Spherical vs. major | Mild vs. major | |
| >2 mm COR shift | 85 | 53.8% | 39 | 60.9% | 23 | 62.2% | .332 | .357 | .903 |
| >4 mm COR shift | 22 | 13.9% | 12 | 18.8% | 6 | 16.2% | .366 | .720 | .749 |
ANOVA, analysis of variance; COR, center of rotation.
Preoperative data stratified by humeral head sphericity; patient-reported outcomes, range of motion, and strength.
Patient-reported outcomes
Preoperatively, there were no significant differences in American Shoulder and Elbow Surgeons, visual analog scale pain, Western Ontario Osteoarthritis of the Shoulder, Single Assessment Numeric Evaluation, CM, or Veterans Rand 12 Item Health Surveymental health scores between the three groups except for patients with major aspherical heads had a significantly lower CM score compared to those with spherical heads (P = .025) (Table III). At 2 years postoperatively, there were no significant differences in any of the PROs between those with spherical, mild aspherical, or major aspherical humeral head morphology (Table IV). In addition, there were no statistically significant differences between the three groups in improvement from baseline in any of the PROs (Table V).
Table III.
Preoperative data stratified by humeral head sphericity.
| Outcome measure | Spherical (N = 158) |
Mild aspherical (N = 64) |
Major aspherical (N = 37) |
ANOVA (P values) |
|||||
|---|---|---|---|---|---|---|---|---|---|
| Mean | Standard deviation | Mean | Standard deviation | Mean | Standard deviation | Sphrical vs. mild | Spherical vs. major | Mild vs. major | |
| PROs | |||||||||
| ASES | 43.7 | 17.3 | 42.9 | 18.3 | 39.5 | 16.5 | .952 | .388 | .610 |
| VAS pain | 5.6 | 2.3 | 5.4 | 2.6 | 5.6 | 2.3 | .844 | .992 | .954 |
| WOOS | 38.6 | 19.1 | 36.3 | 18.8 | 34.4 | 17.4 | .686 | .460 | .887 |
| SANE | 33.8 | 23.2 | 34.3 | 23.3 | 30.6 | 21.9 | .983 | .737 | .712 |
| Constant–Murley | 45.1 | 16.7 | 41.6 | 14.6 | 37.3 | 16.1 | .326 | .025 | .400 |
| VR-12 mental | 49.0 | 12.4 | 51.0 | 10.9 | 51.9 | 10.8 | .469 | .356 | .927 |
| ROM | |||||||||
| Active FF (degrees) | 112 | 33 | 106 | 33 | 93 | 25 | .334 | .004 | .156 |
| Active ER at Side (degrees) | 36 | 22 | 25 | 17 | 18 | 16 | <.001 | <.001 | .269 |
| Active ER at 90 (degrees) | 38 | 31 | 28 | 26 | 23 | 25 | .055 | .013 | .655 |
| Active IR (spinal level) | L5 | 3 | L5 | 3 | L5 | 3 | .999 | .999 | .999 |
| Active IR at 90 (degrees) | 22 | 23 | 20 | 21 | 13 | 16 | .736 | .088 | .373 |
| Strength | |||||||||
| Constant–Murley | 7.2 | 5.9 | 5.6 | 4.9 | 6.6 | 5.7 | .146 | .866 | .651 |
| External rotation | 9.0 | 5.0 | 8.1 | 4.5 | 9.8 | 4.9 | .445 | .685 | .249 |
| Belly press | 10.0 | 5.8 | 9.0 | 4.7 | 9.9 | 6.1 | .401 | .989 | .709 |
ASES, American Shoulder Elbow Surgeons score; VAS, visual analog scale; WOOS, Western Ontario Osteoarthritis Score; SANE, Single Assessment Numeric Evaluation; FF, forward flexion; ER, external rotation; IR, internal rotation; ANOVA, analysis of variance; VR-12, Veterans Rand 12 Item Health Survey; ROM, range of motion.
Two-year postoperative data stratified by humeral head sphericity; patient-reported outcomes, range of motion, and strength.
Table IV.
Two-year postoperative data stratified by humeral head sphericity.
| Outcome measure | Spherical (N = 158) |
Mild aspherical (N = 64) |
Major aspherical (N = 37) |
ANOVA (P values) |
|||||
|---|---|---|---|---|---|---|---|---|---|
| Mean | Standard deviation | Mean | Standard deviation | Mean | Standard deviation | Spherical vs. mild | Spherical vs. major | Mild vs. major | |
| PROs | |||||||||
| ASES | 88.4 | 13.8 | 89.5 | 14.1 | 88.0 | 15.0 | .859 | .983 | .856 |
| VAS pain | 0.9 | 1.5 | 0.8 | 1.5 | 1.0 | 1.6 | .819 | .958 | .776 |
| WOOS | 88.9 | 14.9 | 91.5 | 14.0 | 90.1 | 16.3 | .464 | .892 | .896 |
| SANE | 77.5 | 26.5 | 84.7 | 21.2 | 85.9 | 17.2 | .112 | .136 | .965 |
| Constant–Murley | 81.0 | 14.0 | 82.0 | 11.6 | 78.0 | 14.8 | .620 | .450 | .193 |
| VR-12 mental | 54.8 | 10.0 | 54.4 | 9.4 | 54.8 | 9.6 | .967 | 1.000 | .982 |
| ROM | |||||||||
| Active FF (degrees) | 148 | 20 | 150 | 16 | 142 | 22 | .785 | .245 | .142 |
| Active ER at side (degrees) | 57 | 15 | 53 | 17 | 50 | 16 | .265 | .039 | .546 |
| Active ER at 90 (degrees) | 71 | 23 | 71 | 19 | 64 | 21 | 1.000 | .194 | .275 |
| Active IR (spinal level) | L2 | 3 | L1 | 3 | L2 | 3 | .024 | 1.000 | .145 |
| Active IR at 90 (degrees) | 41 | 25 | 44 | 20 | 35 | 20 | .722 | .263 | .133 |
| Strength | |||||||||
| Constant–Murley | 9.9 | 4.5 | 11.4 | 6.4 | 10.4 | 5.0 | .173 | .882 | .621 |
| External rotation | 12.0 | 5.5 | 13.0 | 4.7 | 13.0 | 5.6 | .461 | .583 | 1.000 |
| Belly press | 12.3 | 5.7 | 14.2 | 6.0 | 15.2 | 6.8 | .101 | .027 | .708 |
ASES, American Shoulder Elbow Surgeons score; VAS, visual analog scale; WOOS, Western Ontario Osteoarthritis Score; SANE, Single Assessment Numeric Evaluation; FF, forward flexion; ER, external rotation; IR, internal rotation; ANOVA, analysis of variance; VR-12, Veterans Rand 12 Item Health Survey; ROM, range of motion.
Change from baseline data stratified by humeral head sphericity; patient-reported outcomes, range of motion, and strength.
Table V.
Change from baseline data stratified by humeral head sphericity.
| Outcome measure | Spherical (N = 158) |
Mild aspherical (N = 64) |
Major aspherical (N = 37) |
ANOVA (P values) |
|||||
|---|---|---|---|---|---|---|---|---|---|
| Mean | Standard deviation | Mean | Standard deviation | Mean | Standard deviation | Spherical vs. mild | Spherical vs. major | Mild vs. major | |
| PROs | |||||||||
| ASES | 44.8 | 21.0 | 46.6 | 20.7 | 48.5 | 17.4 | .813 | .572 | .893 |
| VAS pain | −4.7 | 2.6 | −4.7 | 2.9 | −4.6 | 2.3 | .989 | .963 | .991 |
| WOOS | 50.3 | 22.0 | 55.3 | 21.3 | 56.5 | 19.5 | .273 | .273 | .961 |
| SANE | 43.7 | 33.2 | 50.3 | 29.8 | 55.3 | 26.5 | .337 | .110 | .721 |
| Constant–Murley | 35.8 | 21.4 | 41.6 | 14.7 | 40.8 | 17.0 | .112 | .350 | .976 |
| VR-12 mental | 5.7 | 11.0 | 3.4 | 11.4 | 2.9 | 11.2 | .357 | .353 | .970 |
| ROM | |||||||||
| Active FF (degrees) | 35 | 38 | 44 | 30 | 48 | 28 | .205 | .135 | .880 |
| Active ER at side (degrees) | 20 | 23 | 28 | 21 | 31 | 16 | .038 | .031 | .878 |
| Active ER at 90 (degrees) | 33 | 38 | 42 | 30 | 42 | 30 | .152 | .365 | .990 |
| Active IR (spinal level) | −2 | 4 | −5 | 4 | −3 | 4 | .002 | .386 | .387 |
| Active IR at 90 (degrees) | 18 | 30 | 24 | 29 | 22 | 22 | .404 | .728 | .963 |
| Strength | |||||||||
| Constant–Murley | 2.7 | 5.6 | 4.9 | 6.5 | 3.6 | 5.4 | .057 | .686 | .583 |
| External rotation | 3.0 | 5.3 | 4.4 | 4.4 | 3.4 | 6.4 | .163 | .889 | .641 |
| Belly press | 2.2 | 6.7 | 4.8 | 5.7 | 5.2 | 6.4 | .020 | .031 | .951 |
ASES, American Shoulder Elbow Surgeons score; VAS, visual analog scale; WOOS, Western Ontario Osteoarthritis Score; SANE, Single Assessment Numeric Evaluation; FF, forward flexion; ER, external rotation; IR, internal rotation; ANOVA, analysis of variance; VR-12, Veterans Rand 12 Item Health Survey; ROM, range of motion.
Center of rotation data with subanalysis of outliers.
Range of motion
Patients with spherical head morphology had significantly better preoperative active ER with the arm at the side of the body and at 90° of abduction compared to those with mild aspherical and major aspherical head morphology (Table II). Spherical heads also had significantly better preoperative active forward flexion compared to patients with major aspherical heads (P = .004). There were no significant differences between active IR behind the back or active IR at 90° of abduction between the three groups preoperatively. At 2 years postoperatively, patients with spherical heads had significantly better active ER with the arm at the side compared to those with major aspherical heads (57° vs. 50°, P = .039). Patients with mild aspherical heads had significantly better active IR behind the back compared to patients with spherical heads (L1 vs. L2, P = .024). All patients ROM improved significantly from baseline. However, patients with aspherical heads preoperatively had significantly greater improvement from baseline in active ER with the arm at the side compared to those with preoperative spherical heads (Table IV). Patients with spherical heads had a 20° improvement in ER with the arm at the side compared to a 28° improvement and 31° improvement for those with mild aspherical and major aspherical heads, respectively (P = .038 spherical vs. mild aspherical, P = .031 spherical vs. major aspherical).
Strength
There were no significant differences in strength between the three groups preoperatively (Table II). At 2 years postoperatively, patients with major aspherical heads had significantly better strength with modified belly press testing compared to those with spherical heads (15.2 lbs. vs. 12.3 lbs., P = .027) (Table III). Modified belly press strength improved significantly more from baseline in patients with aspherical heads compared to those with spherical heads (Table IV). There was no significant difference in improvement from baseline in CM strength or ER strength (Table IV).
Discussion
In the current study, we expanded on the previous classification used by Habermeyer et al.5 We found that patients with mild aspherical and major aspherical humeral head morphology preoperatively had no differences in PROs at 2 years compared to those with spherical humeral heads. Patients with aspherical head morphology had greater improvement in rotational motion postoperatively from baseline compared to those with spherical heads. In addition, we did not find a significant difference between groups in radiographic COR restoration regardless of humeral head morphology type.
Of the 259 patients included, 158 patients (61%) met classification as spherical, 64 patients (25%) were classified as mild aspherical, and 37 patients (14%) were classified as major aspherical. There was a higher percentage of patients with spherical humeral head pathomorphology in our study compared to what was reported by Habermeyer et al5 (17.8% spherical, 82.2% aspherical).
We found minor aspherical and major aspherical humeral head pathomorphology to be significantly more associated with B2 type glenoid morphology compared to those with spherical humeral heads (46.9% and 59.5% compared to 22.2%, respectively) (P < .001 spherical vs. mild aspherical, P < .001 spherical vs. major aspherical). We also found spherical humeral heads had significant association with A1 type glenoid (P < .001 spherical vs. mild aspherical, P < .001 spherical vs. major aspherical). This is consistent with what was found by Habermeyer et al5 who reported patients with aspherical humeral head morphology had a significant association with type B2 glenoid morphology, while patients with spherical humeral head morphology had significant associations with types A1, A2, and B1 glenoid morphology. These findings suggest that loss of humeral head sphericity is a component of progression of GHOA.
Our study also found male sex was significantly associated with aspherical humeral head morphology (Table I). Prior studies have identified male sex as being associated with greater degrees of eccentric glenoid wear and posterior humeral head subluxation.10,14 This is consistent with the current investigation in that patients with aspherical humeral head morphology were found to have significant association with both male sex and B2 type glenoid morphology.
Several studies have demonstrated the importance of restoration of glenohumeral COR following aTSA.8,21 Hoffman et al reported on use of the best-fit circle method in anatomic reconstruction of the proximal humerus in GHOA. They concluded that utilization of the best-fit circle method in cases of excessive humeral head flattening in patients undergoing aTSA may risk over-sizing the humeral head component and subsequently over-stuffing the joint.6 We initially hypothesized that aspherical humeral head morphology would be associated with higher variation in postoperative restoration of COR compared to spherical humeral heads; however, this was not the case. Our study demonstrated no significant differences in postoperative COR shift from ideal between the three groups (P = .955 spherical vs. mild aspherical, P = .779 spherical vs. major aspherical, P = .920 mild vs. major aspherical). In addition, there were no differences in major outliers of postoperative COR between the groups. This suggests that despite distorted humeral head pathoanatomy, shoulder surgeons are still consistently capable of restoring COR postoperatively through various methods such as 3-dimensional templating and intraoperative techniques to avoid a significant shift in COR or over-stuffing the joint.
Preoperatively, patients with mild aspherical and major aspherical humeral heads had significantly worse ER compared to those with spherical heads. Strength was found to be similar between the three groups (Table II). This is likely secondary to the higher degree of deformity, as well as higher proportion of patients with posterior humeral head decentering and eccentric glenoid wear in the aspherical humeral head groups. Prior studies have demonstrated patients with B2 type glenoid morphology to have worse preoperative ROM compared to other glenoid morphology types.1,4,17 While this study is the first to specifically investigate ROM in relation to humeral head pathomorphology, it is logical that deformity of both the humeral head and glenoid play a role in ROM loss in primary GHOA.
Postoperative clinical outcomes did not differ in patients with spherical and aspherical humeral head morphology, as all patients improved significantly from baseline. Patients with aspherical humeral heads had a significantly greater improvement from baseline at 2 years postoperatively in active ER with the arm at the side and belly press strength compared to those with spherical heads (Table IV); however, there were no significant differences in overall PROs, ROM, and strength in those with spherical, minor aspherical, or major aspherical heads at 2 years (Table III). This may be related to the ability to accurately restore COR in our study despite varying degrees of humeral head pathomorphology.
In this investigation, we present novel information on the association between preoperative humeral head pathomorphology and radiographic and clinical outcomes. Although we were able to utilize a relatively large population with 2-year follow-up, this study still remains limited by its retrospective nature and potential for selection bias. Inn addition, since we only evaluated patients who underwent aTSA in this study, it is possible that some patients with worse (more aspherical) humeral head pathoanatomy and greater degrees of glenoid wear or posterior humeral head subluxation were treated with reverse TSA due to concern for glenoid component stability and thus excluded, which may have skewed clinical outcome results. Further studies are needed to evaluate these areas. This study relies on adequate radiographs to perform the measurements included in the analysis, thus inadequate radiographs may have resulted in additional patients being excluded from the study.
Conclusion
Aspherical head morphology is associated with a higher incidence of male sex and B2 glenoid morphology, as well as worse preoperative ER. Humeral head deformity alone was not shown to be associated with less accurate restoration of glenohumeral COR postoperatively following aTSA. These findings were consistent even in patients who were identified to have major aspherical humeral head morphology preoperatively. Ultimately, patients with aspherical humeral head morphology preoperatively were not found to have worse clinical or radiographic outcomes compared to patients with preoperative spherical heads; however, patients with aspherical humeral heads did make significantly greater improvements from baseline in rotational strength at 2-year follow-up compared to patients with spherical humeral heads.
Disclaimers:
Funding: No funding was disclosed by the authors.
Conflicts of interest: Dr. Brian C Werner, MD reports Arthrex: research funding, paid consultant; Zimmer Biomet: research funding; and Pacira: research funding; Lifenet Health: paid consultant. Dr. Stefan Greiner reports Arthrex: paid speaker and paid consultant. Dr. Patrick J Denard, MD reports Arthrex: royalties, paid consultant, and paid speaker; PT Genie: stock ownership; Kaliber Labs: stock ownership. Dr. Albert Lin reports AAOS: Board or committee member; American Orthopaedic Association: Board or committee member; American Orthopaedic Society for Sports Medicine: Board or committee member; American Shoulder and Elbow Surgeons: Board or committee member; Annals in Joint: Editorial or governing board; Arthrex, Inc. Paid consultant; Arthroscopy: Editorial or governing board; International Society of Arthroscopy, Knee Surgery, and Orthopaedic Sports Medicine: Board or committee member; Knee Surgery, Sports Traumatology, Arthroscopy: Editorial or governing board; Tornier: Paid consultant. Dr. Anthony Romeo reports Arthrex, Inc.: Royalties, paid presenter, paid consultant; Editorial or governing board: Orthopedics Today, Orthopedics, SAGE, SLACK Incorporated, Wolters Kluwer Health; Stock or stock options: Paragen Technologies; Vertex: Research support; Royalties, Financial or Material Support from Publishers: Aunders/Mosby-Elsevier. Dr. Anup Shah reports Arthrex, Inc.: Education/research consultant; Medacta: Royalties. Dr. Asheesh Bedi reports Arthrex, Inc.: Consultant and royalties. Dr. Benjamin W. Sears reports United Orthopaedic Corporation: consultant and royalties; Aeuvumed: consultant and royalties; Shoulder Innovations: consultant and royalties; BioPoly: consultant and royalties; Arthrex, Inc.: research funding/support; Exactech: research funding/support; Stryker: research funding/support; FX Solutions: research funding/support. Dr. Bradford Parsons reports Arthrex, Inc.: consultant and royalties; JBJS reviews: editor. Dr. Brandon Erickson reports AAOS: board or committee member; American Orthopaedic Society for Sports Medicine: board or committee member; American Shoulder and Elbow Surgeons: board or committee member; Arthrex, Inc.: paid consultant, research support; DePuy, A Johnson & Johnson Company: research support; Linvatec: research support; PLOS One: editorial or governing board; Smith & Nephew: research support; Stryker: research support. Dr. Brian Waterman reports AAOS: Board or committee member; American Orthopaedic Society for Sports Medicine: Board or committee member; American Shoulder and Elbow Surgeons: Board or committee member; Arthrex, Inc.: Other financial support (fellowship support); Paid consultant; Paid presenter or speaker; Arthroscopy: Editorial or governing board; Kaliber AI: Stock or stock Options; Unpaid consultant; Smith & Nephew: Other financial or material support (fellowship support); Sparta: Paid presenter or speaker; Stock or stock Options; paid consultant; Vericel: Paid presenter or speaker; Video Journal of Sports Medicine: Editorial or governing board; Journal of Cartilage & Joint Preservation: Editorial or governing board; Vivorte: Stock or stock Options. Dr. Bruce Miller reports AJSM: editorial or governing board; Arthrex, Inc.: paid consultant; FH Orthopedics: royalties. Dr. Christopher O'Grady reports Arthrex, Inc.: education consultant/Speaker; Stryker: education consultant/Speaker; Smith and Nephew: education consultant/Speaker; Mitek: education consultant/Speaker. Dr. Daniel Davis reports Arthrex, Inc.: paid consultant, paid presenter/speaker; Catalyst OrthoScience: stock or stock options; Pennsylvania Orthopaedic Society: board member; Philadelphia Orthopaedic Society: board member. Dr. David Lutton reports Arthrex, Inc.: paid consultant, paid speaker or presenter; Avanos: paid speaker or presenter; CORE: reviewer (not editor). Dr. Dirk Petre reports Arthrex, Inc.: paid consultant, paid presenter/speaker, research support. Dr. Evan Lederman reports Arthrex, Inc.: consultant, royalties, and research support. Dr. Justin Griffin reports Arthrex, Inc.: research support, royalties, paid speaker; Springer: publishing royalties. Dr. John Tokish reports Arthrex, Inc.: IP royalties, paid consultant, paid presenter or speaker; Arthroscopy Association of North America: board or committee member; Journal of Shoulder and Elbow Surgery: editorial or governing board, financial or material support; Orthopedics Today: editorial or governing board. Dr. Jorn Steinbeck reports Journal of Shoulder and Elbow Surgery: reviewer; Journal of Bone and Joint Surgery: reviewer; Arthrex, Inc.: consultant. Dr. Julia Lee reports the following Arthrex, Inc.: Consulting and medical education; American Shoulder Elbow Surgeons: committee member. Dr. Kevin Farmer reports American Orthopaedic Society for Sports Medicine Florida Orthopaedic Society: board or committee member; Arthrex, Inc.: Paid consultant, paid presenter or speaker; Exactech, Inc.: paid consultant. Dr. Mathew Provencher reports Arthrex, Inc.: royalties; Arthrosurface: royalties; Responsive Arthroscopy (2020): royalties; and Anika Therapeutics, Inc.: royalties; Arthrex, Inc.: consulting fees; Joint Restoration Foundation (JRF): consulting fees; Zimmer Biomet Holdings: consulting fees; Arthrosurface: consulting fees; Department of Defense (DoD): grants; the National Institute of Health (NIH): grants; DJO (2020): grants; Flexion Therapeutics: honoria; SLACK, Inc.; editorial board or governing board member; American Association of Nurse Anesthesiology: board or committee member; American Academy of Orthopaedic Surgeons: board or committee member; American Orthopaedic Society for Sports Medicine: board or committee member; American Shoulder and Elbow Surgeons: board or committee member; SDSI: board or committee member; and SOMOs: board or committee member: Musculoskeletal Transplant Foundation: medical board of trustees (through 2018). Mark Dillon reports Arthrex, Inc.: paid consultant; Dupey Synthes: Educational support; ActivArmor: stock; AAOS: Board or committee member; Sage Journals: Editorial or governing board (Shoulder & Elbow). Dr. Michael Bercik reports American Shoulder and Elbow Surgeons: board or committee member; Arthrex, Inc.: paid consultant; WRS Specialists: paid consultant. Dr. Michael Kissenberth reports Arthrex, Inc.: paid consultant; Hawkins Foundation: financial or material support; Hawkins Foundation: board member. Dr. Michael Walton reports Arthrex, Inc.: Paid consultant, paid presenter or speaker; Research support. Dr. Patric Raiss reports Arthrex, Inc.: paid consultant; Zurimed Technologies AG: shareholder. Dr. Peter Habermeyer reports Arthrex, Inc.: Royalties. Dr. Philipp Moroder reports Alyve Medical: consultant, royalties; Arthrex: consultant, royalties; Medacta: consultant, royalties. Dr. Alex Creighton reports American Board of Orthopaedic Surgery, Inc.: board or committee member; American Orthopaedic Society for Sports Medicine: board or committee member; American Shoulder and Elbow Surgeons: board or committee member; Arthrex, Inc.: paid presenter or speaker, research support, other financial or material support; Breg: other financial or material support; Johnson & Johnson: other financial or material support; Orthopedics Today: editorial or governing board; SLACK Incorporated: editorial or governing board; Smith & Nephew: other financial or material support. Dr. G. Russell Huffman reports Arthrex, Inc.: speakers bureau/paid presentations, paid consultat; LIMA: speakers bureau/paid presentations, paid consultant; Catalyst: stock or stock options; PI: LIMA IDE: research support. Dr. Samuel Harmsen reports Arthrex, Inc.: royalties, paid consultant, paid presenter or speaker, research support; Embody, Inc.: royalties, paid consultant; Enovis, Inc.: paid consultant, paid presenterl; Genesis Software Innovations, LLC: royalties, stock or stock options; Shoulder Innovations, Inc.: royalties, paid consultant, paid presenter or speaker; Zimmer US Inc.: paid consultant, paid presenter or speaker, stock or stock options. Dr. Sven Lichtenberg reports Archives of Orthopaedic and Trauma Surgery: editorial or governing board; Arthrex, Inc.: IP royalties, paid consultant, paid presenter or speaker; Exactech, Inc.: paid consultant, paid presenter or speaker; Journals of Shoulder and Elbow Surgery: editorial or governing board; Knee Surgery, Sports Traumatology, Arthroscopy: editorial or governing board. Dr. Tim Lenters reports Arthrex, Inc.: paid consultant; Irispet: research support; American Academy of Orthopaedic Surgeons: social media committee. Dr. Matthew Tyrrell Burrus reports Arthrex, Inc.: paid consultant, paid presenter or speaker, research support; Arthroscopy: editorial or governing board. Dr. Tyler Brolin reports American Academy of Orthopaedic Surgeons: board or committee member; American Shoulder and Elbow Surgeons: board or committee member; Arthrex, Inc.: IP royalties, paid consultant, research support; Elsevier: publishing royalties, financial or material support; Orthofix, Inc.: research support; Orthopedic Clinics of North America: editorial or governing board; Zimmer: research support. The other author, his immediate family, and any research foundation with which he is affiliated have not received any financial payments or other benefits from any commercial entity related to the subject of this article.
Footnotes
Southern Oregon Institutional Review Board approved this study; Study #:15-001.
Contributor Information
Bradley J. Hawayek, Email: hawayekb@gmail.com.
Collaborators, Shoulder Arthroplasty Research Committee (ShARC):
Asheesh Bedi, Michael Bercik, Tyler Brolin, Matthew Tyrrell Burrus, Robert Creighton, Dan Davis, Patrick Denard, Mark Dillon, Brandon Erickson, Kevin Farmer, Stefan Greiner, Justin Griffin, Peter Habermeyer, Samuel Harmsen, G. Russell Huffman, Michael Kissenberth, Evan Lederman, Julie Lee, Tim Lenters, Sven Lichtenberg, Albert Lin, David Lutton, Bruce Miller, Philipp Moroder, Christopher O'Grady, Brad Parsons, Dirk Petre, Matt Provencher, Patric Raiss, Anthony Romeo, Ben Sears, Anup Shah, Jorn Steinbeck, John Tokish, Michael Walton, Brian Waterman, and Brian Werner
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