AllTotal scapulectomy All Total scapulectomy N4826 GenderMale32 ( 66.7%)15 ( 57.7%)Reconstruction Female16 ( 33.3%)11 ( 42.3%)No25 ( 52.1%)8 ( 30.8%) Age46 ± ± 19.4 Humeral suspension21 ( 43.8%)16 ( 61.5%) Dominant sideYes31 ( 64.6%)19 ( 73.1%) Others2 ( 4.2%)2 ( 7.7%) No14 ( 29.2%)6 ( 23.1%)Material for humeral suspensionArtificial ligament8 ( 16.7%)5 ( 19.2%) Unknown3 ( 6.3%)1 ( 3.8%) Autologous ligament5 ( 10.4%)4 ( 15.4%) Enneking surgical stageIB4 ( 8.3%)3 ( 11.5%) Unknown8 ( 16.7%)7 ( 26.9%) IIA2 ( 4.2%)1 ( 3.8%)Blood loss (g)764.1 ± ± IIB29 ( 60.4%)13 ( 50.0%)Surgical duration (min) ± ± 97.4 III1 ( 2.1%)1 ( 3.8%)Tumor originScapula40 ( 83.3%)23 ( 88.5%) IIIB3 ( 6.3%)3 ( 11.5%)Soft tissue7 ( 14.6%)2 ( 7.7%) Benign2 ( 4.2%)1 ( 3.8%) Humerus1 ( 2.1%)1 ( 3.8%) Metastasis7 ( 14.6%)4 ( 15.4%)Follow-up term (mons) 58.8 ± ± 53.1 ChemotherapyYes22 ( 45.8%)14 ( 53.8%) Upper displacement of humerus (cm)-0.17 ± ± 1.46 No26 ( 54.2%)12 ( 46.2%) Radiation therapyYes6 ( 12.5%)4 ( 15.4%)Enneking functional score No42 ( 87.5%)22 ( 84.6%)Pain4.6 ± ± 0.8 Type of resectionTotal scapulectomy26 ( 54.2%)26 (100.0%)Function2.8 ± ± 1.1 Acromion preserved7 ( 14.6%)0 ( 0.0%)Emotional acceptance3.7 ± ± 1.2 Glenoid preserved3 ( 6.3%)0 ( 0.0%)Hand positioning2.9 ± ± 1.4 Both acromion and glenoid preserved10 ( 20.8%)0 ( 0.0%)Dexterity4.5 ± 14.3 ± 1.2 Resection of lower half2 ( 4.2%)0 ( 0.0%)Lifting ability2.9 ± ± 0.9 MarginWide42 ( 87.5%)24 ( 92.3%)Total21.1 ± ± 3.7 Marginal4 ( 8.3%)1 ( 3.8%) ROM Intralesional2 ( 4.2%)1 ( 3.8%)Flexion42.7 ± ± 25.9 Length of resected humerus (cm) 2.25 ± ± 3.66Abduction39.7 ± ± 19.6 Resected musclesInternal rotation49.6 ± ± 35.5 Supraspinatus37 ( 77.1%)26 (100.0%)External rotation16.8 ± ± 20.4 Infraspinatus46 ( 95.8%)26 (100.0%) Teres minor34 ( 70.8%)20 ( 76.9%) Teres major31 ( 64.6%)20 ( 76.9%) Subscapularis43 ( 89.6%)26 (100.0%) Deltoid11 ( 22.9%)10 ( 38.5%) Trapezius9 ( 18.8%)8 ( 30.8%) Lattisimus dorsi11 ( 22.9%)8 ( 30.8%) Rhomboids18 ( 37.5%)11 ( 42.3%) Biceps3 ( 6.3%)2 ( 7.7%) Triceps8 ( 16.7%)5 ( 19.2%) Number of resected muscles5 ± 2.26 ± 1.9 Resected nerve Axillary12 ( 25.0%)10 ( 38.5%) Table S1 Patient characteristics

Summary statisticUnivariate Multivariate: initial model P<0.05 in univariate Multivariate: final model P<0.05 in step-down method FactorCategory NAverageSD 95% CIP value 95% CIP value 95% CIP value All －－ －－ －－ GenderMale － [0.031 *] － [0.292] Female (-5.616, )0.031 * (-3.674, 1.140)0.292 Age< － [0.396] ≥40 to < (-2.307, 4.116)0.573 ≥ (-1.021, 5.402)0.176 Dominant sideYes － [0.256] No (-1.177, 4.630)0.237 Unknown (-1.755, 9.066)0.180 Enneking surgical StageIB － [0.225] IIA (-3.849, )0.324 IIB (-7.247, 2.155)0.280 III 120.0( , 6.560)0.507 IIIB ( , 0.118)0.054 Benign ( , 4.349)0.392 Metastasis (-6.607, 4.392)0.686 ChemotherapyNo － [0.036 *] － [0.108] Yes (-5.330, )0.036 * (-4.101, 0.425)0.108 Radiation therapyNo － [0.126] Yes (-6.877, 0.877)0.126 Resection rangeTotal scapulectomy － [0.003 **] － [0.118] － [0.006 **] Acromion preserved (0.245, 6.898)0.036 *(0.074, 6.279)0.045 *(0.503, 6.593)0.024 * Glenoid preserved (-2.420, 7.087)0.327(-2.236, 6.409)0.334(-1.799, 6.881)0.243 Both of acromion and glenoid preserved (2.643, 8.691)<0.001 ***(0.517, 6.970)0.024 *(2.615, 8.137)<0.001 *** Resection of lower half (1.283, )0.018 * (-4.650, 9.931)0.467 (-5.511, 8.696)0.652 MarginWide － [0.619] Marginal (-3.075, 6.475)0.477 Intralesional (-8.648, 4.548)0.534 Length of resected humerus － [0.763] >0 to < (-3.117, 3.310)0.952 ≥5≥ (-4.766, 2.348)0.497 Number of resected muscles≤3≤ － [0.835] ≥4 to ≤ (-4.221, 2.398)0.581 ≥7≥ (-3.574, 3.241)0.922 Resected nerveNo － [0.017 *] － [0.246] Axillary (-6.390, )0.017 * (-4.061, 1.076)0.246 ReconstructionNo － [0.241] Humeral suspension: artificial ligament (-5.361, 1.861)0.333 Humeral suspension: autologous ligament (-8.749, )0.047 * Humeral suspension: Unknown (-3.514, 4.086)0.880 Others ( , 3.010)0.284 Blood loss (g)< － [0.126] ≥300 to < (-4.666, 2.254)0.486 ≥ (-6.650, )0.034 * Unknown (-8.235, 0.768)0.102 Surgical duration (min)< － [0.299] ≥200 to < (-5.325, 1.592)0.282 ≥ (-6.370, 0.656)0.108 Unknown (-8.553, 0.953)0.114 Tumor originScapula － [0.576] Soft tissue (-1.814, 5.664)0.305 Humerus (-7.999, )0.792 Follow-up term (mons)< － [0.002 **] － [0.039 *] － [0.005 **] ≥20 < (2.038, 7.799)0.001 **(0.357, 5.804)0.028 *(1.182, 6.362)0.005 ** ≥ (0.658, 6.583)0.018 *(1.016, 6.463)0.009 **(1.451, 6.807)0.003 ** Unknown (4.040, )0.004 ** (-2.096, )0.111 (2.085, )0.019 * Upper displacement of humerus< － [0.077] (-1.173, 5.681)0.192 > (-2.652, 5.708)0.465 Unknown (-6.527, 1.833)0.264 Table S2 Total Enneking score in all cases

Summary statistics Multivariate: final model P<0.05 in step-down method Summary statistics Multivariate: final model P<0.05 in step-down method FactorCategory NAverageSD 95% CIP value FactorCategory N Averag e SD 95% CIP value Total score of Enneking's function (all cases)Abduction (all cases) Resection rangeTotal scapulectomy － [0.006 **] Resection rangeTotal scapulectomy － [<0.001 ***] Acromion preserved (0.503, 6.593)0.024 * Acromion preserved ( , )0.355 Glenoid preserved (-1.799, 6.881)0.243 Glenoid preserved ( , )0.554 Both acromion and glenoid preserved (2.615, 8.137)<0.001 *** Both acromion and glenoid preserved (52.691, )<0.001 *** Resection of lower half (-5.511, 8.696)0.652 Resection of lower half ( , )0.917 Pain score (all cases)Internal rotation (all cases) Length of resected humerus － [0.048 *] Resected nerveNo － [0.012 *] >0 to < (-0.197, 0.677)0.274 Axillary ( , )0.012 * ≥5≥ (-1.005, 0.035)0.067External rotation (all cases) Function score (all cases) Radiation therapyYes － [0.026 *] Resected nerveNo － [0.018 *] No ( , )0.026 * Axillary (-1.490, )0.018 * Resection rangeTotal scapulectomy － [0.016 *] Hand positioning score (all cases) Acromion preserved ( , )0.979 Resection rangeTotal scapulectomy － [0.035 *] Glenoid preserved (6.669, )0.018 * Acromion preserved (-0.507, 1.462)0.332 Both acromion and glenoid preserved (2.972, )0.027 * Glenoid preserved (-2.265, 0.356)0.149 Resection of lower half (8.347, )0.021 * Both acromion and glenoid preserved (0.188, 2.134)0.021 *Dexterity score (total scapulectomy cases) Resection of lower half (-0.244, 2.996)0.093 ReconstructionNo － [0.016 *] Dexterity score (all cases) Humeral suspension: artificial ligament (0.606, 2.894)0.005 ** Resected nerveNo － [0.019 *] Humeral suspension: autologous ligament (0.021, 2.479)0.046 * Axillary (-1.216, )0.019 * Humeral suspension: Unknown (0.667, 2.833)0.003 ** Flexion (all cases) Others (-0.836, 2.336)0.336 Resection rangeTotal scapulectomy － [<0.001 ***]Internal rotation (total scapulectomy cases) Acromion preserved (-6.335, )0.134 Resected nerveNo － [0.011 *] Glenoid preserved (-3.213, )0.072 Axillary ( , )0.011 * Both acromion and glenoid preserved (39.562, )<0.001 *** Tumor originScapula － [0.016 *] Resection of lower half (20.023, )0.005 ** Soft tissue 20.0 ( , )0.016 * Table S3 Summary of significant difference in multivariate analysis