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Midterm results of stemless impaction shoulder arthroplasty for primary osteoarthritis: a prospective, multicenter study

Open AccessPublished:September 23, 2022DOI:https://doi.org/10.1016/j.jseint.2022.09.001

      Abstract

      Background

      Stemless shoulder arthroplasty using four open-fin press-fit anchors has been showing promising short-term clinical and radiographic results for patients primary osteoarthritis. This prospective, multicenter study presents 5-year postoperative clinical and radiological outcomes of a stemless shoulder arthroplasty for primary osteoarthritis.

      Methods

      Between November 2012 and December 2015, 100 patients were treated for primary osteoarthritis with the Sidus® stem-free shoulder system at 7 European centers. Clinical assessment included the Constant-Murley score (CS), American Shoulder and Elbow Standardized Shoulder Assessment Form score (ASES), Subjective Shoulder Value (SSV) and range of motion (ROM). True anteroposterior, axial and lateral radiographs were reviewed for osteolysis, glenoid and humerus loosening, heterotopic ossification, radiolucent lines, component migration and humeral bone resorption. In addition to a Kaplan-Meier survival analysis, a comparative analysis between total shoulder and hemiarthroplasty was performed.

      Results

      Seventy-one patients (36 females) with a mean age of 63.8 years (range: 47-79 years) were available for the 5-year clinical and radiographic follow-up (range: 52-79 months). There was a significant increase (p < .0001) in all outcome scores compared to baseline values. Patients with total shoulder arthroplasty (n=48) achieved significantly better functional outcome than patients with shoulder hemiarthroplasty (n=23) with regard to the absolute and relative CS, ASES and SSV as well as greater abduction strength and ROM in forward elevation and external rotation (p ≤ .004).
      There were no cases of osteolysis or humeral loosening. There were some cases of heterotopic ossification (1.4%), radiolucency around the humerus (1.4%) or glenoid (25%), glenoid migration (2.1%), inferior osteophytes (1.4%) or humerus bone resorption (9.9%). The 5-year survival was 94%.

      Conclusion

      Patients treated with the Sidus® stem-free shoulder system for primary osteoarthritis continue to achieve good clinical and radiographic results without any signs of aseptic humeral implant loosening at 5 years postsurgery.

      Keywords

      Since stemless implants were first introduced in 2004,
      • Kim S.H.
      • Wise B.L.
      • Zhang Y.
      • Szabo R.M.
      Increasing incidence of shoulder arthroplasty in the United States.
      there has been a steady increase in stemless anatomical shoulder arthroplasty.
      • Best M.J.
      • Aziz K.T.
      • Wilckens J.H.
      • McFarland E.G.
      • Srikumaran U.
      Increasing incidence of primary reverse and anatomic total shoulder arthroplasty in the United States.
      • Trofa D.
      • Rajaee S.S.
      • Smith E.L.
      Nationwide trends in total shoulder arthroplasty and hemiarthroplasty for osteoarthritis.
      The stem-free method has proven to be a reliable treatment option with good clinical function and high patient satisfaction for primary osteoarthritis (OA) as well as secondary forms of osteoarthritis including post-traumatic, postinfectious and instability-induced OA.
      • Habermeyer P.
      • Lichtenberg S.
      • Tauber M.
      • Magosch P.
      Midterm results of stemless shoulder arthroplasty: a prospective study.
      • Hawi N.
      • Magosch P.
      • Tauber M.
      • Lichtenberg S.
      • Habermeyer P.
      Nine-year outcome after anatomic stemless shoulder prosthesis: clinical and radiologic results.
      • Huguet D.
      • DeClercq G.
      • Rio B.
      • Teissier J.
      • Zipoli B.
      • Group T.
      Results of a new stemless shoulder prosthesis: radiologic proof of maintained fixation and stability after a minimum of three years' follow-up.
      • Uschok S.
      • Magosch P.
      • Moe M.
      • Lichtenberg S.
      • Habermeyer P.
      Is the stemless humeral head replacement clinically and radiographically a secure equivalent to standard stem humeral head replacement in the long-term follow-up? A prospective randomized trial.
      These newer implants offer several advantages including decreased surgical time with lower blood loss,
      • Berth A.
      • Pap G.
      Stemless shoulder prosthesis versus conventional anatomic shoulder prosthesis in patients with osteoarthritis: a comparison of the functional outcome after a minimum of two years follow-up.
      • Harmer L.
      • Throckmorton T.
      • Sperling J.W.
      Total shoulder arthroplasty: are the humeral components getting shorter?.
      less stress shielding,
      • Habermeyer P.
      • Lichtenberg S.
      • Tauber M.
      • Magosch P.
      Midterm results of stemless shoulder arthroplasty: a prospective study.
      less risk of a diaphyseal stress riser,
      • Berth A.
      • März V.
      • Wissel H.
      • Awiszus F.
      • Amthauer H.
      • Lohmann C.H.
      SPECT/CT demonstrates the osseointegrative response of a stemless shoulder prosthesis.
      • Bohsali K.I.
      • Wirth M.A.
      • Rockwood Jr., C.A.
      Complications of total shoulder arthroplasty.
      less lateralization,
      • Kadum B.
      • Wahlström P.
      • Khoschnau S.
      • Sjödén G.
      • Sayed-Noor A.
      Association of lateral humeral offset with functional outcome and geometric restoration in stemless total shoulder arthroplasty.
      • Nyffeler R.W.
      • Sheikh R.
      • Jacob H.A.C.
      • Gerber C.
      Influence of humeral prosthesis height on biomechanics of glenohumeral abduction. An in vitro study.
      and greater bone preservation
      • Berth A.
      • Pap G.
      Stemless shoulder prosthesis versus conventional anatomic shoulder prosthesis in patients with osteoarthritis: a comparison of the functional outcome after a minimum of two years follow-up.
      • Churchill R.S.
      • Athwal G.S.
      Stemless shoulder arthroplasty-current results and designs.
      • Harmer L.
      • Throckmorton T.
      • Sperling J.W.
      Total shoulder arthroplasty: are the humeral components getting shorter?.
      • Hawi N.
      • Magosch P.
      • Tauber M.
      • Lichtenberg S.
      • Habermeyer P.
      Nine-year outcome after anatomic stemless shoulder prosthesis: clinical and radiologic results.
      , which facilitate a simplified revision when indicated and the potential conversion to reverse shoulder arthroplasty with new convertible implants.
      The Sidus® stem-free shoulder system (Zimmer Biomet, Warsaw, IN, USA) is a metaphyseal anchored prosthesis with excellent short-term clinical and radiological results.
      • Krukenberg A.
      • McBirnie J.
      • Bartsch S.
      • Bohler N.
      • Wiedemann E.
      • Jost B.
      • et al.
      Sidus Stem-Free Shoulder System for primary osteoarthritis: short-term results of a multicenter study.
      In comparison to a historical control group of stemmed humeral implants, the stemless system was found to have a similar clinical success rate of 87% (versus 85%) based on a 2-year composite endpoint of an improved American Shoulder and Elbow Surgeons Standardized Shoulder Assessment Form score (ASES), no radiological signs of radiolucency and migration or subsidence, and no device-related severe adverse events and revisions or reoperations during follow-up.
      • Athwal G.S.
      • Krupp R.J.
      • Carlson G.
      • Bicknell R.T.
      A multicenter, prospective 2-year analysis of the Sidus stem-free shoulder arthroplasty system.
      The need for mid- to long-term data was emphasized to confirm recent findings as well as the importance of increasing the clinical data on stemless implants in general. The aim of this IRB-approved, prospective multicenter study was to evaluate the 5-year postoperative clinical and radiological results of this stemless implant in primary OA patients.

      Materials and methods

      Study population

      Between November 2012 and December 2015, 148 patients (151 shoulders) with primary or secondary OA were treated with the Sidus® stem-free shoulder system at nine European institutions. This analysis focuses only on included patients who were treated for primary OA (126 shoulders). Initially, all patients met the inclusion (Table I) and exclusion criteria (Table II) and provided written consent for study participation. Of the nine institutions included in the short-term follow-up study,
      • Krukenberg A.
      • McBirnie J.
      • Bartsch S.
      • Bohler N.
      • Wiedemann E.
      • Jost B.
      • et al.
      Sidus Stem-Free Shoulder System for primary osteoarthritis: short-term results of a multicenter study.
      two withdrew their participation from this investigation due to logistic reasons leaving 26 patients unable to comply with the extended follow-up program. Therefore, these patients were excluded from this midterm evaluation, which included a total of 100 patients.
      Table IInclusion criteria
      The patient is aged 18-80 years old.
      The patient is skeletally mature.
      The patient has severe shoulder pain and disability requiring unilateral or bilateral hemiarthroplasty or total shoulder arthroplasty based on physical examination findings and medical history.
      Conservative treatment has failed.
      The patient meets the following indication: osteoarthritis.
      The patient is willing and able to cooperate with the required postoperative therapy.
      The patient is willing and able to complete scheduled follow-up evaluations as described during the informed consent process.
      The patient has participated in the informed consent process and signed the ethics committee-approved “informed consent” form.
      Table IIExclusion criteria
      The patient is unwilling or unable to give consent or to comply with the follow-up program.
      The patient has any condition that would, in the judgment of the investigator, place the patient at undue risk or interfere with the study. Any patient who is institutionalized, is known to abuse drugs, is known to have alcoholism, or cannot understand what is required of him or her is excluded.
      The patient is known to be pregnant or breastfeeding.
      The patient meets 1 of the following contraindications:
       Soft or inadequate humeral bone (including osteoporosis and extensive avascular necrosis or rheumatoid arthritis) leading to poor implant fixation
       Metaphyseal bony defect (including large cysts)
       Post-traumatic tuberosity nonunion
       Signs of infection
       Irreparable cuff tear
       Revision from failed stemmed prosthesis
       Charcot shoulder (neuroarthropathy)
      Implant description, surgical technique and postoperative rehabilitation protocol have already been published.
      • Krukenberg A.
      • McBirnie J.
      • Bartsch S.
      • Bohler N.
      • Wiedemann E.
      • Jost B.
      • et al.
      Sidus Stem-Free Shoulder System for primary osteoarthritis: short-term results of a multicenter study.

      Clinical evaluation

      Patients were assessed before (baseline) and during surgery as well as at the postoperative time points of six months, one year, two and five years.
      All patients were evaluated based on the absolute as well as age- and gender-modified Constant-Murley score (CS), the ASES and Subjective Shoulder Value (SSV).
      • Constant C.R.
      • Murley A.H.
      A clinical method of functional assessment of the shoulder.
      • Gilbart M.K.
      • Gerber C.
      Comparison of the subjective shoulder value and the Constant score.
      • Michener L.A.
      • McClure P.W.
      • Sennett B.J.
      American Shoulder and Elbow Surgeons Standardized Shoulder Assessment Form, patient self-report section: reliability, validity, and responsiveness.
      Abduction strength was measured, pain was assessed using the CS scale of 0 to 15 points (15 = no pain; 0 = excruciating pain) and patient satisfaction was also evaluated at each follow-up examination. In addition, active range of motion (ROM) including anterior forward elevation, internal rotation, and external rotation at 0° and 90° abduction was documented.

      Radiographic evaluation

      Preoperative radiographic assessment was made on standardized true anteroposterior (AP), axillary and Y-view radiographs. Humeral and glenoid defects, bone quality, glenoid morphology according to Walch
      • Bercik M.J.
      • Kruse 2nd, K.
      • Yalizis M.
      • Gauci M.O.
      • Chaoui J.
      • Walch G.
      A modification to the Walch classification of the glenoid in primary glenohumeral osteoarthritis using three-dimensional imaging.
      • Walch G.
      • Badet R.
      • Boulahia A.
      • Khoury A.
      Morphologic study of the glenoid in primary glenohumeral osteoarthritis.
      and fatty infiltration of the rotator cuff
      • Goutallier D.
      • Postel J.M.
      • Bernageau J.
      • Lavau L.
      • Voisin M.C.
      Fatty muscle degeneration in cuff ruptures. Pre- and postoperative evaluation by CT scan.
      were determined on computer tomography scans. In cases of unclear rotator cuff status, an additional magnetic resonance image was performed and assessed.
      Five-year postoperative radiographic assessment was performed again using true AP, axillary and Y-view images to identify osteolysis, loosening (in terms of subsidence or shift in position), heterotopic ossification according to Brooker et al
      • Brooker A.F.
      • Bowerman J.W.
      • Robinson R.A.
      • Riley Jr., L.H.
      Ectopic ossification following total hip replacement. Incidence and a method of classification.
      , the development of (inferior) osteophytes,
      • Samilson R.L.
      • Prieto V.
      Dislocation arthropathy of the shoulder.
      and component migration. Furthermore, bone-implant interface was evaluated for bone resorption and radiolucency lines (RLL) in millimeters
      • Franklin J.L.
      • Barrett W.P.
      • Jackins S.E.
      • Matsen 3rd, F.A.
      Glenoid loosening in total shoulder arthroplasty. Association with rotator cuff deficiency.
      in 10 different humeral zones on AP and axillary views (Fig. 1) and in 3 glenoid zones as outlined by Lazarus et al.
      • Lazarus M.D.
      • Jensen K.L.
      • Southworth C.
      • Matsen 3rd, F.A.
      The radiographic evaluation of keeled and pegged glenoid component insertion.
      Figure thumbnail gr1
      Figure 1Ten zones at bone-implant interface for radiographic evaluation and classification of osteolysis, radiolucent lines and bone resorption in true anteroposterior and axial radiographs (classification by Zimmer Biomet).

      Adverse events

      All intraoperative and postoperative surgery and implant related complications were documented as adverse events within the follow-up period of five years.

      Survival analysis

      Implant survival was described using a Kaplan-Meier survival curve using revision as endpoint.

      Data management and statistical analysis

      All data were collected on case report forms and uploaded to the Oracle® Clinical Remote Data Capture system, Release 5.2.2 (Oracle Corporation, Redwood Shores, CA, USA).
      Statistical analysis was performed using SAS Version 9.4 (SAS Institute, Cary, NC, USA). Patient demographics, glenoid status and functional parameters were tabulated using standard descriptive statistics. Paired t-tests were performed to compare pre- and postoperative functional scores. Comparative analyses were also made between total shoulder arthroplasty (TSA) and hemiarthroplasty (HSA) patients, those with concentric versus posterior glenoid deformities as well as those with and without ipsilateral shoulder surgery using the Wilcoxon rank sum test. For the radiographic analysis, unpaired t-tests were used. The Fisher’s exact t-test was used to assess the preoperative distribution of glenoid deficiency. Significance level was set to 0.05.

      Results

      Seventy-one patients (35 males, 36 females) with a mean age of 63.8 years (standard deviation [SD]: 8; range: 47-79 years) were available for the 5-year clinical and radiographic follow-up. The average follow-up occurred at 61 months (range: 52-79 months). Sixty-three patients (89%) of those patients were examined after at least 60 months, however in 8 cases a follow-up of up to 9 months earlier was performed due to logistic reasons. Drop out of the 5-year analyses occurred due to death (n=5), loss to follow-up (n=15), withdrawal from this clinical study (n=3) and device explantation (n=6). The reasons for explantation are outlined further below because these events were considered as “adverse events”.
      Of the 71 patients available for midterm evaluation (Table III), 16 had undergone previous ipsilateral shoulder surgery including rotator cuff repair (n=4), capsulolabral repair or reconstruction (n=1) or subacromial decompression and débridement (n=11). There were no significant differences comparing patients with and without previous ipsilateral surgery with regards to preoperative or postoperative function at one, two or five years.
      Table IIIBaseline demographics and distribution based on arthroplasty type and glenoid classification for stemless shoulder arthroplasty patients
      HSATSATotalp-value
      Fisher’s exact test
      N (women in %)23 (35%)48 (59%)71 (51%)
      Age at surgery (years) (mean ± SD)64.5 ± 963.2 ± 863.6 ± 8
      (range)(47-79)(48-79)(47-79)
      Glenoid classification
      According to Walch et al.44 for patients with a 5-year follow-up
      0.0283
       A1101626
       A251015
       B1088
       B251419
       C303
      HSA = shoulder hemiarthroplasty; TSA = total shoulder arthroplasty; SD = standard deviation
      Fisher’s exact test
      According to Walch et al.44 for patients with a 5-year follow-up

      Functional results

      There was a significant increase (p < 0.001) in all clinical outcome scores as well as ROM compared to baseline (Table IV) at 5 years postsurgery; this trend increased steadily until the 2-year examination and reached a plateau by 5 years (Figure 2 and 3). The majority (91.5%) of patients were satisfied (n=11) or very satisfied (n=54) with their shoulder function at 5 years compared to 6 remaining patients who were either somewhat satisfied (n=3) or did not answer this question at all (n=3).
      Table IVComparison of clinical scores and range of motion at baseline vs. 5 year follow-up
      Baseline

      Mean ± SD (range)
      5 year FU

      Mean ± SD (range)
      p-value
      paired t-test
      Absolute CS (points)26.7 ± 12.2 (10-79)72.5 ± 15 (20-98)<.0001
      Relative CS (%)34.7 ± 15.4 (13-104)95.2 ± 20.9 (21-138)<.0001
      ASES score (points)37.4 ± 18.4 (6.7-80.0)87.0 ± 15.5 (22.7-100.0)<.0001
      SSV (%)35.1 ± 17.7 (0-85)84.5 ± 13.5 (30-100)<.0001
      Pain scale (0 = excruciating pain; 15 = no pain)5.7 ± 3.5 (0-15)13.9 ± 2.3 (4-15)<.0001
      Abduction strength (kg)0.6 ± 1.9 (0-12.5)6.0 ± 4.0 (0.5-20.0)<.0001
      Range of motion
      Anterior forward elevation (°)89 ± 27 (40-170)153 ± 23 (70-180)<.0001
      External rotation in 90° abduction (°)14 ± 19 (-20-60)58 ± 20 (10-90)<.0001
      External rotation in 0° abduction (°)13 ± 16 (-10-60)41 ± 18 (0-80)<.0001
      Internal rotation (CS points)2.6 ± 2.3 (0-8)7.0 ± 2.0 (2-10)<.0001
      FU = follow-up; SD = standard deviation; CS = Constant-Murley Score; ASES = American Shoulder and Elbow Standardized Shoulder Assessment; SSV = Subjective Shoulder Value
      paired t-test
      Figure thumbnail gr2
      Figure 2Functional outcome with respect to baseline, one year, two and five years postoperatively for the absolute (a) and relative (b) Constant Score, American Shoulder and Elbow Standardized Shoulder Assessment Form score (c), Subjective Shoulder Value (d), pain (15=pain-free, 0=excruciating pain) (e), abduction strength (f), forward elevation (g), and external rotation in 90° abduction (h) and with arm at side (i).
      Figure thumbnail gr3
      Figure 3Internal rotation with respect to baseline, one year, two and five years postoperatively.
      The subgroup analysis of shoulder function showed that TSA patients achieved significantly better functional outcome over HSA patients with regard to the absolute and relative CS, ASES and SSV (P ≤ 0.001) as well as abduction strength and greater ROM in forward elevation, external and internal rotation (p ≤ 0.0105) (Table V). Satisfaction was also significantly greater for TSA patients at 5 years (Table VI). In addition, patients with posterior glenoid erosion tended to have slightly better functional results, although this trend was not statistically significant (Table V).
      Table VComparison of 5 year clinical results for HSA vs TSA as well as for concentric vs posterior glenoid defects
      5 year FU

      Mean ± SD (range)
      HSA (n=23)TSA (n=48)p-value
      Wilcoxon Rank Sum test
      A1, A2
      According to Walch et al. 40 for patients with a 5-year follow-up
      (n=41)
      B1, B2, C
      According to Walch et al. 40 for patients with a 5-year follow-up
      (n=30)
      p-value
      Wilcoxon Rank Sum test
      Absolute CS (points)59.3 ± 15.9 (20-83)78.5 ± 9.4 (5-68)<.000172.1 ± 16.3 (20-96)73.3 ± 12.2 (48-98).74
      Relative CS (%)77.1 ± 21.3 (21-109)103.3 ± 14.9 (79-138)<.000194.2 ± 22.8 (21-138)96.5 ± 18.1 (61-138).98
      ASES score (points)73.7 ± 20.1 (22.7-100)93.0 ± 7.6 (71.7-100)<.000185.1 ± 18.3 (22.7-100)89.7 ± 10.6 (53.8-100).68
      SSV (%)75.9 ± 15.7 (30-95)88.1 ± 10.8 (60-100).001282.7 ± 14.4 (30-100)87.1 ± 11.9 (60-100).18
      Pain scale (0 = excruciating pain; 15 = no pain)12.7 ± 3.4 (4-15)14.4 ± 1.2 (10-15).058713.5 ± 2.7 (4-15)14.4 ± 1.3 (10-15).10
      Abduction strength (kg)4.0 ± 3.5 (0-12.0)6.9 ± 3.9 (1.5-20.0).00376.5 ± 4.1 (0-20.0)5.3 ± 3.7 (0.9-17.2).14
      Range of motion
      Anterior forward elevation (°)134 ± 28 (70-170)163 ± 10 (135-180)<.0001149 ± 25.5 (70-170)159 ± 16 (100-180).10
      External rotation in 90° abduction (°)43 ± 21 (10-80)65 ± 15 (30-90)<.000158 ± 20 (20-80)58 ± 20 (10-90).97
      External rotation in 0° abduction (°)29 ± 18 (0-60)48 ± 14 (20-80)<.000140 ± 19 (0-70)44 ± 16 (10-80).51
      Internal rotation (CS points)6.0 ± 2.1 (2-10)s7.3 ± 1.9 (2-10).01057.0 ± 2.0 (2-10)7.3 ± 1.5 (4-10).29
      FU = follow-up; SD = standard deviation; HSA = hemi shoulder arthroplasty; TSA = total shoulder arthroplasty; CS = Constant-Murley Score; ASES = American Shoulder and Elbow Standardized Shoulder Assessment; SSV = Subjective Shoulder Value
      Wilcoxon Rank Sum test
      According to Walch et al.
      • Walch G.
      • Badet R.
      • Boulahia A.
      • Khoury A.
      Morphologic study of the glenoid in primary glenohumeral osteoarthritis.
      for patients with a 5-year follow-up
      Table VIBaseline demographics and distribution based on arthroplasty type and glenoid classification for stemless shoulder arthroplasty patients
      HSA

      N (%)
      TSA

      N (%)
      Total

      N (%)
      p-value
      Fisher’s exact test comparing satisfaction for HSA vs. TSA
      Very satisfied10 (44%)44 (92%)54 (76%)0.0002
      Satisfied7 (30%)4 (8%)11 (16%)
      Somewhat satisfied3 (13%)-3 (4%)
      Disappointed---
      No data3 (13%)-3 (4%)
      HSA = shoulder hemiarthroplasty; TSA = total shoulder arthroplasty;
      Fisher’s exact test comparing satisfaction for HSA vs. TSA

      Radiographic results

      There were no cases of osteolysis or loosening of the humerus anchor reported in our cohort at the 5-year postoperative follow-up.
      There were single cases each of Grade 1 heterotopic ossification, development of an inferior osteophyte (< 3 mm) and RLL around the humerus in Zones 1 (3 mm) and 2 (2 mm). None of these radiographic changes were associated with impaired shoulder function.
      Glenoid-associated RLL were documented in a quarter of all patients treated with TSA in this follow-up period (12/48). Of these twelve patients, five patients had RLL, which were initially observed at the 6-month follow-up that were no longer apparent at the 5-year examination. They did not show impaired function. Those seven patients with persistent glenoid RLL at midterm had significantly worse modified CS (p=.029), ASES (p =.042), SSV (p=.049), active (p=.028) and passive (p=.048) external rotation in 90° abduction.
      Only one patient (2.1%) was reported with glenoid migration (< 5 mm) at 5 years, but did not indicate any functional impairment based on a relative CS of 85%, ASES score of 92 points and a SSV of 80%.
      In 7 patients (9.9%), bone resorption around the humerus was documented at the 5-year examination (Table VII): Bone resorption according to Lazarus et al correlated with lower clinical outcome in absolute (p=.037) and relative (p=.040) CS, SSV (p=.021), active forward elevation (p=.005), external rotation in 90° abduction (p=.043) and with arm at side (p=.018) as well as in strength of abduction (p=.53).
      Table VIIListing of patients and with humeral bone resorption and their clinical outcome
      PatientHSA / TSAHumeral Bone Resorption ZoneAbsolute CS (points)Relative CS (%)ASES score (points)SSV (%)Pain scale (min=0; max=15)Strength of abduction (kg)Active forward elevationActive ER with arm at sideActive ER with arm at 90°Active IR
      1HSAZone5477360,8701241001030L3
      2TSAZone1, Zone4, Zone6, Zone7, Zone9, Zone106810093,785132,51405060L3
      3HSAZone5, Zone107010092,2901481505060SAC
      4HSAZone5, Zone10202122,76041700.SAC
      5HSAZone57995100771581401020SAC
      6HSAZone5748583801381503040L3
      7HSAZone1, Zone2718371,760154,61603550L5
      HSA = hemi shoulder arthroplasty; TSA = total shoulder arthroplasty; CS = Constant Score; ASES = American Shoulder and Elbow Standardized Shoulder Assessment; SSV = Subjective Shoulder Value; ER = external rotation; IR = internal rotation; L3 = 3rd lumbar vertebra; L5 = 5th lumbar vertebra; SAC = sacrum

      Adverse events

      Four intraoperative adverse events were noted in our cohort: One patient showed an intraoperative fracture of the greater tuberosity caused during anchor placement who did not need further treatment, since there was no dislocation and the anchor was well fixed. Two anchors had to be exchanged intraoperatively for larger ones because of unstable fixation due to diminished bone quality. The fourth patient experienced partial temporary paresis of the brachial plexus that could be treated conservatively.
      Postoperatively, two patients with HSA were converted to TSA due to shoulder pain and glenoid erosion, one of which had to be revised to a stemmed implant due to persistent pain and functional deficit since their first follow-up visit. The second HSA patient underwent conversion to a TSA, which involved leaving the anchor in situ while replacing the humeral head and resurfacing the glenoid. Another 4 patients (2 TSA and 2 HSA) underwent conversion to a reverse shoulder arthroplasty. Patients with HSA were converted due to rotator cuff insufficiency (n=2) with additional glenoid erosion (n=1), whereas one patient with TSA was converted to RSA due to pseudoparalysis after a traumatic posterosuperior rotator cuff tear. One patient (TSA) was revised due to infection. This resulted in a complication rate of 8.5% leading to revision. All revisions are summarized in table VIII.
      Table VIIIListing of patients with revision surgery
      PatientDate of surgeryDate of revisionImplant typeAdverse EventReoperation Procedure
      103.07.201327.12.2017HSAShoulder trauma during weight lifting resulting in SSP and ISP tearsExplantation and revision to RSA
      212.06.201414.07.2016HSAShoulder pain and glenoid erosionConversion to TSA, which involved leaving the anchor intact while replacing the humeral head and resurfacing the glenoid
      309.04.201301.08.2013TSAPseudoparalysis after subluxation, resulting in a tear of the superior rotator cuff and superior head migrationExplantation and revision to RSA
      425.11.201302.11.2016HSApersistent pain and functional deficit since their first follow-up visitExplantation and revision to a stemmed TSA
      505.11.201307.11.2017HSARotator cuff insufficiency with postero-superior glenoid defectExplantation and revision to RSA
      613.05.201414.05.2018TSADeep shoulder infectionExplantation, spacer implantation and revision to RSA
      HSA = hemi shoulder arthroplasty; TSA = total shoulder arthroplasty; SSP = supraspinatus; ISP = infraspinatus; RSA = reverse shoulder arthroplasty

      Kaplan-Meier survival

      As shown in Figure 4, the Sidus® stem-free shoulder system had a survival rate of 94% (confidence interval: 87–98%) after 5 years with revision as the endpoint.

      Discussion

      The Sidus® stem-free shoulder system shows very good midterm results for patients with primary OA. All clinical and patient-rated outcomes measured in our study improved significantly between baseline and the 5-year follow-up. Over 90% of our patients were satisfied or very satisfied with the procedure at midterm, and the complication rate for this stemless implant was 8.5% with a total survival rate for the humeral anchor of 94%.
      Numerous studies show that stemless implants achieve the same clinical results as stemmed implants in case enough metaphyseal bone stock is available for proper fixation
      • Aldinger P.R.
      • Raiss P.
      • Rickert M.
      • Loew M.
      Complications in shoulder arthroplasty: an analysis of 485 cases.
      • Berth A.
      • Pap G.
      Stemless shoulder prosthesis versus conventional anatomic shoulder prosthesis in patients with osteoarthritis: a comparison of the functional outcome after a minimum of two years follow-up.
      • Denard P.J.
      • Raiss P.
      • Gobezie R.
      • Edwards T.B.
      • Lederman E.
      Stress shielding of the humerus in press-fit anatomic shoulder arthroplasty: review and recommendations for evaluation.
      • Gonzalez J.F.
      • Alami G.B.
      • Baque F.
      • Walch G.
      • Boileau P.
      Complications of unconstrained shoulder prostheses.
      • Maier M.W.
      • Lauer S.
      • Klotz M.C.
      • Bulhoff M.
      • Spranz D.
      • Zeifang F.
      Are there differences between stemless and conventional stemmed shoulder prostheses in the treatment of glenohumeral osteoarthritis?.
      • Raiss P.
      • Edwards T.B.
      • Deutsch A.
      • Shah A.
      • Bruckner T.
      • Loew M.
      • et al.
      Radiographic changes around humeral components in shoulder arthroplasty.
      ; this factor helps to avoid stem-related complications such as periprosthetic fractures, loosening or stress shielding. A finite element study demonstrated that stemless humeral implants are better at distributing trabecular force and mimic cortical stress in a near identical manner to that of a native joint, and far better than short-stem or standard stemmed implants.
      • Razfar N.
      • Reeves J.M.
      • Langohr D.G.
      • Willing R.
      • Athwal G.S.
      • Johnson J.A.
      Comparison of proximal humeral bone stresses between stemless, short stem, and standard stem length: a finite element analysis.
      While short-term results are promising, pertinent mid- to long-term follow-up data for stemless implants so far focus on three implants that have been assessed for five or more postoperative years.
      • Berth A.
      • März V.
      • Wissel H.
      • Awiszus F.
      • Amthauer H.
      • Lohmann C.H.
      SPECT/CT demonstrates the osseointegrative response of a stemless shoulder prosthesis.
      • Krukenberg A.
      • McBirnie J.
      • Bartsch S.
      • Bohler N.
      • Wiedemann E.
      • Jost B.
      • et al.
      Sidus Stem-Free Shoulder System for primary osteoarthritis: short-term results of a multicenter study.
      • Raiss P.
      • Edwards T.B.
      • Deutsch A.
      • Shah A.
      • Bruckner T.
      • Loew M.
      • et al.
      Radiographic changes around humeral components in shoulder arthroplasty.
      The Biomet Total Evolutive Shoulder System (T.E.S.S.®) has an 8-year survival rate of 93.5% and satisfactory long-term results in 31 patients with a mean CS of 69 points.
      • Beck S.
      • Beck V.
      • Wegner A.
      • Dudda M.
      • Patsalis T.
      • Jäger M.
      Long-term survivorship of stemless anatomical shoulder replacement.
      However, 20 out of 22 patients (91%) showed RLL around the glenoid component, four of which showed some degree of migration, and the revision rate was 10%. Magosch et al recently published long-term results for the Arthrex Eclipse™ stemless shoulder prosthesis.
      • Raiss P.
      • Edwards T.B.
      • Deutsch A.
      • Shah A.
      • Bruckner T.
      • Loew M.
      • et al.
      Radiographic changes around humeral components in shoulder arthroplasty.
      Seventy-five patients achieved an average CS of 68 points with a mean follow-up period of 11 years. The 5-year survival rate was 99% and remained high (96.5%) for the stemless humerus component at the 10-year follow-up. Glenoid loosening was reported in 11.4% of the study cohort and the overall revision rate was 15.1%. There was a trend towards a higher complication rate for TSA over HSA patients. At five years, this cohort of primary and post-traumatic OA patients achieved a mean CS of 65 points; the complication rate was 12.8% with a revision rate of 9%.
      • Habermeyer P.
      • Lichtenberg S.
      • Tauber M.
      • Magosch P.
      Midterm results of stemless shoulder arthroplasty: a prospective study.
      A multicenter study investigated the Mathys Affinis Short stemless prosthesis in 150 patients with primary OA who achieved a CS of 74 points after 4 years.
      • Jordan R.W.
      • Kelly C.P.
      • Pap G.
      • Joudet T.
      • Nyffeler R.W.
      • Reuther F.
      • et al.
      Mid-term results of a stemless ceramic on polyethylene shoulder prosthesis - A prospective multicentre study.
      In the entire heterogenous cohort of 207 patients, 13 (6.3%) required revision surgery, and this revision rate tended to be higher for HSA (9.1%) versus TSA patients (5.3%).
      Current meta-analyses have projected an overall complication rate of 8% to 10% with an overall revision rate of 5% to 6% for stemless implants.
      • Liu E.Y.
      • Kord D.
      • Horner N.S.
      • Leroux T.
      • Alolabi B.
      • Khan M.
      Stemless anatomic total shoulder arthroplasty: a systematic review and meta-analysis.
      • Willems J.I.P.
      • Hoffmann J.
      • Sierevelt I.N.
      • van den Bekerom M.P.J.
      • Alta T.D.W.
      • van Noort A.
      Results of stemless shoulder arthroplasty: a systematic review and meta-analysis.
      Therefore, the Sidus® stem-free shoulder system presents comparable midterm functional outcomes and rates of complication and revision to the 3 stemless implants presented in literature so far.
      There was simply one patient with RLL around the humerus which did not affect function with regards to worse ROM or greater pain levels. Therefore, it is safe to say that the humeral component and anchor shows no signs of loosening at 5 years (with one being potentially at risk for loosening in the long-term).
      A study by Alikhah et al has shown that stemless shoulder arthroplasty implants relying on either “press-fit” impaction or screw fixation techniques have been shown to share similar results in terms of clinical and radiographic outcomes.
      • Alikhah A.
      • Imiolczyk J.P.
      • Krukenberg A.
      • Scheibel M.
      Screw fixation in stemless shoulder arthroplasty for the treatment of primary osteoarthritis leads to less osteolysis when compared to impaction fixation.
      Although medial calcar resorption was documented at a higher rate in patients with the impaction-fitted prosthesis, there were no significant differences in clinical function when compared to patients who were treated with a screw fixation designs.
      • Alikhah A.
      • Imiolczyk J.P.
      • Krukenberg A.
      • Scheibel M.
      Screw fixation in stemless shoulder arthroplasty for the treatment of primary osteoarthritis leads to less osteolysis when compared to impaction fixation.
      The authors hypothesized that impaction-fitted implants are more prone to medial calcar resorption, whereas the screw fixation prosthesis permits a better load distribution due to its baseplate and constant rim load. Further theories suggest that particles from the breakdown of polyethylene may be responsible for the occurrence of “humeral notching”
      • Raiss P.
      • Edwards T.B.
      • Deutsch A.
      • Shah A.
      • Bruckner T.
      • Loew M.
      • et al.
      Radiographic changes around humeral components in shoulder arthroplasty.
      when there is impingement of the medial calcar against the glenoid component. Further investigation is needed as this aspect will become immensely important when improved convertible systems emerge and greater focus is placed on bone stock quality at the medial calcar of the humerus.
      RLL around the glenoid did, opposed to those at the humerus, affect the function of those patients in our cohort. This finding with our impaction type prosthesis stands in contrast to the midterm results of Heuberer et al
      • Heuberer P.R.
      • Brandl G.
      • Pauzenberger L.
      • Laky B.
      • Kriegleder B.
      • Anderl W.
      Radiological changes do not influence clinical mid-term outcome in stemless humeral head replacements with hollow screw fixation: a prospective radiological and clinical evaluation.
      using a hollow screw fixation, where neither bone resorption nor RLL did impact clinical function. If RLL were still present at the 5-year follow-up, worse outcomes of the modified CS, ASES score and SSV as well as decreased active and passive external rotation in 90° abduction can be expected. This may be an early sign of prosthesis micromotion and/or bone remodeling due to stress around the glenoid component, which may either occur because of a greater force and load or due to poor bone stock that compromises stability. Interestingly, patient function was not inferior when glenoid RLL disappeared after two years. Hence, persistent RLL around the glenoid at mid-term follow-up may indicate glenoid loosening. Long-term follow-up is needed to emphasize this hypothesis. The time frame between two and five years may be important for integration and bone remodeling around this stemless prosthesis. Glenoid loosening in terms of shift in position, additional migration of the implant or subsidence remains unobserved after five years. While one patient showed radiographic glenoid migration (< 5 mm) at 5 years, due to its excellent clinical outcome and no RLLs, we have not considered this is not as loosening.
      In a similar manner to stemmed shoulder arthroplasty, patients with glenoid resurfacing show better results in terms of clinical outcomes, pain relief and subjective satisfaction than patients with HSA. This difference may be the result of glenoid erosion after HSA. Nevertheless, TSA operations are associated with higher operation times, more blood loss and higher costs as a primary procedure.
      • Gartsman G.M.
      • Roddey T.S.
      • Hammerman S.M.
      Shoulder arthroplasty with or without resurfacing of the glenoid in patients who have osteoarthritis.
      • Sperling J.W.
      • Cofield R.H.
      • Rowland C.M.
      Minimum fifteen-year follow-up of Neer hemiarthroplasty and total shoulder arthroplasty in patients aged fifty years or younger.
      Our study incorporates all the advantages that are associated with its multicenter and prospective design. Furthermore, we only included patients with primary OA who were under the age of 80 years, which resulted in a homogeneous cohort. However, this work has several limitations. By presenting the 5-year follow-up outcomes, long-term effects are still outstanding. Our drop-out rate of 23% is quite high, although this level of patient loss is comparable to that in the literature (19-20%) at five years.
      • Habermeyer P.
      • Lichtenberg S.
      • Tauber M.
      • Magosch P.
      Midterm results of stemless shoulder arthroplasty: a prospective study.
      • Jordan R.W.
      • Kelly C.P.
      • Pap G.
      • Joudet T.
      • Nyffeler R.W.
      • Reuther F.
      • et al.
      Mid-term results of a stemless ceramic on polyethylene shoulder prosthesis - A prospective multicentre study.
      Moreover, our multicenter study may, in fact, be a confounding factor based on the heterogeneity in clinical practice and rehabilitation protocols among the participating institutions. A final limitation is the selection bias of patients under the age of 80 years that potentially exclude those study candidates with poor bone stock.

      Conclusion

      Patients treated with the Sidus® stem-free shoulder system for primary osteoarthritis continue to achieve good clinical and radiographic midterm results without any signs of aseptic implant loosening at five years postsurgery.

      Uncited reference

      • Hudek R.
      • Werner B.
      • Abdelkawi A.F.
      • Schmitt R.
      • Gohlke F.
      Radiolucency in stemless shoulder arthroplasty is associated with an imaging phenomenon.
      .

      Acknowledgments

      The authors thank M. Wilhelmi, PhD (medical writer at Schulthess Clinic) for the editing and final preparation of this manuscript. The authors thank O. Schätti, PhD (Project Leader at Zimmer Biomet) for the valuable coordination and project administration.
      Given his role as Editor in Chief, Dr. Pierre Mansat had no involvement in the peer-review of this article and has no access to information regarding its peer-review. Full responsibility for the editorial process for this article was delegated to Dr. William J. Mallon.

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