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Does non-spherical humeral head with inlay glenoid re-center the glenohumeral joint?

Published:February 18, 2021DOI:https://doi.org/10.1053/j.sart.2021.01.004

      Abstract

      Background

      Treatment of glenohumeral osteoarthritis (OA) with Walch type B glenoid poses a challenge for orthopedic surgeons. Although various techniques have been described, it is still a major concern in terms of management and long-term results. We hypothesized that total shoulder arthroplasty (TSA) using a combination of non-spherical humeral head resurfacing (HHR) and inlay glenoid replacement would re-center the glenohumeral joint in patients with Walch type B glenoid without surgical correction of glenoid version.

      Methods

      We retrospectively screened patients who underwent TSA using a combination of non-spherical HHR and inlay glenoid replacement for primary glenohumeral OA with posteriorly subluxated humeral head (HH) (Walch Type B1, B2 and B3) between 2015 and 2019. Ratios of preoperative and postoperative HH subluxation were compared using Walch index and the point of contact ratio method. Two orthopedic surgeons performed radiographic measurements blinded to each other. Means of 2 independent measurements were included in the final analysis for each shoulder. We also screened for postoperative complications, dislocation events and radiographic loosening.

      Results

      Initial cohort included 49 patients. A total of 29 shoulders in 28 patients were eligible for screening. The numbers of shoulders with Walch type B1, B2, and B3 glenoids were 3, 22, and 4, respectively. Mean preoperative and postoperative Walch indices were 56.57 ± 6.08% and 49.47 ± 4.78%, respectively. The mean preoperative and postoperative point of contact ratios were 62.97 ± 8.45% and 50.08 ± 3.87%, respectively. The difference between preoperative and postoperative subluxation ratios was significant for both methods (P < .01). Inter-rater reliability was found to be good-excellent. The overall complication rate at a mean follow-up period of 37.79 months was 10.34% (3/29). One patient experienced deep vein thrombosis (DVT) (3.22%) on postoperative day 8. Two patients experienced infection (6.45%), one of which required a revision TSA (3.22%) at 19 months after surgery. No patient experienced shoulder dislocation and no loosening was detected on postoperative radiographs.

      Conclusion

      When coupled with an inlay glenoid component in patients with eccentric glenoid wear and posterior subluxation, glenohumeral re-centering was consistently observed in this challenging patient population without the use of joint correction or augmentation procedures. It will be important to follow the clinical outcomes over the long-term to determine whether these observations translate to better clinical results than other techniques currently employed to deal with eccentric erosion and posterior subluxation of the arthritic glenohumeral joint although recent published mid-term results suggest results equal to or better than previously reported results in literature with different reconstructive techniques

      Level of evidence

      Level IV; Retrospective cohort

      Keywords

      The prevalence of glenohumeral osteoarthritis (OA) has been increasing with the aging population, reaching up to 30% in people over the age of 60 [
      • Menge TJ
      • Boykin RE
      • Byram IR
      • Bushnell BD.
      A comprehensive approach to glenohumeral arthritis.
      ,
      Prevention CfDCa
      National Center for Chronic Disease Prevention and Health Promotion.
      ]. In the last few decades, the increase in the number of people maintaining an active lifestyle throughout their adulthood, and advances in shoulder arthroplasty implants and techniques have resulted with an increase in the number of patients undergoing surgery for glenohumeral OA at an earlier age.
      Glenohumeral OA causes a variety of morphological pathologies. Walch et al classified the glenoid morphology in advanced glenohumeral OA using computed tomography (CT) in 1999, and revised their original classification in 2016 [
      • Bercik MJ
      • Kruse 2nd, K
      • Yalizis M
      • Gauci MO
      • 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.
      ]. In the original classification, they reported the incidence of type B (eccentric) glenoid as 32% and distinguished it by the posterior translation of the humeral head (HH) on glenoid. Type B1 glenoid is characterized by a posteriorly subluxated HH on the glenoid, with no accompanying bony erosion. In type B2 glenoid, posterior glenoid bony erosion accompanies the posteriorly subluxated HH causing a biconcave glenoid. The newly added type B3 is characterized with a mono-concave glenoid with posterior wear in addition to >15° of retroversion, and/or >70% posterior HH subluxation [
      • Bercik MJ
      • Kruse 2nd, K
      • Yalizis M
      • Gauci MO
      • 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.
      ]. Levine et al classified glenoid into 2 types [
      • Levine WN
      • Djurasovic M
      • Glasson J-M
      • Pollock RG
      • Flatow EL
      • Bigliani LU.
      Hemiarthroplasty for glenohumeral osteoarthritis: Results correlated to degree of glenoid wear.
      ]. Type I (concentric) is characterized with a degenerative, but concentric glenoid with no flattening or significant bone loss. Type II (eccentric) is characterized with an eccentric glenoid with posterior bone loss resulting a posterior shift of the HH. They reported the incidence of eccentric glenoid in primary and secondary glenohumeral OA as 60% and 48%, respectively [
      • Levine WN
      • Djurasovic M
      • Glasson J-M
      • Pollock RG
      • Flatow EL
      • Bigliani LU.
      Hemiarthroplasty for glenohumeral osteoarthritis: Results correlated to degree of glenoid wear.
      ].
      Operative treatment of glenohumeral OA with a posteriorly subluxated humeral head is indicated in patients with persistent and debilitating pain and functional impairment despite non-operative treatment. Current surgical options include hemiarthroplasty (HA) with glenoid reaming (ream and run), total shoulder arthroplasty (TSA) with asymmetric reaming of the high side, TSA with bone grafting of the posterior glenoid, TSA with an augmented glenoid component, reverse shoulder arthroplasty (RSA), TSA with inset glenoid [
      • Gunther SB
      • Lynch TL.
      Total shoulder replacement surgery with custom glenoid implants for severe bone deficiency.
      ,
      • Gunther SB
      • Lynch TL
      • O'Farrell D
      • Calyore C
      • Rodenhouse A
      Finite element analysis and physiologic testing of a novel, inset glenoid fixation technique.
      ,
      • Gunther SB
      • Tran SK.
      Long-term follow-up of total shoulder replacement surgery with inset glenoid implants for arthritis with deficient bone.
      ] and humeral head resurfacing (HHR) with inlay glenoid [
      • Egger AC
      • Peterson J
      • Jones MH
      • Miniaci A.
      Total shoulderarthroplasty with nonspherical humeral head and inlay glenoid replacement: clinical results comparing concentric and nonconcentric glenoid stages in primary shoulder arthritis.
      ,
      • Radnay CS
      • Setter KJ
      • Chambers L
      • Levine WN
      • Bigliani LU
      • Ahmad CS.
      Total shoulder replacement compared with humeral head replacement for the treatment of primary glenohumeral osteoarthritis: a systematic review.
      ] and the goal of all the techniques is to re-center the humeral head and each technique has a different method of trying to achieve this recentering.
      In this study, we examined the effects of TSA using a combination of non-spherical HHR and inlay glenoid replacement on re-centering the humeral head in patients with an eccentric posterior subluxated humeral head on a B glenoid. We hypothesized that inlay TSA would re-center the humeral head without necessitating surgical correction of glenoid version which could simplify the procedure without potentially compromising the results [
      • Egger AC
      • Peterson J
      • Jones MH
      • Miniaci A.
      Total shoulderarthroplasty with nonspherical humeral head and inlay glenoid replacement: clinical results comparing concentric and nonconcentric glenoid stages in primary shoulder arthritis.
      ]. We also screened for postoperative complications, dislocation events and radiographic loosening.

      Materials and methods

      We performed a retrospective chart review of a prospective cohort of patients who underwent TSA using a combination of non-spherical HHR and inlay glenoid replacement (HemiCAP OVO/Inlay Glenoid Total Shoulder System; Arthrosurface, Franklin, MA, USA) for primary glenohumeral OA with posteriorly subluxated HH (Walch Type B1, B2 and B3) between February 2015 and February 2019. The institutional review board (IRB) approval was obtained for the study (IRB no: 19-962).
      Patients undergoing TSA using a combination of non-spherical HHR and inlay glenoid replacement for primary glenohumeral OA with a posteriorly subluxated HH (Walch type B), with an intact rotator cuff, and with no history of prior shoulder surgeries other than an arthroscopic débridement were included. Exclusion criteria were patients operated for secondary glenohumeral OA or glenohumeral instability and patients with a history of shoulder arthroscopy for rotator cuff tear, instability or labral lesions.
      Initial cohort included 49 patients. Of these, 11 patients were excluded for glenohumeral OA in conjunction with an instability procedure, 8 were excluded for glenohumeral OA other than Walch type B, and 2 patients were lost to follow-up leaving a total of 29 shoulders in 28 patients (Fig. 1).
      Figure 1
      Figure 1Strobe diagram showing patient cohort.

       Surgical technique

      All surgeries were performed by the senior author (AM). Surgery was performed using the technique described by Egger et al earlier [
      • Egger AC
      • Peterson J
      • Jones MH
      • Miniaci A.
      Total shoulderarthroplasty with nonspherical humeral head and inlay glenoid replacement: clinical results comparing concentric and nonconcentric glenoid stages in primary shoulder arthritis.
      ]. A standard deltopectoral approach was used in all patients. A subscapularis tenotomy was performed approximately 1.5 cm medial to the insertion on the lesser tuberosity, stay sutures were placed in the leading edge of the tendon, and the joint was exposed through a capsulotomy passed the 6 o'clock position on the inferior glenoid border.
      A guide pin was inserted perpendicular to the surface into the marked intersection and a centering shaft was then placed with the stop set at the level of the humeral surface. A surface reamer, based on the smaller AP dimension, was placed over the centering shaft and the HH was reamed to match the undersurface of the prosthesis. All periarticular osteophytes were carefully removed to optimize postoperative range of motion. A trial implant of corresponding diameter and offsets allowed verification of proper fit, and a fixation post was placed using calibrated depth control.
      Attention was then turned to the glenoid, and a guide pin was inserted using a 30° off-axis drill guide. The guide wire was set posterior, not central, as the glenoid is reamed at an angle using a semicircular paddle reamer to a depth stop. The angled guide and reamer were designed to allow access to the glenoid without resecting the HH. A trial was inserted to verify placement with slight recession to the glenoid periphery. Cement holes were made in the glenoid vault and a central peg hole was drilled. Cement was pressurized multiple times inside the implant bed with meticulous attention to a proper technique that included additional backside cement application before placing the implant with digital compression and an impactor. The final HH prosthesis was then placed on the taper screw and impacted until the 2 components engaged with the morse taper and were firmly seated on the prepared bone bed. A standard closure with subscapularis repair was performed to conclude the procedure.

       Radiographic assessment

      Preoperative images included true AP (Grashey) and axillary view radiographs [
      • Hsu JE
      • Somerson JS
      • Russ SM
      • Matsen FA.
      Does postoperativeglenoid retroversion affect the 2-year clinical and radiographic outcomes for total shoulder arthroplasty?.
      ,
      • Somerson JS
      • Neradilek MB
      • Hsu JE
      • Russ SM
      • Matsen III FA
      Clinical and radiographic outcomes of the ream-and-run procedure for primary glenohumeral arthritis.
      ], and either a shoulder CT or MRI for all patients. Postoperatively, we obtained true AP and axillary view radiographs immediately after surgery (Day 0), at 3 months and at last follow-up. We used Walch index [
      • Walch G
      • Badet R
      • Boulahia A
      • Khoury A.
      Morphologic study of the glenoid in primary glenohumeral osteoarthritis.
      ] and the point of contact ratio method, described by Matsen [
      • Matsen FA
      • Gupta A.
      Axillary view: arthritic glenohumeralanatomy and changes after ream and run.
      ] to compare preoperative and postoperative HH subluxation (Fig. 2). Preoperative and postoperative measurements were performed using the last available axial radiograph. All measurements were performed by 2 orthopedic surgeons blinded to each other. One of the surgeons was fellowship trained and the other in training and none of them performed surgeries. Means of 2 independent measurements were included in the final analysis for each shoulder. Periprosthetic lucency was evaluated using Sperling classification [
      • Sperling JW
      • Cofield RH
      • Schleck CD
      • Harmsen WS.
      Total shoulder arthroplasty versus hemiarthroplasty for rheumatoid arthritis of the shoulder: results of 303 consecutive cases.
      ].
      Figure 2
      Figure 2Pre- and postoperative measurement of humeral head subluxation using Walch index (A and B), and point of contact ratio method (C and D).

       Clinical outcomes

      A chart review was conducted to screen for postoperative complications and dislocation events.

       Statistical analysis

      Data analysis was performed using SPSS v.25 (IBM, Armonk, NY, USA). Descriptive statistics of categorical variables were reported with frequencies and percentages. Analysis of continuous variables was performed using the Student t-test. Significance was determined at P < .05. Inter-rater reliability of the reviewers is reported as Cronbach`s alpha values. Values under 0.5 were defined as poor reliability, values between 0.5 and 0.75 were defined as moderate reliability, values between 0.75 and 0.9 were defined as good reliability, and values greater than 0.9 were defined as excellent reliability [
      • Portney LG
      • Watkins MP.
      Foundations of clinical research: applications to practice.
      ].

      Results

      A total of 29 shoulders in 28 patients were included (Fig. 1). The numbers of shoulders with Walch type B1, B2 and B3 glenoids were 3, 22 and 4, respectively.
      Demographic data including age, gender and BMI is shown on TableI. Left shoulder was operated in 12 patients, right shoulder was operated in 16 patients and bilateral shoulders were operated in 1 patient. The mean follow-up period was 37.79 ± 13.22 (3-56) months (TableII). Preoperatively, 15 patients had CT and 23 patients had MRI, while 9 patients had both CT and MRI.
      Table IDemographic data and Glenoid characteristics.
      Demographic data
      Age (years)61.00 ± 9.63 (41-79)
      Sex (male/female)24/4(85.7% vs 14.3%)
      BMI (kg/m2)28.48 ± 4.18 (21.57-38.68)
      Follow-up period (months)37.79 ± 13.22 (3-56)
      Operated shoulder (left/ right)13/16 (44.82% vs 55.18%)
      Cronbach`s alpha values of the interrater reliability revealed excellent for preoperative Walch index, preoperative and postoperative point of contact ratio measurements, and good for postoperative Walch index (TableII). Mean preoperative and postoperative Walch indices were 56.57 ± 6.08% and 49.47 ± 4.78%, respectively. Mean preoperative and postoperative point of contact ratios were 62.97 ± 8.45% and 50.08 ± 3.87%, respectively (TableIII). The difference between preoperative and postoperative subluxation ratios was significant for both methods (P < .01).
      Table IIInterrater reliability.
      MeasurementCronbach's alpha
      Preoperative Walch index0.957
      Postoperative Walch index0.858
      Preoperative point of contact ratio0.970
      Postoperative point of contact ratio0.930
      Table IIIComparison of preoperative and postoperative values.
      VariableMean ± SDPvalue
      Walch indexPreoperative56.57 ± 6.08<.01
      Postoperative49.47 ± 4.78
      Point of contact ratioPreoperative62.97 ± 8.45<.01
      Postoperative50.08 ± 3.87
      The overall complication rate at a mean follow-up period of 37.79 months was 10.34% (3/29). One patient experienced deep vein thrombosis (DVT) (3.22%) on postoperative day 8. Two patients experienced infection (6.45%), one of which required a revision TSA (3.22%) at 19 months after surgery. No patient experienced shoulder dislocation and no loosening was detected on postoperative radiographs.

      Discussion

      The management of glenohumeral OA with a posteriorly subluxated HH (Walch type B) poses a challenge. Long-term results are not satisfactory and revision rates are consistently reported to be high [
      • Aleem AW
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      Survivorship of hemiarthroplasty with concentric glenoid reaming for glenohumeral arthritis in young, active patients with a biconcave glenoid.
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      The prognosis for improvement in comfort and function after the ream-and-run arthroplasty for glenohumeral arthritis: an analysis of 176 consecutive cases.
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      Long-term follow-up of shoulder hemiarthroplasty for glenohumeral osteoarthritis.
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      • Mizuno N
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      Reverse total shoulder arthroplasty for primary glenohumeral osteoarthritis in patients with a biconcave glenoid.
      ,
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      • et al.
      Simulation of surgical glenoid resurfacing using three-dimensional computed tomography of the arthritic glenohumeral joint: the amount of glenoid retroversion that can be corrected.
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      Treatment of severe cuff tear arthropathy with the humeral head resurfacing arthroplasty: two-year minimum follow-up.
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      • Radnay CS
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      Total shoulder replacement compared with humeral head replacement for the treatment of primary glenohumeral osteoarthritis: a systematic review.
      ,
      • Raiss P
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      Treatment of osteonecrosis of the humeral head with cementless surface replacement arthroplasty.
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      • Sabesan V
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      ,
      • Thomas SR
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      ,
      • Walch G
      • Moraga C
      • Young A
      • Castellanos-Rosas J.
      Results of anatomic nonconstrained prosthesis in primary osteoarthritis with biconcave glenoid.
      ,
      • Wang T
      • Abrams GD
      • Behn AW
      • Lindsey D
      • Giori N
      • Cheung EV.
      Posterior glenoid wear in total shoulder arthroplasty: eccentric anterior reaming is superior to posterior augment.
      ]. In this study, we demonstrated that re-centering the humeral head on the glenoid was possible with TSA using a combination of non-spherical HHR and inlay glenoid replacement utilizing 2 different radiographic methods in this patient population. Other important findings include a low revision rate (3.22%) mostly due to infection and not instability or implant failure and no radiologic loosening at a mean follow-up period of 37.79 ± 13.22 months. This is the first study to report radiologic outcomes of TSA using a combination of non-spherical HHR and inlay glenoid replacement.
      Techniques to address eccentric glenoid utilize either eccentric reaming, augmenting or replacing the glenoid all with the intent of correcting version and recentering the humeral head. Despite the availability of many different options, centering the humeral head on the glenoid is still a problem [
      • Greiner S
      • Berth A
      • Kääb M
      • Irlenbusch U.
      Glenoid morphology affects the incidence of radiolucent lines around cemented pegged polyethylene glenoid components.
      ,
      • Mehta SK
      • Aleem AW.
      Management of the B2 glenoid in glenohumeral osteoarthritis.
      ]. Proposed mechanisms leading to failure include glenoid component malposition or under correction of the pathologic retroversion [
      • Denard PJ
      • Walch G.
      Current concepts in the surgical management of primary glenohumeral arthritis with a biconcave glenoid.
      ,
      • Iannotti JP
      • Norris TR.
      Influence of preoperative factors on outcome of shoulder arthroplasty for glenohumeral osteoarthritis.
      ,
      • Kany J
      • Katz D.
      How to deal with glenoid type B2 or C? How to prevent mistakes in implantation of glenoid component?.
      ,
      • Walch G
      • Moraga C
      • Young A
      • Castellanos-Rosas J.
      Results of anatomic nonconstrained prosthesis in primary osteoarthritis with biconcave glenoid.
      ]. This procedure took a different approach to glenoid version and subluxation. An inlay glenoid component was utilized without corrective reaming, bone graft or wedges or preoperative planning. The technique also utilizes a unique non-spherical humeral head component which may also contribute to our findings since this has been shown to improve our abilities to restore more accurately the center of rotation and improve joint stability [
      • Jun BJ
      • Iannotti JP
      • McGarry MH
      • Yoo JC
      • Quigley RJ
      • Lee TQ.
      The effects of prosthetic humeral head shape on glenohumeral joint kinematics: a comparison of non-spherical and spherical prosthetic heads to the native humeral head.
      ,
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      • Shin SJ
      • Iannotti JP.
      The effects of prosthetic humeral head shape on glenohumeral joint kinematics during humeral axial rotation in total shoulder arthroplasty.
      ]. In this study, we were able to demonstrate consistent re-centering of the humeral head on the glenoid without changing the version of the glenoid. A benefit of this technique is the preservation of the bone anatomy of both the glenoid and the humeral head [
      • Burgess DL
      • McGrath MS
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      • Mont MA.
      Shoulder resurfacing.
      ,
      • Copeland S.
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      • Duralde XA.
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      ,
      • Levy O
      • Copeland S.
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      • Copeland SA.
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      ,
      • Rodosky MW
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      On the rarity of glenoid component failure.
      ].
      We assessed the effects of central glenoid reaming with insertion of an inlay polyethylene glenoid component. We noted that the HH re-centered itself postoperatively in all patients. The underlying reasons for this observation remain unclear, however, ream-and-run studies have reported similar findings, particularly in patients with B2 glenoids [
      • Getz CL
      • Kearns KA
      • Padegimas EM
      • Johnston PS
      • Lazarus MD
      • Williams Jr, GR
      Survivorship of hemiarthroplasty with concentric glenoid reaming for glenohumeral arthritis in young, active patients with a biconcave glenoid.
      ,
      • Matsen FA
      • Gupta A.
      Axillary view: arthritic glenohumeralanatomy and changes after ream and run.
      ]. Our findings were similar for B1 and B3 glenoids, which may have benefited from osteophyte removal, surface replacement, and implant combination.
      The majority of humeral components used in TSA are spherical [
      • Egger AC
      • Peterson J
      • Jones MH
      • Miniaci A.
      Total shoulderarthroplasty with nonspherical humeral head and inlay glenoid replacement: clinical results comparing concentric and nonconcentric glenoid stages in primary shoulder arthritis.
      ]. Our study included the use of a non-spherical HH implant, which was suggested to have 3 times better fit to anatomy than spherical implants, better replicate humeral anatomy and establish the center of rotation (COR) closer to the normal anatomical position than traditional sphere models. The fit was best in the nonspherical portion of the humeral head which is impacted by the rotation of the shoulder in this biomechanical model. This certainly may also contribute to the re-centering effect in vivo. Although we did not change the version of the glenoid, use bone graft or performed anterior glenoid reaming to correct version, posterior subluxation was reduced in all cases at the last follow-up. These findings support the use of non-spherical HH and inlay glenoid as an alternative surgical method in patients with posterior humeral head subluxation with the benefit of being simpler than onlay techniques, not requiring expensive preoperative planning software, yet achieving similar results of providing a stable recentered glenohumeral joint. This study was meant to evaluate recentering of the humeral head and was not a clinical follow-up although a similar cohort has been reported previously [
      • Egger AC
      • Peterson J
      • Jones MH
      • Miniaci A.
      Total shoulder arthroplasty with nonspherical humeral head and inlay glenoid replacement: clinical results comparing concentric and nonconcentric glenoid stages in primary shoulder arthritis.
      ]. We believe that clinical results with this technique are at least similar [
      • Egger AC
      • Peterson J
      • Jones MH
      • Miniaci A.
      Total shoulder arthroplasty with nonspherical humeral head and inlay glenoid replacement: clinical results comparing concentric and nonconcentric glenoid stages in primary shoulder arthritis.
      ] if not better than other methods that have been used to reconstruct these difficult cases although it is technically easier, not requiring surgical navigation or preoperative planning and potentially avoids some of the complications and risks associated with grafts, augments while at the same time being technically easier and less expensive.
      What is the reason for recentering with this technique when the version is left roughly in situ and no attempts are made to reconstruct the bone defects. We believe that the re-centering of the humeral head on the glenoid could be explained as a result of the mechanical effect of the removal of the ridge on the glenoid while reaming, which is the actual cause of the biconcavity however it could also be related to the soft tissue releases performed at the time of surgery. This is consistent with the fact that humeral head re-centers immediately intraoperatively and is evident even on the postoperative radiographs taken in the recovery room. We don`t anticipate that the re-centering effect is caused by a dynamic factor. In the ream and run technique, a center reaming is performed which creates an articulation between the humeral head and glenoid eliminating the posterior subluxation of the humeral head which have also reported this effect. This technique is not identical but very similar to the “ream and run “ but uses the addition of an inlay glenoid so it is more of a “ream and fill” technique.
      Although patient reported outcomes was not a specific aim of this study, previous studies have reported on patient outcomes with this technique. In a recent study, Egger et al [
      • Egger AC
      • Peterson J
      • Jones MH
      • Miniaci A.
      Total shoulderarthroplasty with nonspherical humeral head and inlay glenoid replacement: clinical results comparing concentric and nonconcentric glenoid stages in primary shoulder arthritis.
      ] reported clinical outcomes of HHR with a non-spherical HH and inlay glenoid replacement on 24 patients with Walch B glenoid with a mean follow-up period of 42.6 months. They suggested the technique to be a promising option for GHOA even in the presence of posterior glenoid erosion, but did not measure re-centering and posterior subluxation. In this study, we used the same arthroplasty construct and assessed whether this total shoulder arthroplasty resulted in a re-centered joint.
      TSA with an inset glenoid is another similar technique that has been utilized and reported to address posterior glenoid wear. Recently, Gunther et al reported excellent long-term clinical and radiologic outcomes of TSA with inset glenoids on 17 cases with GHOA at a mean follow-up of 8.7 years [
      • Gunther SB
      • Tran SK.
      Long-term follow-up of total shoulder replacement surgery with inset glenoid implants for arthritis with deficient bone.
      ]. They included a similar patient population and suggested inset glenoid as an alternative for the treatment of GHOA with posteriorly subluxated humeral head.
      There are limitations to our study. The retrospective design may have introduced selection bias although it was not meant to be a comparative clinical study but was primarily a radiographic study to assess whether this technique resulted in joint re-centering or not. There were no cases of instability in this group. Egger et al [
      • Egger AC
      • Peterson J
      • Jones MH
      • Miniaci A.
      Total shoulderarthroplasty with nonspherical humeral head and inlay glenoid replacement: clinical results comparing concentric and nonconcentric glenoid stages in primary shoulder arthritis.
      ] and Cvetanovich et al [
      • Cvetanovich GL
      • Naylor AJ
      • O'Brien MC
      • Waterman BR
      • Garcia GH
      • Nicholson GP.
      Anatomic total shoulder arthroplasty with an inlay glenoid component: clinical outcomes and return to activity.
      ] recently reported the functional and clinical results of similar patient cohorts using the same implant with excellent clinical outcomes even in the presence of posterior humeral head subluxation associated with B glenoids. We used plain radiographs for measurements instead of CT. Nevertheless, previous studies have used similar measurement methods, which supports the comparability of our results [
      • Davis DE
      • Acevedo D
      • Williams A
      • Williams G.
      Total shoulder arthroplasty using an inlay mini-glenoid component for glenoid deficiency: a 2-year follow-up of 9 shoulders in 7 patients.
      ,
      • Edwards TB
      • Boulahia A
      • Kempf J-F
      • Boileau P
      • Némoz C
      • Walch G.
      Shoulder arthroplasty in patients with osteoarthritis and dysplastic glenoid morphology.
      ,
      • Iannotti JP
      • Norris TR.
      Influence of preoperative factors on outcome of shoulder arthroplasty for glenohumeral osteoarthritis.
      ,
      • Matsen FA
      • Gupta A.
      Axillary view: arthritic glenohumeralanatomy and changes after ream and run.
      ,
      • Shukla DR
      • McLaughlin RJ
      • Lee J
      • Cofield RH
      • Sperling JW
      • Sánchez-Sotelo J.
      Intraobserver and interobserver reliability of the modified Walch classification using radiographs and computed tomography.
      ].

      Conclusion

      A non-spherical humeral head implant when coupled with an inlay glenoid component in patients with eccentric glenoid wear and posterior subluxation, resulted in glenohumeral re-centering observed on a consistent basis. We understand that this is a challenging patient population but we were able to achieve the goals of recentering of the joint without the use of joint correction or augmentation procedures, navigation, patient specific instrumentation or preoperative planning programs. It will be important to better understand the underlying factors effecting the re-centering and follow the clinical outcomes over the long-term to determine whether these observations translate to better clinical results when compared to other techniques currently employed to deal with eccentric erosion and posterior subluxation of the arthritic glenohumeral joint.

      Disclaimer

      Conflict of interest: Anthony Miniaci received consulting fees and royalties from Arthrosurface related to intellectual property related to the subject of this work. All other authors, their immediate families, and any research foundations with which they are affiliated have not received any financial payments or other benefits from any commercial entity related to the subject of this article.
      Funding: No funding was disclosed by the authors.

      Acknowledgments

      We would like to thank Elizabeth Sosic, Jennifer Turczyk and Brian Strippy for their help during IRB approval process. We also want to thank Sage O`Bryant for creating the online data collection sheet. “Does non-spherical humeral head with inlay glenoid re-center the glenohumeral joint?”

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