Durable humeral component fixation in shoulder arthroplasty is necessary to prevent painful aseptic loosening and resultant humeral bone loss. Causes of humeral component loosening include stem design and material, stem length and geometry, ingrowth vs. ongrowth surfaces, quality of bone available for fixation, glenoid polyethylene debris osteolysis, exclusion of articular particulate debris, joint stability, rotator cuff function, and patient activity levels. Fixation of the humeral component may be achieved by cement fixation either partial or complete and press-fit fixation. During the past two decades, uncemented humeral fixation has become more popular, especially with short stems and stemless press fit designs. Cemented humeral component fixation risks difficult and complicated revision surgery, stress shielding of the tuberosities and humeral shaft periprosthetic fractures at the junction of the stiff cemented stem and the remaining humeral shaft. Press fit fixation may minimise these cemented risks but has potential for stem loosening. A randomised clinical trial of 161 patients with cemented vs. press fit anatomic total shoulder replacements found that cemented fixation of the humeral component provided better quality of life, strength, and range of motion than uncemented fixation but longer operative times. Another study found increased humeral osteolysis (43%) associated with glenoid component loosening and polyethylene wear, while stress shielding was seen with well-fixed press fit humeral components. During reverse replacement the biomechanical forces are different on the humeral stem. Stem loosening during reverse replacement may have different factors than anatomic replacement. A systemic review of 41 reverse arthroplasty clinical studies compared the functional outcomes and complications of cemented and uncemented stems in approximately 1800 patients. There was no difference in the risk of stem loosening or revision between cemented and uncemented stems. Uncemented stems have at least equivalent clinical and radiographic outcomes compared with cemented stems during reverse shoulder arthroplasty. Durable humeral component fixation in shoulder arthroplasty is associated with fully cemented stems or well ingrown components that exclude potential synovial debris that may cause osteolysis

Over the last decade stemless shoulder arthroplasty has become increasingly popular. However, stability of metaphyseal loading humeral components remains a concern. This study aimed to assess the stability of the Affinis stemless humeral component using Radiostereometric analysis (RSA). Patients underwent total shoulder arthroplasty via a standardised technique with a press-fit stemless humeral component and a cemented pegged glenoid. Tantalum beads were inserted into the humerus at the time of operation. RSA of the relaxed shoulder was completed at weeks 1, 6, 13, 26, 52 and 104 post-operatively. Stressed RSA with 12 newtons of abduction force was completed from week 13 onwards. ABRSA 5.0 software (Downing Imaging Limited, Aberdeen) was used to calculate humeral component migration and induced movement. 15 patients were recruited. Precision was: 0.041, 0.034, 0.086 and 0.101 mm for Superior, Medial, Posterior and Total Point Motion (TPM) respectively. The mean TPM over 2 years was 0.24 (0.30) mm, (Mean (Standard deviation)). The mean rate of migration per 3 month time period decreased from 0.45 (0.31) to 0.02 (0.01) mm over 2 years. Mean inducible movement TPM peaked at 26 weeks at 0.1 (0.08) mm, which reduced to 0.07 (0.06) mm by 104 weeks when only 3 patients had measurable inducible motion. There was no clear trend in direction of induced movement. There were no adverse events or revisions required. We conclude migration of the humeral component was low with little inducible movement in the majority of patients implying initial and 2 year stability of the stemless humeral component

Removal of a well-fixed humeral component during revision shoulder arthroplasty presents a challenging problem. If the humeral component cannot be extracted simply from above, an alternate approach must be taken that may include compromising bone architecture to remove the implant. Two potential solutions to this problem that allow removal of the well-fixed prosthesis are making a humeral window or creating a longitudinal split in the humerus. A retrospective review was performed at the Mayo Clinic to determine the complications associated with performing humeral windows and longitudinal splits during the course of revision shoulder arthroplasty. This study included 427 patients from 1994–2010 at Mayo Clinic undergoing revision shoulder arthroplasty. From this cohort, those who required a humeral window or a longitudinal split to assist removal of a well-fixed humeral component were identified. Twenty-seven patients had a humeral window produced to remove a well-fixed humeral component. Six intra-operative fractures were reported from this group: 5 were in the greater tuberosity and 1 was in the distal humeral shaft. At the latest radiographic follow-up, 24 of 27 windows healed, 2 patients had limited inconclusive radiographic follow-up (1 and 2 months), and 1 did not have follow-up at our institution. Twenty-four patients underwent longitudinal osteotomy to extract a well-fixed humeral component. From this group, 1 had intra-operative fracture in the greater tuberosity. At most recent radiographic follow-up, 22 of 24 longitudinal splits healed, 1 had short follow-up (1 ½ months) with demonstrated signs of healing, and 1 did not have follow-up at our institution. In both groups, there were no cases of window malunion and no components have developed clinical loosening. Data from this study suggests humeral windows and longitudinal splits can assist with controlled removal of well-fixed humeral components with a high rate of union and a low rate of intra-operative and post-operative sequelae

Purpose: Loosening of the humeral component is rarely a cause for revision shoulder surgery. Most long-term series are not large enough to stratify the many risk factors that might influence the survivorship of humeral component designs. The purpose of this study was to determine long-term survivorship of the Neer and Cofield humeral components and to define the risk factors associated with humeral component removal or revision. Method: 1584 primary Neer and Cofield shoulder arthroplasties (1423 patients) were performed at our institution from 1984 to 2004. There were 619 men (694 shoulders) and 804 women (890 shoulders), with a mean age at arthroplasty of 65.6 years (range, 16–94 years). Kaplan-Meier survivorship analysis was used to determine the effect of etiology of the disease, gender, age, surgery type (hemi versus total), fixation type (cemented versus noncemented), and the humeral component type (Neer II, Cofield I or II) on the estimated survival free of humeral component revision or removal. Results: There were 108 revisions and 17 removals of the humeral component. The overall rate of removal or revision of the humeral component was 7.9% with an average followup of 8.1 years. The rates of survivorship free of revision or removal of the humeral component for any reason was 94.8% at 5 years, 92% at 10 years, 86.7% at 15 years and 82.8% at 20 years. Seventy-one of 632 shoulders (11.2%) in patients younger than 65 years required humeral component revision or removal, whereas only 54 of 952 shoulders (5.7%) in patients 65 years and older required humeral component revision or removal (Odds ratio=2.1; 95% confidence interval, 1.5–3, p=0.001). Patients with posttraumatic arthritis had a higher risk of needing revision or removal of the humeral component (Odds ratio=2.1, 95% confidence interval 1.3–3.3) compared to osteoarthritis. Eighty-four of 526 shoulders (16.0%) with metal-back glenoid components required humeral component revision or removal, whereas only 41 of 1058 shoulders (3.9%) with non metal-backed glenoid components required humeral component revision or removal (Odds ratio=4.7; 95% confidence interval, 3.2–7, p=0.001). Conclusion: Younger age, replacement due to post-traumatic arthritis and presence of a metal-backed glenoid increased the likelihood of humeral component failure. Similar short-term survival can be achieved with Cofield II and Neer II humeral components

Purpose: While computer-assisted techniques can improve the alignment of the implant articulation with the native structure, stem abutment in the intramedullary canal may impede achievement of this alignment. In the current study, the effect of a fixed valgus (6 degree) stemmed humeral component on the alignment of navigated total elbow arthroplasty was investigated. Our hypothesis was that implantation of a humeral component with a reduced stem length would be more accurate than implantation of the humeral component with a standard length stem. Method: Thirteen cadaveric distal humeri were imaged using a CT scanner, and a 3D surface model was reconstructed from each scan. Implantation was performed using two implant configurations. The first set was unmodified (Regular) while the second set was modified by reducing the length of the humeral stem to 25% of the original stem (Reduced). A surface model of the humeral component was aligned with the flexion-extension (FE) axis of the CT-based surface model, which was registered to the landmarks of the physical humerus using the iterative closest point algorithm. Navigated implant positioning was based on aligning a 3D computer model calibrated to the implant with a 3D model registered to the distal humerus. Results: Implant alignment error was significantly lower for the Reduced implant, averaging 1.3±0.5 mm in translation and 1.2±0.4° in rotation, compared with 1.9±1.1 mm and 3.6±2.1° for the Regular implant. Abutment of the implant stem with the medullary canal of the humerus prevented optimal alignment of the Regular humeral component as only four of the 13 implantations were aligned to within 2.0° using navigation. Conclusion: These results demonstrate that a humeral component with a fixed valgus angulation cannot be accurately positioned in a consistent fashion within the medullary canal of the distal humerus without sacrificing alignment of the FE axis due to stem abutment. Improved accuracy of implant placement can be achieved by introducing a family of humeral components, with three valgus angulations of 0°, 4° and 8°. Based on humeral morphology for these specimens, 12 of the 13 implants may be positioned to within 2° of the native FE axis using one of these 3 valgus angulations

Purpose: This study evaluated the accuracy of humeral component alignment in total elbow arthroplasty. An image-based navigated approach was compared against a conventional non-navigated technique. We hypothesized that an image-based navigation system would improve humeral component positioning, with navigational errors less than or approaching 2.0mm and 2.0°. Method: Eleven cadaveric distal humeri were imaged using a CT scanner, from which 3D surface models were reconstructed. Non-navigated humeral component implantation was based on a visual estimation of the flexion-extension (FE) axis on the medial and lateral aspects of the distal humerus, followed by standard instrumentation and positioning of a commercial prosthesis by an experienced surgeon. Positioning was based on the estimated FE axis and surgeon judgment. The stem length was reduced by 75% to evaluate the navigation system independent of implant design constraints. For navigated alignment, the implant was aligned with the FE axis of the CT surface model, which was registered to landmarks of the physical humerus using the iterative closest point algorithm. Navigated implant positioning was based on aligning a 3D computer model calibrated to the implant with a 3D model registered to the distal humerus. Each alignment technique was repeated for a bone loss scenario where distal landmarks were not available for FE axis identification. Results: Implant alignment error was significantly lower using navigation (P< 0.001). Navigated implant alignment error was 1.2±0.3 mm in translation and 1.3±0.3° in rotation for the intact scenario, and 1.1±0.5 mm and 2.0±1.3° for the bone loss scenario. Non-navigated alignment error was 3.1±1.3 mm and 5.0±3.8° for the intact scenario, and 3.0±1.6 mm and 12.2±3.3° for the bone loss scenario. Without navigation, 5 implants were aligned outside 5° for intact bone while 9 were aligned outside 10° for the bone loss scenario. Conclusion: Image-based navigation improved the accuracy of humeral component placement to less than 2.0 mm and 2.0°. Further, outliers in implant positioning were reduced using image-based navigation, particularly in the presence of bone loss. Implant malalignment may well increase the likelihood of early implant wear, instability and loosening. It is likely that improved implant positioning will lead to fewer implant related complications and greater prosthesis longevity

Introduction. Reverse total shoulder arthroplasty continues to have a high complication rate, specifically with component instability and scapular notching. Therefore, the purpose of this study was to quantify the effects of humeral component neck angle and version on impingement free range of motion. Methods. A total of 13 cadaveric shoulders (4 males and 9 females, average age = 69 years, range 46 to 96 years) were randomly assigned to two studies. Study 1 investigated the effects of humeral component neck angle (n=6) and Study 2 investigated the effects of humeral component version (n=7). For all shoulders, Tornier Aequalis® Reversed Shoulder implants (Edina, MN) were used. For study 1, the implants were modified to 135, 145 and 155 degree humeral neck shaft angles and for Study 2 a custom implant that allowed control of humeral head version were used. For biomechanical testing, a custom shoulder testing system that permits independent loading of all shoulder muscles with six degree of freedom positioning was used. (Figure 1) Internal control experimental design was used where all conditions were tested on the same specimen. Study 1. The adduction angle and internal/external humeral rotation angle at which impingement occurred were measured. Glenohumeral abduction moment was measured at 0 and 30 degrees of abduction, and anterior dislocation forces were measured at 30 degrees of internal rotation, 0 and 30 degrees of external rotation with and without subscapularis loading. Study 2. The degree of internal and external rotation when impingement occurred was measured at 0, 30 and 60 degrees of glenohumeral abduction in the scapular plane with the humeral component placed in 20 degrees of anteversion, neutral version, 20 degrees of retroversion, and 40 degrees of retroversion. Statistical analysis was performed with a repeated measures analysis of variance with a Tukey post-hoc test with a significance level of 0.05. Results. Study 1. Adduction deficit angles for 155, 145, and 135 degree neck-shaft angle were 2 ± 5 degrees of abduction, 7 ± 4 degrees of adduction, and 12 ± 2 degrees of adduction (P <0.05), respectively. Impingement-free angles of humeral rotation and abduction moments were not statistically different between the neck-shaft angles. The anterior dislocation force was significantly higher for the 135degree neck-shaft angle at 30 degrees of external rotation and significantly higher for the 155 degree neck shaft angle at 30 degrees of internal rotation (P<.01). The anterior dislocation forces were significantly higher when the subscapularis was loaded (P <0.01). Study 2. Maximum external rotation was the limiting position for impingement particularly at 0 degrees of abduction. Maximum external rotation before impingement occurred increased significantly with increasing humeral retroversion (p < 0.05) (Figure 2). No impingement or subluxation occurred at any humeral version in 60 degrees of glenohumeral abduction. Conclusion. In reverse shoulder arthroplasty, 155 degree neck-shaft angle was more prone to impingement with adduction but had the advantage of being more stable. In addition, 40 degrees of retroversion has the largest range of humeral rotation without impingement

Purpose: Aseptic loosening is one of the leading causes of failure in total elbow arthroplasty. It is logical to postulate that incorrect implant positioning and alignment may lead to excessive loading and wear which can induce the loosening cascade. However, the effect of implant malalignment on wear inducing loads in the elbow is not yet known. This in-vitro study determined the effect of anterior malpositioning, and varus-valgus (VV) and internal-external (IE) malrotations on humeral stem loading in total elbow arthroplasty. Method: The humeral, ulnar, and radial components of a linked total elbow arthroplasty were optimally positioned using computer navigation in eight cadaveric elbows, mounted in a load/motion control elbow simulator (age 75yrs, range 42–93; 5 male). A modular, humeral component was employed to generate implant malpositioning errors of ±6° VV, ±8° IE, and 5mm anterior. The implant was instrumented with strain gauges to quantify VV and IE bending loads during elbow flexion with the forearm in supination. Load output was combined using a sum-of-squares technique. Passive flexion was performed with the arm in the varus and valgus orientations; passive and active flexion were performed with the arm in the vertical orientation. Results: With the arm (humerus) in the vertical orientation, bending loads increased between 418Nmm and 1618Nmm for all malaligned implant positions (p< 0.05). Passive flexion (1354±859Nmm) produced higher resultant loads for the optimally positioned implant than active (819±891Nmm) flexion (p< 0.05). Although it varied during flexion, loading with the arm in varus (2928±1273Nmm) or valgus (2494±743Nmm) orientations resulted in up to a three-fold increase in loading when compared to the vertical orientation (p< 0.01). Conclusion: These data demonstrate that humeral component malpositioning increases loading in the implant, however further studies are required to determine the long term effect on polyethylene wear and component loosening. Prosthesis designs that replicate the native flexion-extension axis and make use of sophisticated instrumentation or computer assistance to achieve precise positioning during implantation should lead to improved arthroplasty durability. Also, loading was higher with the arm in varus or valgus orientations, suggesting that patients should avoid activities post-operatively that require their elbow to be positioned in this way

Aims

The objective of this study was to compare simulated range of motion (ROM) for reverse total shoulder arthroplasty (rTSA) with and without adjustment for scapulothoracic orientation in a global reference system. We hypothesized that values for simulated ROM in preoperative planning software with and without adjustment for scapulothoracic orientation would be significantly different.

Introduction

Cement pressurisation in the distal humerus is technically difficult due to the anatomy of the humeral intramedullary (IM) cavity. Conventional cement restrictors often migrate proximally or leak, reducing the effect of pressurisation during implantation. Theoretically with a better cement bone interdigitation, the longevity of the elbow replacement can be improved. The aim of this cadaveric study was to evaluate the usefulness of a novel technique for cementation.

The 2021 Australian Orthopaedic Association National Joint Replacement Registry report indicated that total shoulder replacement using both mid head (TMH) length humeral components and reverse arthroplasty (RTSA) had a lower revision rate than stemmed humeral components in anatomical total shoulder arthroplasty (aTSA) - for all prosthesis types and diagnoses. The aim of this study was to assess the impact of component variables in the various primary total arthroplasty alternatives for osteoarthritis in the shoulder. Data from a large national arthroplasty registry were analysed for the period April 2004 to December 2020. The study population included all primary aTSA, RTSA, and TMH shoulder arthroplasty procedures undertaken for osteoarthritis (OA) using either cross-linked polyethylene (XLPE) or non-cross-linked polyethylene (non XLPE). Due to the previously documented and reported higher revision rate compared to other anatomical total shoulder replacement options, those using a cementless metal backed glenoid components were excluded. The rate of revision was determined by Kaplan-Meir estimates, with comparisons by Cox proportional hazard models. Reasons for revision were also assessed. For a primary diagnosis of OA, aTSA with a cemented XLPE glenoid component had the lowest revision rate with a 12-year cumulative revision rate of 4.7%, compared to aTSA with cemented non-XLPE glenoid component of 8.7%, and RTSA of 6.8%. The revision rate for TMH was lower than aTSA with cemented non-XLPE, but was similar to the other implants at the same length of follow-up. The reason for revision for cemented aTSR was most commonly component loosening, not rotator cuff deficiency. Long stem humeral components matched with XLPE in aTSA achieve a lower revision rate compared to shorter stems, long stems with conventional polyethylene, and RTSA when used to treat shoulder OA. In all these cohorts, loosening, not rotator cuff failure was the most common diagnosis for revision

The advent of modern anatomic shoulder arthroplasty occurred in the 1990's with the revelation that the humeral head dimensions had a fixed ratio between the head diameter and height. As surgeons moved from the concept of balancing soft tissue tension by using variable neck lengths for a given humeral head diameter, a flawed concept based on lower extremity reconstruction, improvements in range of motion and function were immediately observed. Long term outcome has validated this guiding principle for anatomic shoulder replacement with improved longevity of implants, improved patient and surgeon expectations and satisfaction with results. Once the ideal humeral head prosthesis is identified, and its position prepared, the surgeon must use a method to fix the position of the head that is correct in three dimensions and has the security to withstand patient activities and provide maximal longevity. Based again on lower extremity concepts, long stems were the standard of care, initially with cement, and now, almost universally without cement for a primary shoulder replacement. The incredibly low revision rates for humeral stem aseptic loosening shifted much of the attempted innovation to the challenges on the glenoid side of the reconstruction. However, glenoid problems including revision surgery, infections, periprosthetic fractures, and other complications often required the removal of the humeral stem. And, in many cases, the overall results of the procedure and the patient's long-term outcome was affected by the difficulty in removing the stem, leading surgeons to compromise the revision procedure, avoid revision surgery, or add to the overall morbidity with humeral fractures and substantial bone loss. With improved technology, including bone ingrowth methods, better matching of the proximal stem geometry to the humerus, and an understanding that the center of rotation (torque) on the humeral component is at the level of the humeral osteotomy, shorter stems and stemless humeral components were developed, now more than 10 years ago, primarily in Europe. With more than a decade of experience, our European colleagues have shown us that stemless humeral component replacement with a device that has both cortical and cancellous fixation is as effective as a stemmed device, easier to implant as well as revise when needed. The short-term results of the cancellous fixation stemless devices are acceptable, but longer follow-up is needed. Currently, the most widely used humeral components in the USA are short stem components, although the recent FDA approval of numerous stemless devices has initiated a shift from short stems to stemless devices. The truth is, short stem devices have a firm position in the USA surgeons' armamentarium today due to regulatory restrictions. A decade ago, without a predicate on the market, it was not conceivable that a stemless device that was already gaining popularity in Europe would be able to get 510K approval, and therefore would require a lengthy and expensive FDA IDE process. However, shorter stems had already been approved in the USA, as long as the stem length was 7 centimeters, matching the market predicate. Now, in 2018, based on evidence and outcomes, stemless humeral components should be the first choice when treating primary osteoarthritis of the glenohumeral joint. Short stem or longer stem devices should be reserved for those cases where stemless fixation is not possible, which is less than 10% of patients with primary OA of the shoulder

In older patients (>75 years of age), with an intact rotator cuff, requiring a total shoulder replacement (TSR) there is, at present, uncertainty whether an anatomic TSR (aTSR) or a reverse TSR (rTSR) is best for the patient. This comparison study of same age patients aims to assess clinical and radiological outcomes of older patients (≥75 years) who received either an aTSR or a rTSA. Consecutive patients with a minimum age of 75 years who received an aTSR (n=44) or rTSR (n=51) were prospectively studied. Pre- and postoperative clinical evaluations included the ASES score, Constant score, SPADI score, DASH score, range of motion (ROM) and pain and patient satisfaction for a follow-up of 2 years. Radiological assessment identified glenoid and humeral component osteolysis, including notching with a rTSR. Postoperative improvement for ROM and all clinical assessment scores for both groups was found. There were significantly better patient reported outcome scores (PROMs) in the aTSR group compared with the rTSR patients (p<0.001). Both groups had only minor osteolysis on radiographs. No revisions were required in either group. The main complications were scapular stress fractures for the rTSR patients and acromioclavicular joint pain for both groups. This study of older patients (>75 years) demonstrated that an aTSR for a judiciously selected patient with good rotator cuff muscles can lead to a better clinical outcome and less early complications than a rTSR

The use of shorter humeral stems in reverse shoulder arthroplasty has been reported as safe and effective. Shorter stems are purported to be bone preserving, easy to revise, and have reduced surgical time. However, a frequent radiographic finding with the use of uncemented short stems is stress shielding. Smaller stem diameters reduce stress shielding, however, carry the risk of varus or valgus malalignment in the metadiaphyseal region of the proximal humerus. The aim of this retrospective radiographic study was to measure the true post-operative neck-shaft (N-S) angle of a curved short stem with a recommended implantation angle of 145°. True anteroposterior radiographs of patients who received RTSA using an Ascend Flex short stem at three specialized shoulder centres (London, ON, Canada, Lyon, France, Munich, Germany) were reviewed. Radiographs that showed the uncemented stem and humeral tray in orthogonal view without rotation were included. Sixteen patients with proximal humeral fractures or revision surgeries were excluded. This yielded a cohort of 124 implant cases for analysis (122 patients, 42 male, 80 female) at a mean age of 74 years (range, 48 – 91 years). The indications for RTSA were rotator cuff deficient shoulders (cuff tear arthropathy, massive cuff tears, osteoarthritis with cuff insufficiency) in 78 patients (63%), primary osteoarthritis in 41 (33%), and rheumatoid arthritis in 5 (4%). The humeral component longitudinal axis was measured in degrees and defined as neutral if the value fell within ±5° of the humeral axis. Angle values >5° and < 5 ° were defined as valgus and varus, respectively. The filling-ratio of the implant within the humeral shaft was measured at the level of the metaphysis (FRmet) and diaphysis (FRdia). Measurements were conducted by two independent examiners (SA and TW). To test for conformity of observers, the intraclass correlation coefficient (ICC) was calculated. The inter- and intra-observer reliability was excellent (ICC = 0.965, 95% confidence interval [CI], 0.911– 0.986). The average difference between the humeral shaft axis and the humeral component longitudinal axis was 3.8° ± 2.8° (range, 0.2° – 13.2°) corresponding to a true mean N-S angle of 149° ± 3° in valgus. Stem axis was neutral in 70% (n=90) of implants. Of the 34 malaligned implants, 82% (n=28) were in valgus (mean N-S angle 153° ± 2°) and 18% (n=6) in varus position (mean N-S angle 139° ± 1°). The average FRmet and FRdiawere 0.68 ± 0.11 and 0.72 ± 0.11, respectively. No association was found between stem diameter and filling ratios (FRmet, FRdia) or cortical contact with the stem (r = 0.39). Operative technique and implant design affect the ultimate positioning of the implant in the proximal humerus. This study has shown, that in uncemented short stem implants, neutral axial alignment was achieved in 70% of cases, while the majority of malaligned humeral components (86%) were implanted in valgus, corresponding to a greater than 145° neck shaft angle of the implant. It is important for surgeons to understand that axial malalignment of a short stem implant does influence the true neck shaft angle

Abstract. Aim. Excessive glenoid retroversion and posterior wear leads to technical challenges when performing anatomic shoulder replacement. Various techniques have been described to correct glenoid version, including eccentric reaming, bone graft, posterior augmentation and custom prosthesis. Clinical outcomes and survivorship of a Stemless humeral component with cemented pegged polyethylene glenoid with eccentric reaming to partially correct retroversion are presented. Patients and Methods. Between 2010– 2019, 115 Mathys Affinis Stemless Shoulder Replacements were performed. 50 patients with significant posterior wear and retroversion (Walch type B1, B2, B3 and C) were identified. Measurement of Pre-operative glenoid retroversion and Glenoid component version on a post op axillary view was performed by method as described by Matsen FA. Relative correction was correlated with clinical and radiological outcome. Results. 4 were lost to follow up. 46 patients were therefore reviewed. The mean follow up was 4 years (2–8.9 years). Walch B1, Pre op Retroversion: 12 (8–20), post op retroversion :11.8 (−4 to 19), correction= 0.2. Walch B2, Pre op Retroversion :18.4 (10–32), post op retroversion: 13.2 (1 −22), correction= 5.2. Walch B3, Pre op Retroversion: 19.1 (13–32)post op retroversion : 16.1 (9–25), correction= 3.0. Walch C, Pre op Retroversion: 33.3 (28–42) post op retroversion: 16.0 (6–27), correction= 17.3. 3 patients required revision surgery for rotator cuff failure. Conclusion. Partial correction of glenoid retroversion with eccentric reaming and implantation of cemented pegged polyethylene component leads to satisfactory clinical outcomes at midterm follow up. No revisions for aseptic loosening of the glenoid were required

Summary Statement. The current biomecahnical study demonstrated that the stemless peripheral leg humeral component prototype and central screw humeral component prototype achieved similar initial fixation as stemmed Global Advantage humeral component in terms of resultant micromotion in total shoulder arthroplasty. Introduction. A stemless humeral component may offer a variety of advantages over its stemmed counterpart, e.g. easier implantation, preservation of humeral bone stock, fewer humeral complications, etc. However, the initial fixation of a stemless humeral component typically depends on cementless metaphyseal press-fit, which could pose some challenges to the initial stability. Long-term success of cementless implants is highly related to osseous integration, which is affected by initial implant-bone interface motion. 1. The purpose of the study was to biomechanically compare micromotion at the implant-bone interface of three humeral components in total shoulder arthroplasty. Patients & Methods. Three humeral components were evaluated: Global Advantage, a central screw prototype, and a peripheral leg prototype. All components were the smallest sizes available. Global Advantage is a stemmed design. Both central screw prototype and peripheral leg prototype are stemless designs. Five specimens were tested for each design. Composite analogue humeral models were utilized to simulate the humeral bone. The cortical wall had a thickness of 3 mm and a density of 481 kg/m. 3. , while the cancellous density was 80 kg/m. 3. The model was custom fabricated to accommodate 40 mm humeral component and had a 45° resected surface and a square base to facilitate test setup. Each humeral component was implanted per its surgical technique. The construct was clamped in a vise with the humeral shaft angled at 27°. A MTS test system was employed to conduct the test. A sinusoidal compressive load from 157 N to 1566 N (2BW) was applied to the humeral component at 1 Hz for 100 cycles. The implant-bone interface micromotion was measured with a digital image correlation system which had a resolution of less than 1 micron. The micromotion measurement was transformed to 2 components: 1 was parallel and the other perpendicular to the humeral resection surface. Peak-valley micromotion from the last 10 cycles were averaged and utilised for data analyses. A one-way ANOVA and post-hoc Tukey tests were performed to compare the micromotion of different designs (α=0.05). Results. Micromotion of Global Advantage parallel to the resection (X-Axis) was significantly less than that of central screw prototype and peripheral leg prototype. Micromotion of peripheral leg prototype perpendicular to the resection (Y-Axis) was significantly less than Global Advantage and central screw prototype. There was no significant difference between different designs in resultant micromotion. Discussion/Conclusion. Clinical studies have shown that current stemless shoulder prosthesis yielded encouraging results in mid-term follow-ups. Particularly, the stemless Arthrex Eclipse humeral component, a central screw design, has been reported to have a secure bony fixation and ingrowth at an average of 23 months postoperatively. 4. The current study demonstrated that the stemless peripheral leg prototype and central screw prototype achieved similar initial fixation as stemmed Global Advantage in terms of resultant micromotion, and provided biomechanical evidence that stemless humeral components could have comparable initial stability to stemmed counterparts

The purpose of this study is to report the clinical and radiological outcomes of patients undergoing primary or revision reverse total shoulder arthroplasty using custom 3D printed components to manage severe glenoid bone loss with a minimum of 2-year follow-up. After ethical approval (reference: 17/YH/0318), patients were identified and invited to participate in this observational study. Inclusion criteria included: 1) severe glenoid bone loss necessitating the need for custom implants; 2) patients with definitive glenoid and humeral components implanted more than 2 years prior; 3) ability to comply with patient reported outcome questionnaires. After seeking consent, included patients underwent clinical assessment utilising the Oxford Shoulder Score (OSS), Constant-Murley score, American Shoulder and Elbow Society Score (ASES), and quick Disabilities of the Arm, Shoulder, and Hand Score (quickDASH). Radiographic assessment included AP and axial projections. Patients were invited to attend a CT scan to confirm osseointegration. Statistical analysis utilised included descriptive statistics (mean and standard deviation) and paired t test for parametric data. 3 patients had revision surgery prior to the 2-year follow-up. Of these, 2/3 retained their custom glenoid components. 4 patients declined to participate. 5 patients were deceased at the time of commencement of the study. 21 patients were included in this analysis. The mean follow-up was 36.1 months from surgery (range 22–60.2 months). OSS improved from a mean 16 (SD 9.1) to 36 (SD 11.5) (p < 0.001). Constant-Murley score improved from mean 9 (SD 9.2) to 50 (SD 16.4) (p < 0.001). QuickDASH improved from mean 67 (SD 24) to 26 (SD 27.2) (p = 0.004). ASES improved from mean 28 (SD 24.8) to 70 (SD 23.9) (p = 0.007). Radiographic evaluation demonstrated good osseointegration in all 21 included patients. The utility of custom 3D-printed components for managing severe glenoid bone loss in primary and revision reverse total shoulder arthroplasty yields significant clinical improvements in this complex patient cohort

Humeral resurfacing arthroplasty has been advocated as an alternative to stemmed humeral component designs given its ability to preserve proximal bone stock. Further, these implants have become more attractive given the possibility of stem-related complications including humeral fracture, stress shielding, and osteolysis; complications that may necessitate fixation, revision to long stem components, or reverse total shoulder arthroplasty. As more total shoulder arthroplasties are performed in younger patient populations, the likelihood of increased revision procedures is inevitable. Maintaining proximal bone stock in these cases with use of a resurfacing arthroplasty not only facilitates explant during revision arthroplasty, but preservation of proximal metaphyseal bone facilitates reimplantation of components. Clinical results of these resurfacing components have demonstrated favorable results similar to stemmed designs. Unfortunately, resurfacing arthroplasty may not be as ideal as was hoped with regard to recreating native humeral anatomy. Further, resurfacing arthroplasty may increase the risk of peri-prosthetic humeral fracture, and lack of a formal humeral head cut makes glenoid exposure more difficult, which may be associated with a higher degree of neurovascular injury. Stemless humeral components are designed for strong metaphyseal fixation and avoid the difficulty with glenoid exposure seen in resurfacing designs, as these components require a formal humeral head cut. Early clinical outcomes of a single stemless design demonstrated significant improvements in clinical outcome scores, without evidence of component migration, subsidence or loosening. The only mid-term clinical results of stemless design implants are seen with the Arthrex Eclipse system (Arthrex, Naples, FL). In a prospective study involving 78 patients at 5-year follow-up, significant improvements were observed in clinical outcome scores. While there was evidence of proximal stress shielding in an older population, this did not influence shoulder function. The overall revision rate was 9% at 5 years, with no component necessitating revision as a result of humeral component loosening. Resurfacing arthroplasty and stemless humeral components in total shoulder arthroplasty remain attractive options to preserve proximal metaphyseal bone stock, avoiding stem-related complications. Early and mid-term clinical outcomes are comparable to stemmed designs and demonstrate no evidence of humeral component loosening

Introduction. Good outcomes in reverse shoulder arthroplasty (RSA) rely in part on stability of the humeral component. Traditionally humeral components have been cemented, however there has been recent interest in press-fit fixation of humeral components in RSA. Lateralization of the head center in RSA can impart larger moments on the humeral component than for anatomic reconstructions, increasing the importance of distal humeral canal preparation for implant stability. To date, the primary stability of any type of press-fit humeral prosthesis has been largely unexplored. The goal of this study is to evaluate the effect of over-reaming the distal humeral canal in a press-fit humeral component in RSA. Methods. Computed tomography (CT) data of the shoulder were obtained from 55 shoulders. Images were segmented to produce digital models of the humerus. Humeral components for RSA (2mm diameter size increments) were sized and placed per the surgical technique, including preparation of the humerus with the appropriate reamers (1mm increments). Finite element models for each specimen were created with heterogeneous bone properties derived from the CT scan. Pressfit between the bone and stem was resolved to quantify the initial contact pressure on the stem; each stem was then loaded at 566N oriented 20° lateral and 45° anterior. Overall motion of the stem was measured, as well as interfacial micromotion in the porous coating region (Fig. 1). The effect of line-to-line (L2L) reaming and over-reaming by 1 mm was evaluated using an unpaired Student's t-test, with significance defined at p<0.05. Results. Across all specimens, stem sizes 8 (n=3), 10 (n=25), 12 (n=20), 14 (n=2), and 16 (n=1) were used. Stem motion ranged from approximately 250–750μm; micromotion remained under 300μm (Fig. 2). Stem motion was significantly less for L2L reaming as compared to over-reaming for both size 10 (p=.008) and size 12 (p=.002) stems; micromotion was significantly less for size 12 (p=.002) stems. L2L reaming to a larger diameter stem resulted in significantly reduced stem motion (average 390μm versus 530μm, p<.001) and micromotion (average 53μm versus 135μm, p=.001) than over-reaming and using a smaller diameter stem. Stem rotation following L2L reaming was generally below 0.5°, and exceeded 0.75° when over-reaming. Discussion and Conclusion. Reaming of the humeral canal directly impacts the stability of humeral stems in RSA. Even with satisfactory proximal press-fit, over-reaming enables increased rotation of the stem under functional loading prior to cortical engagement, and results in increased micromotion. In cases in which the reamer and stem offerings result in over-reaming, L2L reaming to the next larger stem significantly reduces stem motion and micromotion. However, reaming up also removes distal cortical bone, and thus the strength of the prepared humerus must be considered. In conclusion, line-to-line reaming significantly reduces the micromotion of humeral stems as compared to over-reaming

Shoulder arthroplasty is effective at restoring function and relieving pain in patients suffering from glenohumeral arthritis; however, cortex thinning has been significantly associated with larger press-fit stems (fill ratio = 0.57 vs 0.48; P = 0.013)1. Additionally, excessively stiff implant-bone constructs are considered undesirable, as high initial stiffness of rigid fracture fixation implants has been related to premature loosening and an ultimate failure of the implant-bone interface2. Consequently, one objective which has driven the evolution of humeral stem design has been the reduction of stress-shielding induced bone resorption; this in-part has led to the introduction of short stems, which rely on metaphyseal fixation. However, the selection of short stem diametral (i.e., thickness) sizing remains subjective, and its impact on the resulting stem-bone construct stiffness has yet to be quantified. Eight paired cadaveric humeri (age = 75±15 years) were reconstructed with surgeon selected ‘standard’ sized and 2mm ‘oversized’ short-stemmed implants. Standard stem sizing was based on a haptic assessment of stem and broach stability per typical surgical practice. Anteroposterior radiographs were taken, and the metaphyseal and diaphyseal fill ratios were quantified. Each humerus was then potted in polymethyl methacrylate bone cement and subjected to 2000 cycles of compressive loading representing 90º forward flexion to simulate postoperative seating. Following this, a custom 3D printed metal implant adapter was affixed to the stem, which allowed for compressive loading in-line with the stem axis (Fig.1). Each stem was then forced to subside by 5mm at a rate of 1mm/min, from which the compressive stiffness of the stem-bone construct was assessed. The bone-implant construct stiffness was quantified as the slope of the linear portion of the resulting force-displacement curves. The metaphyseal and diaphyseal fill ratios were 0.50±0.10 and 0.45±0.07 for the standard sized stems and 0.50±0.06 and 0.52±0.06 for the oversized stems, respectively. Neither was found to correlate significantly with the stem-bone construct stiffness measure (metaphysis: P = 0.259, diaphysis: P = 0.529); however, the diaphyseal fill ratio was significantly different between standard and oversized stems (P < 0.001, Power = 1.0). Increasing the stem size by 2mm had a significant impact on the stiffness of the stem-bone construct (P = 0.003, Power = 0.971; Fig.2). Stem oversizing yielded a construct stiffness of −741±243N/mm; more than double that of the standard stems, which was −334±120N/mm. The fill ratios reported in the present investigation match well with those of a finite element assessment of oversizing short humeral stems3. This work complements that investigation's conclusion, that small reductions in diaphyseal fill ratio may reduce the likelihood of stress shielding, by also demonstrating that oversizing stems by 2mm dramatically increases the stiffness of the resulting implant-bone construct, as stiffer implants have been associated with decreased bone stimulus4 and premature loosening2. The present findings suggest that even a small, 2mm, variation in the thickness of short stem humeral components can have a marked influence on the resulting stiffness of the implant-bone construct. This highlights the need for more objective intraoperative methods for selecting stem size to provide guidelines for appropriate diametral sizing. For any figures or tables, please contact the authors directly