Onlay versus inlay reverse total shoulder arthroplasty: a retrospective comparison of radiographic and clinical outcomes

IntroductionRecent innovations in reverse shoulder arthroplasty (RSA) have presented 2 distinct humeral stem designs: an onlay system that rests above the anatomic neck and an inlay component that rests within the metaphysis. The purpose of this study is to compare clinical and radiographic outcomes between inlay and onlay-designed humeral stems in lateral center of rotation RSA implant systems.MethodsA retrospective cohort study was performed on primary RSA patients treated by 2 surgeons at 2 separate hospitals with a minimum 2-year follow-up. Patients were categorized based on treatment with an onlay or inlay humeral design and matched 1:1 by indication and age. Patient-reported outcome measures (PROMs), including the Simple Shoulder Test, American Shoulder and Elbow Surgeons, and Visual Analog Score for pain, as well as active motion (forward elevation, internal rotation) were recorded at pre- and postoperative intervals. An Inlay-Onlay index assessed the degree of inset or offset of each particular implant referencing the anatomic neck. Radiographic analysis focused on scapular notching, bone resorption around the humeral stem, and acromion stress fractures.ResultsA total of 92 patients participated in the 1:1 matched analysis (46 each group). Cohorts were similar in age, gender, indication, follow-up length, and preoperative PROMs, with the exception of Simple Shoulder Test. At the most recent follow-up, there were no differences in all PROMs between groups. There were no differences in active internal rotation, but patients with an onlay-configuration demonstrated greater external rotation (P< .001) and forward flexion (P< .001). Greater tuberosity and calcar resorption occurred in 34 (74%) and 18 (39%) patients with an onlay-designed prosthesis, compared to 13 (28%) and 1 (2%) in the inlay group, respectively (P< .0001). Both groups had low rates of scapular notching (P= 1.0), while acromial fractures occurred in 6 patients with an onlay stem and in 4 patients with the inlay stem (P= .73).ConclusionThere were no differences in clinical outcomes or incidence of acromial fractures following RSA with an onlay- or inlay-style humeral stem prosthesis. Bone resorption of the proximal humerus occurred more frequently in patients with an onlay prosthesis, suggesting that an inlay prosthesis may afford better prevention of humeral stress shielding.Level Of EvidenceLevel III; Retrospective Comparative Study     

Effect of the neck-shaft angle on stability in the onlay type of reverse shoulder arthroplasty: a cadaveric study

BackgroundAlthough reverse shoulder arthroplasty (RSA) has been indicated for treating patients suffering from cuff tear arthropathy, instability is a severe complication. The relationship between the humeral neck-shaft angle and joint stability in RSA as well as the clinical effect of subscapularis tendon repair on postoperative stability after RSA remain controversial. This study is primarily aimed to investigate the relationship between humeral neck-shaft angle and stability using the onlay type of RSA with preserved shoulder girdle muscles using fresh frozen cadavers. Moreover, we aimed to investigate the effect of subscapularis tendon repair after RSA placement.MethodsAn onlay type RSA of not-lateralized glenosphere in a massive rotator cuff tear model with preserved shoulder component muscles was placed on 7 fresh frozen cadavers, and traction tests were performed to dislocate by changing the neck-shaft angle of the stem to 135°, 145°, and 155°. The anterior dislocation force (DF) was evaluated in 6 patterns as follows: 2 patterns at 30° and 60° of abduction and 3 patterns at 30° of internal rotation, in neutral rotation, and 30° of external rotation. DF was recorded at neck-shaft angles of 135°, 145°, and 155° and with and without subscapularis tendon repair.ResultsAt 30° abduction, DF was significantly higher at a neck-shaft angle of 155° regardless of the rotational position (P < .05), and at abduction 60°, there was no difference in DF according to any rotational position and any neck-shaft angle. Regardless of the neck-shaft angle, the DF was significantly higher at 60° abduction than at 30° abduction (P < .05). Furthermore, the DF was significantly higher with subscapularis tendon repair (P < .01).ConclusionOur results showed some relationship between humeral neck-shaft angle and stability in the onlay type of RSA with preserved shoulder component muscles using fresh frozen cadavers. Moreover, a neck-shaft angle of 155° showed the highest anterior DF among neck-shaft angles of 135° and 145° at 30° abduction, and there was no difference at abduction 60° among any neck-shaft angle. Furthermore, subscapularis tendon repair also contributed to anterior stability.     

Clinical results of humeral stem lateralization in reverse shoulder arthroplasty: Comparative study of 145° onlay curved stem vs 155° inlay straight stem

BackgroundThe main limits of Grammont's reverse shoulder arthroplasty (RSA) design are loss of external rotation and scapular notching. These limits can be addressed with glenoid and/or humeral lateralization. Currently, there is no uniformity in the literature regarding the best option to improves these outcomes. Lateralization of the humeral side should be an option. The aim of the present study was to compare outcomes of a 145 degree onlay curved stem vs a 155 degree inlay straight stem.MethodsA retrospective analysis of 96 consecutive patients undergoing RSA (98 shoulders) was performed. Of these, 47 patients (48 shoulders) underwent RSA with a Aequalis Reversed II Stem (Group A) and 49 (50 shoulders) with a lateralized humeral stem (Ascend Flex©) (Group B). The exclusion criteria included any relevant glenoid bone loss in the horizontal plane or vertical plane and patients with post-traumatic conditions including humeral head necrosis. Patient with teres minor fatty infiltration superior to grade 2 according to Goutallier's classification were also excluded. Constant score, muscular strength and range of motion (ROM), were evaluated preoperatively and for 2 years postoperatively. Radiographs were examined for scapular notching.ResultsComparing clinical outcomes, there were significant improvements with active ROM using lateralized shoulder stem (Group B) in flexion, abduction and external rotation (P > .05). However, while evaluating the Constant score and muscular strength, no important difference emerged between the two groups. Scapular notching was observed in 29.17% of cases (24 shoulders) of Group A and in 12% of cases (6 shoulders) of Group B. Moreover, the average degree of notching was reduced in Group B in which the grade 1 was observed in 4 shoulders out of 50. Grade 2 was observed in 7 shoulders in Group A and in 2 shoulders in Group B. Grade 3 and grade 4 were observed only in 1 patient in Group A, and no one in Group B.ConclusionsThe lateralized humeral stem (145°, onlay, curved stem) in RSA improves ROM, particularly external rotation and abduction compared to Aequalis Reversed II Stem. No significant difference was found between the two groups regarding muscular strength. Both designs provide an overall improvement on function and pain relief. Moreover, the incidence of scapular notching is lower in a lateralized humeral stem implant (12% of cases) compared to traditional reverse prostheses with an Aequalis Reversed II Stem (29.17% of cases).Level of EvidenceIII     

Radiographic outcomes of patients undergoing reverse shoulder arthroplasty using inlay versus onlay components: is there really a difference?

IntroductionAchieving soft tissue tension in RSA occurs by displacement of the humerus from the glenoid. We compared the lateral and inferior humeral displacement of two RSA systems radiographically. Each system utilized a humeral implant with a 135-degree neck-shaft angle and offered lateralized glenospheres. One had an onlay component and the other an inlay. Our primary hypothesis was that an alteration of surgical technique would negate the differences in their geometries radiographically. Secondarily, we sought to determine if a difference in complications or revisions occurred with these different designs.MethodsTwo hundred and eleven patients underwent RSA by a single surgeon with either an inlay or onlay prosthesis over a 2-year period. A true AP Grashey radiograph was utilized to measure: 1) Glenohumeral offset (GHO); 2) Acromiohumeral distance (AHD); 3) Pivot point (PP); 4) Humeral head cut surrogate (HHC) and 5) Humeral Socket Depth (HSD). Complications recorded included postoperative acromial fractures, revision for any reason, instability, and infections.ResultsThere was no significant difference in GHO or AHD between the two groups. There was a difference in PP and HHC between the groups (P < .001). The onlay group had an HHC 1.8 mm larger than inlay. Of the inlay group patients, 66% had their humeral tray placed above the level of the humeral osteotomy.DiscussionA larger HHC in the onlay group and implanting the inlay above the humeral osteotomy negates differences in AHD and GHO.Level of evidenceLevel III; Retrospective Comparative Study     

Effect of reverse total shoulder arthroplasty humeral inclination on glenohumeral range of motion,deltoid force,and glenoid strain: a biomechanical study

BackgroundReverse total shoulder arthroplasty (RSA) primarily varies between 2 implant design options: a 135 humeral stem inclination that closely resembles anatomic orientation, versus the Grammont-style 155 humeral stem inclination that further medializes and distalizes the center of rotation (COR). The purpose of this study was to compare deltoid force, glenoid strain, and simulated glenohumeral range of motion (ROM) between RSA 135 and RSA 155 designs, with a series of standardized permutations of glenosphere offset and rotator cuff pathology.MethodsTwelve fresh-frozen cadaveric shoulder specimens were studied using a shoulder simulator. Native shoulder motion profiles for reproducible abduction range of motion were established using a customized testing device. Optical 3-dimensional tracking and pressure sensors were used to accurately record glenohumeral range of motion (ROM), deltoid force, and glenoid strain for RSA 135 and RSA 155 designs. For each cohort, all combinations of glenosphere offsets and rotator cuff tendon involvement were evaluated.ResultsThere was no significant difference in the overall abduction ROM between the 155 and the 135 humeral stem implants (P = .75). Resting abduction angle and maximum abduction angle were significantly greater with a 155 + STD (standard offset) construct than with a 135 + STD construct (P < .001 and P = .01, respectively). Both stem inclinations decreased combined deltoid force requirements as compared the native shoulder with a massive cuff tear. Effective glenoid strain did not vary significantly between 135 + STD and 155 + STD constructs (P = .66).ConclusionOverall, range of motion between the 135 and the 155 humeral stem inclinations was not significantly different. The cumulative deltoid force was lower in RSA shoulders when compared to native shoulders with massive rotator cuff tears, highlighting the utility of both implant designs. The Grammont-style 155 stem coupled with a 2.5 mm inferior offset glenosphere required less deltoid force to reach maximum abduction than did the more anatomic, lateralized 135 stem coupled with a 4 mm lateral offset glenosphere.Level of EvidenceBasic Science, Biomechanics Controlled Laboratory Study     

肱骨近端骨折肩关节置换术假体高度确定的解剖学研究

目的 探讨肱骨近端骨折肩关节置换术中确定假体植入高度的方法.方法 选择成人尸体标本11具,男7具,女4具,共22个肩关节.测量胸大肌肱骨止点上缘至肱骨头关节面顶点的距离(PMT)、大结节高度(HT)及肱骨长度(HL),计算PMT/HL. 结果 所有标本PMT平均为(5.10±0.54)cm,HT平均为(0.78±0.19)cm,HL平均为(28.9±1.9)cm,PMT/HL的平均值为17.6%.所有标本HL的测量结果均乘以17.6%,分别与其PMT的测量结果比较偏差不超过0.5 cm.PMT、HT、HL左侧和右侧的测量结果差异均无统计学意义(P＞0.05).PMT和HL的测量结果呈正相关,HT和HL的测量结果无明显相关性. 结论 胸大肌腱止点上缘可作为肱骨近端骨折肩关节置换术中确定假体植入高度的可靠参照.术中可以根据国人PMT的平均值5.10 cm或个体化的数值,即将测量的术前健侧HL乘以固定的系数17.6%来推测患侧PMT,从而决定假体顶点至胸大肌腱肱骨止点上缘的距离.     

Insertion anatomy of the pectoralis major tendon

BackgroundPectoralis major tendon tears are encountered in young active patients.MethodsIn 10 fresh cadaveric shoulders we measured-1. Proximal to distal insertion width of the pectoralis major tendon.2. The distance of the superior border of the tendon from the supero-medial tip of the greater tuberosity (GT).ResultsThe average insertion width was 46 mm. The average distance between the superior border of the tendon and the tip of the GT was 48.5 mm.ConclusionThe superior border of the tendon should be repaired with two anchors at a distance of 48.5 mm from the tip of the GT so as to cover a width of 46 mm.     

Pectoralis major tendon reference (PMT): a new method for accurate restoration of humeral length with hemiarthroplasty for fracture

For hemiarthroplasty reconstruction of a proximal humeral fracture, accurate restoration of humeral head position is challenging, and incorrect prosthetic placement is associated with a poor outcome of surgical treatment. The purpose of this study was to validate the pectoralis major tendon as a reproducible landmark for accurate restoration of humeral length with hemiarthroplasty reconstruction. We dissected 20 cadavers (40 shoulders), and the distance between the upper border of the pectoralis major tendon insertion on the humerus and the top of the humeral head was measured (PMT). The PMT averaged 5.6 +/- 0.5 cm (with a confidence level of 95%). In only 4 of 40 shoulders did this distance exceed 6.0 cm, and there was no correlation between the size of the patient and this measurement. The PMT is a useful landmark that will aid in accurate restoration of humeral length when reconstructing complex proximal humeral fractures where landmarks are otherwise lost because of fracture comminution.     

The effect of stem length on reverse total shoulder humeral fixation

BackgroundThe purpose of this study was to evaluate the relative contribution of the reverse shoulder arthroplasty (RSA) humeral stem length on initial implant fixation, which may contribute to the long-term success of uncemented shoulder implants.MethodsThree RSA humeral components were randomly divided into the following testing groups: (1) 100% Stem length (n = 7); (2) 50% Stem length (n = 7); (3) 0% Stem length (n = 7). Each humeral stem was press-fit into twenty-one 4th Generation Osteoporotic Sawbones humeri. Torque and compressive axial load were applied to the humerus for 10,000 cycles at ±2.5 Nm and −392 N, respectively. Rotational micromotion of the implant was measured.ResultsMicromotion for all 3 testing groups was below the 150 µm micromotion threshold throughout testing. The overall micromotion in Group 2 was significantly larger than Group 1 (P < .001) and Group 3 (P < .001). Overall micromotion between Group 1 and Group 3 were not significantly different (P = .686).ConclusionAll stem lengths studied maintained micromotion below the 150 µm threshold, suggesting that any of these treatment groups would provide adequate initial fixation to allow bony on-growth. Clinically, stemless or short-stemmed prosthesis design offer theoretical benefits such as the degree of freedom for humeral stem placement independent of diaphysis. This study concluded that the zero-length stem will allow for this and provide adequate fixation comparable to the full-length stem.Level of EvidenceBasic Science Study.     

Optimizing humeral stem fixation in revision shoulder arthroplasty with the cement-within-cement technique: A biomechanical evaluation

BackgroundA previous clinical study suggested that a smaller stem with more cement may reduce humeral loosening. Our hypothesis is that utilizing a smaller stem diameter with more cement compared to a larger diameter stem will result in greater rotational stability.Materials and methodsTwo RSA humeral components of varying stem sizes were divided into the following testing groups: (I) 6 mm stem diameter with (2.5 cm bone loss [n=5], and 5 cm bone loss [n=5]) and (II) 10 mm stem diameter (2.5 cm bone loss [n=5], and 5 cm bone loss [n=5]). A 12 mm diameter humeral stem was instrumented using standard cementation technique into twenty, Sawbones humerii with either 2.5 cm or 5 cm of bone loss. The 12 mm stem was extracted and either a 6 mm or 10 mm stem was cemented -within-the existing cement mantle. Torque was applied for 1,000 cycles in increments of 2.5 N-m to 17.5 N-m on both revision stems.ResultsThere was a decrease in rotational stability in the 6 mm diameter stems when compared with the 10 mm diameter stems (p < 0.001) in the 2.5 cm and 5 cm bone loss models The larger stem was stable in both bone loss models whereas the smaller stem was unstable irrespective of bone loss.ConclusionsWe disproved our hypothesis in this biomechanics model. Larger stems have greater resistance to torsional stress and are more stable even in cases of greater proximal bone loss whereas smaller stems were found to be unstable even with 2.5 cm of proximal bone loss.Level of evidenceBasic Science Study.     

The pectoralis major tendon as a reference for restoring humeral length and retroversion with hemiarthroplasty for fracture

The success of anatomic reattachment of the tuberosities in proximal humeral fractures, treated with hemiarthroplasty, correlates with functional results. The purpose of this study was to determine the value of the upper edge of the pectoralis major insertion (PMI) as a landmark to establish the proper height and version of hemiarthroplasty implanted for proximal humeral fractures. Twenty cadaveric humeri were studied by CT scan to analyze the relationship between the PMI and humeral height and retroversion. The mean distance from the PMI to the tangent to the humeral head was 5.64 cm. The mean distance of the PMI to the posterior fin of the prosthesis was 1.06 cm. The mean angle between the PMI and the posterior fin of the prosthesis was 24.65 degrees. The upper edge of the pectoralis major insertion constitutes a reproducible reference point to restore proper humeral height and retroversion in hemiarthroplasty for proximal humeral fracture.     

Biomechanical analysis of the subscapularis,infraspinatus and teres minor length and moment arm after reverse shoulder arthroplasty: a cadaveric study

BackgroundReverse shoulder arthroplasty (RSA) affects the length and moment arm of the deltoid and rotator cuff. Currently, RSA is commonly considered for cuff-intact conditions, such as primary glenohumeral osteoarthritis. As such, understanding the effect of contemporary lateralized designs on the rotator cuff is paramount. The purpose of this study was to determine changes in length and moment arm of the subscapularis, infraspinatus and teres minor with implantation of one of 3 RSA designs.MethodsA previously validated model was used in 6 hemi-toraces with the shoulder attached. Suture lines were run through pneumatic cylinders from the insertion to the origin of 10 muscles to apply a constant, stabilizing load. Electromagnetic tracking sensors were fixed to the thorax, scapula, and humerus to record 3-dimensional kinematics. Coordinate systems were established according to ISB recommendations. The origin and insertion of the subscapularis, infraspinatus and teres minor were digitized and tracked. Testing consisted of manually rotating the humerus through 5 cycles of its internal-external rotation arc. Kinematic data was collected at 120 Hz. Testing was performed in 3 positions of abduction: 0°, 30°, and 60°. After testing the intact shoulder, RSA was performed using 3 different configurations: an onlay 135-degree humeral component matched with a 2-mm lateralized glenosphere, the same humeral component with a 6-mm lateralized glenosphere, and an inlay 135-degree humeral component matched with a 10 mm lateralized glenosphere. Minimal muscle operative lengths, maximal muscle operative lengths, and muscle moment arms were computed.ResultsWhen compared with the native shoulder, all 3 configurations of RSA resulted in statistically significant increases in both the minimal and maximal operative lengths of the subscapularis in all abduction positions. The teres minor only showed a statistically significant increase in minimal and maximal length at 60° of abduction. The infraspinatus showed a statistically significant increase in tendon excursion at 0° and 30° of abduction. In 40° of abduction and 40° of internal rotation, all RSA configurations translated in a decreased subscapularis internal rotation moment arm. On the contrary, RSA increased the external rotation moment arm of the infraspinatus in neutral rotation and 0° of abduction.ConclusionImplantation of contemporary lateralized RSA implants led to increased length of the subscapularis to a greater extent than the increased length experienced by the infraspinatus and teres minor. The moment arm of the subscapularis decreased, whereas the moment arm of the teres minor in neutral rotation with the arm in abduction increased.Level of EvidenceLevel III; Basic Science, Biomechanics Study     

Axillary nerve proximity to the humeral guide pin during stemless total shoulder arthroplasty

BackgroundThe proximity of the axillary nerve to the humeral head guide pin has not been described in current literature. Therefore, we aimed to elucidate the anatomical relationship through a cadaveric study.MethodsTen fresh-frozen cadaveric specimen were included in this study. The standard deltopectoral approach was utilized for appropriate exposure. The subscapularis and the long head of the biceps tendon were tenotomized to access the glenohumeral joint. Humeral head cut was then visually performed with humeral sizing and positioning. A Steinmann Pin was placed and advanced into the lateral cortex. Following dissection and visualization, the distance from the axillary nerve to the point of lateral humeral cortex was measured.ResultsOn average, the axillary nerve was found 7.2 ± 3.1 mm from the tip of the Steinmann Pin at the level of the lateral humeral cortex and distal to the site of cortical penetration.DiscussionSurgeons should be aware of the relationship between the axillary nerve and the humeral guide pin, and care should be taken to protect the axillary nerve during piercing of the lateral humeral cortex during pin placement. This relationship continues to be of importance, even with evolving stemless implant systems in total shoulder arthroplasty.     

以胸大肌肱骨止点确定肱骨假体高度的临床体会

目的探讨胸大肌肌腱肱骨止点(pectoralismajor tendon,PMT)上缘作为半肩置换术中假体高度定位参考的临床应用。方法2014年1月至2014年12月间行切开解剖复位钢板内固定的肱骨近端骨折病例12例,男4例,女8例;年龄56~72岁,平均(65.3±5.2)岁。测量PMT上缘到肱骨头最高点的平均距离为(5.21±0.42)cm。2015年1月至2018年12月的38例老年严重肱骨近端骨折行半肩置换的患者,参照PMT上缘到肱骨头最高点的距离5.2 cm确定肱骨假体高度,男7例,女31例;年龄60~82岁,平均(72.0±6.5)岁。术后3个月拍摄双侧肱骨全长X线片并测量长度,比较双侧差异是否有统计学意义。根据对侧肱骨长度(humeruslength,HL),采用HL×0.176计算PMT到肱骨头最高点距离,与(5.21±0.42)cm比较差异是否有统计学意义。结果所有患者均随访3个月,半肩置换侧肱骨全长与对侧肱骨全长分别为(32.41±2.47)cm、(31.93±2.82)cm,比较差异无统计学意义。根据对侧HL×0.176计算PMT到肱骨头最高点距离为(5.61±2.82)cm,与(5.21±0.42)cm比较差异无统计学意义。结论PMT可以作为肱骨假体高度的可靠参照,PMT上缘到肱骨头最高点距离为(5.21±0.42)cm,可以作为参考数值之一。     

Anatomical relationships of the transmuscular portal to its surrounding structures in arthroscopic treatment of superior labrum anterior posterior lesions: A cadaveric study and preliminary report

ObjectiveThis study aims to investigate the anatomical relationships of the transmuscular portal to its surrounding structures in arthroscopic treatment of superior labrum anterior posterior (SLAP) lesions in a human cadaveric model.MethodsIn this anatomic study, bilateral shoulder girdles of 12 adult formalin embalmed cadavers were used. All cadavers were male, and the mean age was 63.4±7.3 years. The portal entry point was determined as midway between the anterior and posterior borders of the acromion, approximately 1 cm lateral from the edge of the acromion. After a guidewire was placed in the glenoid cavity at the 12 o’clock position where the SLAP lesion typically occurs, a switching stick was inserted there. Each glenoid was then drilled with a 2.4 mm drill through an arthroscopic cannula. Subsequently, anatomical dissection was executed to assess the relationship of the transmuscular portal with the suprascapular nerve, axillary nerve, supraspinatus tendon, acromion, and biceps tendon. Lastly, the shortest distance between the aforementioned structures with the drill was measured by a sensitive caliper to determine whether there was a penetration of the structures. Differences between the right and left sides were analyzed.ResultsThe mean distance between the portal and the axillary nerve was 55.5 mm±6.0 mm, and the mean length of the suprascapular nerve was 61.2 mm±7.0 mm. The mean distance between the portal and the supraspinatus tendon was 2.8 mm±1.5 mm. No penetration of the axillary nerve, suprascapular nerve, and supraspinatus tendon was observed in any cadaver. No differences were detected for measured anatomical parameters between the right and left sides (p>0.05).ConclusionFindings from this cadaveric study revealed that the transmuscular portal may allow for a reliable anchor placement without any nerve or tendon penetration during arthroscopic SLAP repair.Level of EvidenceLevel V     

The influence of over-reaming on stem stability in reverse shoulder arthroplasty

BackgroundContemporary cementless reverse total shoulder arthroplasty (RSA) systems utilize a range of interference conditions based on the geometric relationships between the system instrumentation and the prosthesis design. The impact of prosthesis/bone interference, however, on the primary stability of the stemmed humeral component has not been characterized. The aim of this study was to evaluate the effect of over-reaming, standard reaming, and use of an upsized stem on stem stability in press fit reverse shoulder arthroplasty.MethodsThree-dimensional humeral models were generated from CT data of 59 non-arthritic shoulders. Each model was prepared following the intended surgical technique, including resection of the humeral head and reaming of the humeral canal, assuming 1 mm spacing in reamer diameters. The appropriate humeral stem (2 mm increments in distal stem diameter) was then placed to represent instances of over-reaming (increased distal clearance between stem and reamed bone), standard reaming, and use of an upsized stem. Finite element analysis was performed to predict the primary stability of the humeral stem subjected to expected loads in RSA.ResultsOver-reaming was associated with both increased stem subsidence as well as stem-bone micromotion, as compared to standard bone preparation (P < 001). No significant differences in stem translation or stem-bone micromotion were found between standard bone preparation and use of an upsized stem. Over-reaming was associated with approximately 50% increased rotation of the stem following functional loading, as compared to stems placed using standard preparation or upsized stems.ConclusionOver-reaming of the humeral canal in cementless reverse shoulder arthroplasty results in increased micromotion and decreased primary stability of the humeral stem when subjected to loading representative of daily activities. Use of an upsized stem can recover the primary stability expected for standard reaming.Level of EvidenceBiomechanical Study     

Revision to reverse total shoulder arthroplasty: do short stem and stemless implants reduce the operative burden compared to convertible stems?

BackgroundRevision of prior hemiarthroplasty (HA) or total shoulder arthroplasty (TSA) to reverse shoulder arthroplasty (RSA) is a technically challenging procedure with high complication rates. The purpose of this study was to compare intraoperative complications between convertible humeral stems and nonconvertible humeral stems stratified by stem length for conversion of TSA or HA to RSA.Materials and methodsA multicenter retrospective analysis of patients undergoing revision of a primary TSA or HA to RSA was conducted. Patients were divided into 2 groups based on convertible or nonconvertible humeral stem design from the index surgery. The primary outcome measures were the following intraoperative variables and complications: total operative time, blood loss, intraoperative fracture, overall complication rate, and blood transfusions. Rates were compared between groups and analyzed according to primary stem length for the nonconvertible group.ResultsA total of 279 patients were included in the study, 70 with convertible stems and 209 with nonconvertible stems. About 70% of convertible stems were successfully retained. Operative time was similar between the 2 groups overall. Patients with nonconvertible stems had higher intraoperative blood loss (P = .0001), higher overall complication rate (P = .009), and greater risk of intraoperative fracture (P = .002). Revising stemless and short stems to RSA had significantly reduced operative time compared to standard length stems (97 and 116 minutes vs. 141 minutes, P < .0001 and P = .035, respectively). When revising stemless implants, there was a significantly lower rate of intraoperative fracture (3.6%) compared to short stems (24%, P = .004) and standard stems (23.4%, P = .001). When revising stemless implants to RSA, there was shorter operative time (P= .0001) and similarly low rate of intraoperative fracture (P= .820) compared to convertible stems.ConclusionIn revision of anatomic TSA to RSA, convertible stems lead to lower blood loss and intraoperative fracture rate compared to nonconvertible stems when broadly including all stem types. However, differences appear to be based on stem type. Among nonconvertible stems, revision of short stem and stemless implants are associated with reduced operative time compared to standard length stems. Revision of stemless implants to RSA is associated with the shortest operative time of all implant types as well as a similar rate of intraoperative fracture compared to convertible stems.Level of EvidenceLevel III; Retrospective Cohort Comparative Study     

Does implant modularity affect radiographic outcome following anatomic shoulder arthroplasty?

BackgroundModularity in shoulder implants is a feature that is thought to allow for better anatomical recreation and subsequently improve clinical outcomes. This hypothesis was tested by retrospectively comparing the radiographic outcomes of 2 patient groups that received either modular (adaptable) or nonmodular shoulder implants during arthroplasty.Methods: Radiographic variables were measured to provide a comprehensive analysis of recreated shoulder anatomy.ResultsThe modular group demonstrated significant changes in humeral head height, greater tuberosity height, the radiographic distance from humeral head to acromion and center of rotation difference. In contrast, the nonmodular group demonstrated significant changes to humeral head height. A higher frequency of humeral radiolucent lines was noted in the non-modular group compared to the modular group.ConclusionsImplant modularity may produce measurable differences in radiographic anatomy and a lower measure of implant loosening in anatomic shoulder arthroplasty.Level of EvidenceLevel III; Retrospective Cohort Comparative Study     

Subpectoral Biceps Tenodesis of the Shoulder: Indications and Technique Options

Subpectoral biceps tenodesis of the shoulder may be a useful tool that can address a wide range of disorders in the setting of pathology of the long head of the biceps tendon. Primary indications include (1) zone 2 or zone 3 tendon pathology and (2) failed previous proximal tendon tenodesis. Secondary indications include (1) an overhead athlete or thrower, (2) chronic tendinopathy, and (3) surgeon preference. A subpectoral technique allows tendon fixation directly posterior (deep) to the pectoralis tendon high in the bicipital fossa or in the mid fossa or fixation low in the fossa inferior to the pectoralis tendon (infrapectoral). Fixation technique options include an onlay suture anchor, onlay unicortical button, inlay bicortical button, or inlay interference screw. Potential surgical complications include humeral fracture, loss of fixation, tendon pullout or rupture, and neurovascular injury. Regardless of the specific location or technique used, subpectoral tenodesis is a valuable tool for the treatment of proximal biceps tendon pathology.     

Reconstruction of humeral length and centering of the prosthetic head in hemiarthroplasty for proximal humeral fractures

Anatomic reconstruction of humeral length in hemiarthroplasty for complex proximal humeral fractures is difficult because reliable surgical landmarks are missing or are destroyed by the fracture. The pectoralis major tendon is a reliable landmark to determine prosthetic height intraoperatively. This study analyzed the clinical outcome, reconstruction of humeral length, centering of the prosthetic head in the glenoid, and tuberosity positioning and healing, using the pectoralis major tendon as a reference intraoperatively. The study included 30 patients. In 21 patients (group 1), humeral length reconstruction was performed using the pectoralis major tendon as a reference; in 9 (group 2), this reference was not used. Patients underwent a clinical and radiologic evaluation at a mean of 22.7 months. Group 1 showed significantly better results in clinical and radiologic values, especially in anatomic reconstruction of humeral length, than group 2. Clinical outcome depended significantly on greater tuberosity healing and centering of the prosthetic head in the glenoid.