Anatomic total shoulder arthroplasty for severe glenoid bone loss: Still a viable option

Anatomic total shoulder arthroplasty has been the gold standard for glenohumeral osteoarthritis without rotator cuff tear. There is a subset of patients with severe glenoid bone loss and glenoid retroversion that have predictably worse outcomes with component loosing and posterior instability, making reverse shoulder arthroplasty an attractive solution. Although reverse shoulder arthroplasty solves many issues with glenoid component loosing, it has concerns of higher complication rates and reduced functional outcomes. With a deeper understanding of biomechanics, there are several strategies including augmented glenoid components to make anatomic total shoulder arthroplasty a more viable option for severe glenoid bone loss.     

The effect of humeral component anteversion on shoulder stability with glenoid component retroversion

BACKGROUND: Posterior glenoid bone loss is often seen in association with glenohumeral osteoarthritis. This posterior asymmetric wear can lead to retroversion of the glenoid component and posterior instability after total shoulder arthroplasty. Options for the treatment of this asymmetric wear include eccentric reaming of the so-called high side, bone-grafting, and/or anteverting the humeral component. Although anteverting the humeral component has been advocated by many, it has not been substantiated on the basis of biomechanical data. The purpose of the present study was to determine whether anteverting the humeral component increases the stability of a total shoulder replacement with a retroverted glenoid component. METHODS: A total shoulder arthroplasty was performed in eight human cadaveric shoulders. The glenoid component was placed in 15 degrees of retroversion. Two humeral versions were tested for each specimen: anatomic version and 15 degrees of anteversion relative to anatomic version. The specimens were mounted supine in a custom fixture on a servohydraulic testing system. The humerus was translated posteriorly by one-half of the width of the glenoid. Three positions of humeral rotation were tested for each position of humeral version. Both the energy and the peak load were analyzed as measures of joint stability. RESULTS: There was no significant difference in either energy or peak load between the tests performed with the humeral component in 15 degrees of anteversion and those performed with the component in anatomic version in any of the three rotational positions (p > 0.05). CONCLUSIONS: Although anteverting the humeral component during total shoulder arthroplasty to compensate for glenoid retroversion has been advocated, these data suggest that compensatory anteversion of the humeral component does not increase the stability of a shoulder replacement with a retroverted glenoid component.     

Risks of loosening of a prosthetic glenoid implanted in retroversion

Osteoarthritis of the shoulder is frequently associated with posterior glenoid wear, which may be difficult to correct during shoulder arthroplasty. This study was designed to evaluate the risks that a prosthetic glenoid implanted in retroversion will loosen. The scapula, the humerus, the rotator cuff, and a total shoulder prosthesis were reconstructed with a 3-dimensional finite element model. The glenoid was placed in 5 different angles of retroversion (0 degrees , 5 degrees , 10 degrees , 15 degrees , and 20 degrees ). Location of the glenohumeral contact point, articular pressure, bone and cement stress, and micromotion around the glenoid implant were calculated during internal and external rotation. Glenoid retroversion induced a posterior displacement of the glenohumeral contact point during internal and external rotation, inducing a significant increase of stress within the cement mantel (+326%) and within the glenoid bone (+162%). Furthermore, a major increase of micromotion was measured at the bone-cement interface (+706%). According to this study, glenoid retroversion exceeding 10 degrees should be corrected during total shoulder arthroplasty. If the correction is impossible, not replacing the glenoid should be considered.     

Severe glenoid retroversion is best treated with asymmetric reaming in total shoulder arthroplasty–Opposes

Degenerative arthritis of the shoulder is a common orthopaedic condition, and the number of total shoulder arthroplasty procedures is increasing with the aging population. During total shoulder arthroplasty, reconstruction of the glenoid side of the joint can be particularly difficult in the face of posterior wear or excessive retroversion. Treatment options for posterior wear or excessive retroversion of the glenoid include asymmetric reaming of the high anterior side, bone grafting, or posterior augmentation of the glenoid component. A posterior augmented glenoid component allows the surgeon to maintain bone stock while correcting the posterior deficiency of the glenoid and avoiding the potential for medialization of the humeral component with anterior high side reaming. Bone grafting can be beneficial but relies on graft healing to successfully obtain stability.     

Biomechanical benefits of anterior offsetting of humeral head component in posteriorly unstable total shoulder arthroplasty: A cadaveric study

Restoration of joint stability during total shoulder arthroplasty can be challenging in the face of severe glenoid retroversion. A novel technique of humeral head component anterior‐offsetting has been proposed to address posterior instability. We evaluated the biomechanical benefits of this technique in cadaveric specimens. Total shoulder arthroplasty was performed in 14 cadaveric shoulders from 7 donors. Complementary shoulders were assigned to either 10° or 20° glenoid retroversion, with retroversion created by eccentric reaming. Two humeral head component offset positions were tested in each specimen: The anatomic (posterior) and anterior (reverse). With loads applied to the rotator cuff and deltoid, joint contact pressures and the force and energy required for posterior humeral head translation were measured. The force and energy required to displace the humeral head posteriorly increased significantly with the anterior offset position compared to the anatomic offset position. The joint contact pressures were significantly shifted anteriorly, and the joint contact area significantly increased with the anterior offset position. Anterior offsetting of the humeral head component increased the resistance to posterior humeral head translation, shifted joint contact pressures anteriorly, and increased joint contact area, thus, potentially increasing the joint stability in total shoulder arthroplasty with simulated glenoid retroversion. © 2015 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 34:666–674, 2016.     

Long-term results of total shoulder arthroplasty following bone-grafting of the glenoid.

BACKGROUND: The marked loss of glenoid bone volume or alteration of glenoid version can affect glenoid component fixation in patients undergoing total shoulder arthroplasty. The purpose of this study was to evaluate the long-term results associated with the use of bone-grafting for restoration of glenoid volume and version at the time of total shoulder arthroplasty. METHODS: Twenty-one shoulders received an internally fixed, corticocancellous bone graft for the restoration of peripheral glenoid bone stock at the time of total shoulder arthroplasty between 1980 and 1989. Grafting was indicated when glenoid bone stock was insufficient to maintain adequate version or fixation of the prosthesis. Seventeen shoulders were available for follow-up; the average duration of follow-up for the thirteen shoulders that did not have prosthetic failure within the first two years was seventy months. Total shoulder arthroplasty was performed because of osteoarthritis in five shoulders, chronic anterior fracture-dislocation in five, capsulorrhaphy arthropathy in three, inflammatory arthritis in two, recurrent dislocation in one, and failure of a previous arthroplasty in one. All patients had some form of anterior or posterior instability preoperatively. There were five anterior and twelve posterior glenoid defects. Bone from the resected humeral head was used for grafting in fifteen shoulders, and bicortical iliac-crest bone was used in two. RESULTS: The average glenoid version after grafting was 4 degrees of retroversion, with an average correction of 33 degrees. The graft failed to maintain the original correction in three shoulders due to nonunion, dissolution, or shift. Five total shoulder replacements failed, necessitating glenoid revision at two to ninety-one months postoperatively. The failures were associated with recurrent massive cuff tears (one shoulder), persistent instability (two shoulders), improper component placement (one shoulder), and loss of graft fixation (one shoulder). There were no humeral component failures. According to the criteria of Neer et al., the functional result was rated as excellent in three shoulders, satisfactory in six, and unsatisfactory in eight. CONCLUSIONS: Despite the finding that eight shoulders had an unsatisfactory functional result at the time of longterm follow-up, corticocancellous grafting of the glenoid successfully restored glenoid version and volume in fourteen of the seventeen shoulders in the present study. Patients with glenoid deficiency often have associated glenohumeral instability, which may affect the results of total shoulder arthroplasty. Bone-grafting of the glenoid is a technically demanding procedure that can restore bone stock in patients with structural defects.     

Glenoid bone loss in primary total shoulder arthroplasty: evaluation and management

Glenohumeral osteoarthritis is the most common reason for shoulder replacement. Total shoulder arthroplasty provides reliable pain relief and restoration of function, with implant survivorship reported at 85% at 15 years. Glenoid component wear and aseptic loosening are among the most common reasons for revision. Glenoid wear characteristics have been correlated with, among other things, the degree of anatomic glenoid version correction. Anatomic glenoid reconstruction is particularly challenging in the presence of glenoid bone deficiency. Walch classified glenoid morphology into five types: type A, centered, without posterior subluxation but with minor erosion (A1) or major erosion (A2); type B, posteriorly subluxated (B1) or posteriorly subluxated with posterior glenoid erosion (B2); and type C, excessive glenoid retroversion. The type A glenoid represents only 59% of patients; thus, the need to address glenoid deformity is common. Methods of correction include asymmetric reaming of the anterior glenoid, bone grafting of the posterior glenoid, and implanting a specialized glenoid component with posterior augmentation. In many cases of type C or hypoplastic glenoid, the humerus is concentrically reduced in the deficient glenoid and glenoid deformity may not need to be corrected. Severely hypoplastic glenoid may require the use of bone-sparing glenoid components or reverse total shoulder arthroplasty.     

Intraoperative CT navigation for glenoid component fixation in reverse shoulder arthroplasty

CT navigation has been shown to improve component positioning in total shoulder arthroplasty. The technique can be useful in achieving strong initial fixation of the metal backed glenoid in reverse shoulder arthroplasty. We report a 61 years male patient who underwent reverse shoulder arthroplasty for rotator cuff arthropathy. CT navigation was used intraoperatively to identify best possible glenoid bone and to maximize the depth of the fixation screws that anchor the metaglene portion of the metal backed glenoid component. Satisfactory positioning of screws and component was achieved without any perforation or iatrogenic fracture in the scapula. CT navigation can help in maximizing the purchase of the fixation screws that dictate the initial stability of the glenoid component in reverse shoulder arthroplasty. The technique can be extended to improve glenoid component position [version and tilt] with the availability of appropriate software.     

Safety and utility of computer-aided shoulder arthroplasty

This study evaluated the safety and utility of a novel, image-free, shoulder navigation system in a cadaver and in an initial cohort of shoulder arthroplasty patients. Shoulder arthroplasty was performed on a cadaver and 27 patients using an image-free navigation system (NaviProtrade mark; Kinamed Navigation Systems LLC, Camarillo, CA). Optical trackers were attached to the proximal humerus and the coracoid process. Prior to and following humeral head resection, the anatomic neck axis (retroversion, inclination) and humeral head diameter were measured with the navigation system. Native glenoid surface orientation was registered, and a navigation tracker was attached to the glenoid reamer. The navigation system recorded change in inclination and version relative to the native glenoid during reaming. The cadaver results demonstrated that the trackers did not impede surgical performance and that system accuracy was 2.6 degrees +/- 2.5 degrees . In the clinical series, the navigation system reported the anatomic humeral neck measurements (retroversion 30.0 degrees +/- 16.0 degrees ; inclination 137.0 degrees +/- 11.7 degrees ), the humeral head diameters (major axis 46.2 mm +/- 4.8 mm; minor axis 43.2 mm +/- 3.8 mm), the humeral neck resection angles (retroversion 29.9 degrees +/- 15.1 degrees and inclination 135.6 degrees +/- 9.1 degrees ), and glenoid reaming orientation relative to the native glenoid (+3.0 degrees +/- 6.3 degrees of version; -6.7 degrees +/- 4.4 degrees of inclination). This initial clinical experience with computer-aided shoulder navigation demonstrates that the procedure is safe and can provide valuable intraoperative measurements. With an anatomic humeral implant system, the navigation system provides real-time feedback on the humeral resection as it relates to anatomic neck geometry. The system also provides real-time angulation of the glenoid reamer relative to preoperative glenoid deformity.     

An optimised method for quantifying glenoid orientation

A robust quantification method is essential for inter-subject glenoid comparison and planning of total shoulder arthroplasty. This study compared various scapular and glenoid axes with each other in order to optimally define the most appropriate method of quantifying glenoid version and inclination.Six glenoid and eight scapular axes were defined and quantified from identifiable landmarks of twenty-one scapular image scans. Pathology independency and insensitivity of each axis to inter-subject morphological variation within its region was tested. Glenoid version and inclination were calculated using the best axes from the two regions.The best glenoid axis was the normal to a least-square plane fit on the glenoid rim, directed approximately medio-laterally. The best scapular axis was the normal to a plane formed by the spine root and lateral border ridge. Glenoid inclination was 15.7° ± 5.1° superiorly and version was 4.9° ± 6.1°, retroversion.The choice of axes in the present technique makes it insensitive to pathology and scapular morphological variabilities. Its application would effectively improve inter-subject glenoid version comparison, surgical planning and design of prostheses for shoulder arthroplasty.     

Comparison of two-dimensional manual and three-dimensional SurgiCase and BLUEPRINT planning software measurements of glenoid version,inclination, and humeral subluxation

IntroductionVirtual planning for shoulder arthroplasty using preoperative computed tomography (CT) has been gaining popularity, and it is imperative for surgeons to recognize any differences in measurements that may exist amongst software platforms. The purpose of this study is to compare measurements of glenoid version, inclination, and humeral head subluxation between a manual approach and two varying automated software platforms using either a best-fit sphere technique (Wright-Medical BLUEPRINT) or an anatomic landmarks technique (Materalise SurgiCase).MethodsA case control study of 289 CT images from patients preoperatively planned for a total shoulder arthroplasty or reverse shoulder arthroplasty using SurgiCase (v3.0.110.5) were also successfully analyzed by BLUEPRINT (v2.1.6). Glenoid version, inclination, and subluxation were measured manually in a blind fashion by two separate investigators using axial and coronal images oriented to the scapular plane; interobserver and intraobserver reliabilities were measured using intraclass correlation coefficients (ICCs). Concordance correlation coefficients (CCCs), mean differences, and clinically relevant agreement in measurements between the software platforms and with the manual technique were compared. The impact of greater glenoid retroversion on the differences in measurements between the software platforms was further studied by correlation analysis.ResultsThe mean differences between SurgiCase and BLUEPRINT were + 0.5° for glenoid inclination (P = .064; CCC = 0.84), -0.9° for glenoid version (P < .001; CCC = 0.92), and -1.4% for humeral subluxation (P = .002; CCC = 0.88). Agreement within 5 units was 78.9% for inclination, 89.3% for version, and 64.1% for subluxation. Glenoid retroversion had no relation with the degree of variation in measured inclination (P = .59) or version (P = .56). There were significant differences between manual and 3D software measurements for glenoid inclination, version, and subluxation (P < .001). Both software measurements were more inferiorly inclined (average difference, SurgiCase -3.2° and BLUEPRINT -3.9°), more retroverted (average difference, SurgiCase -4.0° and BLUEPRINT -3.2°), and more posteriorly subluxated (average difference, SurgiCase + 3.4% and BLUEPRINT + 4.8%).ConclusionThe SurgiCase and BLUEPRINT preoperative planning software yield clinically similar measurements for glenoid version, inclination, and subluxation. The degree of glenoid retroversion does not impact the variability of inclination or version between the landmark and best-fit sphere software techniques. Compared to the 2D manual technique, both 3D software programs reported greater inferior inclination, retroversion, and posterior subluxation.Level of evidenceLevel III; Retrospective Diagnostic Study     

Effects of increased retroversion angle on glenoid baseplate fixation in reverse total shoulder arthroplasty: a finite element analysis

BackgroundIncreased glenoid retroversion occurs in patients with severe arthritis but its effect on baseplate fixation of a reverse total shoulder arthroplasty (rTSA) is not clear. The purpose of this study is to determine the effects of increasing glenoid retroversion on baseplate fixation in rTSA using finite element analysis (FEA) modeling.MethodsFive sets of computerized tomographic images of healthy normal shoulders were selected and segmented with Amira (Thermo Fisher Scientific) to obtain the solid geometries. Scapula FEA models with 5°, 10°, 15°, 20°, and 25° retroversion angles were generated for each healthy scapula geometry and a rTSA glenoid baseplate was implanted on each model. Maximum stress at the anterior and posterior portions of the glenoid and the micromotion between the bone and baseplate were recorded. After simulation with normal scapular bone material properties (Young's modulus 4 GPa and Poisson's ratio 0.3), another set of simulations was run on each subject with a 25° retroversion angle and poor bone quality (Young's modulus 500 MPa and Poisson's ratio 0.3) to study a worst-case scenario. Micromotions in each model were also recorded. All statistical analysis was done with SPSS.ResultsSimulation results of models generated from the same subject but with different retroversion angles showed a clear pattern: as retroversion angle increased, the stresses increased posteriorly and decreased anteriorly. Also, micromotion between the bone and the baseplate increased with the increase of retroversion angle. With analysis of variance, we found that all three values change significantly as the retroversion angle increases (P< .001). The simulation results also showed that micromotion was large in shoulders with small glenoid size and poor bone quality. However, even in the model with the worst-case scenario (smallest glenoid size, poorest bone quality and 25° retroversion angle), the maximum micromotion and the maximum stresses are still within the safe range.DiscussionIn all cases with both normal and poor bone quality, the stresses and micromotion stayed below the threshold to allow for bone ingrowth of the glenoid baseplate to occur. Based on these results, for glenoid baseplates with a central peg/post and 4 screws for fixation, rTSA baseplate retroversion does not need to be corrected to less than 10° to provide good initial fixation as has been recommended for a cemented glenoid component and can withstand the initial stresses and micromotion up to 25° of retroversion.Level of evidenceBasic Science Study; Computer Modeling     

Retrieved glenoid components: a classification system for surface damage analysis.

There have been many reports describing modes of damage in retrieved total hip and total knee arthroplasty components. The most common mechanism in total hip arthroplasties has been shown to be surface wear. Fatigue failure shown as pitting and delamination are observed more often in total knee components. There has been no previous analysis of retrieved polyethylene glenoid components. This study evaluated the wear mechanisms contributing to failure of total shoulder glenoid components. Polyethylene glenoid components from 10 consecutive total shoulder arthroplasties have been retrieved and analyzed. Wear mechanisms were analyzed under low-power magnification, and a classification system was designed for total shoulder arthroplasties. This classification system is an adaptation of previous models of hip and knee surface damage. The severity of each damage mode was graded in 4 separate quadrants. The most prevalent damage modes were abrasion, pitting, and delamination. These data show a combination of abrasive wear and fatigue in retrieved total shoulder specimens. Surface wear and subsurface fatigue failure mechanisms both contribute to glenoid implant failure.     

Posterior shoulder instability following anatomic total shoulder arthroplasty: A case report and review of management

We report a case of posterior shoulder instability following anatomic total shoulder arthroplasty (TSA). In addition, we present guidelines to aid in the management of posterior instability after TSA. A 50-year-old male underwent anatomic TSA for glenohumeral osteoarthritis. Postoperatively, the patient developed posterior instability secondary to glenoid retroversion. He did not improve despite conservative treatment. He underwent an arthroscopic posterior bone block procedure, 4-month after his index arthroplasty. At 14-month follow-up, the patient had regained near full motion and strength, and radiographs demonstrated osseous integration with no evidence of component loosening. Posterior instability following TSA is a relatively rare complication and challenging to manage. The posterior, arthroscopic iliac crest bone block grafting procedure represents a treatment option for posterior instability in the setting of a stable glenoid prosthesis following TSA.     

Shoulder arthroplasty for osteoarthritis secondary to glenoid dysplasia

BACKGROUND: Between 1980 and 1997, six patients (seven shoulders) with glenoid dysplasia and osteoarthritis underwent shoulder arthroplasty at our institution because of moderate or severe shoulder pain. There were four hemiarthroplasties and three total shoulder arthroplasties. METHODS: All six patients (seven shoulders) were followed for a minimum of two years or until the time of revision surgery. The average duration of follow-up was 7.3 years (range, 1.3 to sixteen years). RESULTS: One shoulder treated with total shoulder arthroplasty underwent revision surgery because of infection and loosening of the glenoid component 5.8 years following the arthroplasty. Three shoulders treated with hemiarthroplasty underwent revision to total shoulder arthroplasty as a result of glenoid arthrosis at sixteen months, twenty months, and thirty-four months. In each of these shoulders, glenoid deficiency and cartilage loss were not addressed at the time of the original hemiarthroplasty. The one shoulder that did not undergo revision after hemiarthroplasty had a glenoid osteotomy performed at the time of the hemiarthroplasty. CONCLUSIONS: The data from this study suggest that glenoid deficiency and cartilage wear should be addressed in some way at the time of shoulder arthroplasty in patients with glenoid dysplasia.     

The effect of glenoid version on internal and external rotation in reverse total shoulder arthroplasty

BackgroundThere is currently limited understanding of the contribution of glenoid version to postoperative internal (IR) and external rotation (ER) after reverse total shoulder arthroplasty (RTSA). The purpose of this study was to determine the impact of glenoid version on postoperative rotation after RTSA.MethodsForty-five 3-dimensional (3D) computer models of human scapulae were created from de-identified computed tomography (CT) scans. The scapulae were divided into 3 separate groups based on glenoid version: normal (10° to -10°), moderate (-10 to -25°), and severe (< -25°). The scapulae then underwent virtual implantation with a Grammont-style RTSA prosthesis at either 0°, -20°, or -30° of retroversion based on the severity of the native glenoid version (normal, moderate, severe). Internal, external, and total rotation (TR) were determined for each construct at both 30° and 60° of humeral abduction.ResultsGlenoids with a narrow width (< 25 mm) were noted to have minimal bony impingement on rotational testing and were excluded. In the remaining scapulae (n = 34), the achievable TR and IR for the humeral component decreased as glenoid retroversion increased. Changes in rotation for all categories were in general more pronounced at 60° of humeral abduction. Overall, ER generally increased as glenoid retroversion increased, with the largest increase occurring when going from 0° to -20° of retroversion, and minimal increase from -20° to -30° of retroversion regardless of humeral abduction.ConclusionPlacement of the glenoid component in increasing retroversion during RTSA results in a loss of IR and a corresponding increase in ER.Level of EvidenceBasic Science Study     

Measurement of glenoid version: conventional radiographs versus computed tomography scans

Glenoid version seems to play an important role in the stability and loading of the glenohumeral joint. The purpose of this study was to compare measurements of glenoid version on axillary views and computed tomography (CT) scans. Radiographs and CT scans of 25 patients evaluated predominantly for glenohumeral joint instability and 25 patients after implantation of a total shoulder prosthesis were analyzed by 3 independent observers. In all patients glenoid version was determined on an axillary view and on a CT scan at the mid-glenoid level. The mean glenoid version measured on CT scans was 3 degrees of retroversion in the instability group (range, 7 degrees of anteversion to 16 degrees of retroversion) and 2 degrees of anteversion in the total shoulder prosthesis group (range, 16 degrees of anteversion to 23 degrees of retroversion). Glenoid retroversion was overestimated on plain radiographs in 86%. The mean difference between measurements of glenoid version on axillary views and CT cuts was 6.5 degrees (range, 0 degrees -21 degrees ), and the coefficient of correlation between these measurements was 0.33 in the instability group and 0.67 in the prosthesis group. In conclusion, glenoid version cannot be determined accurately on standard axillary radiographs, either preoperatively or postoperatively. Studies that assess the role of glenoid component orientation should use a reproducible method of assessment such as CT.     

The cemented humerus and non-cemented glenoid: The optimal hybrid solution for total shoulder arthroplasty

Hybrid fixation of total joint arthroplasty has been recognized as an accepted form of surgical approach in multiple joints. Principles of implant fixation should focus on durability and on providing secure long-term function. To date, there is no conclusive evidence that pressed-fit humeral stem fixation has an advantage over well-secured cemented humeral fixation. Although revision may require cement removal, a well-fixed bone—ingrowth implant may require slatting and osteotomy of the humerus. On the contrary, need for revision in arthroplasty due to inadequate implant fixation has almost universally revolved around the failure of cement fixation and loosening of the glenoid component. A case will be made based on 30 years of experience of a surgeon performing total shoulder arthroplasty using secure modern cement-fixation techniques of humeral components. More recently, over the past 10 years an extremely high rate of durable secure glenoid implant fixation has been achieved using press-fit tantalum porous anchorage of polyethylene glenoid components. This has resulted in no cases of loosening of glenoid fixation and only one case of glenoid component fracture with greater than 95% survivorship over a 10-year period. A combination of well-cemented humeral stem and trabecular metal anchorage of the glenoid has provided durable and long-lasting function in primary total shoulder arthroplasty.     

Baseplate placement in failed total shoulder replacement: Builder’s choice

Glenoid component loosening has been recognized as one of the common indications for revision surgery after total shoulder arthroplasty. Replacement with a standard glenoid component is sometimes possible when bone loss is minimal and contained within the glenoid vault. If glenoid bone stock is poor, more complex revision strategies include bone graft reconstruction, custom implants, and the use of augmented components. Reverse total shoulder arthroplasty has also developed into a platform for revision surgery. However, surgeons must be aware that when used for revision, complication rates are higher and survival times are shorter. Glenoid revision is technically demanding even for an experienced shoulder surgeon and may lead to early revision failures if done improperly. Shoulder surgeons must have a detailed understanding of expected outcomes, proper indications and current bone grafting techniques when attempting glenoid reconstruction.     

Optimizing glenoid component position using three-dimensional computed tomography reconstruction

Glenoid implant design and alignment are critical to the success of shoulder arthroplasty. Computer-aided design models of 3 glenoid implant designs (keel, standard pegs, and modified pegs) were virtually implanted into 3-dimensional computed tomography-reconstructed models of 40 normal scapulae. The incidence of perforation on 3-dimensional computed tomography preoperative templating varied from 8% to 18% for the 3 models. Malalignment of the implants in retroversion was better tolerated than anteversion and varied with implant design. Tolerance for medialization of the implant to correct for glenoid wear was limited (range, 0 degrees-18 degrees ) and varied with implant design. The modified peg design had the lowest incidence of perforation, the greatest tolerance for malalignment, and the ability to correct for glenoid wear effects. These results emphasize the need for accurate preoperative templating and for developing alignment guides or surgical navigation tools for shoulder arthroplasty and may be used to improve implant fixation designs.