Shoulder arthroplasty: the socket perspective

Surgical management of osteoarthritis in the shoulder and elbow

Interesting recent trends are apparent in the setting of shoulder and elbow pathology. There is an increase in utilization of shoulder arthroplasty for osteoarthritis and post traumatic arthritis. At the same time, there remain limited options for osteoarthritis of the elbow particularly in the young and or active patient. This manuscript details surgical options for osteoarthritis at the elbow and shoulder.

Conversion of anatomic total shoulder arthroplasty to reverse shoulder arthroplasty using a unique hybrid glenoid component: technique and preliminary results

Background

Degenerative arthritis of the shoulder is a common condition that is successfully treated with anatomic total shoulder arthroplasty (TSA). Rotator cuff disease has evolved as a leading cause of failure of anatomic TSA, requiring revision to reverse shoulder arthroplasty (RSA). This revision procedure can be extremely complex, particularly if removal of a well-fixed glenoid component is necessary. This case series outlines the technique and preliminary clinical results of conversion of anatomic TSA to RSA utilizing both modular humeral and hybrid glenoid components.

Methods

From July 2017 to December 2019, the senior author (PMC) performed 84 consecutive anatomic TSA procedures utilizing a modular humeral arthroplasty system and a unique hybrid glenoid component. Three cases (3/84, or 3.6%) required conversion from anatomic TSA to RSA because of postoperative traumatic rotator cuff failure. All modular revision cases were performed without humeral stem removal and with utilization of the existing, well-fixed hybrid glenoid central titanium peg as the foundation for glenoid component revision. Preoperative and postoperative American Shoulder and Elbow Surgeons scores, visual analog scale pain scores, forward flexion, and patient satisfaction were analyzed in this modular revision group. In addition, several perioperative variables including operative time, blood loss, and length of stay were compared between this modular revision group and a nonmodular anatomic TSA to RSA revision comparative cohort.

Results

At an average follow-up of 24 months, average active forward flexion, postoperative American Shoulder and Elbow Surgeons scores, and visual analog scale pain scores improved significantly compared with preoperative scores in the modular revision group. All three patients were satisfied with their outcome. The average total operative time (109 minutes vs. 154 minutes, P = .02), blood loss (183 cc vs. 500 cc, P = .08), and length of hospital stay (26.3 hours vs. 36.6 hours P < .05) were lower in the modular revision group than those in a nonmodular revision cohort.

Conclusion

Revision of anatomic TSA to RSA utilizing a modular humeral system and a convertible hybrid glenoid component that does not require removal of a well-fixed central titanium peg which serves as the foundation for glenoid component revision was performed efficiently, safely, and successfully in three cases. This technique results in significantly improved clinical outcomes when revision to RSA is needed while potentially decreasing perioperative complications in the revision setting.

Cartilage decisively shapes the glenoid concavity and contributes significantly to shoulder stability

PURPOSE

Glenohumeral joint injuries frequently result in shoulder instability. However, the biomechanical effect of cartilage loss on shoulder stability remains unknown. The aim of the current study was to investigate biomechanically the effect of two severity stages of cartilage loss in different dislocation directions on shoulder stability.

METHODS

Joint dislocation was provoked in 11 human cadaveric glenoids for 7 different directions between 3 o'clock (anterior) and 9 o'clock (posterior). Shoulder stability ratio (SSR) and concavity gradient were assessed in three states: intact, 3 mm and 6 mm simulated cartilage loss. The influence of cartilage loss on SSR and concavity gradient was statistically evaluated.

RESULTS

Both SSR and concavity gradient decreased significantly between intact state and 6 mm cartilage loss in every dislocation direction (p ≤ 0.038), except concavity gradient in 4 o'clock direction. Thereby, anterior-inferior dislocation directions were associated with the highest decrease in both SSR and concavity gradient of up to 59.0% and 49.4%, respectively, being significantly bigger for SSR compared with all other dislocation directions (p ≤ 0.040). Correlations between concavity gradient and SSR for pooled dislocation directions were significant in each separate specimen's state (p < 0.001).

CONCLUSION

From a biomechanical perspective, articular cartilage of the glenoid contributes significantly to the concavity gradient, correlating strongly with the associated loss in glenohumeral joint stability. The biggest effect of cartilage loss is observed in the most frequently occurring anterior-inferior dislocation directions, suggesting that surgical interventions to restore cartilage's surface and concavity should be considered for recurrent shoulder dislocations in presence of cartilage loss.

Subluxation in the Arthritic Shoulder

»

The term "subluxation" means partial separation of the joint surfaces. In the arthritic shoulder, "arthritic glenohumeral subluxation" refers to displacement of the humeral head on the surface of the glenoid.

»

The degree of arthritic glenohumeral subluxation can be measured using radiography with standardized axillary views or computed tomography (CT).

»

Shoulders with a type-B1 or B2 glenoid may show more posterior subluxation on an axillary radiograph that is made with the arm in an elevated position than on a CT scan that is made with the arm at the side.

»

The degree of arthritic glenohumeral subluxation is not closely related to glenoid retroversion.

»

The position of the humeral head with respect to the plane of the scapula is related to glenoid retroversion and is not a measure of glenohumeral subluxation.

»

Studies measuring glenohumeral subluxation before and after arthroplasty should clarify its importance to the clinical outcomes of shoulder reconstruction.

Osteoarthritis of the shoulder in under-50 year-olds: A multicenter retrospective study of 273 shoulders by the French Society for Shoulder and Elbow (SOFEC)

INTRODUCTION

Osteoarthritis (OA) of the shoulder in under-50 year-olds is rare, and treatment is delicate. Shoulder replacement incurs frequent long-term risk of progression and a high revision rate, making it unsuited to young active patients. The aim of the present study was to determine the epidemiology of shoulder OA in under-50 year-olds and to assess the clinical results of the various treatment options.

HYPOTHESIS

The main study hypothesis was that well-conducted non-operative treatment can allow shoulder replacement to be postponed. The secondary hypothesis was that anatomic total shoulder arthroplasty (TSA) is the treatment of choice when other options fail.

MATERIALS AND METHODS

A multicenter retrospective study included primary (POA) and post-instability osteoarthritis (PIOA) in patients aged≤50years at symptom onset. Exclusion criteria comprised post-traumatic OA, rheumatoid arthritis and necrosis. Two hundred and sixty-six patients for 273 shoulders were included from 13 shoulder surgery centers: 2 types of non-operative treatment (28 by platelet-rich plasma [PRP] and 88 by viscosupplementation), 73 arthroscopies, and 150 implantations (62 humeral hemiarthroplasties [HA], comprising 10 hemi-metal, 24 hemi-pyrocarbon and 28 hemi-resurfacing; 77 anatomic total prostheses, and 11 reverse prostheses). Minimum follow-up was 12 months for non-operative treatment and 24 months for arthroplasty (some patients having both). Endpoints comprised Constant score, Subjective Shoulder Value (SSV) and number of complications/revision procedures.

RESULTS

Mean age at treatment was 43 years (range, 23-65 years), with 75% male predominance. Symptom onset was earlier in PIOA than in POA: 36 vs. 39 years (range, 20-50 years). PRP and viscosupplementation postponed implantation by a mean 3.5 years in 86% of cases, as did arthroscopy in 56%. ER1 restriction was the most negative factor. At 74 months' follow-up for HA and 95 months for TSA, mean Constant score was significantly lower for HA (56 vs. 67; p=0.004), with higher rates of complications (31% vs. 11%) and implant exchange (13% vs. 9%).

DISCUSSION/CONCLUSION

PRP, viscosupplementation and arthroscopy allow implantation to be postponed until the shoulder becomes stiff and painful. In case of failure, TSA is the most effective solution in the medium-term.

LEVEL OF EVIDENCE

IV a; therapeutic study - investigating the results of treatment.

The glenoid and humeral head in shoulder osteoarthritis: A comprehensive review

The key management of glenohumeral osteoarthritis is shoulder arthroplasty which aims to reduce pain and restore full shoulder function: it has increased in recent years. A detailed understanding of the anatomy of the glenoid and humeral head, as well as morphological changes of the glenoid in osteoarthritis, are important factors to consider when deciding on replacement components. This review begins with a brief introduction of the glenohumeral joint itself, and then considers the detailed anatomy of the glenoid fossa and humeral head, both of which are reported to have variable morphology. Several studies have been undertaken to assess various parameters, especially of the glenoid fossa including its shape, height, width, and articular surface area, version and inclination, in an attempt to define a standard classification that can be applied to surgical intervention. Nevertheless, no definitive consensus concerning the classification of these morphologies has been forthcoming, hence the need for this review. Following a consideration of these morphologies, the current state of knowledge regarding glenoid deformity in osteoarthritis, as well as its surgical management, is considered.

CT-Based 3D Printing of the Glenoid Prior to Shoulder Arthroplasty: Bony Morphology and Model Evaluation

To demonstrate the 3D printed appearance of glenoid morphologies relevant to shoulder replacement surgery and to evaluate the benefits of printed models of the glenoid with regard to surgical planning. A retrospective review of patients referred for shoulder CT was performed, leading to a cohort of nine patients without arthroplasty hardware and exhibiting glenoid changes relevant to shoulder arthroplasty planning. Thin slice CT images were used to create both humerus-subtracted volume renderings of the glenoid, as well as 3D surface models of the glenoid, and 11 printed models were created. Volume renderings, surface models, and printed models were reviewed by a musculoskeletal radiologist for accuracy. Four fellowship-trained orthopaedic surgeons specializing in shoulder surgery reviewed each case individually as follows: First, the source CT images were reviewed, and a score for the clarity of the bony morphologies relevant to shoulder arthroplasty surgery was given. The volume rendering was reviewed, and the clarity was again scored. Finally, the printed model was reviewed, and the clarity again scored. Each printed model was also scored for morphologic complexity, expected usefulness of the printed model, and physical properties of the model. Mann-Whitney-Wilcoxon signed rank tests of the clarity scores were calculated, and the Spearman's ρ correlation coefficient between complexity and usefulness scores was computed. Printed models demonstrated a range of glenoid bony changes including osteophytes, glenoid bone loss, retroversion, and biconcavity. Surgeons rated the glenoid morphology as more clear after review of humerus-subtracted volume rendering, compared with review of the source CT images (p = 0.00903). Clarity was also better with 3D printed models compared to CT (p = 0.00903) and better with 3D printed models compared to humerus-subtracted volume rendering (p = 0. 00879). The expected usefulness of printed models demonstrated a positive correlation with morphologic complexity, with Spearman's ρ 0.73 (p = 0.0108). 3D printing of the glenoid based on pre-operative CT provides a physical representation of patient anatomy. Printed models enabled shoulder surgeons to appreciate glenoid bony morphology more clearly compared to review of CT images or humerus-subtracted volume renderings. These models were more useful as glenoid complexity increased.

Glenohumeral kinematics after soft tissue interposition graft and glenoid reaming: A cadaveric study

BACKGROUND

The management of young patients with glenohumeral arthritis is controversial. Resurfacing of the glenoid with biologic interposition and reaming of the glenoid have been suggested as potential treatment options. The goal of this study was to determine the change in glenohumeral contact pressures in interposition arthroplasty, as well as glenoid reaming in an arthritis model. We hypothesized that interposition with meniscal allograft will lead to the best normalization of contact pressure throughout the glenohumeral range of motion.

MATERIALS AND METHODS

Eight fresh-frozen cadaveric shoulders were tested in static positions of humeral abduction with a compressive load. Glenohumeral contact area, contact pressure, and peak force were determined sequentially for (1) intact glenoid (2) glenoid with cartilage removed (arthritis model) (3) placement of lateral meniscus allograft (4) placement of Achilles allograft (5) arthritis model with reamed glenoid.

RESULTS

The arthritis model demonstrated statistically higher peak pressures than intact glenoid and glenoid with interpositional allograft. Meniscal and Achilles allograft lowered mean contact pressure and increased contact area to a level equal to or more favorable than the control state. In contrast, the reamed glenoid did not show any statistical difference from the arthritis model for any of the recorded measures.

CONCLUSION

Glenohumeral contact pressure is significantly improved with interposition of allograft at time zero compared to an arthritic state. Our findings suggest that concentric reaming did not differ from the arthritic model when compared to normal. These findings favor the use of allograft for interposition as a potential treatment option in patients with glenoid wear.

No differences in early results of a hybrid glenoid compared with a pegged implant

BACKGROUND

Glenoid component loosening after total shoulder arthroplasty is one of the most common causes of failure. A hybrid glenoid that uses peripherally cemented pegs and a central press-fit post may improve implant longevity.

QUESTIONS/PURPOSES

We asked, compared with polyethylene pegged glenoid implants, do hybrid glenoid implants with a titanium post provide (1) better ingrowth with fewer radiolucencies, (2) better outcome and pain scores, and (3) lower risk of complications and revisions?

METHODS

Between 2009 and 2010, 126 patients underwent primary total shoulder arthroplasty for osteoarthritis. Patients were included in this retrospective study if they consented for inclusion in a shoulder arthroplasty registry, had complete baseline and 2-year data, and had complete radiographs. Eighty-three (67%) were available at an average followup of 3.2 years (range, 24-45 months). Forty received a conventional all-polyethylene pegged glenoid and 43 received a hybrid component. During the period in question, four of the participating surgeons used only one implant, and four used only the other; there was one high-volume surgeon in each of the study groups. Radiographs were taken at the 2-year followup and analyzed for radiolucent lines. CT scans were obtained randomly for 10 patients with hybrid glenoid implants to assess bone ongrowth. American Shoulder and Elbow Surgeons score, VAS score, complications and revisions were recorded.

RESULTS

At final followup, radiolucent lines between the two study groups were not different (hybrid, 1.0 ± 0.4; pegged, 1.6 ± 0.3; mean difference, 0.6; 95% CI, 0.85-1.72; p = 0.323). Final VAS pain scores were not different (hybrid, 1.2 ± 0.2; pegged, 1.5 ± 0.3; p = 0.056). Change in American Shoulder and Elbow Surgeons scores were not different (hybrid, 33.7 ± 7.3; pegged, 35.5 ± 8.2; p = 0.283). There were no differences in complication risk (hybrid, one of 43 [2.3%]; pegged, three of 40 [7.5%]; relative risk, 2.3; 95% CI, 0.82-3.12; p = 0.061).

CONCLUSIONS

With the numbers available and at early followup, there were no differences between the hybrid and pegged glenoids in terms of fixation, functional outcome, pain scores, and complications. CT scans confirmed bone ongrowth on the porous titanium post in a small subcohort of patients. Further studies are needed to determine how this new implant will perform with time. Until then, its use should be initiated with caution.

LEVEL OF EVIDENCE

Level III, therapeutic study.

Posterior augmented glenoid designs preserve more bone in biconcave glenoids

BACKGROUND AND HYPOTHESIS

Total shoulder arthroplasty is recommended treatment for severe osteoarthritis of the glenohumeral joint, which often results in excessive posterior wear. Two recent glenoid components with posterior augments have been designed to correct excessive posterior wear and retroversion. Our primary hypothesis was that posterior augmented glenoid designs require less bone removal than a standard glenoid design.

METHODS

Ten arthritic scapulae classified as Walch B2 glenoids were virtually implanted with standard, stepped, and wedged components. The volume of surgical bone removal, the maximum reaming depth, and the portion of the implant surface in contact with cancellous vs. cortical bone were calculated for each implant.

RESULTS

The neoglenoid made up an average of 65% ± 12% of the glenoid width. Mean surgical bone volume removed was least for the wedged (2857 ± 1618 mm(3)) compared with the stepped (4307 ± 1485 mm(3); P < .001) and standard (5385 ± 2348 mm(3); P < .001) designs. Maximum bone depth removed for the wedged (4.2 ± 2.0 mm) was less than for the stepped (7.6 ± 1.2 mm; P < .001) and standard (9.9 ± 3.2 mm; P < .001). The mean percentage of the implant's back surface supported by cancellous bone was 18.2% for the standard, 8.8% for the stepped (P = .02), and 4.3% for the wedged (P = .01).

DISCUSSION

Both augmented components corrected glenoid version to neutral and required less bone removal, required less reaming depth, and were supported by more cortical bone than in the standard implant. The least amount of bone removed was with the wedged design.

Anatomic shoulder arthroplasty: an update on indications, technique, results and complication rates

A shoulder replacement is indicated in patients affected by glenohumeral arthropathy with severely reduced range of motion, persistent pain, especially at night, and loss of strength. There is much discussion in the scientific community about the prosthetic options for these cases: hemiarthroplasty, anatomic total shoulder arthroplasty, and reverse total shoulder arthroplasty. We analyzed the indications for, results of, and complications associated with this kind of surgery, focusing on anatomic arthroplasty and on the concept of modularity.

The ream and run: not for every patient, every surgeon or every problem

PURPOSE

The purpose of this paper is to provide some essential and basic information concerning the ream and run technique for shoulder arthroplasty.

METHODS

In a total shoulder arthroplasty, the humeral head prosthesis articulates with a polyethylene glenoid surface placed on the bone of the glenoid. Failure of the glenoid component is recognised as the principal cause of failure of total shoulder arthroplasty. By contrast, in the ream and run procedure, the humeral head prosthesis articulates directly with the glenoid, which has been conservatively reamed to provide a stabilising concavity and maximal glenohumeral contact area for load transfer. While no interpositional material is placed on the surface of the glenoid, animal studies have demonstrated that the reamed glenoid bone forms fibrocartilage, which is firmly fixed to the reamed bony surface. Glenohumeral motion is instituted on the day of surgery and continued daily after surgery to mold the regenerating glenoid fibrocartilage. When the healing process is complete - as indicated by a good and comfortable range of motion - exercises and activities are added progressively without concern for glenoid component failure. 

RESULTS

The experience to date indicates that a technically well done ream and run procedure can restore high levels of comfort and function to carefully selected patients with osteoarthritis, capsulorrhaphy arthroplathy, and posttraumatic arthritis.

CONCLUSIONS

Patients considering the ream and run procedure should understand that this technique avoids the risks and limitations associated with a polyethylene glenoid component, but that it requires strong motivation to follow through on a rehabilitation course that may require many months. The outcome of this procedure depends on the body's regeneration of a new surface for the glenoid and requires rigorous adherence to a daily exercise program. This paper explains in detail the principal factors in patient selection and the key technical elements of the procedure. Clinical examples and outcomes are demonstrated.

Augmented wedge-shaped glenoid component for the correction of glenoid retroversion: a finite element analysis

BACKGROUND

This study undertook a computational analysis of a wedged glenoid component for correction of retroverted glenoid arthritic deformity to determine whether a wedge-shaped glenoid component design with a built-in correction for version reduces excessive stresses in the implant, cement, and glenoid bone. Recommendations for correcting retroversion deformity are asymmetric reaming of the anterior glenoid, bone grafting of the posterior glenoid, or a glenoid component with posterior augmentation. Eccentric reaming has the disadvantages of removing normal bone, reducing structural support for the glenoid component, and increasing the risk of bone perforation by the fixation pegs. Bone grafting to correct retroverted deformity does not consistently generate successful results.

METHODS

Finite element models of 2 scapulae models representing a normal and an arthritic retroverted glenoid were implanted with a standard glenoid component (in retroversion or neutral alignment) or a wedged component. Glenohumeral forces representing in vivo loading were applied and stresses and strains computed in the bone, cement, and glenoid component.

RESULTS

The retroverted glenoid components generated the highest compressive stresses and decreased cyclic fatigue life predictions for trabecular bone. Correction of retroversion by the wedged glenoid component significantly decreased stresses and predicted greater bone fatigue life. The cement volume estimated to survive 10 million cycles was the lowest for the retroverted components and the highest for neutrally implanted glenoid components and for wedged components.

CONCLUSION

A wedged glenoid implant is a viable option to correct severe arthritic retroversion, reducing the need for eccentric reaming and the risk for implant failure.

Use of a custom alignment guide to improve glenoid component position in total shoulder arthroplasty

PURPOSE

Total and reverse total shoulder arthroplasty (TSA) are used to treat patients with glenohumeral joint osteoarthritis. The revision rate remains high compared with hip and knee arthroplasty. Glenoid component loosening is an important complication and may be caused by poor positioning of the component. We aimed to evaluate the safety and accuracy of a custom glenoid jig created using preoperative computed tomography (CT) imaging with 3D modelling for glenoid component implantation.

METHODS

Preoperative CT scans of each shoulder (N = 7) were obtained. Implants were virtually aligned and custom templates were created for intraoperative use. A two-part custom jig was manufactured for alignment of the central peg and the peripheral screws. Three-dimensional orientation of the component and screws was evaluated in postoperative CT scans. The difference between the preoperative plan and the result was then calculated.

RESULTS

No technical difficulties or complications occurred. The mean absolute difference between the planned alignment and the postoperative placement of the glenoid component in the three-dimensional space was 3.4 mm (SD = 1 mm). The total average difference for all screws (N = 10) was 6.3° (SD = 3.2°).

CONCLUSION

A CT-based custom glenoid component alignment can reliably guide the placement of the glenoid component during conventional and reverse TSA. This custom jig may be useful for optimizing glenoid component position in the setting of reverse and TSA.

Midterm results of a total shoulder prosthesis fixed with a cementless glenoid component

BACKGROUND

The aim of this study was to evaluate the midterm results and complications of a total shoulder arthroplasty implanted with a metal-backed, bone-ingrowth glenoid component.

MATERIALS AND METHODS

In total, 62 patients (65 shoulders) diagnosed with primary osteoarthritis were treated with total shoulder arthroplasty with a cementless glenoid component. The mean age was 66 years (range, 54-85 years). Fifty-three patients were evaluated after a mean of 64 months (range, 26-85 months). Functional results were documented by use of the age- and sex-adjusted Constant score. Radiolucent line (RLL) assessment of the glenoid component was performed by use of true anteroposterior and axillary views.

RESULTS

The Constant score improved significantly from 49% preoperatively to 89.8% postoperatively (P < .0001). Active range of motion improved significantly for flexion (from 118° to 146°), abduction (from 87° to 133°), and external rotation (from 21° to 44°) (P < .0001). In 3 cases (5.7%), RLLs of 1 mm or less were present, and 1 case (1.8%) had an RLL of 2 mm or less in 1 zone. Glenoid component loosening occurred in 5 cases (9.4%) because of breakage of the cage screw. Four of these patients presented preoperatively with a type B1 glenoid and one patient with type A2. Two of the patients who underwent revision also had a complete tear of the rotator cuff. The revision rate was 11.3% (6 patients) after a mean of 68 months.

CONCLUSION

After midterm follow-up, clinical outcomes of patients operated on with a cementless, metal-backed glenoid implant improved significantly. However, an unacceptable rate of complications and revisions was found. Glenoid loosening predominantly occurred in patients with preoperative eccentric glenoid morphology and was also related to cranial migration of the proximal humerus during the follow-up period.

Incidence of early radiolucent lines after glenoid component insertion for total shoulder arthroplasty: a radiographic study comparing pressurized and unpressurized cementing techniques

BACKGROUND

Total shoulder arthroplasty (TSA) is commonly performed for arthritic conditions of the shoulder. The outcome after TSA is generally good, but there are several modes of failure, with one of the more common reasons being glenoid loosening. One possible cause for glenoid loosening is inadequate cementation technique. The purpose of this study was to evaluate the incidence of lucent lines on the first postoperative radiograph using 2 different cementation techniques.

MATERIALS AND METHODS

One hundred consecutive patients had a pegged glenoid placed with 1 of 2 different cementation techniques. In 26 consecutive patients, the pegged glenoid component was cemented with a traditional minimal manual pressurization technique, whereas 74 underwent a contemporary 3-step pressurization cementation technique before implant insertion. The first postoperative radiograph was evaluated using the system of Lazarus et al, looking at the frequency of lucent lines. The radiographs were deidentified and were randomized and evaluated by 2 independent observers on 3 separate occasions.

RESULTS

The Kruskal-Wallis test showed significant differences between grades of radiolucent lines for pressurized versus unpressurized cementation techniques. There were significantly (P < .05) fewer lucent lines identified in the group that underwent contemporary 3-step pressurization as opposed to the group that underwent minimal manual pressurization. Intraobserver reliability and interobserver reliability with Cronbach α coefficients were good.

CONCLUSION

The 3-step pressurized cementation technique resulted in a low incidence of radiolucent lines around the glenoid implant in patients undergoing TSA.

LEVEL OF EVIDENCE

Level II, Prospective Cohort, Treatment Study.

Glenoid or not glenoid component in primary osteoarthritis

The optimal choice for the treatment of end-stage primary glenohumeral osteoarthritis remains controversial, with alternatives including total shoulder replacement (TSR) and humeral head replacement (HHR). The objective of this review is to analyze the effect of TSR compared with HHR on rates of pain relief, range of motion, patient satisfaction and revision surgery in patients with primary glenohumeral osteoarthritis. Compared with HHR, TSR provided significantly greater pain relief, gain in forward elevation, and gain in external rotation and patient satisfaction. Furthermore, TSR required significantly less revision surgery glenoid component loosening than patients undergoing HHR (progression of osteoarthritis changes with subchondral sclerosis, joint space narrowing and glenoid subsidence). A convex-back pegged glenoid component with a modern instrumented cement pressurization technique achieves risk of loosening. For 10 years, a high interest regarding new designs of un-cemented metal back glenoid components has developed with promising results, because they allow glenoid bone graft in case of glenoid erosion or dysplasia and a one-stage glenoid bone reconstruction in case of revision surgery.

Glenoid morphology after reaming in computer-simulated total shoulder arthroplasty

BACKGROUND

The relationships between reaming parameters for glenoid-implant surface area and bone loss in total shoulder arthroplasty have not been well established. The hypotheses of this study are: (1) for large version corrections, a large reaming depth of 5 mm is not sufficient to obtain complete glenoid implant contact; (2) glenoid bone is removed in a linear proportion with reaming depth; and (3) initial reamer placement has no effect on glenoid bone removal.

METHODS

Ten computer models from computed tomography scans of patients with advanced osteoarthritis were created for computer-simulated reaming as performed during total shoulder arthroplasty. Reaming variables studied included reaming depth, reamer placement, and version correction. The resulting reamed glenoid surface area available for implantation and bone volume removed were calculated for each permutation.

RESULTS

Reamed surface area significantly increased with larger depths of reaming (P < .0001) and smaller version corrections (P < .0001). Bone volume removed and reaming depth had a strong quadratic relationship (r(2) = 0.999). With off-center reamer placement, volume removed when deviating in the posterior direction was significantly greater than when deviating in the anterior, superior, or inferior direction (P < .05).

CONCLUSION

Performing smaller version corrections allows for greater attainable implant-bone surface contact because increasing reaming depth results in small increases in conforming surface area but large losses in glenoid bone stock. Bone volume removed was most sensitive to off-center position errors in the posterior direction.

The glenoid in total shoulder arthroplasty

Management of glenohumeral arthrosis with a total shoulder prosthesis is becoming increasingly common. However, failure of the glenoid component remains one of the most common causes for failure. Our understanding of this problem has evolved greatly since the first implants were placed in the 1970's. However glenoid failure remains a challenging problem to address and manage. This article reviews the current knowledge regarding the glenoid in total shoulder arthroplasty touching on anatomy, component design, implant fixation, causes of implant failure, management of glenoid failure and alternatives to glenoid replacement.

Management of glenohumeral arthritis in the young adult

The majority of cases of glenohumeral arthritis in older adults are primary osteoarthritis and treatment algorithms are well defined, with shoulder arthroplasty providing reliable pain relief and functional improvement of satisfactorily duration. In younger adults, however, diagnoses are more complex and arthroplasty outcomes are less durable. Arthroscopy may be useful both as a diagnostic tool for characterizing lesions and as a therapeutic tool for debridement. Arthroscopic debridement is most likely to benefit patients with mild glenohumeral arthritis, small lesions, and involvement of only one side of the glenohumeral joint. Reconstruction of the humeral joint surface may consist of cartilage repair or reconstruction, resurfacing arthroplasty, or arthroplasty with a stemmed component. Patients treated with hemiarthroplasty avoid glenoid implant loosening, but the procedure provides less predictable pain relief than does total shoulder arthroplasty and may lead to increased postoperative glenoid erosion.

A quantitative method for determining medial migration of the humeral head after shoulder arthroplasty: preliminary results in assessing glenoid wear at a minimum of two years after hemiarthroplasty with concentric glenoid reaming

HYPOTHESIS

Glenoid erosion and medial migration of the humeral head prosthesis have been observed after most types of shoulder arthroplasty. A method of measuring the change in humeral head position with time after shoulder prosthetic arthroplasty was applied it to 14 shoulders that underwent humeral hemiarthroplasty with concentric glenoid reaming. We hypothesized that the measurement technique would be reproducible and that the rate of wear would be small in the series of shoulders studied.

MATERIALS AND METHODS

Standardized anteroposterior and axillary radiographs were obtained after surgery. Two examiners measured the position of the humeral head center in relation to scapular reference coordinates for the anteroposterior and axillary projections and plotted these values against time after surgery. The change in position was characterized as the slope of this plot. Shoulders were included if there were at least 3 sets of postoperative films, the last being at least 2 years after surgery.

RESULTS

The slopes measured by the 2 examiners agreed within 0.5 mm/y for the anteroposterior and the axillary projections. For the series of shoulder arthroplasties, the rate of movement of the head center toward the scapula was less than 0.4 mm/y for either examiner in either projection.

DISCUSSION

Medial migration is a concern after any type of shoulder arthroplasty, whether a hemiarthroplasty, a biological interpositional arthroplasty, or a total shoulder arthroplasty. Quantifying the rate of medial migration over time after shoulder arthroplasty is an important element of clinical follow-up.

CONCLUSIONS

This is an inexpensive, practical, and reproducible method that can be used to determine the rate of medial migration of the humeral head on plain radiographs after shoulder arthroplasty. The average rate of medial migration in the shoulders in this study was small.

Bone presence between the central peg's radial fins of a partially cemented pegged all poly glenoid component suggest few radiolucencies

BACKGROUND

Cement penetration problems and/or cement-induced bone necrosis may contribute to glenoid component failures. An all polyethylene component was developed that promotes biologic fixation between radial fins of its central peg and utilizes minimal cement fixation for its peripheral pegs, but it has little published data. We hypothesized better bone presence between the radial fins would be associated with less overall radiolucencies. This study's purpose was to utilize computed tomography (CT) and plain films to assess for bone between the central peg's radial fins and to assess overall component radiolucencies.

MATERIALS AND METHODS

Thirty-five of 48 consecutively performed total shoulder arthroplasties (TSA) for primary glenohumeral osteoarthritis were in patients able to participate a minimum 2 years after surgery. All had reamed humeral head bone packed between radial fins of the central peg and minimal cement for the peripheral pegs. Thin cut (0.625 mm) CT scans, standardized plain films, Simple Shoulder Tests (SST), and Constant scores were obtained. A musculoskeletal radiologist calculated Yian CT scores, bone presence between fins on CT, and Lazarus radiolucency scores.

RESULTS

At a mean of 43 months, by CT: 1) better Yian scores correlated with more bone between fins, and 2) bone was present in 6/6 inter-fin compartments in 23/35 shoulders, averaging 4.5/6 overall. Mean Lazarus radiolucency score was 0.45. Mean SST and Constant scores were 10.3 and 81.3, respectively.

CONCLUSION

TSA utilizing autologous bone in inter-fin compartments of the central peg and minimal peripheral peg cement maintained bone presence a minimum 2 years post-op. More bone imparted fewer overall component radiolucencies.

Treatment of glenohumeral arthrosis

The successful diagnosis and treatment of glenohumeral arthrosis in the young and active patient can be challenging to even the most experienced of clinicians. A thorough preoperative evaluation, including a detailed understanding of patient expectations, facilitates the selection of a treatment strategy. Arthroscopy is the gold standard for detecting chondral injuries, and it is increasingly used as an effective first line of management. In patients who fail arthroscopic debridement and reparative techniques, further treatment should proceed with an algorithmic decision-making approach encompassing patient-based and disease-based factors. Restorative and reconstructive techniques may provide improvements in pain and functional outcome while delaying the need for total shoulder arthroplasty, although the longevity of these treatments has yet to be established in the literature. Hemiarthroplasty and total shoulder arthroplasty have historically proven to be the most durable and reliable options in properly selected patients. However, concerns about progressive glenoid erosion and glenoid component loosening have led many to pursue alternative nonarthroplasty techniques for the management of arthrosis in active young individuals.

Mechanical properties of glenoid cancellous bone

BACKGROUND

Loosening of the glenoid component in total shoulder arthroplasty is the main late complication of this procedure; it may be assumed that it is highly dependent on the quality of the glenoid cancellous bone. Very little is known about the mechanical properties of this cancellous bone. The aim of this study was to determine these properties (Young's modulus and strength) as well as bone density in different parts of the glenoid cancellous bone to assess their variations.

METHODS

Eleven scapulas were obtained from six fresh-frozen, unembalmed human cadavers. Eighty-two cubic cancellous bone specimens were extracted and tested using a uniaxial compression test; then the specimens were defatted and correlations with bone density were determined.

FINDINGS

The study showed significant differences in the mechanical properties with anatomic location and directions of loading. Young's modulus and strength were found to be significantly higher at the posterior part of the glenoid with the weakest properties at the antero-inferior part. Cancellous bone was found to be anisotropic with higher mechanical properties in the latero-medial direction perpendicular to the articular surface of the glenoid. The apparent density was on average equal to 0.29 g/cm(3) with the higher values at the posterior and superior part of the glenoid. Good correlation between apparent density and elastic modulus was found only in the sagittal planes but not in the coronal and axial plane.

INTERPRETATION

The mechanical properties determined in this study showed the anisotropy of the glenoid cancellous bone; values of these properties could provide input data for finite element method analyses in shoulder prosthesis designs.

Glenohumeral contact kinematics in patients after total shoulder arthroplasty

BACKGROUND

Knowledge of in vivo glenohumeral joint contact mechanics after total shoulder arthroplasty may provide insight for the improvement of patient function, implant longevity, and surgical technique. The objective of this study was to determine the in vivo glenohumeral joint contact locations in patients after total shoulder arthroplasty. We hypothesized that the glenohumeral joint articular contact would be centered on the glenoid surface because of the ball-in-socket geometric features of the implants.

METHODS

Dual-plane fluoroscopic images and computer-aided design models were used to quantify patient-specific glenohumeral articular contact in thirteen shoulders following total shoulder arthroplasty. The reconstructed shoulder was imaged at arm positions of 0 degrees, 45 degrees, and 90 degrees of abduction (in the coronal plane) and neutral rotation and at 90 degrees of abduction with maximum internal and external rotation. The patients were individually investigated, and their glenohumeral joint contact centroids were reported with use of contact frequency.

RESULTS

In all positions, the glenohumeral joint contact centroids were not found at the center of the glenoid surface but at an average distance (and standard deviation) of 11.0 +/- 4.3 mm from the glenoid center. Forty (62%) of the sixty-five total contact occurrences were found on the superior-posterior quadrant of the glenoid surface. The position of 0 degrees of abduction in neutral rotation exhibited the greatest variation of quadrant contact location; however, no contact was found on the superior-anterior quadrant of the glenoid surface in this position.

CONCLUSIONS

In vivo, glenohumeral joint contact after total shoulder arthroplasty is not centered on the glenoid surface, suggesting that kinematics after shoulder arthroplasty may not be governed by ball-in-socket mechanics as traditionally thought. Although contact locations as a function of arm position vary among patients, the superior-posterior quadrant seems to experience the most articular contact in the shoulder positions tested.

Total shoulder arthroplasty in dislocation arthropathy

Follow-up examinations of 45 patients who received shoulder arthroplasty for osteoarthritis following shoulder instability were conducted after 44 months. The goal of this study was to describe the clinical findings associated with advanced glenohumeral arthritis due to shoulder instability and instability repairs and to present the clinical results and complications of treating this with shoulder arthroplasty. The weighted average Constant score increased significantly from 49.4 to 81.3 points. There was no significant difference in the type of arthroplasty with 35 cases of total shoulder replacements and ten cases of hemiarthoplasty. The rate of complications was 40% (18/45 patients) with 20% (9/45 patients) requiring an operative revision. Patients with arthritis after instability repair showed great improvement in all qualities of the Constant score. Nonetheless, further analyses are required to determine why such a relatively young group of patients showed high complication rates.

The glenoid in shoulder arthroplasty

Total shoulder arthroplasty is a common treatment for glenohumeral arthritis. One of the most common failure modes of total shoulder arthroplasty is glenoid loosening, causing postoperative pain, limitation of function, and potentially, the need for revision surgery. The literature has devoted considerable attention to the design of the glenoid component; efforts to better understand the biomechanics of the reconstructed glenohumeral joint and identify factors that contribute to glenoid component loosening are ongoing. This article reviews the current state of knowledge about the glenoid in total shoulder arthroplasty, summarizing the anatomic parameters of the intact glenoid, variations in component design and fixation, the mechanisms of glenoid loosening, the outcomes of revision surgery in the treatment of glenoid component failure, and alternative treatments for younger patients.