Preliminary Results of a Novel Hybrid Cage Glenoid Compared to an All-Polyethylene Glenoid in Total Shoulder Arthroplasty

INTRODUCTION

The aim of this study was to evaluate the preliminary outcomes of a hybrid cage glenoid design in comparison to pegged all-polyethylene glenoid components in anatomic total shoulder arthroplasty (aTSA).

MATERIALS AND METHODS

Ninety-two patients undergoing primary anatomic total shoulder arthroplasty with minimum two-year follow-up were reviewed. Forty-six patients had an ultra-high molecular weight polyethylene (UHMWPE) cemented pegged glenoid component, and 46 had a hybrid cage glenoid component. Patient data was retrospectively reviewed from prospectively acquired data in a multi-institutional IRB approved database. These age, gender, and follow-up matched patients were evaluated and scored preoperatively and a latest follow-up using the SST, UCLA, ASES, Constant, and SPADI scoring metrics. Additional measures included active abduction, elevation, and external rotation. Radiolucent line assessment of the glenoid was performed by use of a Grashey and axillary radiograph at latest follow-up. A Student's two tailed, unpaired t-test was used to identify differences in preoperative and postoperative results, where p < 0.05 denoted a significant difference.

RESULTS

All patients demonstrated significant improvements in pain and function following treatment with the primary aTSA. The database contained three complications for the aTSA patients with a cage glenoid, and three complications for patients with a UHMWPE pegged glenoid. Radiographic data was available for 37 of 46 cage glenoid patients and 29 of 46 UHMWPE pegged glenoid patients. Five of 37 cage glenoid patients had a radiolucent line (13.5%) with an average radiographic line score of 0.22. Eight of 29 UHMWPE peg glenoid patients had a radiolucent line (27.6%) with an average radiographic line score of 0.57. Cage aTSA patients were associated with significantly less blood loss than aTSA UHMWPE pegged glenoid patients (avg. blood loss = 242 vs. 337; p = 0.022).

CONCLUSION

At minimum two-year follow-up, hybrid cage aTSA components show equal clinical outcomes to UHMWPE pegged glenoids. However, the hybrid cage components had significantly fewer radiolucent lines and less intra-operative blood loss. Additional and longer-term clinical and radiographic follow-up is necessary to confirm these promising early results.

Subscapularis Preserving Technique in Anatomic Total Shoulder Arthroplasty. The Superior and Inferior Approach

Subscapularis tenotomy for anatomic total shoulder arthroplasty has been the standard approach for shoulder surgeons that use the deltopectoral approach. The risk of subscapularis insufficiency after this approach has been well documented. In order to avoid subscapularis complications, subscapularis sparing approaches through the rotator interval have been developed. We present two alternative subscapularis preserving techniques that are performed through the deltopectoral interval and allow more complete osteophyte excision and accurate humeral head sizing. These techniques require modified instrumentation and are facilitated by the use of an adaptable prosthesis with dual eccentricity. Future studies will examine the comparative clinical and radiographic outcomes of these techniques.

Improving Distal Fixation with Total Shoulder Arthroplasty in Cases of Severe Humeral Bone Loss

The usage of and indications for total shoulder arthroplasty have grown in recent years. Certain aspects of these arthroplasty procedures can be very complex, especially in revision and fracture cases, often leading to proximal humerus bone loss. For cases with significant bone loss, there is a need for improved devices with additional options to treat a wider range of deformities while also mitigating existing complications and rates, such as poor distal fixation, inadequate soft tissue reattachment options, and joint instability. To that end, a fatigue and torsional test was conducted on two different devices to assess the ability of each to survive an extreme fatigue and torsional load when assembled in worst-case configurations. Evaluation of the Equinoxe® humeral reconstruction prosthesis demonstrated superior fixation in both the fatigue loading scenario and also the torsional loading scenario as compared to the 8 mm x 215 mm cemented humeral long stem, where each had only 80 mm of cemented fixation. The results of the fatigue test demonstrated that despite the humeral reconstruction prosthesis being subjected to a 960 N force and 45 Nm bending moment (which was significantly more challenging than the 576 N force and 24.2 Nm bending moment subjected to the cemented humeral long stem), the humeral reconstruction prosthesis completed 1 M cycles without fracture or failure. Additionally, the Equinoxe® humeral reconstruction prosthesis was associated with a significantly greater torsional resistance in both the torque to initial slip (29.4 Nm versus 8.2 Nm; p = 0.0002) and also the maximum torque to failure (44.3 Nm versus 12.1 Nm; p < 0.0001). These significant improvements in fixation are at least partially attributed to the application of a novel distal fixation ring, which is press fit around the diaphysis of the humerus to supplement the cemented fixation of the distal stem. These fatigue and torsional test results paired with several novel features of fer the potential for the Equinoxe® humeral reconstruction prosthesis to be an improved treatment option for patients with proximal humeral bone loss, though clinical follow-up is necessary to confirm these positive biomechanical results.

Preliminary Results of a Posterior Augmented Glenoid Compared to an all Polyethylene Standard Glenoid in Anatomic Total Shoulder Arthroplasty

INTRODUCTION

Osteoarthritis of the shoulder often results in significant posterior glenoid wear. The options for treating this have been eccentric glenoid reaming and occasionally bone grafting. More recently reverse total shoulder arthroplasty (rTSA) with or without bone grafting and posterior augmented glenoids (PAGs) has been introduced. The PAG restores the native joint line while reaming a minimal amount of glenoid bone. The purpose of this study is to compare osteoarthritic shoulders with significant posterior glenoid wear treated with anatomic total shoulder arthroplasty (aTSA) using a PAG to shoulders without glenoid wear treated with aTSA using a standard all poly pegged glenoid.

METHODS

The patients' data in this study were retrospectively queried from prospectively acquired data in a multi-institutional IRB approved database. The study population consisted of 24 patients with osteoarthritis and posterior glenoid wear who were treated with aTSA using a PAG with a minimum of two-year follow-up. This population was age, sex, and follow-up matched to patients treated with an all poly non-augmented pegged glenoid (NAG) for osteoarthritis. Seven females and 17 males with an average age of 65.8 ± 11.5 years received a posterior augmented glenoid. The control group consisted of 7 females and 17 males with an average age of 66.4 ± 9.1 years who underwent aTSA for osteoarthritis using an all poly standard glenoid. These age, gender, and follow-up matched patients were evaluated and scored preoperatively and at latest follow-up using the SST, UCLA, ASES, Constant, and SPADI scoring metrics; active abduction, elevation, and external rotation were also measured. A Grashey and axillary lateral radiograph was evaluated at two-year follow-up. The Shoulder Arthroplasty Subluxation Index was used to determine the degree of humeral component subluxation on the glenoid component. A Student's two-tailed, unpaired t-test was used to identify differences in preoperative and postoperative results, where p < 0.05 denoted a significant difference.

RESULTS

All patients demonstrated significant improvements in pain and function with the primary aTSA. Sixty per-cent of PAG shoulders had a radiolucent line with an average radiographic line score of 1.10, and 33.3% of NAG had a radiolucent line with an average radiographic line score of 0.438. One glenoid in the PAG group is radiographically but not clinically loose. In the PAG group, the Grashey view showed that 18/20 humeral heads were centered with the two remaining joints demonstrating superior subluxation. On the axillary lateral in the PAG group, 17/20 humeral heads were centered, and three were anteriorly subluxated; none were posteriorly subluxated. There were no differences in any of the measured postoperative clinical outcomes or any difference in improvement between the two groups.

DISCUSSION

At a minimum of two-year follow-up, there were no statistical clinical differences between the PAG and NAG groups despite the PAG group being disadvantaged with posterior worn glenoids. There were no revisions in either group. No humeral heads resubluxated posteriorly. The PAG group had a higher incidence of lucent lines. Based on this short-term follow-up, a posterior augmented glenoid is a viable option for the posterior worn osteoarthritic glenoid.

Reverse Shoulder Arthroplasty Augments for Glenoid Wear. Comparison of Posterior Augments to Superior Augments

INTRODUCTION

Patients who are candidates for a reverse total shoulder arthroplasty (rTSA) may have varying amounts and patterns of glenoid wear. The usual treatment of these deformities has been eccentric reaming or bone grafting. Eccentric reaming often removes a large amount of subchondral bone. Bone grafting is technically more difficult and introduces another mode of failure if the graft does not heal. The purpose of this study is to evaluate patients undergoing a rTSA with concomitant superior or posterior glenoid wear who were treated with a superior augmented baseplate (SAB) or posterior augmented baseplate (PAB) without eccentric reaming or bone grafting.

MATERIALS AND METHODS

Prospectively obtained data were queried from a multi-institutional IRB-approved database. Preoperative and postoperative data were analyzed from 39 patients who received a primary rTSA with either an 8° PAB or a 10° SAB and a minimum of 2 years follow-up. Twenty-four (10 females and 14 males, aged 72.3 ± 8.2 years) received a primary rTSA shoulder with a PAB. Fifteen patients (4 females and 11 males, aged 71.7 ± 9.2 years) received a primary rTSA shoulder with a SAB. Each patient was scored preoperatively and at latest follow-up using the SST, UCLA, ASES, Constant, and SPADI metrics. Active abduction, forward flexion, and active and passive external rotation with the arm at the side were also measured. The average follow-up for rTSA patients with a PAB was 25.6 ± 3.1 months, and the average follow-up for rTSA patients with a SAB was 32.5 ± 6.5 months. A Student's two-tailed, unpaired t-test was used to identify differences in preoperative and postoperative results, where p < 0.05 denoted a significant difference.

RESULTS

All patients in both groups demonstrated significant improvements in pain and function following treatment with the reverse shoulder arthroplasty. The PAB rTSA cohort had a scapular notching rate of 6.3%, whereas the SAB rTSA cohort had a scapular notching rate of 14.3%. The PAB outperformed the SAB with the ASES, Constant, and active forward elevation measures.

DISCUSSION

The PAB group outperformed the SAB group with the ASES and Constant outcome scores and forward flexion. The reason for this is unknown; however, it may be due to the posterior augment baseplate itself tensioning the remaining external rotators better than the superior augment, or it may be that the posterior augment group had a better posterior cuff. Both implant groups had no revisions or dislocations and had a low notching rate. It appears that a SAB for superior glenoid wear and a PAB for posterior glenoid wear are viable simple solutions in patients undergoing a rTSA, where each preserves glenoid bone and eliminates the need for glenoid bone grafting.

Evaluation of Preoperative Implant Placement in Total Shoulder Arthroplasty

INTRODUCTION

New technology to assist with glenoid placement in shoulder arthroplasty has evolved to include preoperative planning tools and intraoperative guides. These tools provide surgeons with a more complete understanding of glenoid anatomy prior to surgery. However, there have been no studies identifying the information that most influences surgical decision making. Further, there have been few studies that quantify intraoperative identification of scapular landmarks required to execute a preoperative plan. The purpose of this study is to examine the variables that are considered when making a preoperative plan in shoulder arthroplasty.

METHODS

The first part of this study was a cadaveric lab in which three surgeons identified the neutral axis in surgical simulation. The second part of the study utilized a preliminary software tool in which surgeons were able to place glenoid implants in a set of CT reconstructions utilizing standard pegged glenoid components. In the third part of the study, surgeons utilized a novel planning software that included the ability to view the 3D reconstructed glenoid in all planes simultaneously and place either standard or augmented glenoid implants. The results of these three studies were compared.

RESULTS

The center of the glenoid identified in the cadaver lab was 1.69 mm ± 1.58 mm anterior and 1.99 mm ± 2.49 mm superior to center. The identified neutral axis was tilted 14.2° ± 9.2° superior to the Friedman axis with 11.8° ± 7.9° of retroversion relative to that axis. Using the novel preoperative planning tool, the surgeons placed implants less than 0.5 mm from the center of the glenoid (AP = -0.07 mm ± 0.42 mm, SI = 0.44 mm ± 0.82 mm) with an average retroversion of less than 1° (-0.96° ± 3.04°).

CONCLUSION

There was a discernible difference between the neutral axis identified in the cadaveric simulation (aver age of 14.2° superior and 11.8° retroverted) and the implant orientation planned using preoperative software (average of 3.26° superior and 0.96° retroverted). Based on the variability of position and orientation seen cadaverically, it is concluded that additional intraoperative guidance is needed alongside a preoperative plan in order to execute ideal placement of the glenoid component.

Stemless and Short Stem Humeral Components in Shoulder Arthroplasty

Humeral-sided arthroplasty design evolution continues to be supported by the published literature in the transition away from traditional stemmed devices. Early studies have shown not only absence of failure with these newer shorter and stemless designs but also equivalence in terms of early outcomes compared to traditional stemmed devices with the benefits of shorter operative time, less blood loss, easier revision, and the potential to reduce stress shielding and periprosthetic fractures. We will review the literature available on the different designs of both short stem and stemless humeral devices.

Distribution of Glenoid Implant Options for Correcting Deformities Using a Preoperative Planning Tool

Preoperative planning tools in shoulder arthroplasty are a recently developing technology with the advantage of being able to clearly assess patient anatomy and deformities before entering the OR. Addressing retroverted glenoids remains one of the most difficult aspects of primary shoulder arthroplasty. In this study, five surgeons were provided with a preoperative planning tool with posterior augmented glenoid implant options (0°, 8°, and 16°) to treat 10 cadaveric cases with a range of versions from 7.8° anteversion to 25.1° retroversion. Surgeons were able to remove less bone using 8° augmented implants over standard non-augmented implants (2.8° reamed vs. 6.4° reamed) and were able to correct each case on average within ± 1.8° of neutral version. Slight glenoid vault perforation was observed in 18% of the plans. Eight degrees posterior augmented implants were used in scans averaging 9.0° retroversion, and 16° posterior augmented implants were used in scans averaging 20.6° retroversion. Results were then compared to 14 preoperative CT scans provided by one of the surgeons in which both 8° and 16° posterior augmented glenoid implants were used in actual patients, showing 8° posterior augmented implants were used in cases averaging 12.3° retroversion, and 16° posterior augmented implants were used in cases averaging 20.7° retroversion. The study shows that surgeons can effectively and predictably use a preoperative planning tool to correct glenoid abnormalities using augmented implant solutions while minimizing both scapular bone removal and vault perforation and maximizing version correction.

Optimizing Deltoid Efficiency with Reverse Shoulder Arthroplasty Using a Novel Inset Center of Rotation Glenosphere Design

INTRODUCTION

Paul Grammont's hemispherical gleno sphere concept medializes the center of rotation (CoR) to the glenoid face to increase deltoid abductor moment arms and improve muscle efficiency. Reducing glenosphere thickness to less than half its spherical radius further medializes the CoR and offers the potential for even greater improvements in efficiency. To that end, this study quantifies deltoid abducttor moment arms for six different rTSA prostheses during scapular abduction from 0° to 140°.

METHODS

A 3D computer model was developed in Uni graphics to quantify deltoid moment arms during scapular abduction for the normal anatomic shoulder, the 36 mm Grammont Delta III (Depuy, Inc.), 36 mm BIO-RSA ® (Tornier, Inc.), the 32 mm RSP® (DJO, Inc.), and the Equinoxe® rTSA (Exactech, Inc.) with three different glenosphere geometries: 38 mm x 21 mm, 46 mm x 25 mm, and the novel 46 mm x 21 mm. Each muscle was simulated as three lines from origin to insertion as the arm was elevated; positional data was exported to Matlab where the abductor moment arms were calculated for the anterior, middle, and posterior deltoid from 0° to 140° humeral abduction in the scapular plane using a 1.8:1 scapular rhythm.

RESULTS

The 46 mm x 21 mm glenosphere had the larg est average abductor moment arms and also the largest efficiency for all three heads of the deltoid, having a 4.8% to 40.7% increase in the average deltoid efficiency relative to all other designs tested. The glenosphere design with the next most efficient deltoid was the 36 mm Delta III, which had the next most medialized CoR. The two least efficient designs were the BIO-RSA ® and the DJO RSP® , which had the most lateral CoR.

DISCUSSION

These results provide new biomechanical insights on the impact of glenosphere geometry on deltoid abductor moment arms and demonstrate that subtle changes in rTSA prosthesis design can result in dramatic improvements. Increasing glenosphere diameter while also decreasing thickness to be less than half its spherical radius may minimize the muscle forces required to perform activities of daily living. Clinical follow-up is necessary to demonstrate a reduction in complications related to joint over-loading and also demonstrate greater increases in range of motion for patients with weak musculature.

Revision Total Shoulder Arthroplasty without Humeral Component Removal. A Preliminary Report on the Role of a Platform Humeral Component

BACKGROUND

Revision total shoulder arthroplasty to a reverse system without removing the humeral component-- i.e., a platform system--has been in use since 2006. This preliminary report compares the outcomes of revision total shoulder replacement in patients who underwent revision utilizing a platform system as compared to those patients requiring stem removal.

METHODS

The data banks from two academic centers were utilized to review patients who underwent revision total shoulder surgery requiring removal of a well fixed humeral stem and those revised with a well fixed platform humeral stem. All patients underwent revision to reverse total shoulder arthroplasty. Measured variables were pre and postoperative Constant scores, blood loss, operating room time, complications, and cost.

RESULTS

The use of a platform system resulted in fewer complications, less operating room time, and a decrease in blood loss (p < 0.05). The Constant scores were not significantly different between the two groups. The cost of implants and operating room time was also less in the platform system group.

CONCLUSION

Revision total shoulder arthroplasty utilizing a platform system that does not require humeral component removal resulted in a significant decrease in complications, blood loss, and operating room time compared with revisions that did not utilize a platform system. The Constant score was similar between the two groups. The overall cost of the procedure was less when the platform system was used.

The Impact of Posterior Wear on Reverse Shoulder Glenoid Fixation

INTRODUCTION

Achieving glenoid fixation with posterior bone loss can be challenging. The purpose of this study was to quantify the impact of two different sizes of posterior glenoid defects (10° and 20°) on reverse shoulder arthroplasty (rTSA) glenoid baseplate fixation and determine if utilizing different sizes of posterior augmented baseplates (8° and 16°) with off-axis reaming provides comparable fixation to using a standard baseplate with different amounts of eccentric reaming.

METHODS

We quantified the impact of 10° and 20° posterior glenoid defects on rTSA baseplate fixation in composite scapulae using the ASTM F2028-14 rTSA glenoid loosening test method. Forty-two total implants (N = 7 for each size defect and for each type of baseplate) were tested at 750 N for 10,000 cycles. Baseplate displacement was measured before and after cyclic loading in the superior-inferior and anterior-posterior directions. Statistical analysis was performed with a two-tailed unpaired Student's t-test (significance defined as p < 0.05) to compare prosthesis displacements relative to each scapula (10° and 20° posterior defects for each type of baseplate versus the non-defect control) before and after cyclic loading.

RESULTS

All glenoid baseplates remained well-fixed after cyclic loading in composite scapulae without a defect and in scapulae with posterior defects. Increased pre- and post-cyclic displacement was observed with increased posterior defect size and differences in displacement were observed between standard and augmented baseplates. Augmented baseplates were observed to remove significantly less bone than standard baseplates when correcting posterior defects, regardless of size.

DISCUSSION

Both standard baseplates with eccentric reaming and two different sizes of augmented baseplates with off-axis reaming successfully maintained fixation following cyclic loading in composite scapula with corrected 10° and 20° posterior glenoid defects. Augmented glenoids may be more advantageous long-term from a fixation perspective as they preserve more subchondral glenoid bone due to the minimal reaming occurring by the off-axis method. Mid and long-term clinical follow-up comparisons of outcomes are necessary between these two techniques.

Posterior glenoid wear in total shoulder arthroplasty: eccentric anterior reaming is superior to posterior augment

BACKGROUND

Uncorrected glenoid retroversion during total shoulder arthroplasty may lead to an increased likelihood of glenoid prosthetic loosening. Augmented glenoid components seek to correct retroversion to address posterior glenoid bone loss, but few biomechanical studies have evaluated their performance.

QUESTIONS/PURPOSES

We compared the use of augmented glenoid components with eccentric reaming with standard glenoid components in a posterior glenoid wear model. The primary outcome for biomechanical stability in this model was assessed by (1) implant edge displacement in superior and inferior edge loading at intervals up to 100,000 cycles, with secondary outcomes including (2) implant edge load during superior and inferior translation at intervals up to 100,000 cycles, and (3) incidence of glenoid fracture during implant preparation and after cyclic loading.

METHODS

A 12°-posterior glenoid defect was created in 12 composite scapulae, and the specimens were divided in two equal groups. In the posterior augment group, glenoid version was corrected to 8° and an 8°-augmented polyethylene glenoid component was placed. In the eccentric reaming group, anterior glenoid reaming was performed to neutral version and a standard polyethylene glenoid component was placed. Specimens were cyclically loaded in the superoinferior direction to 100,000 cycles. Superior and inferior glenoid edge displacements were recorded.

RESULTS

Surviving specimens in the posterior augment group showed greater displacement than the eccentric reaming group of superior (1.01 ± 0.02 [95% CI, 0.89-1.13] versus 0.83 ± 0.10 [95% CI, 0.72-0.94 mm]; mean difference, 0.18 mm; p = 0.025) and inferior markers (1.36 ± 0.05 [95% CI, 1.24-1.48] versus 1.20 ± 0.09 [95% CI, 1.09-1.32 mm]; mean difference, 0.16 mm; p = 0.038) during superior edge loading and greater displacement of the superior marker during inferior edge loading (1.44 ± 0.06 [95% CI, 1.28-1.59] versus 1.16 ± 0.11 [95% CI, 1.02-1.30 mm]; mean difference, 0.28 mm; p = 0.009) at 100,000 cycles. No difference was seen with the inferior marker during inferior edge loading (0.93 ± 0.15 [95% CI, 0.56-1.29] versus 0.78 ± 0.06 [95% CI, 0.70-0.85 mm]; mean difference, 0.15 mm; p = 0.079). No differences in implant edge load were seen during superior and inferior loading. There were no instances of glenoid vault fracture in either group during implant preparation; however, a greater number of specimens in the eccentric reaming group were able to achieve the final 100,000 time without catastrophic fracture than those in the posterior augment group.

CONCLUSIONS

When addressing posterior glenoid wear in surrogate scapula models, use of angle-backed augmented glenoid components results in accelerated implant loosening compared with neutral-version glenoid after eccentric reaming, as shown by increased implant edge displacement at analogous times.

CLINICAL RELEVANCE

Angle-backed components may introduce shear stress and potentially compromise stability. Additional in vitro and comparative long-term clinical followup studies are needed to further evaluate this component design.

Reverse Shoulder Arthroplasty Prosthesis Design Classification System

Multiple different reverse total shoulder arthroplasty (rTSA) prosthesis designs are available in the global marketplace for surgeons to perform this growing procedure. Subtle differences in rTSA prosthesis design parameters have been shown to have significant biomechanical impact and clinical consequences. We propose an rTSA prosthesis design classification system to objectively identify and categorize different designs based upon their specific glenoid and humeral prosthetic characteristics for the purpose of standardizing nomenclature that will help the orthopaedic surgeon determine which combination of design configurations best suit a given clinical scenario. The impact of each prosthesis classification type on shoulder muscle length and deltoid wrapping are also described to illustrate how each prosthesis classification type impacts these biomechanical parameters.

The Subscapularis-Sparing Approach in Humeral Head Replacement

INTRODUCTION

Failure of the subscapularis repair can be detrimental to patient outcome and shoulder function in shoulder replacement surgery. This report details an approach to resurfacing the humeral head that preserves the majority of the subscapularis attachment to the humerus, allowing a more rapid rehabilitation and minimizing post-operative subscapularis insufficiency.

METHODS

In this approach, only the inferior 30% to 50% of the subscapularis tendon is detached from the humerus, leaving the critical superior aspect of the tendon attached to the lesser tuberosity. In a previous study, we evaluated this approach in 43 patients. Nineteen had postoperative magnetic resonance imaging (MRI), and 24 patients had ultrasound (US) evaluation. Physical examination included belly press and lift-off tests; follow-up included visual analog scale (VAS), American Shoulder and Elbow Surgeons (ASES), Constant, UCLA, Rowe, and SF-12 scores.

RESULTS

All patients had a minimum 2-year follow-up (range 2 to 6, average 4). All patients had subscapularis strength equal to the opposite side as measured by lift-off, belly press, and bear hug tests. Average postoperative scores included ASES, 74.4; Constant, 78.3; UCLA, 27; Rowe, 81.7; and VAS, 2.2; SF-12 averages all showed statistically significant improvement except for general health, which showed improvement approaching significance. All had an intact subscapularis tendon attachment as evaluated by either MRI or US imaging. None had atrophy in the muscle belly.

CONCLUSIONS

The subscapularis-sparing, minimally-invasive approach to the glenohumeral joint provides adequate exposure for shoulder replacement surgery and provides a decreased risk of postoperative failure (rupture or atrophy) of the subscapularis tendon.

Prosthesis design and placement in reverse total shoulder arthroplasty

The management of irreparable rotator cuff tears associated with osteoarthritis of the glenohumeral joint has long been challenging. Reverse total shoulder arthroplasty (RSA) was designed to provide pain relief and improve shoulder function in patients with severe rotator cuff tear arthropathy. While this procedure has been known to reduce pain, improve strength and increase range of motion in shoulder elevation, scapular notching, rotation deficiency, early implant loosening and dislocation have attributed to complication rates as high as 62%. Patient selection, surgical approach and post-operative management are factors vital to successful outcome of RSA, with implant design and component positioning having a significant influence on the ability of the shoulder muscles to elevate, axially rotate and stabilise the humerus. Clinical and biomechanical studies have revealed that component design and placement affects the location of the joint centre of rotation and therefore the force-generating capacity of the muscles and overall joint mobility and stability. Furthermore, surgical technique has also been shown to have an important influence on clinical outcome of RSA, as it can affect intra-operative joint exposure as well as post-operative muscle function. This review discusses the behaviour of the shoulder after RSA and the influence of implant design, component positioning and surgical technique on post-operative joint function and clinical outcome.

Patient-specific targeting guides compared with traditional instrumentation for glenoid component placement in shoulder arthroplasty: a multi-surgeon study in 70 arthritic cadaver specimens

HYPOTHESIS AND BACKGROUND

The purpose of this study was to compare the accuracy of patient-specific guides for total shoulder arthroplasty (TSA) with traditional instrumentation in arthritic cadaver shoulders. We hypothesized that the patient-specific guides would place components more accurately than standard instrumentation.

MATERIALS AND METHODS

Seventy cadaver shoulders with radiographically confirmed arthritis were randomized in equal groups to 5 surgeons of varying experience levels who were not involved in development of the patient-specific guidance system. Specimens were then randomized to patient-specific guides based off of computed tomography scanning, standard instrumentation, and anatomic TSA or reverse TSA. Variances in version or inclination of more than 10° and more than 4 mm in starting point were considered indications of significant component malposition.

RESULTS

TSA glenoid components placed with patient-specific guides averaged 5° of deviation from the intended position in version and 3° in inclination; those with standard instrumentation averaged 8° of deviation in version and 7° in inclination. These differences were significant for version (P = .04) and inclination (P = .01). Multivariate analysis of variance to compare the overall accuracy for the entire cohort (TSA and reverse TSA) revealed patient-specific guides to be significantly more accurate (P = .01) for the combined vectors of version and inclination. Patient-specific guides also had fewer instances of significant component malposition than standard instrumentation did.

CONCLUSION

Patient-specific targeting guides were more accurate than traditional instrumentation and had fewer instances of component malposition for glenoid component placement in this multi-surgeon cadaver study of arthritic shoulders. Long-term clinical studies are needed to determine if these improvements produce improved functional outcomes.

Understanding and Controlling Cost in Total Joint Arthroplasty

Total joint arthrosplasty (TJA) is both a commonly performed successful intervention and an expensive procedure.As our population ages, the expense of these interventions is expected to grow and hence its impact on healthcare costs will also grow. To ensure that TJA is available to all those who would benefit, it is incumbent that healthcare providers control the cost of these procedures. As orthopaedic surgeons, we must be at the forefront of this effort. The purpose of this review is to outline strategies to control or even decrease TJA cost without negatively affecting outcomes.This concept is at the center of value-based medicine and must guide our decision-making processes.

Can the ream and run procedure improve glenohumeral relationships and function for shoulders with the arthritic triad?

BACKGROUND

The arthritic triad of glenoid biconcavity, glenoid retroversion, and posterior displacement of the humeral head on the glenoid is associated with an increased risk of failure of total shoulder joint replacement. Although a number of glenohumeral arthroplasty techniques are being used to manage this complex pathology, problems with glenoid component failure remain. In that the ream and run procedure manages arthritic pathoanatomy without a glenoid component, we sought evidence that this procedure can be effective in improving the centering of the humeral head contact on the glenoid and in improving the comfort and function of shoulders with the arthritic triad without the risk of glenoid component failure.

QUESTIONS/PURPOSES

We asked, for shoulders with the arthritic triad, whether the ream and run procedure could improve glenohumeral relationships as measured on standardized axillary radiographs and patient-reported shoulder comfort and function as recorded by the Simple Shoulder Test.

METHODS

Between January 1, 2006 and December 14, 2011, we performed 531 primary anatomic glenohumeral arthroplasties for arthritis, of which 221 (42%) were ream and run procedures. Of these, 30 shoulders in 30 patients had the ream and run procedure for the arthritic triad and had two years of clinical and radiographic follow-up. These 30 shoulders formed the basis for this case series. The average age of the patients was 56 ± 8 years; all but one were male. Two of the 30 patients requested revision to total shoulder arthroplasty within the first year after their ream and run procedure because of their dissatisfaction with their rehabilitation progress. For the 28 shoulders not having had a revision, we determined on the standardized axillary views before and after surgery the glenoid type, glenoid version (90° minus the angle between the plane of the glenoid face and the plane of the body of the scapula), and location of the humeral contact point with respect to the anteroposterio dimension of the glenoid (the ratio of the distance from the anterior glenoid lip to the contact point divided by the distance between the anterior and posterior glenoid lips). We also recorded the patient's self-assessed shoulder comfort and function before and after surgery using the 12 questions of the Simple Shoulder Test.

RESULTS

For the 28 unrevised shoulders the mean followup was 3.0 years (range, 2-9.2 years). In these patients, the ream and run procedure resulted in improved centering of the humeral head on the face of the glenoid (preoperative: 75% ± 7% posterior; postoperative: 59% ± 10% posterior; mean difference 16% [95% CI, 13%-19%]; p < 0.001), notably this improved centering was achieved without a significant change in the glenoid version. Patient-reported function was improved (preoperative Simple Shoulder Test: 5 ± 3, postoperative Simple Shoulder Test: 10 ± 4, mean difference 5 [95% CI, 4-6], p < 0.001).

CONCLUSIONS

For shoulders with the arthritic triad, the ream and run procedure can provide improvement in humeral centering on the glenoid and in patient-reported shoulder comfort and function without the risk of glenoid component failure. In that ream and run is a new procedure, substantial additional clinical research with long-term follow-up is needed to define specifically the shoulder characteristics, the patient characteristics and the technical details that are most likely to lead to durable improvements in the comfort and function of shoulders with the challenging pathology known as the arthritic triad.

LEVEL OF EVIDENCE

Level IV, therapeutic study.

Report: Osteocyte enhancement function of bisphosphonates in prosthetic replacement

Aseptic loosening after prosthetic replacement is the primary cause of shortened service life and lowered stability of prosthesis, and increased revision rate after joint replacement. Factors of causing the loosening of joint prosthesis include mechanical factors and biological factors. The mechanical effect of bisphosphonates (BP) is quite obvious, which can enhance osteocyte function, accelerate the generation of new bone and lower bone resorption activity of osteoclast and macrophage. In animal experiment and adjuvant therapy of patients after joint replacement, BP also shows up the functions of reducing osteolysis induced by wear debris, preventing stress shielding and interface fretting and enhancing bone density. This paper elaborated the mechanism of BP adjusting bone metabolism, and analyzed the action principle and the vital function of it in prosthetic replacement. It has proved that BP can effectively reduce the early peri-prosthesis bone absorption after total hip replacement and improve bone mass peri-prosthesis. It is currently the significant choice of preventing bone lose of peri-prosthesis after operation.

The TESS reverse shoulder arthroplasty without a stem in the treatment of cuff-deficient shoulder conditions: clinical and radiographic results

BACKGROUND

Reverse total shoulder arthroplasty (RSA) is a recent concept that enables good functional outcomes in cases of massive rotator cuff tear and cuff tear arthropathy. Design parameters influence the functional results and complications. The purpose of this study is to present the results of a novel RSA, the Total Evolutive Shoulder System (TESS; Biomet, Warsaw, IN, USA), based on a reverse corolla without a stem.

METHODS

We enrolled 101 patients with 105 RSAs in a prospective study, with a minimum follow-up period of 24 months. The analysis concerned 91 RSAs in 87 patients (61 men and 26 women), with a mean age of 73 years, at a mean follow-up of 41 months (range, 24-69 months).

RESULTS

Ninety-six percent of patients rated their satisfaction as good or excellent. Mean flexion was 143° (range, 90°-170°), and mean external rotation was 39° (range, 20°-70°). The Constant score improved from 40 points preoperatively to 68 points at last follow-up (P < .001). The mean American Shoulder and Elbow Surgeons score was 24 points. The mean neck-shaft angle was 154° (range, 142°-165°). Inferior scapular notching occurred in 17 cases (19%). The notching rate was higher when the glenometaphyseal angle increased (P < .001), when the inferior tilt decreased (P = .003), and when the neck-shaft angle increased. There was no evidence of component loosening.

CONCLUSION

TESS RSA provided encouraging midterm results with favorable outcomes and a low rate of complications. The stemless TESS with a reverse corolla is a reliable, less invasive system.

Reverse shoulder arthroplasty using an implant with a lateral center of rotation: outcomes, complications, and the influence of experience

Reverse shoulder arthroplasty (RSA) has revolutionized treatment of arthritis and rotator cuff insufficiency and is performed using implants with either a medial or a lateral center of rotation. We conducted a study of the outcomes and the effect of surgeon learning after the first 60 consecutive lateral-center-of-rotation RSAs implanted by a single surgeon unaffiliated with the design team for this particular reverse shoulder prosthesis. At minimum 2-year followup, mean improvements in active forward elevation, abduction, and external rotation were 69°, 55°, and 23°, respectively; mean active internal rotation improved significantly as well (P < .001 for all). Mean Simple Shoulder Test (SST) scores improved from 1.8 (range, 0-6) to 6.9 (range, 0-12) (P < .0001), and mean final American Shoulder and Elbow Surgeons score was 72 (range, 27-100). Final radiographs showed scapular notching in 5 shoulders (11%). Gains in SST scores, active forward elevation, and active abduction were lower for the first 15 cases than for the next 45 cases, and 5 of the 8 reoperations were performed after the first 15 cases. Overall improvements in active motion and self-assessed shoulder function in this series are comparable to those previously reported by the design team. Experience with RSA appears to influence efficacy, but the learning curve may not be as steep as previously reported.

Quantifying opportunities for hospital cost control: medical device purchasing and patient discharge planning

OBJECTIVES

To quantify the potential reduction in hospital costs from adoption of best local practices in supply chain management and discharge planning.

STUDY DESIGN

We performed multivariate statistical analyses of the association between total variable cost per procedure and medical device price and length of stay, controlling for patient and hospital characteristics.

METHODS

Ten hospitals in 1 major metropolitan area supplied patient-level administrative data on 9778 patients undergoing joint replacement, spine fusion, or cardiac rhythm management (CRM) procedures in 2008 and 2010. The impact on each hospital of matching lowest local market device prices and lowest patient length of stay (LOS) was calculated using multivariate regression analysis controlling for patient demographics, diagnoses, comorbidities, and implications.

RESULTS

Average variable costs ranged from $11,315 for joint replacement to $16,087 for CRM and $18,413 for spine fusion. Implantable medical devices accounted for a large share of each procedure's variable costs: 44% for joint replacement, 39% for spine fusion, and 59% for CRM. Device prices and patient length-of-stay exhibited wide variation across hospitals. Total potential hospital cost savings from achieving best local practices in device prices and patient length of stay are 14.5% for joint replacement, 18.8% for spine fusion;,and 29.1% for CRM.

CONCLUSIONS

Hospitals have opportunities for cost reduction from adoption of best local practices in supply chain management and discharge planning.

Glenoid perforation does not affect the short-term outcomes of pegged all-polyethylene implants in total shoulder arthroplasty

BACKGROUND

The glenoid vault can be perforated during pegged glenoid preparation in total shoulder arthroplasty. The clinical implications of glenoid vault perforation, however, are unknown. The purpose of this study was to determine the effects of perforation of the glenoid during total shoulder arthroplasty on clinical and radiographic outcomes.

MATERIALS AND METHODS

Eighteen patients with known intraoperative glenoid perforations were prospectively identified and compared with 34 patients matched by age, gender, diagnosis, and arm dominance during the same period. Patients were evaluated with multiple outcome scores. Radiographs were evaluated for glenoid lucency immediately postoperatively and at final follow-up.

RESULTS

Average follow-up was 28.1 months for the perforated group and 31.2 months for the matched controls. Both groups had significant improvements in outcome scores postoperatively. American Shoulder and Elbow Surgeons scores increased from 39.8 to 91.0 (P < .001) in the perforated group and from 36.9 to 82.6 (P < .001) in the control group. Constant scores increased from 24.4 to 77.4 (P < .001) in the perforated group and from 36.9 to 75.6 (P < .001) in the control group. Ninety-four percent of the perforated group and 80% of the matched controls were satisfied or very satisfied with their result (P = .896). The presence and number of perforations were not related to the American Shoulder and Elbow Surgeons score (P = .549), Constant score (P = .154), or radiographic lucency grade (P = .584).

CONCLUSIONS

Glenoid perforation during pegged glenoid preparation in total shoulder arthroplasty does not seem to have an adverse effect on clinical or radiographic outcomes at an average of 2 years of follow-up.

Correction of acquired glenoid bone loss in osteoarthritis with a standard versus an augmented glenoid component

BACKGROUND

The magnitude and anatomic consequences of pathologic acquired glenoid retroversion and posterior bone loss that can be surgically corrected with a standard versus an augmented glenoid component have not been studied extensively in a surgical patient population.

MATERIALS AND METHODS

Twenty-nine patients with glenohumeral osteoarthritis, acquired posterior bone loss, and increased retroversion were studied by use of a three-dimensional computer surgical simulation. For each case, amount of medialization was measured as the linear distance from the lateral aspect of the glenoid vault model to the center of the articular implant surface. Simulation of implant placement at 0° or 6° was performed with use of a standard glenoid having a uniform thickness and an asymmetric thickness augmented component.

RESULTS

An increased amount of medialization was seen with the standard glenoid, 8.3 ± 4.1 mm, compared with 3.8 ± 3.3 mm with use of the augmented glenoid implant (P < .001). When glenoid retroversion was corrected to 0°, pathologic version was shown to have strong and significant relationship to the amount of medialization for both the standard (R(2) = 0.825) and augmented (R(2) = -0.68) glenoid implant. There was an increased ability to correct greater amounts of pathologic version with less medialization by use of an augmented step glenoid compared with a standard anchor peg glenoid.

DISCUSSION

Correction of moderate to severe glenoid retroversion by asymmetric reaming cannot always be done with use of a standard component, and if it is done, it will result in greater medialization of the joint line. Use of an augmented component can allow complete correction of retroversion and minimize the effect of medialization.