Optimizing the glenoid contribution to the stability of a humeral hemiarthroplasty without a prosthetic glenoid

The effect of eccentric glenoid reaming in reverse shoulder artrhoplasty for glenohumeral osteoarthritis

Background

The objective of this study was to evaluate the abilitiy of eccentric reaming in reverse total shoulder arthroplasty (RSA), in patients with glenohumeral osteoarthritis (GHOA), to correct preoperative glenoid retroversion and to compare with cuff tear arthopaty (CTA) cases.

Methods

Fifty-nine patients who underwent RSA with GHOA or CTA diagnosis between 2013 and 2022 and who had pre- and postoperative computed tomography scans were included in the study. Preoperative glenoid version and postoperative glenoid component versions of 17 patients with GHOA and 40 patients with CTA were measured by Friedman method.

Results

The median preoperative glenoid versions in GHOA and CTA groups were measured as 16° and 4° retroverted respectively (p < 0.01). The median postoperative glenoid component versions in GHOA and CTA groups were 5° and 3° retroverted respectively (p = 0.09). The version change differences between the two groups varied significantly (p < 0.01).

Conclusions

GHOA is related with higher preoperative glenoid retroversion compared to CTA. However; with eccentric glenoid reaming, adequate version correction and similar postoperative glenoid version can be achieved in GHOA compared to CTA when performing a RSA.

Level of evidence

Level III. Retrospective study. Treatment study.

Hemiarthroplasty versus total shoulder arthroplasty in B2 glenoids with an intact rotator cuff: a long-term matched cohort analysis

Background

Walch B2 glenoids present unique challenges to the shoulder arthroplasty surgeon, particularly in young, active patients who may wish to avoid the restrictions typically associated with an anatomic total shoulder arthroplasty (TSA). Long-term data are limited when comparing hemiarthroplasty (HA) and TSA for patients with an intact rotator cuff. The purpose of our study was to compare the long-term outcomes of HA vs. TSA in a matched analysis of patients with B2 glenoids, primary osteoarthritis (OA), and an intact rotator cuff.

Methods

A retrospective review was performed of all patients who underwent HA or TSA between January 2000 and December 2011 at a single institution. Inclusion criteria were primary OA, Walch B2 glenoid morphology, an intact rotator cuff intraoperatively, at least 2 years of clinical follow-up, or revision within 2 years of surgery. Fifteen HAs met inclusion criteria and were matched 1:2 with 30 TSAs using age, sex, body mass index, and implant selection. Clinical outcomes including range of motion (ROM), visual analog scale (VAS) for pain, subjective shoulder value score, American Shoulder and Elbow Surgeons (ASES) score, complications, and revisions were recorded. Postoperative radiographs were reviewed to assess for stem loosening, humeral head subluxation, glenoid loosening, and glenoid erosion.

Results

A total of 15 HAs and 30 TSAs met inclusion criteria at a mean follow-up of 9.3 years. The mean age at the time of surgery was 60.2 years for HA and 65.4 years for TSA (P = .08). Both cohorts had significant improvements in ROM, subjective shoulder value, and VAS pain scores (P < .001). TSA had higher postoperative ASES scores compared to HA (P = .03) and lower postoperative VAS pain scores (P = .03), although the decrease in pain from preoperatively to final follow-up was not significantly different between HA and TSA (P = .11). HAs were more likely to have posterior humeral subluxation (P < .001) and stem lucencies (P = .02). Revisions occurred in 11.1% of the cohort with no difference for HA and TSA (P = .73).

Conclusions

At nearly 10 years of follow-up, HA and TSA both showed significant improvements in ROM and pain when performed for primary glenohumeral OA in B2 glenoids with intact rotator cuffs. Compared to HA, TSAs had less posterior humeral subluxation, less stem lucencies, higher ASES scores, and lower postoperative VAS pain scores. However, our study failed to demonstrate a difference in ROM, complication, or revision rates between HA and TSA.

The Anatomy of Glenoid Concavity-Bony and Osteochondral Assessment of a Stability-Related Parameter

Glenoid concavity is a crucial factor for glenohumeral stability. However, the distribution of this stability-related parameter has not been focused on in anatomical studies. In this retrospective study, computed tomography (CT) data and tactile measurements of n = 27 human cadaveric glenoids were analyzed with respect to concavity. For this purpose, the bony and osteochondral shoulder stability ratio (BSSR/OSSR) were determined based on the radius and depth of the glenoid shape in eight directions. Various statistical tests were performed for the comparison of directional concavity and analysis of the relationship between superoinferior and anteroposterior concavity. The results proved that glenoid concavity is the least distinctive in anterior, posterior, and anterosuperior direction but increases significantly toward the superior, anteroinferior, and posteroinferior glenoid. The OSSR showed significantly higher concavity than the BSSR for most of the directions considered. Moreover, the anteroposterior concavity is linearly correlated with superoinferior concavity. The nonuniform distribution of concavity indicates directions with higher stability provided by the anatomy. The linear relationship between anteroposterior and superoinferior concavity may motivate future research using magnetic resonance imaging (MRI) data to optimize clinical decision-making toward more personalized treatment of glenoid bone loss.

Shoulder Hemiarthroplasty with Nonprosthetic Glenoid Arthroplasty: The Ream-and-Run Procedure

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Glenoid component wear and loosening are the principal failure modes of anatomic total shoulder arthroplasty (aTSA).

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The ream-and-run (RnR) procedure is an alternative glenohumeral arthroplasty for patients who wish to avoid the risks and limitations of a prosthetic glenoid component.

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During the RnR procedure, the arthritic glenoid is conservatively reamed to a single concavity, while the prosthetic humeral component and soft tissues are balanced to provide both mobility and stability of the joint.

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The success of the RnR procedure depends on careful patient selection, preoperative education and engagement, optimal surgical technique, targeted rehabilitation, and close postoperative communication between the surgeon and the patient.

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While the RnR procedure allows high levels of shoulder function in most patients, the recovery can be longer and more arduous than with aTSA.

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Patients who have undergone an RnR procedure occasionally require a second closed or open procedure to address refractory shoulder stiffness, infection, or persistent glenoid-sided pain. These second procedures are more common after the RnR than with aTSA.

Management of the B2 Glenoid in Glenohumeral Osteoarthritis

The Walch B2 glenoid is characterized by a biconcave glenoid deformity, acquired glenoid retroversion, and posterior humeral head subluxation. Surgical reconstruction of the B2 glenoid remains a challenge. Surgical management options include arthroscopic debridement, hemiarthroplasty, anatomic total shoulder arthroplasty with eccentric reaming, bone grafting or augmented glenoid implants, and reverse total shoulder arthroplasty. Multiple factors dictate the optimal surgical management strategy.. This article describes each of these techniques and presents the current available literature in an effort to guide evidence-based decisions in the surgical management of the B2 glenoid deformity.

Survivorship of Hemiarthroplasty With Concentric Glenoid Reaming for Glenohumeral Arthritis in Young, Active Patients With a Biconcave Glenoid

INTRODUCTION

Hemiarthroplasty with concentric glenoid reaming (known as "ream and run") may be an option for treating glenohumeral arthritis in younger patients with a biconcave glenoid. The goal of this study was to evaluate early results of this technique.

METHODS

Two senior, fellowship-trained shoulder surgeons (G.R.W. and M.D.L.) performed a retrospective review of 23 patients (24 shoulders) with a biconcave glenoid and end-stage degenerative glenohumeral arthritis treated with hemiarthroplasty with concentric glenoid reaming. The mean patient age at the time of surgery was 50 years. We evaluated the Penn Shoulder Score (PSS), Single Assessment Numeric Evaluation (SANE) score, and Simple Shoulder Test (SST) score or the time to revision surgery.

RESULTS

Twenty-four humeral hemiarthroplasties with concentric glenoid reaming were performed in 23 patients. Twenty patients (21 shoulders) reached the end point of 2-year follow-up or revision surgery. Six shoulders (25%) required revision surgery at an average of 2.7 years (range, 0.7 to 7.2 years), and three were lost to follow-up. The remaining 14 patients (15 shoulders) were followed up for an average of 3.7 years (range, 2.3 to 4.9 years). At 2-year follow-up, these 15 shoulders did not require revision surgery and had an average SANE score, PSS, and SST score of 74.5%, 82.9, and 10.4, respectively. Increasing age correlated positively with the SANE score (r = 0.62; P = 0.015), PSS (r = 0.52; P = 0.047), and SST score (r = 0.63; P = 0.012). Early postoperative forward elevation correlated weakly with the PSS (r = 0.24; P = 0.395), and early postoperative external rotation correlated moderately with the PSS (r = 0.53; P = 0.044). Final external rotation correlated moderately with the PSS (r = 0.69; P = 0.005).

DISCUSSION

Modest results were achieved with a hemiarthroplasty and concentric glenoid reaming in young patients with end-stage glenohumeral arthritis and a biconcave glenoid. Younger age and stiffness were associated with worse outcomes. Given the high revision rate and the percentage of patients who had unsatisfactory results, this procedure should be performed only after careful patient selection. Patients who are willing and able to undergo aggressive physical therapy focused on achieving early range of motion are more likely to have a satisfactory outcome after humeral hemiarthroplasty with concentric glenoid reaming.

Quantification of B2 glenoid morphology in total shoulder arthroplasty

BACKGROUND

B2 glenoid morphology is challenging to address with shoulder reconstruction. Deformity often renders current techniques inadequate, necessitating compromises that limit long-term implant durability. The purpose of this study was to perform in vivo measurements of glenoid deformity to better appreciate the orientation of the B2 biconcavity demarcation and erosion that surgeons face intraoperatively.

MATERIALS AND METHODS

A consecutive 106 total shoulder arthroplasty cases for primary glenohumeral osteoarthritis were studied. We classified glenoids by direct visualization and noted lines of biconcavity demarcation and erosion in B2s. We then calculated the "angle of erosion" as that between the back side of the unsupported, smooth-backed glenoid sizer disk and the neoglenoid. We obtained depth measurements throughout the reaming process and monitored subchondral bone.

RESULTS

We classified 43 of 106 glenoids (41%) as B2. A biconcavity demarcation line between the paleoglenoid and the neoglenoid was present, on average, from the 1-o'clock to the 7-o'clock position for a left shoulder. Mean depth of erosion was 4.4 mm, occurring at 114° on a Cartesian coordinate system for a left shoulder. The mean angle of erosion was 18° (range, 8°-43°). Despite reaming, 20 of 43 B2 glenoids (47%) had incompletely supported components at final seating.

CONCLUSIONS

Arthritic B2 glenoids are common, and their maximal erosion is usually posteroinferior. Use of standard glenoid components to reconstruct them may require significant subchondral bone removal to achieve complete bone support. Alternatively, as a compromise, maintenance of subchondral bone in these cases requires implanting components with incomplete bony support.

Self-assessed and radiographic outcomes of humeral head replacement with nonprosthetic glenoid arthroplasty

BACKGROUND

Active and young patients who place frequent demands on their shoulder present a treatment dilemma when glenohumeral arthritis progresses to a point at which surgical intervention is considered. Humeral head replacement with nonprosthetic glenoid arthroplasty ("ream-and-run") has been proposed to address the limitations of total shoulder arthroplasty and hemiarthroplasty in this population. Several reports from a single institution have shown substantial improvement in self-assessed comfort and function after this procedure. However, to the best of our knowledge, no clinical results pertaining to this technique have been reported from other institutions.

METHODS

Hemiarthroplasty with nonprosthetic glenoid arthroplasty was performed in 17 patients with a minimum 2-year follow-up. Patients were clinically evaluated preoperatively and postoperatively with physical examination, Simple Shoulder Test (SST), American Shoulder and Elbow Surgeons score, visual analog scale, and standardized radiographs. Preoperative radiographs and patient demographics were assessed for correlation with outcome measures.

RESULTS

Improvement of >30% of preoperative SST score was noted in 14 of 17 patients at a mean follow-up of 3.9 years (range, 2.0-6.8 years). SST score improved from mean 3.2 ± 3.1 preoperatively to 10.0 ± 2.6 at latest follow-up (P < .0001). American Shoulder and Elbow Surgeons score improved from mean 42 ± 23 to 90 ± 13 (P < .0001). Male patients had higher SST scores (P = .03) and greater external rotation (P = .03) at latest follow-up.

CONCLUSIONS

Nonprosthetic glenoid arthroplasty demonstrated results that correlate with prior data published by the center at which the procedure was initially described. Patients with concentric glenoid morphology preoperatively did not demonstrate results superior to those of patients with eccentric glenoids.

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.

Three-dimensional computed tomography scan evaluation of the pattern of erosion in type B glenoids

BACKGROUND

Type B glenoids according to Walch are subclassified into a group with no posterior erosion (B1) and a group with important posterior erosion (B2) based on 2-dimensional axial computed tomography (CT) scan images. Three-dimensional (3D) CT scan reconstruction seems to improve the accuracy of the measurement of erosion because of its independence from positional errors. The aim is to quantify the direction and amount of posterior erosion of type B glenoids using a reproducible 3D measuring technique.

METHODS

We performed 3D reconstruction of 72 type B glenoids (24 type B1 glenoids and 48 type B2 glenoids) using Mimics (Materialise, Haasrode, Belgium). The native glenoid plane and intermediate glenoid plane were determined by use of 3-Matic (Materialise). The normal glenoid version, eroded retroversion, and difference in retroversion were measured. Next, the maximum erosion and its orientation were quantified.

RESULTS

There was always minimum erosion of 1.7 mm, and the mean erosion was 4.2 mm. There was a significant difference between the mean erosion in type B1 glenoids (3.5 mm) and type B2 glenoids (4.5 mm) (P = .019). The mean orientation of the erosion was mostly to the posteroinferior side (119°; SD, 26.8). There was a significant difference between the mean orientation in type B1 glenoids (132°; SD, 25.2) and type B2 glenoids (113°; SD, 25.5) (P = .004).

CONCLUSIONS

With the use of this newly developed reproducible measuring technique, the maximum erosion in type B glenoids can be adequately quantified. All glenoids showed signs of important erosion. Because the orientation of the maximum erosion in type B1 glenoids is situated more inferiorly, the 2-dimensional CT scan technique can be insufficient to evaluate this erosion.

Current concepts in the surgical management of primary glenohumeral arthritis with a biconcave glenoid

Glenoid morphology has an important impact on outcomes and complication rates after shoulder arthroplasty for primary glenohumeral arthritis. The B2 glenoid, or a biconcave glenoid with posterior humeral head subluxation, in particular has been associated with a poorer outcome with shoulder arthroplasty compared with other glenoid types. A variety of techniques may be used to address the bone deficiency and instability seen with this glenoid type. Studies suggest that total shoulder arthroplasty may have a reasonable result in the short term but be associated with a high complication rate in the mid term because of recurrence of instability and early glenoid loosening when neoglenoid retroversion is greater than 27° or posterior humeral head subluxation is greater than 80%. Particularly in older patients with a substantial B2 deformity, primary reverse shoulder arthroplasty may be a more predictable means of addressing bone deficiency and restoring stability.

Addressing glenoid bone deficiency and asymmetric posterior erosion in shoulder arthroplasty

Glenoid bone deficiency and eccentric posterior wear are difficult problems faced by shoulder arthroplasty surgeons. Numerous options and techniques exist for addressing these issues. Hemiarthroplasty with concentric glenoid reaming may be a viable alternative in motivated patients in whom glenoid component failure is a concern. Total shoulder arthroplasty has been shown to provide durable pain relief and excellent function in patients, and numerous methods and techniques can assist in addressing bone loss and eccentric wear. However, the ideal amount of version correction in cases of severe retroversion has not yet been established. Asymmetric reaming is a commonly used technique to address glenoid version, but correction of severe retroversion may compromise bone stock and component fixation. Bone grafting is a technically demanding alternative for uncontained defects and has mixed clinical results. Specialized glenoid implants with posterior augmentation have been created to assist the surgeon in correcting glenoid version without compromising bone stock, but clinical data on these implants are still pending. Custom implants or instruments based on each patient's unique glenoid anatomy may hold promise. In elderly, sedentary patients in whom bone stock and soft-tissue balance are concerns, reverse total shoulder arthroplasty may be less technically demanding while still providing satisfactory pain relief and functional improvements.

Glenoid articular conformity affects stress distributions in total shoulder arthroplasty

BACKGROUND

The stress applied to the glenoid component in total shoulder arthroplasty (TSA) remains an important concern because of the risk of wear and loosening. The purpose of this study was to determine the stress pattern in the glenoid component with 3 different surface designs.

METHODS

Computer models of 9 scapulae of patients scheduled for TSA were created from computerized tomography images. Each glenoid was virtually reamed, and 3 different glenoid component designs (conforming, nonconforming, and hybrid) were placed. Using finite element analysis, superior translation of the humeral head was modeled. Maximum stress and shear stress were measured at 3 different locations in the glenoid component: center, transition, and superior regions.

RESULTS

All 3 designs showed a similar level of maximum stress at the center and transition regions, while the maximum stress at the superior periphery was significantly higher in the conforming design than in the other 2 designs (P = .0017). The conforming design showed significantly higher shear stress at the superior periphery (P < .0001).

DISCUSSION

Stress from periphery loading is higher than from the center and transition region regardless of component design and is highest in the conforming design. The stress at the transition region of the hybrid design was not higher than the other 2 designs. The hybrid design has favorable characteristics based on its low stress at the periphery and greater contact area with the humeral head at the center.

LEVEL OF EVIDENCE

Basic Science Study, Biomechanical Computer Simulation Study.

The prognosis for improvement in comfort and function after the ream-and-run arthroplasty for glenohumeral arthritis: an analysis of 176 consecutive cases

BACKGROUND

Knowledge of the factors affecting the prognosis for improvement in function and comfort with time after shoulder arthroplasty is important to clinical decision-making. This study sought to identify some of these factors in 176 consecutive patients undergoing the ream-and-run procedure.

METHODS

The time course for improvement in patient function and comfort was determined for the entire group as well as for subsets by sex, age, diagnosis, preoperative function, and surgery date. Patients having repeat surgery were analyzed in detail.

RESULTS

Shoulder comfort and function increased progressively after the ream-and-run procedure, reaching a steady state by approximately twenty months. The shoulders in 124 patients with at least two years of follow-up were improved by a minimal clinically important difference. The shoulders in sixteen patients with at least two years of follow-up were not improved by the minimal clinically important difference. Twenty-two patients had repeat procedures, but only seven had revision to a total shoulder arthroplasty. Fourteen patients did not have either a known revision arthroplasty or two years of follow-up. The best prognosis was for male patients over the age of sixty years, with primary osteoarthritis, no prior surgical procedures, a preoperative score on the simple shoulder test of ≥5 points, and surgery after 2004. Repeat surgical procedures were more common in patients who had a greater number of surgical procedures before the ream-and-run surgery.

CONCLUSIONS

This study is unique in that it characterizes the factors affecting the time course for improvement in shoulder comfort and function after a ream-and-run procedure. Improvement occurs after this procedure for at least 1.5 years. This procedure appears to be best suited for an older male patient with reasonable preoperative shoulder function without prior shoulder surgery.

LEVEL OF EVIDENCE

Prognostic Level II. See Instructions for authors for a complete description of levels of evidence.

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.

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.

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.

Nonprosthetic glenoid arthroplasty with humeral hemiarthroplasty and total shoulder arthroplasty yield similar self-assessed outcomes in the management of comparable patients with glenohumeral arthritis

The risk of glenoid component failure has led us to explore nonprosthetic glenoid arthroplasty coupled with humeral hemiarthroplasty, the "ream and run" (R&R) procedure, for the management of glenohumeral arthritis in active patients. We hypothesized that patients having a R&R procedure would have outcomes comparable with those of similar patients having a total shoulder arthroplasty (TSA). A case-matched control study compared 35 consecutive patients (32 men, 3 women) with an average age of 56 years, after R&R with matched controls having TSA. The respective Simple Shoulder Test (SST) scores for the R&R and TSA groups were 4.5 and 4.0 before surgery, 7.8 and 9.6 at 12 months, 8.3 and 10.2 at 18 months, 8.9 and 9.4 at 24 months, 9.4 and 9.6 at 30 months, and 9.5 and 10.0 at 36 months. The "ream and run" procedure can offer similar functional recovery to patients with total shoulder arthroplasty, although the time to recovery may be longer.

Shoulder arthroplasty: the socket perspective

Although much attention has been directed to the development of the humeral components used in shoulder arthroplasty, the major unsolved challenge lies on the glenoid side of the articulation. This challenge arises from difficulties resisting eccentric loading and providing adequate implant-bone fixation. Current glenoid component designs use polyethylene and polymethyl methacrylate and are prone to loosening, plastic deformation, particulate debris, and third-body wear. Metal-backed components present further challenges, and results have generally been disappointing. There is interest in biologic resurfacing procedures, including the interposition of fascia, capsule, or meniscal allograft and nonprosthetic glenoid arthroplasty, or what has become known as the "ream-and-run" procedure. Despite encouraging results, important questions remain unanswered about these procedures. However, each may warrant further exploration with a goal of providing an effective and durable approach to glenoid arthritis that avoids the risks associated with polymethyl methacrylate and polyethylene.

Treatment of glenohumeral arthritis with a hemiarthroplasty. Surgical technique

BACKGROUND

Glenohumeral hemiarthroplasty is well established as a method to treat glenohumeral arthritis. This study was designed to report longer-term results and to provide a decision model to assist surgeons in achieving successful outcomes. Our selection strategy for hemiarthroplasty included shoulders with (1) a concentric glenoid with eburnated bone, (2) a nonconcentric glenoid that could be converted to a smooth concentric surface, and (3) a humeral head centered within the glenoid after soft-tissue balancing.

METHODS

Fifty-seven consecutive patients (sixty-four shoulders) who had osteoarthritis of the glenohumeral joint, without advanced disease in the glenoid, were treated with hemiarthroplasty. In each instance, a modular prosthesis was implanted. Clinical assessment was performed preoperatively and at one-year intervals postoperatively for at least five years with use of patient self-assessment instruments, including the American Shoulder and Elbow Surgeons questionnaire, the Simple Shoulder Test, and a visual analog pain scale. A detailed radiographic analysis was performed to determine the presence of glenohumeral subluxation, periprosthetic radiolucency, and glenoid bone loss.

RESULTS

Forty-three patients (fifty shoulders) were followed for a minimum of five years (mean, 7.5 years). Of the remaining fourteen patients (fourteen shoulders), ten were lost to follow-up, three had died, and one was excluded. For the Simple Shoulder Test, and for every visual analog scale measure, the results at the final follow-up evaluation were significantly better than the preoperative results (p < 0.0001 for each). The mean Simple Shoulder Test score at the time of the final follow-up was 9.4 positive responses compared with 9.7 positive responses at the two-year evaluation (p = 0.32), and the mean visual analog scale score for pain was 18.6 points compared with 14.9 points at two years (p = 0.45). Radiographic analysis showed the majority of stems had either no lucency or lucencies only near the tip of the stem. Glenoid bone loss and subluxation improved postoperatively, and the results were maintained at the final follow-up evaluation.

CONCLUSIONS

Shoulder hemiarthroplasty provides sustained good-to-excellent pain relief and functional improvement at five to ten years postoperatively in carefully selected patients with osteoarthritis.

Biomechanische Evaluation der glenohumeralen Stabilität durch Muskelkraftvektoranalyse

OBJECTIVES

The aim of the study was to quantify the decrease in glenohumeral stability following a global rotator cuff tear and to evaluate the effect of a decreased glenoid inclination angle through analysis of muscle force vectors in a computer model.

MATERIAL AND METHODS

The lines of action of eight shoulder muscles were integrated into a standard geometric model. Muscle force magnitudes were estimated based on physiological cross-sectional area and normalized electromyographic activity. The magnitude and elevation angle of the resultant force vector was calculated at 0, 30, 60, and 90 degrees of abduction. A rotator cuff tear was simulated by reduction of the corresponding muscle force vectors.

RESULTS

At 0 and 30 degrees of glenohumeral abduction a global rotator cuff tear showed a resultant force vector pointing outside the glenoid. In the computer model, decreasing the inclination angle of the glenoid by 30 degrees increased the stability in rotator cuff-deficient shoulders.

CONCLUSIONS

The results of this study provide a biomechanical rationale for clinical complications of global rotator cuff tear such as superior humeral head translation. The decreased glenoid inclination simulated in the computer model may represent a biomechanical basis for the development of new operative techniques to treat global rotator cuff tears.

Direct injection of blood into the labrum enhances the stability provided by the glenoid labral socket

We tested the hypothesis that the stabilizing function of the labrum can be enhanced by inflating it with blood. In 6 fresh cadaveric glenoids, the anteroinferior stability provided by the glenoid was quantitated by measuring the maximal angle between the glenoid centerline and the direction of the force applied via a ball in the glenoid before the ball dislocated from the glenoid. This stability angle was measured for each of 4 different applied loads. These measurements were repeated after the anteroinferior labrum was augmented by the injection of fresh blood. Injection augmentation of the labrum significantly increased the measured stability angles in 5 of 6 specimens. The 1 outlier had a partial labral tear. The mean increase in stability for all 6 glenoids ranged from 19% to 30% for the different test loads. Labral injection with blood may be a useful adjunct in the surgical management of glenohumeral instability.