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Background and purpose It is unclear whether the increase in temperature during cement curing may cause osteonecrosis, leading to loosening of the glenoid component in shoulder arthroplasty. We therefore analyzed the temperature during implantation of cemented glenoid implants.

Methods 8 keeled and 8 pegged glenoids were implanted in standardized fashion in 8 pairs of scapulas. Temperature and pressure sensors were implanted at the bone-cement interface in the glenoid. Real-time measurements were made of temperature and pressure within the glenoid vault.

Results In no case was the temperature reached high enough to endanger the surrounding bone. The mean increase in temperature was 5° (0.5–6.9) in the keeled group and 2.7° (1.7–3.6) in the pegged group. The mean maximum pressure in the keeled group was 50 kPa (20–100) and in the pegged group it was 113 kPa (60–181). Both differences were statistically significant.

Interpretation The temperatures that occur during implantation of cemented components are low and probably not high enough to cause osteonecrosis in the surrounding bone.

Correct identification of the center point of the glenoid surface guides glenoid component placement. It is unknown whether the center point on the glenoid surface corresponds to the center of the glenoid vault at the medial extent of the glenoid prosthesis. We reviewed 20 consecutive computed tomography scans obtained preoperatively in patients with primary osteoarthritis. A glenoid center point was chosen on the glenoid surface and then projected back into the glenoid vault along the scapular axis and perpendicular to glenoid inclination. The difference from the projection of the glenoid surface center point to the center point at a 1.5-cm depth into the glenoid vault was then measured. The mean deviation of the glenoid center point at a depth of 1.5 cm from the center point at the glenoid articular surface was 1.7 mm anterior and 3.9 mm inferior. The most common deviation of the center point of the glenoid vault at the projected medial limit of the glenoid prosthesis was slightly anterior and inferior to the center point on the glenoid surface. Identifying the center of the glenoid surface coupled with alignment of the glenoid prosthesis in neutral version and anatomic inclination provides a reliable means to guide placement of glenoid components.

Total shoulder arthroplasty is commonly considered a good option for treatment of the rheumatoid shoulder. However, when the rotator cuff and glenoid bone stock are not preserved, the clinical outcome of arthroplasty in the rheumatoid patients remains unclear. Aim of the study is to explore the prognostic value of multiple preoperative and peroperative variables in total shoulder arthroplasty and shoulder hemiarthroplasty in rheumatoid patients. Clinical Hospital for Special Surgery Shoulder score was determined at different time points over a mean period of 6.5 years in 66 rheumatoid patients with total shoulder arthroplasty and 75 rheumatoid patients with shoulder hemiarthroplasty. Moreover, radiographic analysis was performed to assess the progression of humeral head migration and glenoid loosening. Advanced age and erosions or cysts at the AC joint at time of surgery were associated with a lower postoperative Clinical Hospital for Special Surgery Shoulder score. In total shoulder arthroplasty, status of the rotator cuff and its repair at surgery were predictive of postoperative improvement. Progression of proximal migration during the period after surgery was associated with a lower clinical score over time. However, in hemiarthroplasty, no relation was observed between the progression of proximal or medial migration during follow-up and the clinical score over time. Status of the AC joint and age at the time of surgery should be taken into account when considering shoulder arthroplasty in rheumatoid patients. Total shoulder arthroplasty in combination with good cuff repair yields comparable clinical results as total shoulder arthroplasty when the cuff is intact.

During revision total shoulder arthroplasty, bone grafting severe glenoid defects without concomitant reinsertion of a glenoid prosthesis may be the only viable reconstructive option. However, the fate of these grafts is unknown. We questioned the durability and subsidence of the graft and the associated clinical outcomes in patients who have this procedure. We retrospectively reviewed 11 patients with severe glenoid deficiencies from aseptic loosening of a glenoid component who underwent conversion of a total shoulder arthroplasty to a humeral head replacement and glenoid bone grafting. Large cavitary defects were grafted with either allograft cancellous chips or bulk structural allograft, depending on the presence or absence of glenoid vault wall defects, without prosthetic glenoid resurfacing. Clinical outcomes (Penn Shoulder Score, maximum 100 points) improved from 23 to 57 at a minimum 2-year followup (mean, 38 months; range, 24–73 months). However, we observed substantial graft subsidence in all patients, with eight of 11 patients having subsidence greater than 5 mm; the magnitude of graft resorption did not correlate with clinical outcome scores. Greater subsidence was seen with structural than cancellous chip allografts. Bone grafting large glenoid defects during revision shoulder arthroplasty can improve clinical outcome scores, but the substantial resorption of the graft material remains a concern.

Level of Evidence: Level III Prognostic study. See the Guidelines for Authors for a complete description of levels of evidence.

A robust quantification method is essential for inter-subject glenoid comparison and planning of total shoulder arthroplasty. This study compared various scapular and glenoid axes with each other in order to optimally define the most appropriate method of quantifying glenoid version and inclination.

Six glenoid and eight scapular axes were defined and quantified from identifiable landmarks of twenty-one scapular image scans. Pathology independency and insensitivity of each axis to inter-subject morphological variation within its region was tested. Glenoid version and inclination were calculated using the best axes from the two regions.

The best glenoid axis was the normal to a least-square plane fit on the glenoid rim, directed approximately medio-laterally. The best scapular axis was the normal to a plane formed by the spine root and lateral border ridge. Glenoid inclination was 15.7° ± 5.1° superiorly and version was 4.9° ± 6.1°, retroversion.

The choice of axes in the present technique makes it insensitive to pathology and scapular morphological variabilities. Its application would effectively improve inter-subject glenoid version comparison, surgical planning and design of prostheses for shoulder arthroplasty.

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.

Background and purpose

Despite good clinical results with the reverse total shoulder arthroplasty, inferior scapular notching remains a concern. We evaluated 6 different solutions to overcome the problem of scapular notching.

Methods

An average and a “worst case scenario” shape in A-P view in a 2-D computer model of a scapula was created, using data from 200 “normal” scapulae, so that the position of the glenoid and humeral component could be changed as well as design features such as depth of the polyethylene insert, the size of glenosphere, the position of the center of rotation, and downward glenoid inclination. The model calculated the maximum adduction (notch angle) in the scapular plane when the cup of the humeral component was in conflict with the scapula.

Results

A change in humeral neck shaft inclination from 155° to 145° gave a 10° gain in notch angle. A change in cup depth from 8 mm to 5 mm gave a gain of 12°. With no inferior prosthetic overhang, a lateralization of the center of rotation from 0 mm to 5 mm gained 16°. With an inferior overhang of only 1 mm, no effect of lateralizing the center of rotation was noted. Downward glenoid inclination of 0º to 10º gained 10°. A change in glenosphere radius from 18 mm to 21 mm gained 31° due to the inferior overhang created by the increase in glenosphere. A prosthetic overhang to the bone from 0 mm to 5 mm gained 39°.

Interpretation

Of all 6 solutions tested, the prosthetic overhang created the biggest gain in notch angle and this should be considered when designing the reverse arthroplasty and defining optimal surgical technique.

Reconstruction of the anatomy of the proximal humerus is a prerequisite to achieving good long-term clinical results after shoulder arthroplasty. Modern, adjustable prostheses have greater flexibility of inclination, retroversion, and medial and dorsal offset in comparison with older prostheses. Such improvements should allow for better reconstruction of the centre of rotation compared to older prostheses. Reconstruction of the humeral head centre was assessed in 106 modern adjustable (Affinis) and 47 second-generation prostheses. All reconstructions were compared both to the preoperative state and the unoperated shoulder. To describe the pre- and postoperative states, the geometry and position of the humeral head in relation to the glenoid were analysed on patient radiographs. Applying the defined parameters, modern adjustable prostheses showed better reconstruction than second generation prostheses. Parameter values measured in reconstructions using fourth generation prostheses were comparable to those of the unoperated shoulder, but differed significantly from the preoperative state. Second generation prostheses, in contrast, only show non-specific differences in parameter values. This suggests that an approximate reconstruction of normal anatomy can be achieved using a modern fourth generation prosthesis. Reconstruction of the complex anatomy of the proximal humerus is significantly better with modern adjustable prostheses compared to second generation prostheses. Improved clinical outcome can therefore be predicted in a functional and intact rotator cuff. The advantage of using modern prostheses systems over older models is clearly demonstrated in this study.

Glenoid component loosening is one of the most common causes of failed total shoulder arthroplasty. Previous reports indicate that it is desirable to reimplant the glenoid component during revision shoulder arthroplasty. The purpose of our study was to retrospectively evaluate the satisfaction of patients undergoing glenoid revision (reimplantation or resection) following total shoulder replacement specifically for symptomatic glenoid loosening. Twenty-eight shoulders that developed symptomatic glenoid loosening following primary total shoulder arthroplasty were included in the study. Patients were retrospectively evaluated at a minimum of 2 years postoperatively. Patients either underwent resection followed by reimplantation of the glenoid component (13) or resection of the component with or without bone grafting (15). Each patient was evaluated with the UCLA Shoulder Scale and the Constant–Murley Shoulder Assessment. There were seven excellent, 13 good, five fair and three poor results on the UCLA score. Functional outcome scores trended higher in the reimplantation group but were not statistically significant. Both groups reported equal pain relief and satisfaction. Five out of 15 patients underwent arthroscopic resection of the glenoid, and these patients scored as well on the UCLA and Constant scores as the reimplantation group. When symptomatic glenoid loosening is the indication for revision total shoulder replacement, patients tend to achieve good to excellent results. Though functional scores were slightly higher in the reimplantation group, satisfaction was equally high in both groups. Resection, when indicated, should be performed arthroscopically as this improved functional outcome in our series.

Purpose

The purpose of this study is to analyze the morphology of the scapula with reference to the glenoid component implantation in reversed shoulder prosthesis, in order to improve primary fixation of the component.

Methods

Seventy-three 3-dimensional computed tomography of the scapula and 108 scapular dry specimens were analyzed to determine the anterior and posterior length of the glenoid neck, the angle between the glenoid surface and the upper posterior column of the scapula and the angle between the major craneo-caudal glenoid axis and the base of the coracoid process and the upper posterior column.

Results

The anterior and posterior length of glenoid neck was classified into two groups named "short-neck" and "long-neck" with significant differences between them. The angle between the glenoid surface and the upper posterior column of the scapula was also classified into two different types: type I (mean 50°–52°) and type II (mean 62,50°–64°), with significant differences between them (p < 0,001). The angle between the major craneo-caudal glenoid axis and the base of the coracoid process averaged 18,25° while the angle with the upper posterior column of the scapula averaged 8°.

Conclusion

Scapular morphological variability advices for individual adjustments of glenoid component implantation in reversed total shoulder prosthesis. Three-dimensional computed tomography of the scapula constitutes an important tool when planning reversed prostheses implantation.

Asymmetric posterior glenoid wear caused by degenerative glenohumeral arthritis can be addressed by several techniques during total shoulder arthroplasty. The purpose of this study was to evaluate the midterm outcome of a posterior augmented glenoid component to determine the clinical and radiographic outcome, including complications and the need for revision surgery. Between 1995 and 1999, 13 patients (14 shoulders) underwent a shoulder arthroplasty with an augmented glenoid component to treat posterior glenoid bone deficiency. All 14 shoulders had advanced osteoarthritis. The minimum followup for these 13 patients was 2 years (mean, 5 years; range, 2–8 years). The mean age of these patients was 66 years at the time of surgery (range, 52–78 years). The mean active elevation was 160° (range, 120°–180°) and external rotation was 56° (range, 30°–90°). According to a modified Neer result rating system, 36% of patients had an excellent result, 50% a satisfactory result, and 14% an unsatisfactory result. Our results suggest patients undergoing total shoulder arthroplasty with an asymmetric glenoid component for osteoarthritis achieve satisfactory mid-term pain relief and improvement in function; however, instability is not always corrected. The advantage of this component seems marginal, and its use has been discontinued.

Level of Evidence: Level IV, retrospective review. See Guidelines for Authors for a complete description of levels of evidence.

Background

Cuff tear arthropathy is the primary indication for total reverse shoulder arthroplasty. In patients with pseudoparalytic shoulders secondary to irreparable rotator cuff tear, reverse shoulder arthroplasty allows restoration of active anterior elevation and painless shoulder. High rates of glenoid notching have also been reported. We designed a new reverse shoulder arthroplasty with a center of rotation more lateral than the Delta prosthesis to address this problem.

Questions/purposes

Does reduced medialization of reverse shoulder arthroplasty improve shoulder motion, decrease glenoid notching, or increase the risk of glenoid loosening?

Patients and Methods

We retrospectively reviewed 76 patients with 76 less medialized reverse shoulder prostheses implanted for pseudoparalytic shoulder with rotator cuff deficiency between October 2003 and May 2006. Shoulder motion, Constant-Murley score, and plain radiographs were analyzed. Minimum followup was 24 months (mean, 44 months; range, 24–60 months).

Results

The absolute Constant-Murley score increased from 24 to 59, representing an increase of 35 points. The range of active anterior elevation increased by 61°, and the improvement in pain was 10 points. The gain in external rotation with elbow at the side was 15°, while external rotation with 90° abduction increased by 30°. Followup showed no glenoid notching and no glenoid loosening with these less medialized reverse prostheses.

Conclusions

Less medialization of reverse shoulder arthroplasty improves external and medial rotation, thus facilitating the activities of daily living of older patients. The absence of glenoid notching and glenoid loosening hopefully reflects longer prosthesis survival, but longer followup is necessary to confirm these preliminary observations.

Level of Evidence

Level IV, therapeutic study. See Guidelines for Authors for a complete description of levels of evidence.

The uncemented glenoid implants in total anatomical shoulder arthroplasty are likely to be accused of problems like dissociations, secondary rotator cuff tear, and wear of polyethylene (PE). This work is a clinical and radiological prospective review of 143 cases of anatomical total shoulder arthroplasty using a new metal back uncemented glenoid implant (MB) in order to see if this new implant induces those complications. A total of 143 cases were operated between 2003 and 2011. In a first part, the whole series of 143 cases was radiologically studied in order to quantify the lateralisation induced by the MB implant. In a second study, 37 cases had a mean follow-up of 38 months (24–75, mean 32) and served for the clinical and radiological final study. Pre- and postoperative clinical evaluation was done using the Constant–Murley score and the simple shoulder test from Matsen. The final X-rays served to detect an eventual secondary narrowing of the joint space and to analyse the frequency of radio lucent lines (RLL) and loosenings. Despite a small radiological lateralisation in comparison with the normal contralateral side (0.36 cm, p = 0.02), the clinical results after 2 years were similar to the published cemented glenoid implants series but without any RLL, glenoid loosening or joint narrowing. Some dissociations occured in the beginning and definitely eliminated by a design modification of the PE tray. The discussion tried to show that, despite a still short follow-up, this series is encouraging to continue to use this new MB implant. Different applications of the concept of universality and conversion are discussed, this tray been also the support of a glenosphere in reverse arthroplasty.

Background

Scapular notching, prosthetic instability, limited shoulder rotation and loss of shoulder contour are associated with conventional medialized design reverse shoulder arthroplasty. Prosthetic (ie, metallic) lateralization increases torque at the baseplate-glenoid interface potentially leading to failure.

Questions/purposes

We asked whether bony lateralization of reverse shoulder arthroplasty would avoid the problems caused by humeral medialization without increasing torque or shear force applied to the glenoid component.

Patients and Methods

We prospectively followed 42 patients with rotator cuff deficiency treated with bony increased-offset reverse shoulder arthroplasty. A cylinder of autologous cancellous bone graft, harvested from the humeral head, was placed between the reamed glenoid surface and baseplate. Graft and baseplate fixation was achieved using a lengthened central peg (25 mm) and four screws. Patients underwent clinical, radiographic, and CT assessment at a minimum of 2 years after surgery.

Results

The humeral graft incorporated completely in 98% of cases (41 of 42) and partially in one. At a mean of 28 months postoperatively, no graft resorption, glenoid loosening, or postoperative instability was observed. Inferior scapular notching occurred in 19% (eight of 42). The absolute Constant-Murley score improved from 31 to 67. Thirty-six patients (86%) were able to internally rotate sufficiently to reach their back over the sacrum.

Conclusions

Grafting of the glenoid surface during reverse shoulder arthroplasty effectively creates a long-necked scapula, providing the benefits of lateralization. Bony increased-offset reverse shoulder arthroplasty is associated with low rates of inferior scapular notching, improved shoulder rotation, no prosthetic instability and improved shoulder contour. In contrast to metallic lateralization, bony lateralization has the advantage of maintaining the prosthetic center of rotation at the prosthesis-bone interface, thus minimizing torque on the glenoid component.

Level of Evidence

Level IV, therapeutic study. See Guidelines for Authors for a complete description of levels of evidence.

The reverse total shoulder prosthesis provides successful functional outcome in many patients with rotator cuff tear arthropathy. However, scapular notching, a direct consequence of mechanical impingement between the humeral prosthesis and the glenoid, remains a major concern. We presumed a better knowledge of the anatomy of the scapula would enable design or placement modifications to minimize this phenomenon. After establishing a uniform spatial reference system using easy locatable surgical reference points and planes, we analyzed 200 dry bony scapulae and defined the glenoid and infraglenoid anatomy relative to the reference system. The bony rim of the two inferior quadrants of the glenoid forms a semicircle the center of which can be used perioperatively as an easy locatable bony reference point. The infraglenoid tubercle varies in width and length, and can interfere with the humeral part of the reverse prosthesis, creating scapular notching. To avoid notching, we suggest using a convex base plate with a smaller radius than currently used, placing it as low as possible with a 42-mm glenosphere eccentrically assembled to create a posterior offset. If prosthetic overhang cannot be obtained, we suggest removing part of the infraglenoid tubercle.

Background

Superior glenoid inclination, which is a relatively upward facing of the glenoid in the plane of the scapula, has been associated with rotator cuff pathology. Increased glenoid inclination may cause superior humeral head migration, which can cause impingement of the supraspinatus tendon. The purpose of this study was to test the hypothesis that inclination angle affects the probability of superior humeral head migration.

Methods

A three-dimensional model of the glenohumeral joint was developed in which muscle forces were modeled as random variables. Monte Carlo simulation was used to compute the probability that the glenohumeral reaction force was directed such that superior humeral head migration should occur. An electromyogram-driven model was used to estimate shoulder muscle forces in healthy volunteers performing arm elevation.

Findings

The model predicted that the probability of superior humeral head migration increased as glenoid inclination angle was increased. This finding was independent of the assumed shape of the muscle force probability distributions.

Interpretation

The results support the theory that glenoid inclination may be a risk factor for rotator cuff pathology.

The purpose of this prospective study was to describe cementless humeral surface replacement arthroplasty (CHSRA) as a bone preserving treatment option for patients with fixed anterior glenohumeral dislocation. Ten patients with post-traumatic fixed anterior glenohumeral dislocation underwent CHSRA with a mean follow-up of 24 months. All patients were evaluated clinically using the Constant score and with radiographs in two planes. There were two reoperations: one patient developed glenoid erosion and was revised and in another case redislocation occurred. Clinical or radiographical signs of implant loosening were not found. The humeral head centred in the glenoid in nine out of ten cases radiographically. The Constant score increased from 20 points preoperatively to 61 points postoperatively (p < 0.007). CHSRA is a viable treatment option for elderly patients with fixed anterior glenohumeral dislocation and bone defects of the humeral head. Good clinical results and a moderate complication rate were found in the short term.

Glenoid inclination has been associated with rotator cuff tears and superior humeral translation, but the relationship between glenoid inclination and superior humeral translation has not been assessed in-vivo. The objective of this study was to compare glenoid inclination between repaired and contralateral shoulders of unilateral rotator cuff repair patients. As a secondary analysis, we assessed the relationship between glenoid inclination and in-vivo superior humeral translation. Glenoid inclination was measured from patient-specific, CT-based bone models. Glenohumeral joint motion was measured from biplane x-ray images collected during coronal-plane abduction of 21 rotator cuff repair patients. Glenoid inclination was significantly lower for the rotator cuff tear shoulders (90.7°) than the asymptomatic, contralateral shoulders (92.3°, p=0.04). There was no significant correlation between increased glenoid inclination and superior/inferior translation of the uninjured shoulder (p>0.30). This study failed to support the theory that glenoid inclination is responsible for superior humeral translation and the development of subacromial impingement.

Failed shoulder arthroplasty associated with glenoid bony deficiency is a difficult problem. Revision surgery is complex with unpredictable outcome. We asked whether revision shoulder arthroplasty with glenoid bone grafting could lead to good outcome. We retrospectively reviewed 21 patients who underwent glenoid bone grafting using corticocancellous bone grafting or impaction grafting using cancellous bone graft. Three patients underwent revision TSA, five patients hemiarthroplasty, 10 patients hemiarthroplasty with biologic resurfacing of the glenoid, and three patients revision to reverse TSA. The patients had minimum 25 months followup (average, 45 months; range, 25–92 months). All patients had improvement in their range of motion and the Constant-Murley score. Most improvement occurred in patients with glenoid reimplantation. Patients who underwent revision reverse TSA had improvement in shoulder flexion but decrease in external rotation motion. We conclude revision shoulder arthroplasty with glenoid bone grafting can produce good short-term outcome and glenoid component reinsertion should be attempted whenever possible.

Level of Evidence: Level IV, therapeutic study. See the Guidelines for Authors for a complete description of levels of evidence.

Background

Early failure due to glenoid loosening with anatomic total shoulder arthroplasty in patients with severe rotator cuff deficiency led to the development of the reverse ball-and-socket shoulder prosthesis. The literature reports improved short-term pain and function scores following modern reverse total shoulder arthroplasty (RTSA) in patients with cuff tear arthropathy (CTA).

Questions/purposes

We therefore sought to confirm previously reported short-term improvements in pain, function scores, and range of motion, in patients treated with RTSA for CTA and to identify clinical complications and radiographic notching.

Methods

We retrospectively reviewed 67 patients who underwent 71 primary RTSAs for CTA. The average age was 74 years (range, 54–92 years). All were preoperatively and postoperatively assessed using Constant-Murley and American Shoulder and Elbow Society (ASES) scores. We identified complications and examined radiographs for notching. The minimum followup was 12 months (average, 24 months; range, 12–58 months).

Results

Average Constant-Murley scores improved from 28 preoperatively to 62 postoperatively. Average ASES scores improved from 26 to 76. Subjective Shoulder Value (SSV) improved from 23 to 77. Active forward flexion improved from 61° preoperatively (range, 0°–137°) to 121° postoperatively (range, 52°–170°). Active external rotation was not affected. Thirty-five of the 71 shoulders (49%) showed radiographic notching. The overall complication rate was 23%. No patient required reoperation. One patient required closed reduction of a perioperative dislocation.

Conclusions

RTSA for CTA results in functional improvement, with a low complication rate. However, the longevity of the device is currently unknown.

Level of Evidence

Level IV, therapeutic study. See Guidelines for Authors for a complete description of levels of evidence.

Introduction

Throughout the field of orthopedic surgery, there has been a trend toward using smaller incisions and implants that preserve as much normal anatomy as possible. The use of bone sparing technology, such as partial and full surface replacements of the humeral head, while attractive in younger patients, does not allow the best exposure for proper glenoid replacement. Additionally, there are other situations when the use of surface replacements is contraindicated. There are also patients with an existing total elbow replacement or a humeral malunion or deformity in which a traditional long-stem component would not fit. For these reasons, a mini-stem humeral component for total shoulder arthroplasty was developed.

In this study, we hypothesized that total shoulder replacement using the mini-stem humeral component could provide low complication rates and good to excellent results, as measured by postoperative Constant–Murley and UCLA shoulder scores at minimum 2 years postoperatively.

Materials and Methods

This was a retrospective review of the first 49 mini-stem shoulder replacements (47 patients) for primary osteoarthritis. There were 26 male and 23 female patients. UCLA Shoulder Score and Constant Murley Scores were obtained on all patients at a minimum of 2 years postoperatively (average 29 months; range 24–43 months). Radiographs were interpreted by a musculoskeletal radiologist. Intraoperative blood loss was documented as was postoperative pain using a visual analog pain scale.

Results

Patients experienced over 90% good to excellent results at minimum 2 year follow up. ROM improved significantly in all parameters. Postoperative UCLA scores at final follow up averaged 27.5 while Constant–Murley scores averaged 91. Small lucent lines (<1 mm) were noted in 11 patients. Five of 49 stems were placed in varus but the postoperative result was not affected in any of these patients. One patient suffered an acute subscapularis rupture that required repair.

Conclusions

This is the first report to document the efficacy of mini-stemmed humeral components used during total shoulder arthroplasty. Our study group showed good to excellent results as well as improvement in range of motion at minimum 2-year follow-up. The results presented in this study are comparable to previous outcomes achieved with conventional length humeral components, and suggest that mini-stem humeral components are an effective option for total shoulder arthroplasty.

Shoulder arthroplasty has been the subject of marked advances over the last few years. Modern implants provide a wide range of options, including resurfacing of the humeral head, anatomic hemiarthroplasty, total shoulder arthroplasty, reverse shoulder arthroplasty and trauma-specific implants for fractures and nonunions. Most humeral components achieve successful long-term fixation without bone cement. Cemented all-polyethylene glenoid components remain the standard for anatomic total shoulder arthroplasty. The results of shoulder arthroplasty vary depending on the underlying diagnosis, the condition of the soft-tissues, and the type of reconstruction. Total shoulder arthroplasty seems to provide the best outcome for patients with osteoarthritis and inflammatory arthropathy. The outcome of hemiarthroplasty for proximal humerus fractures is somewhat unpredictable, though it seems to have improved with the use of fracture-specific designs, more attention to tuberosity repair, and the selective use of reverse arthroplasty, as well as a shift in indications towards internal fixation. Reverse shoulder arthroplasty has become extremely popular for patients with cuff-tear arthropathy, and its indications have been expanded to the field of revision surgery. Overall, shoulder arthroplasty is a very successful procedure with predictable pain relief and substantial improvements in motion and function.

Fixation failure of glenoid components is the main cause of unsuccessful total shoulder arthroplasties. The characteristics of these failures are still not well understood, hence, attempts at improving the implant fixation are somewhat blind and the failure rate remains high. This lack of understanding is largely due to the fundamental problem that direct observations of failure are impossible as the fixation is inherently embedded within the bone.

Twenty custom made implants, reflecting various common fixation designs, and a specimen set-up was prepared to enable direct observation of failure when the specimens were exposed to cyclic superior loads during laboratory experiments. Finite element analyses of the laboratory tests were also carried out to explain the observed failure scenarios.

All implants, irrespective of the particular fixation design, failed at the implant–cement interface and failure initiated at the inferior part of the component fixation. Finite element analyses indicated that this failure scenario was caused by a weak and brittle implant–cement interface and tensile stresses in the inferior region possibly worsened by a stress raiser effect at the inferior rim.

The results of this study indicate that glenoid failure can be delayed or prevented by improving the implant/cement interface strength. Also any design features that reduce the geometrical stress raiser and the inferior tensile stresses in general should delay implant loosening.

Purpose

Failures in total shoulder replacements are often due to aseptic loosening of the glenoid component; the subchondral bone plate is an important factor governing primary fixation of implant materials. Therefore, we investigated characteristic mineralisation patterns of the subchondral bone plate, which demonstrate long-term stress on articular surfaces, age-related changes, postsurgical biomechanical situations and regions of fixation. Using computed tomography osteo-absorptiometry (CT-OAM), these distribution patterns can be demonstrated in vivo. The aim of this study was to investigate the relationship between subchondral bone-plate mineralisation measured with CT-OAM and the mechanical strength measured by indentation.

Methods

A total of 32 cadaverous glenoid cavities were evaluated by CT-OAM and indentation testing. Linear regression was used to compare mineralisation and strength of the subchondral bone plate.

Results

Results showed two patterns of mineralisation distribution. Twenty-eight cavities were related to bicentric distribution pattern and four showed a single maximum. The correlation coefficient between CT-OAM density and subchondral bone-plate strength was determined to be between 0.62 and 0.96 (P < 0.02).

Conclusions

Long-term stress affects not only the subchondral but also the underlying cancellous bone. It therefore can be assumed that mineralisation patterns of the subchondral bone plate continue in cancellous bone. Areas of high density could serve as anchoring locations for orthopaedic implants in resurfacing the glenoid cavity.

The reverse shoulder arthroplasty emerged as a potential solution for those patients who could not be managed effectively with a conventional total shoulder arthroplasty. Grammont revolutionized the design by medializing and distalizing the center of rotation and utilizing a large convex glenoid surface and concave humeral component with a neck-shaft angle of 155°. This design has been highly successful in cuff deficient shoulders, and indications continue to broaden. Many mid-term studies have improved upon the early encouraging results. Long-term studies are starting to emerge, demonstrating good survivorship, but progressive functional and radiographic deterioration continue to be concerning. Careful patient selection and attention to appropriate technique are required to reduce the current high rate of complications. New prosthesis designs are continuing to develop to address some of these limitations.