CT navigation has been shown to improve component positioning in total shoulder arthroplasty. The technique can be useful in achieving strong initial fixation of the metal backed glenoid in reverse shoulder arthroplasty. We report a 61 years male patient who underwent reverse shoulder arthroplasty for rotator cuff arthropathy. CT navigation was used intraoperatively to identify best possible glenoid bone and to maximize the depth of the fixation screws that anchor the metaglene portion of the metal backed glenoid component. Satisfactory positioning of screws and component was achieved without any perforation or iatrogenic fracture in the scapula. CT navigation can help in maximizing the purchase of the fixation screws that dictate the initial stability of the glenoid component in reverse shoulder arthroplasty. The technique can be extended to improve glenoid component position [version and tilt] with the availability of appropriate software.
Computer-assisted surgery; CT navigation; reverse shoulder arthroplasty; rotator cuff arthropathy
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.
Total shoulder arthroplasty (TSA) is successful in providing pain relief and functional improvements for patients with shoulder arthritis. Outcomes are directly correlated with implant position and fixation, which ultimately affects wear and longevity. Metal-backed glenoid components were introduced as an alternative to the standard cemented glenoid fixation. Early loosening and cavitary glenoid bone loss has been reported as a major complication associated with these metal-backed glenoids, which presents the surgeon with a challenging revision situation. Furthermore, failure of bilateral TSA in patients with metal-backed glenoids is extremely rare. We present two patients with early failure of bilateral TSA secondary to loosening of the metal-backed glenoids. Both patients had significant glenoid bone loss and were treated with four different types of revision techniques. A description of treatments and outcomes of both patients are reported along with the simple shoulder test and American Shoulder and Elbow Surgeons scores. One patient underwent revision to bilateral reverse prosthesis and experienced a much-improved outcome in comparison to the patient revised to a hemiarthroplasty and resection arthroplasty, for each shoulder respectively. In patients who present with failed TSA, revision to a reverse prosthesis with or without staged glenoid bone graft should be considered as an option of treatment. It is also important to rule out infection with intraoperative tissue biopsy before proceeding to revision surgery. However, in patients with catastrophic glenoid bone loss, both hemiarthroplasty and resection arthroplasty can provide an alternative treatment option, but they are associated with a poorer functional outcome and pain relief.
Custom reverse; hemiarthroplasty; illiac crest bone graft; reverse shoulder arthroplasty; revision; total shoulder arthroplasty
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.
rheumatoid arthritis; rheumatoid shoulder; shoulder joint; prosthesis; shoulder prosthesis; shoulder arthroplasty; total shoulder prosthesis; humeral head prosthesis; hemiarthroplasty; glenoid component; loosening; outcome measurement; rotator cuff
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.
Version; inclination; morphology
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.
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.
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°.
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.
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.
Total shoulder arthroplasty; Glenoid component; Hybrid glenoid; Radiolucent lines; Glenoid loosing; Glenoid component failure
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.
revision shoulder arthroplasty; glenoid; loosening; reimplantation
To evaluate the correlation between radiographic parameters and functional assessments of patients with osteoarthritis of the shoulder who underwent shoulder arthroplasty and to describe the functional outcomes of this procedure in our institution.
We evaluated 21 patients (22 shoulders) who underwent shoulder arthroplasty between 1998 and 2010 and with a minimum follow-up of 12 months. Clinical evaluation was performed using the Constant-Murley scale, UCLA, EVA and by measuring the active motion. We analysed preoperative (distance between the top of the head and the humerus and the acromion, superior migration, neck angulation, medial "offset", subluxation, glenoid erosion) and postoperative radiographic parameters (rod inclination, migration of components and loosening).
Patients showed significant improvement in all parameters: flexion (p = 0.0083), abduction (p = 0.0266), external rotation (p = 0.0062), Constant-Murley (p = 0.0001 ), UCLA (p <0.0001) and VAS (p = 0.0002). The superior migration of the humerus showed a significant correlation with UCLA and Constant-Murley scores (p = 0.0480 and p = 0.0110, respectively). The other radiographic parameters showed no correlation with the clinical outcomes.
The superior migration of the humerus is related to worse clinical scores. Level of Evidence IV, Case Series.
Osteoarthritis; Glenohumeral joint; Arthroplasty
Background and purpose
Humeral resurfacing has shown promising results for osteoarthritis, but revisions for glenoid erosion have been reported frequently. We investigated the hypothesis that preoperative glenoid wear and postoperative progress of glenoid erosion would influence the clinical outcome.
We reviewed 61 resurfacing hemiarthroplasties (55 patients) for primary osteoarthritis. 6 patients were lost to follow-up and 5 had undergone revision arthroplasty. This left 50 shoulders in 44 patients (mean age 66 years) that were followed for mean 30 (12–44) months. Complications, revisions, and the age- and sex-related Constant score were assessed. Radiographs were evaluated for loosening and glenoid erosion according to Walch.
Of the 50 shoulders that were functionally assessed, the average age- and sex-related Constant score was 73%. In patients with preoperative type-B2 glenoids, at 49% it was lower than in type-A1 glenoids (81%, p = 0.03) and in type-B1 glenoids (84%, p = 0.02). The average age- and sex-related Constant score for patients with type-A2 glenoids (60%) was lower than for type-A1 and -B1 glenoids and higher than for type-B2 glenoids, but the differences were not statistically significant. In the total population of 61 shoulders, the radiographs showed postoperative glenoid erosion in 38 cases and no humeral prosthetic loosening. Revision arthroplasty was performed in 11 cases after 28 (7–69) months. The implant size had no statistically significant influence on the functional outcome. The size was considered to be adequate in 28 of the 50 functionally assessed shoulders. In 21 cases, the implant size was too large and in 1 case it was too small.
We found frequent postoperative glenoid erosion and a high rate of revision arthroplasty after humeral resurfacing for primary osteoarthritis. Oversizing of the implants was common, but it had no statistically significant influence on the functional outcome. Inferior results were found in the presence of increased eccentric preoperative glenoid wear. Total shoulder arthroplasty should be considered in these patients.
The success of Total Shoulder Arthroplasty (TSA) is believed to depend on the restoration of the natural anatomy of the joint and a key development has been the introduction of modular humeral components to more accurately restore the patient’s anatomy. However, there are no peer-reviewed studies that have reported the degree of glenoid component mal-position achieved in clinical practice and the clinical outcome of such mal-position. The main purpose of this study was to assess the accuracy of glenoid implant positioning during TSA and to relate it to the radiological (occurrence of radiolucent lines and osteolysis on CT) and clinical outcomes.
68 TSAs were assessed with a mean follow-up of 38+/−27 months. The clinical evaluation consisted of measuring the mobility as well as of the Constant Score. The radiological evaluation was performed on CT-scans in which metal artefacts had been eliminated. From the CT-scans radiolucent lines and osteolysis were assessed. The positions of the glenoid and humeral components were also measured from the CT scans.
Four position glenoid component parameters were calculated The posterior version (6°±12°; mean ± SD), the superior tilt (12°±17°), the rotation of the implant relative to the scapular plane (3°±14°) and the off-set distance of the centre of the glenoid implant from the scapular plane (6±4 mm). An inferiorly inclined implant was found to be associated with higher levels of radiolucent lines while retroversion and non-neutral rotation were associated with a reduced range of motion.
this study demonstrates that glenoid implants of anatomic TSA are poorly positioned and that this malposition has a direct effect on the clinical and radiological outcome. Thus, further developments in glenoid implantation techniques are required to enable the surgeon to achieve a desired implant position and outcome.
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.
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.
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°.
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.
Glenoid component failure is the most common complication of total shoulder arthroplasty. It can be correlated with failure of the component itself to resist wear and deformation, failure of fixation or failure of the glenoid bone. Anchor Peg Glenoid component (Depuy®) seems to have a higher bone fixation in biomechanical canine model: it is a all-polyethylene, concave component with one circumferentially fluted, central, interference-fit peg and three small cemented peripheral pegs.
Materials and methods
We realized a prospective study of Anchor Peg total shoulder arthroplasty, included 27 patients suffering from primary arthrosis or arthritis, without rotator cuff tear. A clinical and radiographic evaluation was performed at 3 months, 1 and 2 years; a CT scan was made in postoperative and analyzed central peg’s bone integration 1 year later.
Improvement of postoperative Constant score and radiographic good results were correlated with satisfactory subjective results reported by patients. We observed radiolucent lines under glenoid component in 3 cases. Twenty-six CT scans were available at 1 year: it showed complete bone integration around the central peg in 21 cases and partial peripheral bone integration in four cases. Only one patient had any tissue integration around the peg, probably because of his implantation near cortical bone of scapular spine.
Long-term result of arthroplasty is correlated with glenoid durable fixation to underlying bone: this study shows higher fixation of glenoid component with bone integration of central peg. However, these results will have to be confirmed in a later revision.
Shoulder arthroplasty; Pegged glenoid component; Bone ingrowth; CT scan; Radiolucency
In this investigation, patients with atraumatic posterior instability of the shoulder were appraised in order to evaluate the effectiveness of glenoid osteotomy in the correction of excessive retroversion and flatness of the glenoid. In a series of 32 patients, 17 with posterior instability had no history of trauma. Posterior glenoid osteotomy was performed to correct excessive retroversion and to deepen the glenoid; 95% were re-examined after 5 years. In 81% the results were rated as good or excellent (Constant-Murley and Rowe scores), only 12,5% having had a recurrence. The glenoid could be deepened and on average the angle could be altered from −9.35° to −4,62°. In comparison, 50 volunteers had average angles of −4,4°, thus differing significantly from the preoperative group. Twenty-five per cent of the patiens showed postoperative degenerative changes in the glenohumeral joint. The study shows that excessive retroversion and flatness of the glenoid in persons with atraumatic posterior instability can be successfully treated by a posterior glenoid osteotomy. Nevertheless, the high rate of postoperative degenerative changes must be taken into account.
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.
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.
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).
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.
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.
Glenoid; Osteoarthritis; Shoulder; Total shoulder arthroplasty; Uncemented metal back
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.
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.
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.
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.
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.
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.
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.
The results support the theory that glenoid inclination may be a risk factor for rotator cuff pathology.
shoulder; glenoid; rotator cuff; stochastic; modeling
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.