Dissociation of the glenoid component in cementless total shoulder arthroplasty

Biomechanical Evaluation of Recurrent Dissociation of Modular Humeral Prostheses

The purpose of the study was to evaluate the force and torque required to dissociate a humeral head from the unimplanted modular total shoulder replacement system from different manufacturers and to determine if load and torque to dissociation are reduced in the presence of bodily fluids. Impingement, taper contamination, lack of compressive forces, and interference of taper fixation by the proximal humerus have all been reported as possible causes for dissociation. Experimental values determined in this research were compared with literature estimates of dissociation force of the humeral head under various conditions to gain more understanding of the causes of recurrent dissociations of the humeral head. This study examined biomechanical properties under dry and wet conditions under clinically practiced methods. Mean load to dissociation (1513 N ± 508 N) was found to be greater than that exerted by the activities of daily living (578 N) for all implants studied. The mean torque to dissociation was (49.77 N·m ± 19.07 N·m). Analysis of R² correlation coefficients and p-values (α = 0.05) did not show any significant correlation between dry/bovine, dry/wet, or wet/bovine for load, displacement, or torsional stiffness in the majority of tests performed. Wetting the taper with water or bovine serum did not reduce the dissociation force to a statistically significant degree. Torque and lack of compressive forces at the rotator cuff may be the cause of dissociation at values less than those of activities of daily living. Torque data are provided by this study, but further research is needed to fully appreciate the role of torque in recurrent dissociations.

Clinical and radiologic outcomes of the second-generation Trabecular Metal™ glenoid for total shoulder replacements after 2-6 years follow-up

BACKGROUND

A porous tantalum glenoid component for total shoulder replacements was introduced in 2003 to promote biologic ingrowth. However, reports of component failure prompted design modifications. The purpose of this study is to present the largest series to date, of TSR with the second-generation Trabecular Metal™ glenoid component.

METHOD

A radiologic and clinical evaluation of the second-generation TM glenoid was conducted in consecutive cases of 76 shoulders (66 patients) with a mean follow-up of 43.2 months (range 24-72 months). Pre-operative VAS score, patient self-assessed ASES score, active shoulder range of motion, and radiologic assessment were recorded. Patients were recalled for latest follow-up clinical and radiologic evaluation.

RESULTS

On latest follow-up, the mean VAS scores (pre-op: 6.4-latest: 0.9) and ASES scores (pre-op: 36.9-latest: 88.5) improved. Active range of motion improved in all planes. There was no report of glenoid component migration, loosening, or humeral stem subsidence. The incidence of non-progressive radiolucency in the glenoid was 6.6 % (Franklin 1: 3 cases, Franklin 2: 2 cases). Post-operative complications involved dislocation (n = 2) which were reduced in ED, post-operative stiffness (n = 1), transient axillary nerve neuropraxia (n = 1), and supraspinatus tear which underwent arthroscopic repair at 16 months post-op. There were no revision surgeries for implant loosening nor glenoid component fracture at the peg-base plate junction.

CONCLUSIONS

The modifications established in the second-generation TM glenoid resulted to improve early to mid-term survivorship and clinical outcomes in TSR, with promise of long-term implant stability through bony ingrowth.

LEVEL OF EVIDENCE

Level IV, case series, treatment study.

Acute Failure of a Glenoid Component in Anatomic Shoulder Arthroplasty

Glenoid loosening is the most common cause of failure in primary total shoulder arthroplasty (TSA) and often occurs years after the initial surgery. It is rare for a glenoid component to fail acutely. Several case reports of complete glenoid dissociation appear in the literature. It is important to report these failures to identify technical errors or component design flaws to improve outcomes in TSA. In this case report, we present an unrecognized acute failure of a cemented hybrid glenoid component at the time of surgery.

Indications and outcomes of shoulder arthroscopy after shoulder arthroplasty

BACKGROUND

Arthroscopy is a widely used intervention in the treatment of a variety of shoulder conditions. Arthroscopy has also been selectively used in symptomatic patients after shoulder arthroplasty. The purpose of this systematic review was to determine indications for shoulder arthroscopy in patients after shoulder arthroplasty and to report patient outcomes after these procedures.

MATERIALS AND METHODS

The electronic databases MEDLINE, EMBASE, and PubMed were searched and screened in duplicate for studies involving shoulder arthroscopy in shoulder arthroplasty patients. A full-text review of eligible studies was conducted in duplicate, and references were searched using predetermined inclusion and exclusion criteria.

RESULTS

The review included 11 studies containing 84 patients. All were Level IV evidence. The most common indications for shoulder arthroscopy in the setting of shoulder arthroplasty were pain or loss of range of motion without a clear diagnosis, suspected periprosthetic infection, and rotator cuff assessment. Although 92% of patients were satisfied with the procedure and standardized shoulder scores increased in all studies that reported them, 44% of patients still went on to additional revision surgery after arthroscopy.

CONCLUSIONS

Shoulder arthroscopy in patients after arthroplasty is most frequently used as a diagnostic tool; however, it has utility in treating a number of predetermined pathologies. Despite the low sample size and quality of evidence in our review, patient satisfaction after arthroscopy is high because standardized outcome scores improve, and the risk of complications is low. However, a high percentage of patients who receive arthroscopy later require further surgery.

Catastrophic failure of a low profile metal-backed glenoid component after total shoulder arthroplasty

Context:

The longevity of the glenoid component in total shoulder arthroplasty (TSA) continues to be problematic. All polyethylene glenoid components have been most widely used, but loosening rates with time and the need for revision has resulted in high-profile metal-backed components with the potential for a more stable prosthesis bone interface and liner exchange. High revision rates in the high profile metal backed designs led us to evaluate a low profile metal backed component.

Aims:

To examine the rate and mode of failure of a TSA in a single surgeon consecutive series that has been identified by the Australian National Joint Replacement Registry to have a higher than anticipated rate of revision.

Materials and Methods:

This is a single surgeon retrospective consecutive series of 51 arthroplasties undertaken in 50 patients (18 males and 32 females) with an average age of 70.4 ears (range 51-90) and mean follow-up of 5.5 years (range 3.7-8.1).

Results:

We observed a very high (29%) rate of revision of the metal-backed glenoid components in this series. The primary mode of failure was glenoid baseplate nonintegration which with a well-fixed central cage screw led to bone resorption and implant breakage or disassembly.

Conclusion:

Analysis of the mode of failure of implants identified by robust registries is essential for the development of new prostheses and the pursuit of prosthesis longevity. This low profile metal backed prosthesis has been withdrawn, but without a published mechanism of failure. We feel that any prosthesis withdrawal should be accompanied by appropriate published mechanisms to prevent future component design errors based on similar design problems.

Metal-Backed Glenoid Components Have a Higher Rate of Failure and Fail by Different Modes in Comparison with All-Polyethylene Components: A Systematic Review

BACKGROUND

Glenoid component failure is a common and serious complication of total shoulder arthroplasty. The purpose of this study was to evaluate published evidence on whether metal backing lessens the rate of glenoid component failure.

METHODS

A comprehensive systematic review yielded twenty-one studies on radiolucency, radiographic failure, and revision after arthroplasty with metal-backed glenoid components and twenty-three studies with all-polyethylene components. Our analysis included data on 1571 metal-backed and 3035 all-polyethylene components. The mean duration of follow-up was 5.8 years in the studies with metal-backed components and 7.3 years with all-polyethylene components.

RESULTS

All-polyethylene components had a 42.5% rate of radiolucency compared with 34.9% for metal-backed components (p = 0.0026) and a 21.1% rate of radiographic loosening or failure compared with 16.8% for metal-backed components (p = 0.0005). However, the rate of revision was more than three times higher with metal-backed components (14.0%) than with all-polyethylene components (3.8%, p < 0.0001). Although 77% of the revisions of all-polyethylene components were for loosening, 62% of the revisions of metal-backed components were for other reasons, such as component fracture, screw breakage, component dissociation, polyethylene wear, metal wear, and rotator cuff tear (p < 0.0001).

CONCLUSIONS

The published evidence indicates that metal-backed glenoid components require revision at a significantly higher rate and for different reasons in comparison with all-polyethylene components.

LEVEL OF EVIDENCE

Therapeutic Level IV. See Instructions for Authors for a complete description of levels of evidence.

The evaluation of the failed shoulder arthroplasty

As the incidence of shoulder arthroplasty continues to rise, the orthopedic shoulder surgeon will be increasingly faced with the difficult problem of evaluating a failed shoulder arthroplasty. The patient is usually dissatisfied with the outcome of the previous arthroplasty as a result of pain, but may complain of poor function due to limited range of motion or instability. A thorough and systematic approach is necessary so that the most appropriate treatment pathway can be initiated. A comprehensive history and physical examination are the first steps in the evaluation. Diagnostic studies are numerous and include laboratory values, plain radiography, computed tomography, ultrasound imaging, joint aspiration, nuclear scans, and electromyography. Common causes of early pain after shoulder arthroplasty include technical issues related to the surgery, such as malposition or improper sizing of the prosthesis, periprosthetic infection, neurologic injury, and complex regional pain syndrome. Pain presenting after a symptom-free interval may be related to chronic periprosthetic infection, component wear and loosening, glenoid erosion, rotator cuff degeneration, and fracture. Poor range of motion may result from inadequate postoperative rehabilitation, implant-related factors, and heterotopic ossification. Instability is generally caused by rotator cuff deficiency and implant-related factors. Unfortunately, determining the cause of a failed shoulder arthroplasty can be difficult, and in many situations, the source of pain and disability is multifactorial.

Fully uncemented glenoid component in total shoulder arthroplasty

BACKGROUND

Loosening of the glenoid component remains the most common problem in total shoulder arthroplasty. It has been described that the round-backed, all-polyethylene components with cemented peg fixation perform better biomechanically and clinically than flat-backed, metal-backed, or keeled components. However, side effects of cementing have been described. We hypothesized that cementing of a specific type of all-polyethylene glenoid component with 3 peripheral pegs and 1 central anchor peg is not necessary to obtain good clinical and radiologic results.

MATERIALS AND METHODS

Thirty-four shoulders (34 patients), with a mean follow-up of 28.3 months, were evaluated clinically with the Constant-Murley score and the SF-12 Health Survey score. The fixation of the glenoid component was evaluated with computed tomography scan.

RESULTS

The Constant-Murley score increased from 40.2 points (range, 13-73 points) preoperatively to 72 points (range, 54-93 points) postoperatively. The SF-12 Physical Component Summary score was 45, and the SF-12 Mental Component Summary score was 50. No signs of loosening were seen around the pegs or glenoid in 30 shoulders. Signs of loosening were seen around the central anchor peg and the peripheral pegs in 4 shoulders. There was no statistical difference between the clinical outcome of patients with and without signs of loosening.

CONCLUSION

The clinical and radiologic evaluation of an uncemented all-polyethylene glenoid is promising, with good clinical results and with no signs of loosening in 88% of the patients on computed tomography scans.

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

BACKGROUND

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

MATERIALS AND METHODS

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

RESULTS

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

CONCLUSION

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

Glenoid or not glenoid component in primary osteoarthritis

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

Chronic locked posterior shoulder dislocation with severe head involvement

Arthroplasty is the treatment of choice for severely damaged humeral heads in chronic locked posterior dislocation of the shoulder. We retrospectively reviewed the results of 12 shoulder arthroplasties (11 patients) between 1999 and 2005. Mean follow-up was 37.4 +/- 16.8 months. Mean postoperative Constant score (CS) was 59.4 +/- 21.6 (normative age and gender-related CS 67.1 +/- 24). There was a significant improvement in range of motion for flexion, abduction and external rotation. There was negative correlation (Pearson's coefficient) between the related CS and number of previous operations, pain and duration of symptoms. One patient underwent revision surgery 36 months postoperatively with polyethylene insert exchange. There were two patients with mild and one with severe migration of the humeral head. Shoulder arthroplasty resulted in good midterm results for this patient group with benefits for range of motion, pain and patient satisfaction.

Sports participation after shoulder replacement surgery

BACKGROUND

Return to sports after total hip or knee replacement surgery has been extensively described. However, the return to general sporting activities after shoulder replacement surgery has not been well documented. With improved implant survivorship, patient expectation of function is high.

PURPOSE

The purpose of this study was to assess the outcome and ability of patients returning to sports after shoulder replacement surgery.

STUDY DESIGN

Case series; Level of evidence, 4.

METHODS

Seventy-five patients (86 shoulder replacements) who participated in sports or recreational activities before surgery were followed for a minimum of 2 years. Their preoperative and postoperative sports participation and level of competition were assessed. The frequency of their activity, modifications in activity, and length of time it took to resume sports participation after the operation were all reviewed.

RESULTS

The mean age at follow-up was 65.5 years (range, 24-88). The average follow-up was 3.7 years (range, 2-9.4). Sixty-four percent of the patients stated that one of the reasons they had the surgery performed was participation in sports. Thirty-four of 48 of these patients (71%) demonstrated an improvement in their ability to play their sport and 50% increased their frequency of participation postoperatively. Softball athletes demonstrated the least favorable return; only 2 of 10 patients returned. Swimming, tennis, and golf were the most popular sports; participants in these sports showed the most favorable improvement and actual return. The mean time to partial return to sports was 3.6 months, and 5.8 months to full participation.

CONCLUSION

Patients are able to successfully return to sports after shoulder arthroplasty. Many returned with improved performance and increased frequency in participation in a timely manner.

Glenoid component failure in total shoulder arthroplasty

Glenoid component failure is the most common complication of total shoulder arthroplasty. Glenoid components fail as a result of their inability to replicate essential properties of the normal glenoid articular surface to achieve durable fixation to the underlying bone, to withstand repeated eccentric loads and glenohumeral translation, and to resist wear and deformation. The possibility of glenoid component failure should be considered whenever a total shoulder arthroplasty has an unsatisfactory result. High-quality radiographs made in the plane of the scapula and in the axillary projection are usually sufficient to evaluate the status of the glenoid component. Failures of prosthetic glenoid arthroplasty can be understood in terms of failure of the component itself, failure of seating, failure of fixation, failure of the glenoid bone, and failure to effectively manage eccentric loading. An understanding of these modes of failure leads to strategies to minimize complications related to prosthetic glenoid arthroplasty.

Improvements in survival of the uncemented Nottingham Total Shoulder prosthesis: a prospective comparative study

Background

The uncemented Nottingham Total Shoulder Replacement prosthesis system (Nottingham TSR) was developed from the previous BioModular^® shoulder prosthesis taking into consideration the causes of the initial implant's failure.

We investigated the impact of changes in the design of Nottingham TSR prosthesis on its survivorship rate.

Methods

Survivorship analyses of three types of uncemented total shoulder arthroplasty prostheses (BioModular^®, initial Nottingham TSR and current Nottingham TSR systems with 11, 8 and 4 year survivorship data respectively) were compared. All these prostheses were implanted for the treatment of disabling pain in the shoulder due to primary and secondary osteoarthritis or rheumatoid arthritis. Each type of the prosthesis studied was implanted in consecutive group of patients – 90 patients with BioModular^® system, 103 with the initial Nottingham TSR and 34 patients with the current Nottingham TSR system.

The comparison of the annual cumulative survivorship values in the compatible time range between the three groups was done according to the paired t test.

Results

The 8-year and 11-year survivorship rates for the initially used modified BioModular^® uncemented prosthesis were relatively low (75.6% and 71.7% respectively) comparing to the reported survivorship of the conventional cemented implants. The 8-year survivorship for the uncemented Nottingham TSR prosthesis was significantly higher (81.8%), but still not in the desired range of above 90%, that is found in other cemented designs. Glenoid component loosening was the main factor of prosthesis failure in both prostheses and mainly occurred in the first 4 postoperative years. The 4-year survivorship of the currently re-designed Nottingham TSR prosthesis, with hydroxylapatite coating of the glenoid baseplate, was significantly higher, 93.1% as compared to 85.1% of the previous Nottingham TSR.

Conclusion

The initial Nottingham shoulder prosthesis showed significantly higher survivorship than the BioModular^® uncemented prosthesis, but lower than expected. Subsequently re-designed Nottingham TSR system presented a high short term survivorship rate that encourages its ongoing use

Self-assessed outcome at two to four years after shoulder hemiarthroplasty with concentric glenoid reaming

BACKGROUND

Active and young individuals with glenohumeral arthritis who are treated with total glenohumeral arthroplasty are at risk for loosening or wear of the prosthetic glenoid component. This study tests the hypothesis that patients with severe glenohumeral arthritis have improvement in self-assessed shoulder comfort and function at two to four years after treatment with the combination of humeral hemiarthroplasty and concentric glenoid reaming without tissue or prosthetic component interposition.

METHODS

Thirty-seven consecutive patients (thirty-eight shoulders), with a mean age of fifty-seven years, who were managed by one surgeon were enrolled in this prospective study. The procedure consisted of an uncemented humeral hemiarthroplasty combined with reaming of the glenoid to a diameter 2 mm larger than that of the prosthetic humeral head. The duration of follow-up ranged from two to four years (average, 2.7 years) for thirty-five shoulders. Self-assessed comfort and function was documented with use of the Simple Shoulder Test, and radiographs were evaluated.

RESULTS

Thirty-two shoulders demonstrated improved comfort and function according to patient self-assessment, one demonstrated no change, and two had worse function following the procedure. The total number of Simple Shoulder Test functions that could be performed increased from 4.7 (of a possible 12.0) before surgery to 9.4 at the time of the final follow-up. The patients demonstrated significant improvement in ten of the twelve individual functions of the Simple Shoulder Test (p < 0.022 to p < 0.00001). With the numbers studied, gender, diagnosis, age, glenoid wear, and preoperative glenoid erosion did not significantly affect final shoulder function or overall improvement. The range of motion was significantly improved for all individuals (p < 0.00001). Radiographically, twenty-two patients had a joint space between the glenoid bone and the humeral prosthesis at the time of final follow-up. These shoulders had significantly better function than those without a preserved joint space (p < 0.017). There were no surgical complications and no revisions to total shoulder arthroplasty.

CONCLUSIONS

At a minimum follow-up of two years, a selected series of patients who had humeral hemiarthroplasty with concentric glenoid reaming for the treatment of glenohumeral arthritis showed significant improvement in self-assessed shoulder comfort and function. Further study, however, is needed before routine application of this procedure can be recommended.

LEVEL OF EVIDENCE

Therapeutic Level IV.

Glenoid vault endosteal dimensions: an anthropometric study with special interest in implant design

An understanding of the morphology of the glenoid is important from the viewpoint of implant design and selection. This study describes the endosteal dimensions and shape of the glenoid and correlates these results with age, gender, and the presence of osteoarthritis. This study used 72 scapulae. Data were obtained from computed tomography scans of both cadaveric and in vivo glenoids. The glenoid is relatively straight-sided in the coronal plane and more highly fluted in the transverse plane. The endosteal dimensions were larger for male specimens, but there was no difference in endosteal shape with respect to gender. These findings were not influenced by age or the presence of osteoarthritis. This study suggests that traditional glenoid component designs may not be optimal. To maximize fixation, a rectangular keel may be most effective in the coronal plane and a triangular keel may be most effective in the transverse plane.

Patient functional self-assessment in late glenoid component failure at three to eleven years after total shoulder arthroplasty

Failure of the glenoid component is the most common indication for late revision of a total shoulder arthroplasty (TSA). This is the first study to characterize the deterioration in patient self-assessment of shoulder function occurring with glenoid component failure at times remote from the index surgery. Of 115 total shoulders, 11 had revision by the original surgeon for isolated glenoid loosening. Simple Shoulder Test scores averaged 4.4 before TSA, rose to a mean of 11.3 after surgery, and fell to a mean of 4.6 before revision for glenoid loosening performed at a mean of 7 years after TSA. All shoulders showed a drop of at least 3 points between the peak Simple Shoulder Test score and the prerevision Simple Shoulder Test score. Periodic self-assessment of shoulder function may offer a method of screening patients for the possibility of late glenoid component failure.

Effect of glenoid component inclination on its fixation and humeral head subluxation in total shoulder arthroplasty

OBJECTIVE

To investigate the effect of glenoid component inclination angle on the fixation of cemented glenoid-bone structures and humeral head subluxation.

BACKGROUND

Results of shoulder replacements, in terms of glenoid component fixation and joint functionality, are bad and must be improved. Repeated glenoid component tilting, a result of eccentric contact forces harms glenoid component fixation. However, the effect of glenoid component inclination is unknown.

METHODS

Keeled glenoid components are cemented into bone substitutes and positioned under inclination angles varying between -4.5 degrees and +4.5 degrees . For each inclination angle 5 glenoid specimens are loaded by a horizontal, constant joint compression force (725 (SD 10) N) and a vertical, superior directed subluxation force (shear force), cyclically varying between 0 and 350 (SD 1) N. After 200,000 load cycles, the upper and lower glenoid component rim-displacements are measured during 1500 additional load cycles by custom made displacement sensors.

RESULTS

The maximal superior rim-displacement significantly increased and the minimal inferior rim-displacement dramatically decreased for increasing glenoid component inclination angles up to +4.5 degrees . Maximal ratio of subluxation force over compression force significantly decreased for increasing glenoid component inclination.

CONCLUSIONS

According to this study, decreasing glenoid component inclination angle decreases glenoid component tilting and humeral head subluxation and the results can be used to improve total shoulder replacements.

RELEVANCE

Better understanding of the effect of glenoid component inclination on glenoid component tilting and humeral head subluxation may be useful information for the surgeon to improve results of the total shoulder arthroplasty, when replacing the glenoid surface.

Does keel size, the use of screws, and the use of bone cement affect fixation of a metal glenoid implant?

The objective of this study was to determine the effect of screws and keel size on the fixation of an all-metal glenoid component. A prototype stainless-steel glenoid component was designed and implanted in 10 cadaveric scapulae. A testing apparatus capable of producing a loading vector at various angles, magnitudes, and directions was used. The independent variables included six directions and three angles of joint load, and five fixation modalities-three different-sized cross-keels (small, medium, and large), screws, and bone cement. Implant micromotion relative to bone was measured by four displacement transducers at the superior, inferior, anterior, and posterior sites. The components displayed a consistent response to loading of ipsilateral compression and contralateral distraction. Use of progressively larger keels did not significantly improve implant stability. Stability decreased as the angle of load application increased (P <.05). Screw and cement fixation resulted in the most stable fixation (P <.05).

Cemented polyethylene versus uncemented metal-backed glenoid components in total shoulder arthroplasty: a prospective, double-blind, randomized study

Thirty-nine patients (forty shoulders) with primary osteoarthritis consented to be randomized to receive either a cemented all-polyethylene glenoid component or a cementless metal-backed component at the time of total shoulder arthroplasty. Their mean age was 69 years. Preoperative and postoperative evaluations were completed at 3, 6, 12, 24, and 36 months by history, physical examination, radiographs, and Constant scoring system. The presence of periprosthetic radiolucent lines was significantly greater with polyethylene than with metal-backed glenoids (85% vs 25%, P <.01). Of 20 radiolucent lines, 12 (60%) around polyethylene glenoids were present on immediate postoperative radiographs and 25% were progressive. No significant correlation was found between the presence of radiolucent lines around polyethylene glenoids and functional results (P =.3). By contrast, periprosthetic radiolucent lines around metal-backed glenoids were rare but progressive when present. The incidence of loosening of metal-backed implants (4 cases, 20%) was significantly higher than that observed with polyethylene glenoids (0%, P <.001) and was associated with component shift and severe osteolysis. Metal-backed glenoid loosening significantly correlated with deteriorating functional results and increasing pain (P <.05). Revision surgery was required for 4 patients in the metal-backed group (P =.02), for a subscapularis tear (1 case) and metal-backed glenoid component loosening (3 cases). Computed tomography scan analysis and revision surgery revealed that preoperative posterior humeral subluxation may recur with time despite glenoid reorientation and may cause asymmetric accelerated polyethylene wear, resulting in metal-on-metal contact and severe osteolysis. Reimplantation of a stable cemented glenoid component was possible in 1 case, whereas the cavitary defect was packed with cancellous bone in the 2 other cases. At a minimum of 3 years' follow-up, the results of this study clearly show that (1) the survival rate of cementless, metal-backed glenoid components is inferior to cemented all-polyethylene components and (2) the incidence of radiolucency at the glenoid-cement interface with all-polyethylene components is high and remains a concern. The high rate of loosening, because of the absence of ingrowth and/or the accelerated polyethylene wear, has led us to abandon the use of metal-backed glenoids. Efforts must continue to improve glenoid component design and fixation.

Glenoid revision surgery after total shoulder arthroplasty

Forty-eight shoulders that underwent glenoid component revision surgery were reviewed at a mean of 4.9 years (range, 2 to 12 years). The indications for surgery were glenoid component loosening in 29 shoulders, glenoid implant failure in 14 shoulders, and glenoid component malposition or wear leading to instability in 5 shoulders. Seventeen shoulders had associated instability. Thirty shoulders underwent implantation of a new glenoid component and 18 underwent removal of the component and bone grafting for bone deficiencies. There was significant pain relief, improvement in active elevation and external rotation, and satisfaction with revision glenoid surgery (P <.05). Patients without a glenoid component were significantly less satisfied with the procedure than those patients who underwent reimplantation of a glenoid component (P =.01). Satisfactory pain relief was achieved in 86% of patients with a new glenoid component and 66% of patients who underwent glenoid component removal. Seven shoulders with a new glenoid component (2 for glenoid loosening) and 5 who underwent removal without reimplantation (3 for painful glenoid arthritis) required re-revision surgery. Eleven of the 17 patients with instability were stable at the most recent follow-up. The data from this study suggest that at the time of revision glenoid surgery, patients who have placement of a glenoid component have a higher degree of satisfaction than those undergoing glenoid component removal. Patients who continue to have pain after bone grafting without placement of a component may be candidates for glenoid component placement after graft consolidation.

Resurfacing of the glenoid in total shoulder arthroplasty. A comparison, at a mean of five years, of prostheses inserted with and without cement

BACKGROUND

Clinically evident loosening of a glenoid component inserted with cement in total shoulder arthroplasty is infrequent, but radiographic changes that indicate loosening at the implant-bone interface are common and have been associated with functional limitation. We compared the results of total shoulder arthroplasties in which the glenoid implant had been inserted with cement with those of arthroplasties in which a bone-ingrowth glenoid implant had been inserted without cement.

METHODS

The results of eighty-six consecutive total shoulder arthroplasties, performed by the same surgeon, were retrospectively reviewed between four and seven years after the operation. Fifty-eight shoulders in which the primary glenoid implant was in situ were assessed with use of the Simple Shoulder Test and Short Form-36 questionnaires, clinical examination, and fluoroscopic imaging of the glenoid implant-bone interface. Thirty-two of the glenoid components had been fixed with cement and twenty-six, without cement.

RESULTS

Complications occurred in 16 percent (fourteen) of the eighty-six shoulders, and 9 percent (eight) of the shoulders needed a revision operation. None of the revisions were done because of loosening of the glenoid component. Five of the eight revisions involved implants that had been inserted without cement. Three of these implants were revised because of early instability and two, because the polyethylene component had separated from the metal tray of the glenoid implant. With the numbers available, we could not detect any significant differences between the groups with respect to pain, range of motion, function of the shoulder, or general health. Radiographic analysis demonstrated a high level of interobserver agreement (kappa = 0.89). Radiolucent lines were observed after 41 percent (thirteen) of the thirty-two arthroplasties performed with cement compared with 23 percent (six) of the twenty-six arthroplasties performed without cement. The proportion of implants classified as probably loose was approximately three times greater in the group in which cement had been used. Eccentric wear of the posterior rim of the metal tray and focal osteolysis under the metal tray were observed in the group in which the component had been inserted without cement; these findings may indicate a potential for progression of radiographic loosening with increased durations of follow-up.

CONCLUSIONS

We concluded that, despite the higher rate of early complications, the intermediate-term outcomes of arthroplasties in which the glenoid implant is inserted without cement are comparable with those of arthroplasties with cementing of the glenoid component.