Hybrid Glenoid Designs in Anatomic Total Shoulder Arthroplasty: A Systematic Review

Background:Hybrid glenoid components in total shoulder arthroplasty (TSA) utilize both polyethylene and metal components to provide short-term stability and long-term biologic fixation through bone ingrowth.Questions/Purpose:We sought to systematically review the literature for studies that assessed outcomes of TSA performed using hybrid glenoid components.Methods:PubMed, Medline, Cumulative Index to Nursing and Allied Health Literature (CINAHL), and Embase were searched systematically for articles measuring clinical and patient-reported outcomes and rates of complication and revision following TSA using a hybrid glenoid component.Results:Seven studies with 593 shoulders were included in this review. The mean age of patients was 65 ± 1 years, and 46% of the population was male. Mean follow-up was 50 months (4.2 years). The overall complication rate was 7% and rate of revision was 2.5%; glenoid radiolucency was present in 33% of shoulders at mean follow-up of 50 months. Mean improvements in forward elevation, external rotation, internal rotation score, and abduction were 49°, 28°, 2 points, and 42°, respectively. Mean improvements in Constant, American Shoulder and Elbow Surgeons (ASES), and University of California, Los Angeles (UCLA) scores were 36 points, 52 points, and 17 points, respectively.Conclusion:Our review found that TSA using hybrid glenoid components results in low rates of complication and revision at early follow-up. Long-term studies are warranted to understand more fully the role of hybrid glenoid components in TSA.     

Symptomatic Glenoid Loosening Complicating Total Shoulder Arthroplasty

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.     

Mortality After Shoulder Arthroplasty

One year post-operative mortality among patients with primary elective total shoulder arthroplasty (ETSA) and traumatic shoulder arthroplasty (TSA) were compared to the general population of a large healthcare system. Standardized mortality ratios (SMRs) and 95% confidence intervals (CIs) were calculated. 614 ETSA patients, 1.0% one year mortality, and 168 TSA patients, 5.4% mortality rate, were evaluated. Patients with ETSA (SMR = 0.4, 95% CI 0.1–0.7) had lower odds of mortality than expected, while patients with TSA (SMR = 1.8, 95% CI 0.6–3.0) did not have higher than expected odds of mortality compared to the reference population. Understanding excess mortality following shoulder arthroplasty surgery allows providers to evaluate current practices and identify ways to optimize patients prior to surgery.     

Glenoid Reconstruction in Revision Shoulder Arthroplasty

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.     

Prognostic Factors in Arthroplasty in the Rheumatoid Shoulder

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.     

Bone Grafting Severe Glenoid Defects in Revision Shoulder Arthroplasty

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.     

Alterations in surface geometry in retrieved polyethylene glenoid component.

This study characterized and quantified the changes found in retrieved glenoid polyethylene components found at revision total shoulder arthroplasty (TSA). Twenty components obtained at revision TSA were evaluated, all from a system (Global, DePuy, Warsaw, IN) with a glenoid radius of curvature 3 mm greater than that of the humeral head. Laser surface scanning provided three-dimensional analysis of the surface of the glenoid component. Scans of unused components of similar sizes enabled determination of the changes occurring after implantation. Alterations in radius of curvature were noted in every glenoid. All showed loss of the balance stability angle (BSA, the maximal angle that the net humeral joint reaction force can make with the glenoid center line before the humeral head would dislocate) of at least 5 degrees in one or more directions. Increase in BSA in one direction was seen in 11 of the components. In five of these, the increase was associated with a reduction of the local radius to match that of the humeral component. Glenoid surface morphology and stability can be changed by in vivo use. While correlation with clinical instability in the patients from whom the implants were obtained was not possible, many of the observed changes in surface morphology are of sufficient magnitude to compromise the contribution of the glenoid surface to shoulder stability. Three patterns of wear were identified: "humeral" that showed loss of the mismatch between the humeral and glenoid radii of curvature (5 of 20 components), "diffuse" that showed broad surface irregularity (18 of 20), and "rim" wear with loss of the polyethylene rim of the component (14 of 20). More than one type of wear was possible within a single glenoid.     

Humeral Tray-Taper Failure in Modular Reverse Total Shoulder Arthroplasty

Background

Reverse total shoulder arthroplasty (RTSA) provides reconstructive options in patients previously not candidates for total shoulder arthroplasty (TSA) or who have failed previous anatomic TSA. Revision from anatomic TSA to RTSA previously required removal of all components, a difficult and extensive procedure. Modular humeral components permit conversion from anatomic TSA to RTSA without removal of well-fixed humeral components.

Questions/Purposes

Our purpose is to present a case series of patients treated for the unique and not previously reported complication of humeral tray-taper failure following modular RTSA. Challenges in diagnosis and treatment are described, including the use of dynamic fluoroscopy and manufacturer-specific instruments for component revision.

Methods

Five patients with a total of six humeral tray-taper failures were identified from 300 patients with first-generation (titanium) humeral trays over a 7-year period. Dynamic fluoroscopic evaluation aided in diagnosis in a majority of the cases. All cases have been revised to second-generation (cobalt chrome) humeral trays.

Results

Average follow-up was 22?±?23 months (range 3–60 months). One individual required a second revision for the same complication, but otherwise, no additional procedures were required. Symptom relief was obtained in all patients.

Conclusions

This case series illustrates a previously unpublished complication of humeral tray-taper junction failure following modular RTSA. Clinical and radiographic diagnosis is challenging; however, dynamic fluoroscopic evaluation permits identification of the component failure, and revision surgery results in good outcomes. We must, however, continue to evaluate what activities are recommend for patients following shoulder arthroplasty, specifically reverse total shoulder arthroplasty.

     

Total Shoulder Arthroplasty Utilizing Mini-Stem Humeral Components: Technique and Short-Term Results

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.     

Reverse Total Shoulder Arthroplasty for the Treatment of Defect Arthropathy

Abstract Objective: Total shoulder replacement for restoration of function and for pain relief of damaged glenohumeral joint accompanied by extensive irreparable cuff defect. Indications: Any painful shoulder arthropathy with insufficient and irreparable rotator cuff, especially primary defect arthropathy, rheumatoid arthritis with extensive rotator cuff defect, arthropathy after reconstruction of rotator cuff, mutilating rheumatoid arthritis, and crystal-induced arthropathy. Relative: failure of primary shoulder replacement in the presence of an irreparable cuff defect. Contraindications: Structural or neurogenic lesion of deltoid muscle. Advanced glenoid destruction. Relative: age < 65 years. Surgical Technique: Anterosuperior or deltopectoral approach. Exposure of glenoid. Resection of humeral head at epi-metaphyseal junction. Complete detachment of anterior, inferior, and posterior capsule from glenoid neck. Preparation of glenoid for cement-free fixation of glenoid base plate (metaglène). Preparation of humeral shaft for implantation of humeral component in 0–10° of retroversion. Screwing of glenosphere to base plate. Insertion of cemented or cement-free modular humeral component. Results: Between 10/1997 and 03/2001, a reverse total shoulder arthroplasty was done in 57 patients (14 men, 43 women; average age 70.1 years). Average follow-up time was 18.2 months. 98% of patients would agree to repeat surgery. Average Constant Score adjusted to age and gender was 94%, 97% for patients not having undergone previous surgery. All patients reported complete or almost complete freedom of pain. On the condition that the deltoid muscle was not damaged during previous surgery, a good improvement of power and function could be obtained. All functional parameters were normal for the patient’s age with the exception of a slight limitation of internal rotation (average L5). The power of maintained abduction also corresponded in general to age-specific values. Only grade 1 or 2 inferior glenoid notching was observed but never reaching or surpassing the inferior screw (grade 3 or 4); no glenoid base plate loosening. The following is a reprint from Operat Orthop Traumatol 2005;17:1–24 and continues the new series of articles at providing continuing education on operative techniques to the European trauma community. Reprint from: Operat Orthop Traumatol 2005;17:1–24. DOI 10.1007/s00064-005-1119-1     

Difference in clinical outcome between total shoulder arthroplasty and reverse shoulder arthroplasty used in hemiarthroplasty revision surgery

Introduction:The increase of shoulder replacements will lead to a higher revision rate of shoulder arthroplasties. The aim of this study is to evaluate the clinical results of revision surgery performed in our hospital, distinguish the differences in clinical outcome according to revision indication and differences between total shoulder arthroplasty (TSA) and reverse shoulder arthroplasty (RSA) in hemiarthroplasty (HA) revision surgery.Results:From July 1994 to July 2008, 39 patients (40 shoulders) underwent revision arthroplasty. Of 19 patients (19 shoulders) we obtained a complete follow-up. The mean age at revision surgery 69 ± 10 years (range: 46-83) and the mean follow-up 41 ± 31 months (range: 10-113). In 7 cases TSA was used for revision when the cuff was intact, 12 times RSA was performed. The indications for the revision were glenoid erosion (n = 4), humeral component malposition (n = 2), cuff-pathology (n = 12) and infection (n = 1). Postoperative constant score 51.7 ± 11.4 for TSA and 31.1 ± 18.7 for RSA (P = 0.008). The DASH was 48.3 ± 25.1 and 68.7 ± 17.5, respectively (P = 0.09). DSST showed 6 ± 4 and 4 ± 4 (P = 0.414). OSS 41.3 ± 10.1 and 28.1 ± 10.3 (P = 0.017). SF-36 43.3 ± 22.1 and 24.5 ± 12.8 (P = 0.072). Four shoulders (21%) presented four complications.Conclusions:In this study, revision surgery showed poor to reasonable postoperative results and better clinical outcome for TSA. When a revision after HA was needed, and the soft-tissue component of the shoulder was intact, a TSA proved to be a preferable solution.     

Locked posterior dislocation of the shoulder joint: Report of two cases

Posterior dislocation of the shoulder joint is very rare. Most cases are missed initially because it is difficult to diagnose using conventional radiographic images. Computed tomography (CT) is the best tool for diagnosis. We report two cases of posterior dislocation of the shoulder joint that were missed initially at another hospital. The patients presented with painful disability of the shoulder joint. Posterior dislocation of the shoulder joint was suspected after physical examination. Anteroposterior radiography was unable to confirm the diagnosis because an abnormal posterior relationship of humeral head to glenoid fossa could not be clearly identified. An axillary view was unobtainable because of severe pain and the limited joint motion available. CT showed posterior dislocation of the humeral head. The bony defect of the humeral head was incarcerated by the posterior rim of the glenoid process. Open reduction via an anterior approach was performed on both patients, who recovered with good shoulder function after rehabilitation (the Constant score of Case 1 was 85 and that of Case 2 was 75). We concluded that “Mouzopoulos sign” obtained via an anteroposterior view is helpful for the diagnosis of posterior dislocation of the shoulder joint and that CT is required for a definitive diagnosis. If the dislocation is locked and closed reduction fails, then open reduction should be carried out.     

Shoulder Arthroplasty for Humeral Head Avascular Necrosis Is Associated With Increased Postoperative Complications

Background

Humeral head avascular necrosis (AVN) of differing etiologies may lead to shoulder arthroplasty due to subchondral bone collapse and deformity of the articular surface. There have been no large studies evaluating the complications for these patients after they undergo total shoulder arthroplasty (TSA).

Questions/Purposes

The first objective of this study is to evaluate the complication rate after TSA in patients with humeral head AVN. The secondary objective is to compare the complication rates among the different etiologies of the AVN.

Methods

Patients who underwent TSA were identified in the PearlDiver database using ICD-9 codes. Patients who underwent shoulder arthroplasty for humeral head AVN were identified using ICD-9 codes and were subclassified according to AVN etiology (posttraumatic, alcohol use, chronic steroid use, and idiopathic). Complications evaluated included postoperative infection within 6 months, dislocation within 1 year, revision shoulder arthroplasty up to 8 years postoperatively, shoulder stiffness within 1 year, and periprosthetic fracture within 1 year and systemic complications within 3 months. Postoperative complication rates were compared to controls.

Results

The study cohorts included 4129 TSA patients with AVN with 141,778 control TSA patients. Patients with posttraumatic AVN were significantly more likely to have a postoperative infection (OR 2.47, P < 0.001), dislocation (OR 1.45, P = 0.029), revision surgery (OR 1.53, P = 0.001), stiffness (OR 1.24, P = 0.042), and systemic complication (OR 1.49, P < 0.001). Steroid-associated AVN was associated with a significantly increased risk for a postoperative infection (OR 1.72, P = 0.004), revision surgery (OR 1.33, P = 0.040), fracture (OR 2.76, P = 0.002), and systemic complication (OR 1.59, P < 0.001). Idiopathic and alcohol-associated AVN were not significantly associated with any of the postoperative evaluated complications.

Conclusions

TSA in patients with humeral head AVN is associated with significantly increased rates of numerous postoperative complications compared to patients without a diagnosis of AVN, including infection, dislocation, revision arthroplasty, stiffness, periprosthetic fracture, and medical complications. Specifically, AVN due to steroid use or from a posttraumatic cause appears to be associated with the statistically highest rates of postoperative TSA complications. Given these findings, orthopedic surgeons should be increasingly aware of this association, which should influence the shared decision-making process of undergoing TSA in patients with humeral head AVN.

     

Biomechanical benefits of anterior offsetting of humeral head component in posteriorly unstable total shoulder arthroplasty: A cadaveric study

Restoration of joint stability during total shoulder arthroplasty can be challenging in the face of severe glenoid retroversion. A novel technique of humeral head component anterior‐offsetting has been proposed to address posterior instability. We evaluated the biomechanical benefits of this technique in cadaveric specimens. Total shoulder arthroplasty was performed in 14 cadaveric shoulders from 7 donors. Complementary shoulders were assigned to either 10° or 20° glenoid retroversion, with retroversion created by eccentric reaming. Two humeral head component offset positions were tested in each specimen: The anatomic (posterior) and anterior (reverse). With loads applied to the rotator cuff and deltoid, joint contact pressures and the force and energy required for posterior humeral head translation were measured. The force and energy required to displace the humeral head posteriorly increased significantly with the anterior offset position compared to the anatomic offset position. The joint contact pressures were significantly shifted anteriorly, and the joint contact area significantly increased with the anterior offset position. Anterior offsetting of the humeral head component increased the resistance to posterior humeral head translation, shifted joint contact pressures anteriorly, and increased joint contact area, thus, potentially increasing the joint stability in total shoulder arthroplasty with simulated glenoid retroversion. © 2015 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 34:666–674, 2016.     

Minimum clinically important difference for the American Shoulder and Elbow Surgeons score after revision shoulder arthroplasty

BackgroundPatients undergoing revision total shoulder arthroplasty (TSA) typically achieve smaller improvements in outcome measurements than those undergoing primary TSA. The minimum clinically important difference (MCID) in the American Shoulder and Elbow Surgeons (ASES) questionnaire for primary shoulder arthroplasty ranges from 13.6 to 20.9, but the MCID for revision shoulder arthroplasty remains unclear. This study aims to define the MCID in ASES score for revision TSA and ascertain patient factors that affect achieving the MCID threshold.MethodsPatients were identified from an institutional shoulder arthroplasty database. Prospective data collected included demographic variables, prior shoulder surgeries, primary and revision implants, indication for revision, and pre- and postoperative ASES scores. All patients provided informed consent to participate. An anchor-based method was used with a binary answer choice. The MCID was calculated using the receiver-operator curve (ROC) method, and the sensitivity, specificity, and area under the curve were obtained from the ROC. MCID values were compared between groups using Student's t-test. Multivariate logistic regression modeling was used to determine significant predictors for reaching MCID. Significance was defined as P< .05.ResultsA total of 46 patients underwent revision TSA with minimum 2-year follow-up. The MCID using ROC method was 16.7 with 71% sensitivity and 62% specificity. There was a trend toward males being more likely to reach MCID after revision arthroplasty (P= .058). There were also trends toward increased forward flexion and abduction range of motion in patients who met MCID (P= .08, P= .07). Multivariate logistic regression modeling demonstrated male sex to be associated with achieving MCID (P= .03), while younger age and fewer prior shoulder surgeries demonstrated a trend to association with achieving MCID (P= .06, P= .10).ConclusionThe MCID for ASES score in patients undergoing revision shoulder arthroplasty is similar to previously reported MCID values for patients undergoing primary shoulder arthroplasty. Younger, male patients with fewer prior shoulder surgeries were more likely to achieve MCID after revision TSA.Level of EvidenceLevel III; Retrospective Comparative Treatment Study     

Reconstruction of the articular surface of the humeral head after locked posterior shoulder dislocation: a case report

Posterior dislocations of the glenohumeral joint are extremely rare (2–4% of all shoulder dislocations) and often associated with bone or ligamentary injuries. Though the reverse Hill-Sachs lesion is a common injury associated with posterior shoulder dislocation, there have been only few articles describing specific treatments for this type of humeral head defect. This article describes the successful operative treatment of an acute locked posterior shoulder dislocation by reconstructing the articular surface of the humeral head with the use of autologous bone graft taken from the iliac crest. The patient was doing quite well with no complaints, good range of shoulder motion and no recurrence of posterior shoulder dislocation despite several epileptic seizures, 1.5 years after surgical reconstruction of the anatomy of the humeral head. His right shoulder function revealed to be “excellent” or “good”, assessed with an absolute Constant Score of 76 points and a relative Score of 88% when compared with an age- and sex-matched normal population.     

Eine neue Repositionstechnik für die verhakte hintere Schulterluxation

The case of a 61-year-old male with posterior dislocation of the right shoulder joint is presented and a new technique for closed reduction of posterior locked shoulder dislocation is described. The technique involves four steps: in step 1 a constant traction is applied on the injured arm, in step 2 the arm is internally rotated and in steps 3 and 4 the second arm of the physician is used as a lever arm to lateralize and ventralize the shoulder. Lateralization and ventralization of the humeral head are essential to engage the humeral head and to pass it around the glenoid during reduction. Steps 3 and 4 are performed simultaneously. In the presented case the patient suffered a traumatic shoulder dislocation with a rim fracture of the glenoid. After reduction the shoulder was stable and conservative treatment was performed. A 2 year follow-up examination revealed a pain-free and stable shoulder with free range of motion and an Oxford instability score of 48 points. The described reduction technique for posterior locked shoulder dislocation is a simple and gentle technique, which can be performed easily by one person.Presentation of a reduction technique for locked posterior shoulder dislocation. Constant traction and internal rotation is performed for engaging the locked humeral head. After disengaging the humeral head the reduction is performed by using the arm of the physician as a lever arm.     

Computer-Assisted Surgery in Reverse Shoulder Arthroplasty: Early Experience

BackgroundIn the last decade, new technologies have been applied to shoulder arthroplasty. The aim of this work was to show that navigated RSA allows the surgeon to reach the planned version/inclination in all cases. In this article are shown preliminary data, advantages, disadvantages and limits of the technique.MethodsEighteen computer-assisted reverse shoulder arthroplasty were performed. Preoperative glenoid version and inclination were evaluated with preoperative CT scan using Orthoblue^® (Exactech, Gainesville, FL,USA) software, as well as baseplate type, planned glenoid component seating, planned postoperative version, planned postoperative inclination, intraoperative glenoid version/inclination, screw length and surgical time. A senior shoulder surgeon has analyzed the advantages, disadvantages and limitation of this kind of surgery.ResultsMean surgical time of the primary implants was 92 ± 12 min (min 75–max 110). Mean preoperative inclination was + 2.6° ± 6.4, mean preoperative version was − 7.6° ± 8.4. Mean planned postoperative inclination was − 2.7° ± 2.3, mean planned postoperative version was − 1.6° ± 2.9 and mean planned glenoid seating was 89% ± 8%. Planned settings were reached in all cases during surgery. Baseplate implanted were in nine cases 8° posterior augmented, in six cases standard and in three cases 10° superior augmented. Mean screw length was 33.5 mm ± 4.2 mm. No GPS system failure has been recorded. One coracoid fracture occurred during the first case.DiscussionIntraoperative navigation system is a reliable and user-friendly technology that allows the surgeon to reach planned glenoid positioning during surgery. Furthermore, this technology will allow the surgeon to compare clinical outcomes to component positioning data. The lack of humeral implant navigation is the main limit of this technique.     

Total shoulder arthroplasty — current problems and possible solutions

The concept and design of a cemented unconstrained total shoulder arthroplasty (TSA), introduced by Charles Neer II 25 years ago, has been successful in the management of degenerative and inflammatory conditions of the shoulder, controlling pain and, in many patients, significantly improving function. The clinical outcome is very much determined by the nature and severity of the pathology, as well as by the surgeon's experience and ability to correctly locate and fix the components. Total shoulder arthroplasty is a technically difficult procedure with perhaps a greater potential for technical errors and complications compared with other commonly performed arthroplasties. Current systems are modular on the humeral side, with varying head diameters and neck lengths, allowing more accurate coverage of the cut surface of the humeral neck and improved ability to establish the position of the joint line within the requirements of correct soft tissue tension and balance. Cemented all-polyethylene glenoid components remain the most favored, but the majority now have an increased radius of curvature compared with their corresponding humeral head, to allow translation during movement. Aseptic glenoid component loosening is the most frequently encountered long-term complication and is hastened by conforming prostheses, incorrect positioning, rotator cuff tears, and capsular contractures, but is protected by secure glenoid fixation. Cemented one-piece metal-backed glenoids have been disappointing, but non-cemented glenoids are being trialed with promising early results, although they have introduced their own particular problems of rapid polyethylene wear and component dissociation. Although cemented humeral components have a very low incidence of symptomatic loosening, most surgeons currently use press-fit designs supplemented with metaphyseal porous coating for osseous integration. Based on increased understanding of the morphology of the upper humerus, current designs are evolving with increased modularity, allowing the surgeon to choose the appropriate size, inclination, offset and version of the humeral component. These changes will, it is hoped, result in improved functional recovery and increased survivorship of the glenoid component. Received for publication on April 15, 1998; accepted on July 31, 1998