The management of infected shoulder arthroplasty by two-stage revision.

BACKGROUND: There remains no gold standard management for deep shoulder periprosthetic joint infection (PJI). This case series aims to present our experience of two-stage revision arthroplasty, including eradication of infection and reoperation rates. METHODS: We retrospectively reviewed patients undergoing revision arthroplasty for shoulder PJI between 2006 and 2015. Cases were confirmed using Musculoskeletal Infection Society (MSIS) and American Academy of Orthopaedic Surgeons (AAOS) guidelines. TSA removal, debridement and irrigation preceded antibiotic-loaded cement spacer insertion and a minimum of six weeks intravenous antibiotics. Reimplantation was performed as a second stage following a negative aspirate. RESULTS: Twenty-eight patients underwent a first stage procedure (mean age 69 years; 16 male, 12 female). Propionibacterium acnes, Methicillin-sensitive Staphylococcus aureus, Coagulase-negative Staphylococcus and Staphylococcus epidermidis were the commonest microorganisms cultured. Five cases had mixed growths and six cases provided no growth. Three patients did not proceed to a second stage. Twenty-five patients underwent reimplantation (mean interval 6.7 months), with 80% remaining infection-free (mean follow-up 38.3 months). DISCUSSION: Managing complex and late presentation shoulder PJI with two-stage revision is associated with high rates of infection eradication (80%). In the absence of a management consensus, our experience supports two-stage revision arthroplasty for eradicating infection in this complex patient group.

The management of infected elbow arthroplasty by two-stage revision.

BACKGROUND: Deep prosthetic infection is a potentially devastating complication after total elbow arthroplasty, with an incidence of up to 12%. This study examined the demographics, microbiologic profile, and outcomes of infected total elbow arthroplasty treated with 2-stage revision in a tertiary referral unit. METHODS: We identified 19 consecutive patients (mean age, 65 years) undergoing revision arthroplasty for deep prosthetic infection. All patients underwent a first-stage procedure with removal of implants, débridement, and insertion of an antibiotic-loaded cement spacer, followed by at least 6 weeks of intravenous antibiotics. Fourteen patients required a second-stage revision. RESULTS: Five patients did not undergo a second-stage procedure because of patient choice (n = 2), medical or surgical risk factors (n = 2), and death from an unrelated cause (n = 1). Of the 19 patients undergoing a first-stage procedure, 16 (84%) remained infection free, and 11 of the 14 patients (79%) undergoing reimplantation of an elbow prosthesis remained infection free. Six patients required further surgery (3 for recurrent infection, 3 for noninfective indications). The commonest infecting organism was Staphylococcus aureus (47%). A degree of postoperative ulnar nerve dysfunction occurred in 37% of patients, but all resolved fully without further treatment. CONCLUSIONS: Management of prosthetic joint infection using 2-stage revision can result in high rates of eradication, although rates of reoperation and transient ulnar nerve dysfunction are high.

Temporal case-based reasoning for type 1 diabetes mellitus bolus insulin decision support.

Individuals with type 1 diabetes have to monitor their blood glucose levels, determine the quantity of insulin required to achieve optimal glycaemic control and administer it themselves subcutaneously, multiple times per day. To help with this process bolus calculators have been developed that suggest the appropriate dose. However these calculators do not automatically adapt to the specific circumstances of an individual and require fine-tuning of parameters, a process that often requires the input of an expert. To overcome the limitations of the traditional methods this paper proposes the use of an artificial intelligence technique, case-based reasoning, to personalise the bolus calculation. A novel aspect of our approach is the use of temporal sequences to take into account preceding events when recommending the bolus insulin doses rather than looking at events in isolation. The in silico results described in this paper show that given the initial conditions of the patient, the temporal retrieval algorithm identifies the most suitable case for reuse. Additionally through insulin-on-board adaptation and postprandial revision, the approach is able to learn and improve bolus predictions, reducing the blood glucose risk index by up to 27% after three revisions of a bolus solution.

Complex shoulder arthroplasty in patients with skeletal dysplasia can decrease pain and improve function.

BACKGROUND: Patients with skeletal dysplasia are prone to the development of degenerative shoulder disease requiring shoulder arthroplasty at a younger age than in the general population. To date there have been no published reports on the complexities or outcome of shoulder arthroplasty in this unique patient group. METHODS: This is a review of 13 shoulder arthroplasties in 10 patients with skeletal dysplasia with mean follow-up of 7 years (2-17.6 years). There were 4 men and 6 women with a mean age of 53.1 years (23-76 years), mean height of 148 cm (122-177 cm), and mean weight of 60 kg (27-80 kg). RESULTS: The mean Oxford Shoulder Score increased from 13 (5-20) preoperatively to 28 (18-38) at final follow-up. Patients improved significantly in 2 of 8 Short Form 36 health-related quality of life domains: physical function (P = .04) and bodily pain (P = .04). Function was better in those who underwent nonconstrained total shoulder arthroplasty as opposed to hemiarthroplasty. Four (31%) required reoperation: 1 excision of heterotopic ossification, 1 relocation for anterior instability, and 2 revisions for periprosthetic fracture and glenoid erosion. CONCLUSION: Shoulder arthroplasty is effective at relieving pain, optimizing movement, and improving function for patients with skeletal dysplasia; however, compared with the general population, there is a higher complication rate and function is not as good. Furthermore, this procedure is less effective at restoring health-related quality of life than total hip arthroplasty or total shoulder arthroplasty performed for osteoarthritis in the general population. Custom implants may be required to compensate for short stature and rotator cuff and glenoid deficiency.

Hip-inspired implant for revision of failed reverse shoulder arthroplasty with severe glenoid bone loss. Improved clinical outcome in 11 patients at 3-year follow-up.

BACKGROUND AND PURPOSE: Glenoid reconstruction and inverted glenoid re-implantation is strongly advocated in revisions of failed reverse shoulder arthroplasty (RSA). Nevertheless, severe glenoid deficiency may preclude glenoid reconstruction and may dictate less favorable solutions, such as conversion to hemiarthropasty or resection arthropasty. The CAD/CAM shoulder (Stanmore Implants, Elstree, UK), a hip arthroplasty-inspired implant, may facilitate glenoid component fixation in these challenging revisions where glenoid reconstruction is not feasible. We questioned (1) whether revision arthroplasty with the CAD/CAM shoulder would alleviate pain and improve shoulder function in patients with failed RSA, not amenable to glenoid reconstruction, (2) whether the CAD/CAM hip-inspired glenoid shell would enable secure and durable glenoid component fixation in these challenging revisions. PATIENTS AND METHODS: 11 patients with failed RSAs and unreconstructable glenoids underwent revision with the CAD/CAM shoulder and were followed-up for mean 35 (28-42) months. Clinical outcomes included the Oxford shoulder score, subjective shoulder value, pain rating, physical examination, and shoulder radiographs. RESULTS: The average Oxford shoulder score and subjective shoulder value improved statistically significantly after the revision from 50 to 33 points and from 17% to 48% respectively. Pain rating at rest and during activity improved significantly from 5.3 to 2.3 and from 8.1 to 3.8 respectively. Active forward flexion increased from 25 to 54 degrees and external rotation increased from 9 to 21 degrees. 4 patients required reoperation for postoperative complications. No cases of glenoid loosening occurred. INTERPRETATION: The CAD/CAM shoulder offers an alternative solution for the treatment of failed RSA that is not amenable to glenoid reconstruction.

Validation of the Stanmore percentage of normal shoulder assessment.

BACKGROUND AND PURPOSE: The Stanmore Percentage of Normal Shoulder Assessment (SPONSA) is a patient-reported outcome measure (PROM). The score assesses pain, range of movement, strength, stability and function of the shoulder. The aim of this work was to formally validate the SPONSA. MATERIALS AND METHODS: Validation of this score was carried out by measuring reproducibility, construct validity and sensitivity to change. Time to completion was also recorded. The Oxford Shoulder Score (OSS) and Constant Score (CS) were used for comparison. These assessments were performed with 61 individuals undergoing shoulder interventions. RESULTS: There was excellent preoperative reproducibility in both intra- and inter-observer groups. The SPONSA had a 0.79 correlation with the OSS and 0.78 with the CS. The overall effect size of the SPONSA was 0.72, which was comparable to OSS (0.65) and greater than CS (0.34), implying equal or better sensitivity to change. CONCLUSIONS: The SPONSA is practical and quick to perform and also a reproducible and a sensitive instrument. This simple PROM is a commendable addition to the existing validated scoring methods for the shoulder. LEVEL OF EVIDENCE: I; testing of previously developed diagnostic criteria on consecutive patients (with universally applied reference "gold" standard).

Muscle activation patterns in patients with recurrent shoulder instability.

PURPOSE: The aim of this study is to present muscle patterns observed with the direction of instability in a series of patients presenting with recurrent shoulder instability. MATERIALS AND METHODS: A retrospective review was carried out on shoulder instability cases referred for fine wire dynamic electromyography (DEMG) studies at a specialist upper limb centre between 1981 and 2003. An experienced consultant clinical neurophysiologist performed dual needle insertion into four muscles (pectoralis major (PM), latissimus dorsi (LD), anterior deltoid (AD) and infraspinatus (IS)) in shoulders that were suspected to have increased or suppressed activation of muscles that could be contributing to the instability. Raw EMG signals were obtained while subjects performed simple uniplanar movements of the shoulder. The presence or absence of muscle activation was noted and compared to clinical diagnosis and direction of instability. RESULTS: A total of 140 (26.6%) shoulders were referred for fine wire EMG, and 131 studies were completed. Of the shoulders tested, 122 shoulders (93%) were identified as having abnormal patterns and nine had normal patterns. PM was found to be more active in 60% of shoulders presenting with anterior instability. LD was found to be more active in 81% of shoulders with anterior instability and 80% with posterior instability. AD was found to be more active in 22% of shoulders with anterior instability and 18% with posterior instability. IS was found to be inappropriately inactive in only 3% of shoulders with anterior instability but in 25% with posterior instability. Clinical assessment identified 93% of cases suspected to have muscle patterning, but the specificity of the clinical assessment was only correct in 11% of cases. CONCLUSION: The DEMG results suggest that increased activation of LD may play a role in both anterior and posterior shoulder instability; increased activation of PM may play a role in anterior instability.

An experimental glenoid rim strain analysis for an improved reverse anatomy shoulder implant fixation.

Loosening of glenoid components in TSA is a main cause of failure. In reverse anatomy TSA designs used for unstable joints, fixation is particularly demanding. Strains developed around the glenoid rim of biomechanical sawbone scapulae implanted with (a) the original fixed-fulcrum Bayley-Walker glenoid prosthesis in current clinical use, and (b) a revised version with conical cross-section, were compared. The conical shape of the revised design was hypothesized to produce greater strains in the glenoid rim than the original tapered screw design. The 2D strain field at three accessible locations around the rim of each scapula was measured with three-element rosette strain gauges for two types of simulated cancellous bone fill under applied physiologically relevant loads. The average strain energy densities around the rim for the conical design were greater than for the original design by a factor of 1.55-2.25 for all loading conditions. Results indicate that a significantly greater proportion of load was directed toward cortical bone in the conical design, thus promoting cortical bone loading.

Prospective blinded comparison of surface versus wire electromyographic analysis of muscle recruitment in shoulder instability.

BACKGROUND: This pilot study assesses level of agreement between surface and fine-wire electromyography (EMG), in order to establish if surface is as reliable as fine wire in the diagnosis and treatment of abnormal muscle patterning in the shoulder. METHOD: Eighteen participants (11 female) with unstable shoulders were recruited after written consent and ethical approval. Anthropometric information and mean skinfold size for triceps, subscapular, biceps and suprailiac sites were obtained. Triple-stud self-adhesive surface electrodes ('Triode'; Thermo Scientific, Physio Med Services, Glossop, Derbyshire, England) were placed over pectoralis major (PM), latissimus dorsi (LD), anterior deltoid (AD) and infraspinatus (IS) at standardized locations. Participants performed five identical uniplanar standard movements (flexion, abduction, external rotation, extension and cross-body adduction). After a 20-minute rest period, a dual-needle technique for fine-wire insertion was performed and the standard movements were repeated. An experienced examiner in each technique reported if muscle activation patterns differed from agreed normal during any movement and were blinded to the other test results. Sensitivity, specificity and Kappa values for level of agreement between methods were calculated for each muscle according to the method of Altman (1991). RESULTS: Fifteen participants were successfully tested. Sensitivity, specificity and Kappa values between techniques for each muscle were PM (57%, 50%, 0.07), LD (38%, 85%, 0.22), AD (0%, 76%, -0.19) and IS (85%, 75%, 0.6). Only IS demonstrated high sensitivity and specificity and a moderate level of agreement between the two techniques. There was no correlation between skinfold size and agreement levels. CONCLUSION: The use of surface EMG may help to classify types of shoulder instability and recognize abnormal muscle patterns. It may allow physiotherapists to direct specific rehabilitation strategies, avoiding strengthening of inappropriate muscles. It has a reasonable degree of confidence to evaluate IS but may have poor sensitivity in detecting abnormal patterns in PM, LD and AD. Further work is required to see if investigator interpretation may have been a factor for the poor level of agreement.