Introduction. The interaction between the mobile components of total elbow replacements (TER) provides additional constraint to the elbow motion. Semi-constrained TER depend on a mechanical linkage to avoid dislocation and have greater constraint than unconstrained TER that rely primarily in soft tissue for joint stability. Greater constraint increases the load transfer to the implant interfaces and the stresses in the polyethylene components. Both of these phenomena are detrimental to the longevity of TER, as they may result in implant loosening and increased damage to the polyethylene components, respectively[1]. The objective of this work was to compare the constraint profile in varus-valgus and internal-external rotation and the polyethylene stresses under loads from a common daily activity between two semi-constrained TER, Coonrad/Morrey (Zimmer-Biomet) and Discovery® (DJO), and an unconstrained TER, TEMA (LimaCorporate). Methods. We developed finite element (FE) models of the three TER mechanisms. To reduce computational cost, we did not include the humeral and ulnar stems. Materials were linear-elastic for the metallic components (E. Ti6Al4V. =114.3 GPa, E. CoCr. =210 GPa, v=0.33) and linear elastic-plastic for the polyethylene components (E=618 MPa, v=0.46; S. Y. =22 MPa; S. U. =230.6 MPa; ε. U. =1.5 mm/mm). The models were meshed with linear tetrahedral elements of sizes 0.4–0.6 mm. We assumed a friction coefficient of 0.02 between metal and polyethylene. In all simulations, the ulnar component was fixed and the humeral component loaded. We computed the constraint profiles in full extension by simulating each mechanism from 8° varus to 8° valgus and from 8° internal to 8° external rotation. All other degrees-of-freedom except for flexion extension were unconstrained. Then, we identified the instant during feeding that generated the highest moments at the elbow[2], and we applied the joint forces and moments to each TER to evaluate the stresses in the polyethylene. To validate the FE results, we experimentally evaluated the constraint of the design with highest polyethylene stresses in pure internal-external rotation and compared the results against those from a FE model that reproduced the experimental setup (Fig.1-a). Results. For each design, the constraint profiles in varus-valgus (Fig.2-a) were similar to internal-external rotation (Fig.2-b). All designs showed a lax zone in which the mechanisms rotated freely and an engagement zone in which the mobile components contacted, resulting in load transfer. The laxity of the Coonrad/Morrey and the Discovery® was similar and lower than that of the TEMA. After engagement, the stiffness of the TEMA was less than that of the Discovery® and the Coonrad/Morrey. The TEMA showed the lowest polyethylene stresses of all three designs under demanding loads during feeding. Only Discovery® and Coonrad/Morrey had zones reaching permanent deformation (Fig.3). For the Coonrad/Morrey, with the highest polyethylene stresses, the experimental and computational constraint profiles were similar (Fig.1-b). Discussion. The TEMA unconstrained design transferred less moment than semi-constrained designs, reducing the burden on the implant interfaces. Moreover, the TEMA design had lower stresses in the polyethylene components due to the combination of less constraint and a lack of sharp edges on the articular surfaces. For any figures or tables, please contact the authors directly

As a treatment for end-stage elbow joint arthritis, total elbow replacement (TER) results in joint motions similar to the intact joint; however, bearing wear, excessive deformations and/or early fracture may necessitate early revision of failed implant components. Compared to hips, knees and shoulders, very little research has been focused on the evaluation of the outcomes of TER, possible failure mechanisms and the development of optimal designs. The current study aims to develop computational models of TER implants in order to analyze implant behaviour; considering contact stresses, plastic deformations and damage progression. A geometrical model of a TER assembly was developed based on measurements from a Coonrad-Morrey TER implant (Zimmer, Inc., Warsaw, IN). Ultra high molecular weight polyethylene (UHMWPE) nonlinear elasto-plastic material properties were assigned to the humeral and ulnar bushings. A frictional penalty contact formulation with a coefficient of friction of 0.04 was defined between all of the surfaces of the model to take into account every possible interaction between different implant components in vivo. The loading scenario applied to the model includes a flexion-extension motion, a joint force reaction with variable magnitude and direction and a time varying varus-valgus (VV) moment with a maximum magnitude of 13 N.m, simulating a chair-rise scenario as an extreme loading condition. An explicit dynamic finite element solver was used (ABAQUS Explicit, Dassault Systèmes, Vélizy-Villacoublay, France), due to improved capabilities when performing large deformation analyses. Model results were compared directly with corresponding experimental data. Experimental wear tests were performed on the abovementioned implants using a VIVO (AMTI, Watertown, MA) six degree-of-freedom (6-DOF) joint motion simulator apparatus. The worn TER bushings were scanned after the test using micro computed tomography (µCT) imaging techniques, and reconstructed as 3D models. Comparisons were made based on the sites of damage and deformed geometries between the numerical results and experimental test data. In addition to that, parametric geometrical models were developed using worn geometry of the retrievals in order to account for primary wear and deformations while simulating long-term contact stress and secondary damage progression on the bushings (Fig. 1). Contact pressure distributions on the humeral and ulnar bushings correlate with the sites of damage as represented by the µCT data and gross observation of clinical retrievals. Furthermore, deformation patterns and kinematics of the components are in good agreement with the experimental results (Fig.2). Excessive plastic deformations are evident in both the numerical and the experimental results close to the regions with high contact pressures. Simulating parametric initially-worn geometries results in the formation of secondary damage zones, as well as redistribution of contact stresses and contact locations (Fig. 3). The results demonstrate UHMWPE bushing damage due to different loading protocols. Numerical results demonstrate strong agreement with experimental data based on the location of deformation and creep on bushings and exhibit promising capabilities for predicting the damage and failure mechanisms of TER implants. For figures/tables, please contact authors directly.

Background. The quest for the perfectly designed elbow prosthesis continues as instability and loosening remain the foremost reasons for the failure of total elbow replacement (TER). The Discovery® Elbow System (Biomet, UK) (Figure 1), which has been used in UK since 2003, is one of the latest generations of linked prosthesis. This system was designed to decrease polyethylene-bushing wear, improve anatomic stem design, restore elbow joint biomechanics, and produce a hinge that could be easily revised. This report describes the short term outcome of TER using the Discovery® Elbow System. Patients and Methods. A total of 60 TERs including 48 primary and 12 revisions were performed between 2003 and 2008. Patients included 21 males (37%) and 36 females (63%) with a mean age of 63 years. The indications for primary TER were advanced rheumatoid arthritis (n=19), osteoarthritis (n=16), post traumatic osteoarthritis (n=9), acute fractures (n=3), and haemophilic arthropathy (n=1). The outcome was assessed using pain score, Liverpool Elbow Score (LES), and range of movement during a mean follow-up of 26 months. Associated complications were documented. Radiological assessment included evaluation for loosening, instability and periprosthetic fractures. Results. The mean LES was significantly (p<0.001) improved from 3.8 (±1) pre-operatively to 6.9 (±2) at the final follow- up. Significant improvements were noted in elbow flexion from 100° (±22) to 120° (±15), supination from 41° (±28) to 65° (±20) and pronation from 52° (±22) to 72° (±18). There was no significant change in elbow extension. Mean improvement in flexion-extension and pronation-supination arc was 22° and 44°, respectively. 46 cases (77%) were completely pain-free at the final follow-up. The main complications included deep infection (4 cases – treated with staged revision TER), postoperative ulnar neuropathy (3 cases–treated with decompression), intra-operative fractures of medial condyle (3 cases – treated non-operatively with brace), and elbow haemarthrosis (1 case). Discussion. TER with Discovery® Elbow System resulted in either no pain or mild pain in 87% of cases. Patients undergoing Acclaim, Souter-Strathclyde, GSB III, and Coonrad-Morrey TER have been reported to have no/mild pain in 64%, 67%, 50–92% and 60–100% of cases, respectively. A 22° improvement in flexion-extension arc is comparable to that of Acclaim (23°), Souter-Strathclyde (15°), GSB III (19–33°), and Coonrad-Morrey (17–26°) TER. An improvement of 44° in pronation-supination arc in our series is also comparable to that of 31–67° reported for GSB III and higher than the Coonrad-Morrey prosthesis (21–28°). In terms of complications, an infection rate of 6.7% is consistent with those reported for GSB III TER (7–11%) and Coonrad-Morrey (6–8%). The incidence of persistent ulnar neuropathy was lower compared to GSB III TER (11–14%), Coonrad-Morrey (12–26%), and Acclaim (8%). While the survival of Discovery TER was 93%, the survival of GSB III (5–6 years) and Coonrad-Morrey (5 years) has been reported as 71–85% and 72–90%. The results indicate that Discovery® Elbow System is an effective device for total elbow arthroplasty in terms of functional improvement, pain relief and range of motion at short-term follow-up

Purpose of study:. Total elbow replacement (TER) is one of the surgical options for treatment of severe haemophilic arthropathy of the elbow. There are only a few small series described in the literature. The goal of our study was to evaluate our cases and add these data to the known literature. Methods:. A retrospective analysis of a series of 8 TER's (5 patients) was performed. Patients were seen in clinic and evaluated by physical examination, a VAS score for pain, the Mayo Elbow Performance Score (MEPS, 100 points=excellent) and X-rays of the affected elbow. Mean follow-up was 91 (4–236) months, and 103 months when we excluded a patient with only 4 months follow-up. Primary diagnosis was Hemophilia type A in 4 and von Willebrand disease in 1 patient. 2 patients were positive for Hepatitis C and 3 for HIV. Mean age at primary surgery was 46.7 (31.8–63.1) years. Results:. The mean VAS score for pain improved from 7.9 to 0.5 and the mean Mayo Elbow Performance Score from 36 to 93. The arc for flexion/extension improved from 68° to 91° and from to 75° to 153° for pro- and supination. Revision surgery was performed in 3 out of 8 TER's; 1 because of loosening of the humeral component (18.7 years postop), 1 for loosening of the ulnar component (9.9 years postoperatively) and 1 due to a late deep infection, 4 years postoperatively. The last case was treated with an excision arthroplasty, the others with a revision. No replacement currently shows signs of loosening. Conclusion:. This is a small retrospective study, as are the other studies on TER in haemophilic patients. It demonstrated excellent clinical outcome and an acceptable survival rate of a TER, with a mean follow-up of 7.6 years even in this young patient population

TER is a viable surgical option in patients with advanced RA with painful stiff elbows. We retrospectively analysed 22 TER performed in 21 patients over a 12 year period by a single surgeon, with a mean follow up of 64 months (10–145). Disability of the arm, shoulder and hand (DASH) scores were performed pre-operatively and post-operatively in patients through postal questionnaires. The mean age was 59.1 years (32–78). There were 12 women and 9 men. The mean pre-operative DASH score was 72.3 (45.0–91.7) and post-operatively improved to 46.8 (21.7–94.2). Complications included infection, peri-operative fracture, peri-prosthetic fracture and aseptic loosening. There were 6 revisions performed, 2 for peri-prosthetic fracture, 2 for infection, 1 for intra-operative fracture and 1 for symptomatic aseptic loosening. Four patients had died due to unrelated causes. The 10 year survival rate with symptomatic aseptic loosening as the end point was 93% and revisions for all reasons was 69%. Follow up radiographs (in those without revision) were reviewed and 10 had satisfactory positioning of the prosthesis, 5 had loosening of the humeral or radial component and 1 had inadequate cement mantle but was clinically asymptomatic. TER is a rewarding procedure in with advanced RA. Our results are comparable to other published studies

We retrospectively analysed a single surgeon series of 22 TER in 21 patients over a 12 year period. The mean age and follow up was 59.1 years and 64 months respectively. DASH scores assessed pre and post op confirmed a significant improvement. Complications included infection, intra-operative fracture, peri-prosthetic fracture and aseptic loosening. 6 revisions were performed for various reasons.4 patients had died due to unrelated causes. The 10 year survival rate with symptomatic aseptic loosening as the end point was 93%. 5 patients had radiological loosening but were clinically asymptomatic. TER is a rewarding procedure in with advanced RA

Introduction. The aim of this study is to analyse the effect of the degree of coverage of the Total Elbow implant with cement and the significance of cementation index as a predictor of failure. Material/methods. Fifty elbows in forty seven patients who had undergone the Coonrad-Morrey TER were included in the study. The post-operative radiographs were evaluated for the cementation index. Failures and revisions were documented. Statistical analysis was done to evaluate the cementation index as a predictor of failure. Results. The mean period of follow up was 4.67 ± 2.85 years. The mean cementation index of the humerus (CIH) was 1.22 ± 0.28 (range 0.7 to 2.1). The mean cementation index of the ulna (CIU) was 1.10 ± 0.18 (range 0.77 to 1.72). The Kolmogorov-Smirnov test, used to test the type of distribution, showed that both the indices had a normal distribution (p > 0.05). Both the humeral and ulnar cementation indices were not found to be statistically significant predictors of failure (p > 0.05). Conclusions. The cementation index is an objective method of assessment of the coverage of the implant with cement. In the present series, the cementation index of the humerus varied from 0.7 to 2.1 and that of the ulna varied from 0.77 to 1.72 but both were not found to be statistically significant. A larger study with adequate follow-up should be done to establish the minimum cement mantle that can be considered adequate for the long term survivorship of the prosthesis

In this study we reviewed all Total Elbow Replacements (TER) done in our hospital over eight years period (1997 – 2005), 21 patients (16 females, 5 males) were available for follow up and four were lost (two died and two moved out of the region) with average age of 65 years (range 44 – 77), all procedures were done by two upper limb surgeons (CHB & RGW). 16 patients (14 females, 2 males) had the procedure for Rheumatoid Arthritis and 5 patients (3 males, 2 females) undergone the procedure for post-traumatic arthritis. The average follow up was 61 months (range 12 – 120 months), the Mayo Clinic performance index, the DASH scores and activities of daily living (adopted from Secec Elbow Score) assessment tools were used. In addition, all patients were assessed for loosening using standard AP and lateral radiographs. Sixteen patients had Souter-Starthclyde prosthesis whilst three had Kudo and two had Conrad-Moorey prosthesis. All procedures were done through dorsal approach and all were cemented, the ulnar nerve was not transposed in any of the cases. The average elbow extension lag was 27 degrees (range 15 – 35) with flexion up to 130 degrees (range 110 – 140). Supination was 65 degrees (range 15 – 90) and pronation was 77 (range 55 – 90). The average DASH score was 51.3 (range 19 – 95), the Mayo elbow score was 82 (range 55 – 100) and the average Activities of daily living Secec Score was 17 (range 10 – 20). There were four complications, three ulnar nerve paresis which recovered and one wound complication which needed a flap cover. Two needed revision surgery, one for a periprosthetic fracture and one for loosening. Two patients showed radiological signs of loosening but were asymptomatic. The survival rate with revision as the end point is 95% for aseptic loosening and 90% for any other reason. Our study proves TER has good medium term results with good functional outcome and high patient satisfaction rate

In this study we reviewed all Total Elbow Replacements (TER) done in our hospital over eight years period (1997 – 2005), 21 patients (16 females, 5 males) were available for follow up and four were lost (two died and two moved out of the region) with average age of 65 years (range 44 – 77), all procedures were done by two upper limb surgeons (CHB & RGW). 16 patients (14 females, 2 males) had the procedure for Rheumatoid Arthritis and 5 patients (3 males, 2 females) undergone the procedure for post-traumatic arthritis. The average follow up was 61 months (range 12 – 120 months), the Mayo Clinic performance index, the DASH scores and activities of daily living (adopted from Secec Elbow Score) assessment tools were used. In addition, all patients were assessed for loosening using standard AP and lateral radiographs. Sixteen patients had Souter-Starthclyde prosthesis whilst three had Kudo and two had Conrad-Moorey prosthesis. All procedures were done through dorsal approach and all were cemented, the ulnar nerve was not transposed in any of the cases. The average elbow extension lag was 27 degrees (range 15 – 35) with flexion up to 130 degrees (range 110 – 140). Supination was 65 degrees (range 15 – 90) and pronation was 77 (range 55 – 90). The average DASH score was 51.3 (range 19 – 95), the Mayo elbow score was 82 (range 55 – 100) and the average Activities of daily living Secec Score was 17 (range 10 – 20). There were four complications, three ulnar nerve paresis which recovered and one wound complication which needed a flap cover. Two needed revision surgery, one for a periprosthetic fracture and one for loosening. Two patients showed radiological signs of loosening but were asymptomatic. The survival rate with revision as the end point is 95% for aseptic loosening and 90% for any other reason. Our study proves TER has good medium term results with good functional outcome and high patient satisfaction rate

Non-tuberculous mycobacterial (NTM) infection of the musculoskeletal tissue is a rare disease. An early and accurate diagnosis is often difficult because of the indolent clinical course and difficulty of isolating pathogens. Our goal was to determine the clinical features of musculoskeletal NTM infection and to present the treatment outcomes. A total of 29 patients (nine females, 20 males between 34 and 85 years old, mean age 61.7 years; 34 to 85) with NTM infection of the musculoskeletal system between 1998 to 2011 were identified and their treatment retrospectively analysed. Microbiological studies demonstrated NTM in 29 patients: the isolates were Mycobacterium intracellulare in six patients, M. fortuitum in three, M. abscessus in two and M. marinum in one. In the remaining patients we failed to identify the species. The involved sites were the hand/wrist in nine patients the knee in five patients, spine in four patients, foot in two patients, elbow in two patients, shoulder in one, ankle in two patients, leg in three patients and multiple in one patient. The mean interval between the appearance of symptoms and diagnosis was 20.8 months (1.5 to 180). All patients underwent surgical treatment and antimicrobial medication according to our protocol for chronic musculoskeletal infection: 20 patients had NTM-specific medication and nine had conventional antimicrobial therapy. At the final follow-up 22 patients were cured, three failed to respond to treatment and four were lost to follow-up. Identifying these diseases due the initial non-specific presentation can be difficult. Treatment consists of surgical intervention and adequate antimicrobial therapy, which can result in satisfactory outcomes.

Cite this article: Bone Joint J 2014;96-B:1561–5.