The effect of hemiarthroplasty implant modulus on contact mechanics: an experimental investigation

Elbow hemiarthroplasty and total elbow arthroplasty provided a similar functional outcome for unreconstructable distal humeral fractures in patients aged 60 years or older: a multicenter randomized controlled trial

BACKGROUND

Semiconstrained total elbow arthroplasty (TEA) is an established treatment for elderly patients with distal humeral fractures not amenable to stable internal fixation (unreconstructable). In recent years, there has been increasing interest in elbow hemiarthroplasty (EHA), a treatment option which does not entail restrictions on weight-bearing as opposed to TEA. These 2 treatments have not been compared in a randomized controlled trial (RCT). The aim of this study was to compare the functional outcome of EHA and TEA for the treatment of unreconstructable distal humeral fractures in elderly patients.

MATERIAL AND METHODS

This was a multicenter randomized controlled trial (RCT). Patients were included between January 2011 and November 2019 at one of 3 participating hospitals. The inclusion criteria were an unreconstructable distal humeral fracture, age ≥60 years and independent living. The final follow-up took place after ≥2 years. The primary outcome measure was the Disabilities of the Arm, Shoulder, and Hand (DASH) score. Secondary outcome measures were the Mayo Elbow Performance Score (MEPS), the EQ-5D index, range of motion (flexion, extension, pronation, and supination) and grip strength.

RESULTS

Forty patients were randomized to TEA (n = 20) and EHA (n = 20). Five patients died before completing the final follow-up, leaving 18 EHA and 17 TEA patients for analysis. There were 31 women. The mean age was 74.0 (SD, 8.5) years in the EHA group and 76.9 (SD, 7.6) in the TEA group (P = .30). The mean DASH score was 21.6 points in the EHA group and 27.2 in the TEA group (P = .39), a difference of -5.6 points (95% CI: -18.6 to 7.5). There were no differences between treatment with EHA and TEA for the mean values of the MEPS (85.0 vs. 88.2, P = .59), EQ-5D index (0.92 vs. 0.86, P = .13), extension (29° vs. 29°, P = .98), flexion (126° vs. 136°, P = .05), arc of flexion-extension (97° vs. 107°, P = .25), supination (81° vs. 75°, P = .13), pronation (78° vs. 74°, P = .16) or grip strength (17.5 kg vs. 17.2 kg, P = .89). There were 6 adverse events in each treatment group.

CONCLUSION

In this RCT, both elbow hemiarthroplasty (EHA) and total elbow arthroplasty (TEA) resulted in a good and similar functional outcome for unreconstructable distal humeral fractures in elderly patients at a minimum of 2 years of follow-up.

Distal Humerus Morphological Analysis of Chinese Individuals: A Statistical Shape Modeling Approach

Objective

A detailed analysis of the morphology of distal humeral articulation can help in the creation of anatomic prostheses of hemiarthroplasty. This study used statistical shape modeling to evaluate the 3D morphology of the distal humerus in healthy Chinese individuals and to investigate the proper articular morphology differences.

Methods

A statistical shape model (SSM) of the distal humerus was created using CT scans of 106 survey‐confirmed nonpathologic elbows. In addition, the articular components of each principal component (PC) were selected and fitted on the mean mode. The Euclidean point‐to‐mesh distance of articular modes was calculated as a measurement the proper change in the morphology of the articulation.

Results

The first seven PCs jointly accounted for 80.9% of the total variation (44.4%, 12.2%, 7.9%, 5.9%, 4.1%, 3.4% and 3%, respectively). In the mean model, the distance between the medial and lateral epicondyles was 57.4 mm, the width of the articulation was 42.1 mm, and the angle of the transepicondylar line (TEL) and C line was 4.8°. The articular surface differences of the first PC were significant (RMS: 1.43 mm in the −3 SD model and 2.38 mm in the +3 SD model), whereas under other conditions, the differences were not remarkable despite the maximum deformation not exceeding 1 mm.

Conclusion

A novel method (SSM) was used to evaluate the 3D morphology of the distal humerus in healthy Chinese individuals and investigate the proper articular shape differences. We found the proper shape of articular surface basically transformed into one variation pattern which was relevant to the bone size, even though the morphology of distal humerus possessed complicated variation modes. The findings of this study can be helpful to design the next generation of elbow hemiarthroplasty in the future.