Heath B. Henninger

HINTEGRA Total Ankle Replacement: Survivorship Analysis in 684 Patients

BACKGROUND Total ankle replacement is increasingly recommended for patients with end-stage ankle osteoarthritis. We analyzed the survivorship of 722 arthroplasties performed with one type of three-component total ankle prosthesis. METHODS Seven hundred and seventy-nine primary total ankle arthroplasties (741 patients) were performed between May 2000 and July 2010 with use of the HINTEGRA three-component prosthesis. A logistic multiple regression model was used to identify independent risk factors for prosthesis failure in 684 patients (722 ankles). The mean time to final follow-up (and standard deviation) was 6.3 ± 2.9 years. RESULTS Seven hundred and twenty-two ankles (684 patients) were available for survivorship analysis at the latest follow-up. The overall survival rates were 94% and 84% after five and ten years, respectively. Sixty-one ankles had a revision arthroplasty (twenty-seven both components, thirteen the tibial component only, and fourteen the talar component only) or were converted to a fusion (seven ankles).There were no polyethylene failures. There were no amputations. The generation category of the prosthesis, the cause of ankle osteoarthritis, and the age of the patient were identified as independent risk factors for prosthesis failure. CONCLUSIONS The midterm survivorship of the HINTEGRA implant was comparable with that of other third-generation total ankle replacements.

Validation of computational models in biomechanics

Abstract The topics of verification and validation have increasingly been discussed in the field of computational biomechanics, and many recent articles have applied these concepts in an attempt to build credibility for models of complex biological systems. Verification and validation are evolving techniques that, if used improperly, can lead to false conclusions about a system under study. In basic science, these erroneous conclusions may lead to failure of a subsequent hypothesis, but they can have more profound effects if the model is designed to predict patient outcomes. While several authors have reviewed verification and validation as they pertain to traditional solid and fluid mechanics, it is the intent of this paper to present them in the context of computational biomechanics. Specifically, the task of model validation will be discussed, with a focus on current techniques. It is hoped that this review will encourage investigators to engage and adopt the verification and validation process in an effort to increase peer acceptance of computational biomechanics models.

Total Ankle Replacement Using HINTEGRA, an Unconstrained, Three-Component System: Surgical Technique and Pitfalls

Total ankle replacement (TAR) has become a valuable treatment option in patients with end-stage ankle osteoarthritis. One popular 3-component system, the HINTEGRA TAR, is an unconstrained system that provides inversion-eversion stability. More natural biomechanics of the replaced ankle may be expected when anatomic considerations drive prosthesis design. The HINTEGRA prosthesis includes 2 anatomically contoured metal components and a polyethylene insert, providing axial rotation and physiologic flexion-extension mobility. This article describes the HINTEGRA TAR design and surgical technique. Use of the prosthesis for complex hindfoot reconstruction in patients with an osteoarthritic, varus, or valgus ankle deformity is described.

HINTEGRA Revision Arthroplasty for Failed Total Ankle Prostheses

BACKGROUND When a total ankle replacement fails, arthrodesis has been advocated as the treatment of choice. With the availability of a wide spectrum of implants, revision arthroplasty may become a viable alternative. METHODS We reviewed a consecutive series of 117 cases (116 patients [fifty-six female and sixty male]; mean age, 55.0 ± 12.0 years) in which a total ankle arthroplasty failed after a mean of 4.3 years and was revised with use of the HINTEGRA three-component total ankle prosthesis. The reason for revision involved the metallic components in sixty ankles (51%), the bone in twenty-eight (24%), the soft tissues in twenty (17%), and infection in nine (8%). The talar component was revised in 104 ankles (89%) and the tibial component, in 106 (91%). RESULTS Early complications included a fracture of the malleoli in two ankles and a dislocation of the polyethylene insert in one. Seventeen (15%) of the revision arthroplasties required further revision surgery, in most cases for loosening of one or two of the prosthetic components. The mean American Orthopaedic Foot & Ankle Society (AOFAS) hindfoot score for the remaining 100 ankles (85%) improved from 44 ± 18 preoperatively to 72 ± 19 (p < 0.01) at the time of the latest follow-up (mean, 6.2 years). The estimated survival of the revision arthroplasties at nine years, with loosening of components as the end point, was 83%. The prevalence of component loosening was higher (p < 0.005) with the use of single-coated hydroxyapatite components (six of twenty-three ankles, 26%) than with double-coated components (five of ninety-four ankles, 5%). The correlation between the extent of bone loss at the resection surface and the prevalence of component failure was weak and not significant. CONCLUSIONS The medium-term results of revision arthroplasty after a failed total ankle arthroplasty were similar to those after primary arthroplasty. The key to success was firm anchorage of the components to primary bone stock. A single hydroxyapatite component coating should no longer be used for revision total ankle arthroplasty.

Effect of lateral offset center of rotation in reverse total shoulder arthroplasty: a biomechanical study

BACKGROUND Lateral offset center of rotation (COR) reduces the incidence of scapular notching and potentially increases external rotation range of motion (ROM) after reverse total shoulder arthroplasty (rTSA). The purpose of this study was to determine the biomechanical effects of changing COR on abduction and external rotation ROM, deltoid abduction force, and joint stability. MATERIALS AND METHODS A biomechanical shoulder simulator tested cadaveric shoulders before and after rTSA. Spacers shifted the COR laterally from baseline rTSA by 5, 10, and 15 mm. Outcome measures of resting abduction and external rotation ROM, and abduction and dislocation (lateral and anterior) forces were recorded. RESULTS Resting abduction increased 20° vs native shoulders and was unaffected by COR lateralization. External rotation decreased after rTSA and was unaffected by COR lateralization. The deltoid force required for abduction significantly decreased 25% from native to baseline rTSA. COR lateralization progressively eliminated this mechanical advantage. Lateral dislocation required significantly less force than anterior dislocation after rTSA, and both dislocation forces increased with lateralization of the COR. CONCLUSION COR lateralization had no influence on ROM (adduction or external rotation) but significantly increased abduction and dislocation forces. This suggests the lower incidence of scapular notching may not be related to the amount of adduction deficit after lateral offset rTSA but may arise from limited impingement of the humeral component on the lateral scapula due to a change in joint geometry. Lateralization provides the benefit of increased joint stability, but at the cost of increasing deltoid abduction forces.

Medial distal tibial angle: comparison between weightbearing mortise view and hindfoot alignment view.

Background: The medial distal tibial angle (MDTA) is used to determine ankle alignment. The mortise view is the standard to measure MDTA, but the hindfoot alignment view (HAV) has become popular. The MDTA may vary between views, influencing the choice of surgery. Methods: The MDTA was compared between the mortise and HAV in 146 ankles. MDTA was correlated to age and sagittal tibial tilt for each view. Differences in MDTA by gender and ethnicity were assessed. Diagnostic agreement (varus, valgus, normal) between views was calculated. Clinical assessment of alignment was determined and percent agreement between clinical and radiographic alignment was quantified. Results: The MDTA measured from the mortise view and HAV radiographs was 89.0 (range, 81 to 96 degrees; SD = 2.8) degrees and 86.0 (range, 73 to 95 degrees; SD = 3.5) degrees, respectively. The MDTA was comparable for both genders for mortise (p = 0.356) and HAV (p = 0.621). The MDTA was comparable in all ethnic groups for mortise view (p = 0.616) and HAV (p = 0.916). Correlation between the measured MDTA and age was not statistically significant for both the mortise (r = 0.118; p = 0.158) and HAV (r = 0.148; p = 0.074). In only 47.3% of all ankles was the radiographic diagnosis of alignment the same between views. Agreement between clinical and radiographic classifications was 60.3% for the mortise view and 52.8% for the HAV. Conclusion: Substantial disagreement in primary alignment was found between the mortise and HAV as quantified by the MDTA. Agreement between clinical and radiographic alignment was also poor. Clinical Relevance: Advanced imaging such as CT or MRI may better describe ankle alignment.

Effect of deltoid tension and humeral version in reverse total shoulder arthroplasty: a biomechanical study

BACKGROUND No clear recommendations exist regarding optimal humeral component version and deltoid tension in reverse total shoulder arthroplasty (TSA). MATERIALS AND METHODS A biomechanical shoulder simulator tested humeral versions (0°, 10°, 20° retroversion) and implant thicknesses (-3, 0, +3 mm from baseline) after reverse TSA in human cadavers. Abduction and external rotation ranges of motion as well as abduction and dislocation forces were quantified for native arms and arms implanted with 9 combinations of humeral version and implant thickness. RESULTS Resting abduction angles increased significantly (up to 30°) after reverse TSA compared with native shoulders. With constant posterior cuff loads, native arms externally rotated 20°, whereas no external rotation occurred in implanted arms (20° net internal rotation). Humeral version did not affect rotational range of motion but did alter resting abduction. Abduction forces decreased 30% vs native shoulders but did not change when version or implant thickness was altered. Humeral center of rotation was shifted 17 mm medially and 12 mm inferiorly after implantation. The force required for lateral dislocation was 60% less than anterior and was not affected by implant thickness or version. CONCLUSION Reverse TSA reduced abduction forces compared with native shoulders and resulted in limited external rotation and abduction ranges of motion. Because abduction force was reduced for all implants, the choice of humeral version and implant thickness should focus on range of motion. Lateral dislocation forces were less than anterior forces; thus, levering and inferior/posterior impingement may be a more probable basis for dislocation (laterally) than anteriorly directed forces.

Risk factors for symptomatic deep-vein thrombosis in patients after total ankle replacement who received routine chemical thromboprophylaxis

The aim of this study was to identify the incidence of post-operative symptomatic deep-vein thrombosis (DVT), as well as the risk factors for and location of DVT, in 665 patients (701 ankles) who underwent primary total ankle replacement. All patients received low-molecular-weight heparin prophylaxis. A total of 26 patients (3.9%, 26 ankles) had a symptomatic DVT, diagnosed by experienced radiologists using colour Doppler ultrasound. Most thrombi (22 patients, 84.6%) were localised distally in the operated limb. Using a logistic multiple regression model we identified obesity, a previous venous thromboembolic event and the absence of full post-operative weight-bearing as independent risk factors for developing a symptomatic DVT. The incidence of symptomatic DVT after total ankle replacement and use of low-molecular-weight heparin is comparable with that in patients undergoing total knee or hip replacement.

Supramalleolar osteotomies for degenerative joint disease of the ankle joint: indication, technique and results.

Patients with varus or valgus hindfoot deformities usually present with asymmetric ankle osteoarthritis. In-vitro biomechanical studies have shown that varus or valgus hindfoot deformity may lead to altered load distribution in the tibiotalar joint which may result in medial (varus) or lateral (valgus) tibiotalar joint degeneration in the short or medium term. The treatment of asymmetric ankle osteoarthritis remains challenging, because more than half of the tibiotalar joint surface is usually preserved. Therefore, joint-sacrificing procedures like total ankle replacement or ankle arthrodesis may not be the most appropriate treatment options. The short- and midterm results following realignment surgery, are very promising with substantial pain relief and functional improvement observed post-operatively. In this review article we describe the indications, surgical techniques, and results from of realignment surgery of the ankle joint in the current literature.

Effect of elastin digestion on the quasi-static tensile response of medial collateral ligament.

Elastin is a structural protein that provides resilience to biological tissues. We examined the contributions of elastin to the quasi‐static tensile response of porcine medial collateral ligament through targeted disruption of the elastin network with pancreatic elastase. Elastase concentration and treatment time were varied to determine a dose response. Whereas elastin content decreased with increasing elastase concentration and treatment time, the change in peak stress after cyclic loading reached a plateau above 1 U/ml elastase and 6 h treatment. For specimens treated with 2 U/ml elastase for 6 h, elastin content decreased approximately 35%. Mean peak tissue strain after cyclic loading (4.8%, p ≥ 0.300), modulus (275 MPa, p ≥ 0.114) and hysteresis (20%, p ≥ 0.553) were unaffected by elastase digestion, but stress decreased significantly after treatment (up to 2 MPa, p ≤ 0.049). Elastin degradation had no effect on failure properties, but tissue lengthened under the same pre‐stress. Stiffness in the linear region was unaffected by elastase digestion, suggesting that enzyme treatment did not disrupt collagen. These results demonstrate that elastin primarily functions in the toe region of the stress–strain curve, yet contributes load support in the linear region. The increase in length after elastase digestion suggests that elastin may pre‐stress and stabilize collagen crimp in ligaments.