Acceptable migration of a fully cemented rotating hinge-type knee revision system measured in 20 patients with model-based RSA with a 2-year follow-up.

BACKGROUND AND PURPOSE: Rotating hinged knee implants are highly constrained prostheses used in cases in which adequate stability is mandatory. Due to their constraint nature, multidirectional stresses are directed through the bone-cement-implant interface, which might affect fixation and survival. The goal of this study was to assess micromotion of a fully cemented rotating hinged implant using radiostereometric analysis (RSA). PATIENTS AND METHODS: 20 patients requiring a fully cemented rotating hinge-type implant were included. RSA images were taken at baseline, 6 weeks, and 3, 6, 12, and 24 months postoperatively. Micromotion of femoral and tibial components referenced to markers in the bone was assessed with model-based RSA software, using implant CAD models. Total translation (TT), total rotation (TR), and maximal total point motion (MTPM) were calculated (median and range). RESULTS: At 2 years, TTfemur was 0.38 mm (0.15-1.5), TRfemur was 0.71° (0.37-2.2), TTtibia was 0.40 mm (0.08-0.66), TRtibia was 0.53° (0.30-2.4), MTPMfemur was 0.87 mm (0.54-2.8), and MTPMtibia was 0.66 mm (0.29-1.6). Femoral components showed more outliers (> 1 mm, > 1°) compared with tibial components. CONCLUSION: Fixation of this fully cemented rotating hinge-type revision implant seems adequate in the first 2 years after surgery. Femoral components showed more outliers, in contrast to previous RSA studies on condylar revision total knee implants.

Superior Survival of Fully Cemented Fixation Compared to Hybrid Fixation in a Single Design Rotating Hinge Knee Implant.

BACKGROUND: Clinical observations revealed higher rates of aseptic loosening for hybrid fixated rotating hinge knee implants compared to fully cemented ones. We hypothesize that the use of a fully cemented fixation technique had a higher survival rate for aseptic loosening compared to a hybrid fixation technique in a rotating hinge knee implant. METHODS: All procedures of patients who were treated with the RT-PLUS rotating hinge knee implant (Smith & Nephew, Memphis, TN) between 2010 and 2018 were included. Primary outcome was revision for aseptic loosening. Kaplan-Meier survivorship and Cox proportional hazard regression analysis were performed to calculate survival rates and hazard ratios. RESULTS: A total of 275 hinge knee implants were placed in 269 patients (60 primary procedures, 215 revisions). Median follow-up was 7.3 ± 3.9 years. In total, 24 components (16 hybrid femur, 2 fully cemented femur, 6 hybrid tibia; all revision procedures) in 19 patients were revised for aseptic loosening. Kaplan-Meier survivorship analysis showed superior survival rates of fully cemented components (femur 97.1%; tibia 100%) compared to hybrid fixated components (femur 89.5%; tibia 95.9%) at the 10-year follow-up. Multivariate Cox hazard analysis showed a significantly higher risk of aseptic loosening for hybrid fixated components, a prior stemmed component and the femoral component. CONCLUSION: Fully cemented fixation showed superior survival rates for aseptic loosening compared to hybrid fixation in a single design rotating hinge knee implant. A prior stemmed component appears to be a risk factor for aseptic loosening and the femoral component seems to be more prone to loosening.

Tapered, fluted, modular, titanium stems in Vancouver B periprosthetic femoral fractures: an analysis of 87 consecutive revisions.

AIMS: One of the instruments in the orthopaedic surgeon's armamentarium to face the challenges associated with periprosthetic fracture around the stem of a hip replacement is the tapered, fluted, modular, titanium (TFMT) stem. Our aim was to study its clinical and radiological outcomes. PATIENTS AND METHODS: During the period 2010-2016 86 patients (55 females; median age 78.2 years; mean BMI 26.3 kg/m2; median ASA classification 2) underwent 87 revisions for a Vancouver B periprosthetic fracture using a Stryker Restoration Cone-Conical stem. RESULTS: After a median follow-up of 2.9 years no stem had to be revised and no case of stem fracture was found. Dislocation was the most common complication and occurred in 18% of patients. Other major complications were deep infection (n = 4), subsidence >5 mm (n = 7), and nonunion (n = 5). 3-month and 1-year mortality was 10% and 15% respectively and was strongly correlated with age, deep infection, and ASA classification. The median EQ-5D health state index at final follow-up was 0.78 and all patients were ambulatory. CONCLUSIONS: The complication most commonly encountered was dislocation and can likely be prevented by the use of large heads, adequate reduction and fixation of the trochanteric area and restoration of the native anatomy. Contrary to previous concerns, fracture and subsidence of these modular stems do not appear to be a significant problem in this geriatric population.

Instability, an unforeseen diagnosis of the Legion™ hinge knee system.

BACKGROUND: Instability is an infrequently encountered diagnosis in rotating hinge knee (rHK) implants. With the introduction of a new rHK implant, we encountered multiple patients who complained of instability. This article presents its prevalence while describing our diagnostic and treatment algorithms. METHODS: A retrospective analysis of a cohort of all consecutive patients treated with the Legion™ Hinge Knee System (Smith&Nephew, Memphis, Tennessee) as primary or revision procedure between July 2014 and December 2018 was performed. All patients reporting a sense of instability or having recurrent joint effusion after activity were suspected of experiencing instability. Stress X-rays were performed and brace treatment was started. In patients with insufficient effect of brace treatment, a liner exchange to a thicker liner was performed. Prevalence of instability and the effect of treatment was analysed descriptively. RESULTS: In total, six patients were categorized as patients having instability problems (prevalence 3.5%; male:female ratio 5:1; median age 69.5 years; all revision procedures). Indication for revision to the Legion rHK implant was infection (three), instability (two) and aseptic loosening (one). In two patients, a prior rHK implant was revised. All patients showed tilting beyond the tolerance on stress X-ray examination. Brace treatment was adequate in three patients; in the other three patients a liner exchange was performed, two of which were satisfied. CONCLUSION: Instability is an infrequently encountered diagnosis in rHK implants. The design of the Legion rHK implant seems prone to this problem with a prevalence of 3.5%. If brace treatment is insufficient a liner exchange might be considered.

Surgical treatment of acromioclavicular dislocation associated with midshaft fracture of the ipsilateral clavicle.

Acromioclavicular dislocation combined with a midshaft clavicle fracture is a rare traumatic shoulder problem. Various treatment options have been described in literature. We describe a new technique using a hook plate and coracoclavicular sling to replace the ruptured coracoclavicular ligaments in combination with plate osteosynthesis of the clavicle fracture. Furthermore, we provide a short overview of the few cases described in literature and their treatment options.

Validation of a novel activity monitor in impaired, slow-walking, crutch-supported patients.

BACKGROUND: A growing need in clinical practice of rehabilitation and orthopaedic medicine is for objective outcome tools to estimate physical activity. Current techniques show limited validity or are too demanding for routine clinical use. Accelerometer-based activity monitors (AMs) have shown promise for measuring physical activity in healthy people but lack validity in impaired patients. OBJECTIVES: This study aimed to validate an accelerometer-based AM in impaired, slow-walking, crutch-supported patients after total joint arthroplasty (TJA). METHODS: Shortly after TJA, patients who were safely mobilized with 2 crutches and 8 healthy participants completed a trial of different activities while wearing the AM on the lateral upper leg and being videotaped. Outcome variables (e.g., time walking, number of gait cycles, sit-stand-sit transfers) were compared to video recordings, and sensitivity, predictive value and mean percentage difference (MPD) values were calculated. RESULTS: We included 40 patients (mean age: 65±9 years; mean BMI: 30±6kg/m2; male:female ratio: 18:22) and 8 healthy participants (mean age: 49±20 years; mean BMI: 23±0.7kg/m2; male:female ratio: 5:3). The AM showed excellent sensitivity (>95%) and predictive value (>95%) in identifying activities (e.g., walking, sitting, resting) and detecting the number of gait cycles and sit-stand-sit transfers (mean percentage difference: ±2%). Detection of number of steps ascending and descending stairs and cadence was more difficult but still showed good results (mean percentage difference: ±7%). CONCLUSIONS: This is the first validation study to assess physical activity with an AM in impaired, slow-walking, crutch-supported patients. The AM was a valid tool for measuring physical activity in these patients. The tool may help in evaluating and optimizing rehabilitation programs for patients after TJA, those recovering from stroke or chronic impaired patients.