Batch Fabrication of a Polydimethylsiloxane Based Stretchable Capacitive Strain Gauge Sensor for Orthopedics.

Polymer-based capacitive strain gauges are a novel and promising concept for measuring large displacements and strains in various applications. These novel sensors allow for high strain, well above the maximum values achieved with state-of-the-art strain gauges (Typ. 1%). In recent years, a lot of interest in this technology has existed in orthopedics, where the sensors have been used to measure knee laxity caused by a tear of the anterior cruciate ligament (ACL), and for other ligament injuries. The validation of this technology in the field has a very low level of maturity, as no fast, reproducible, and reliable manufacturing process which allows mass production of sensors with low cost exists. For this reason, in this paper, a new approach for the fabrication of polymer-based capacitive strain gauges is proposed, using polydimethylsiloxane (PDMS) as base material. It allows (1) the fast manufacturing of sensor batches with reproducible geometry, (2) includes a fabrication step for embedding rigid electrical contacts on the sensors, and (3) is designed to produce sensor batches in which the size, the number, and the position of the sensors can be adapted to the patient's anatomy. In the paper, the process repeatability and the robustness of the design are successfully proven. After 1000 large-strain elongation cycles, in the form of accelerated testing caused much higher strains than in the above-mentioned clinical scenario, the sensor's electrical contacts remained in place and the functionalities were unaltered. Moreover, the prototype of a patient customizable patch, embedding multiple sensors, was produced.

Is changing the postoperative pain management in total knee arthroplasty from femoral nerve block to local infiltration analgesia successful? Retrospective trial with the first and last 100 patients.

PURPOSE: In recent years, there has been an increasing interest in local infiltration analgesia (LIA) as a technique to control postoperative pain. We compared this technique to the gold standard the 3 in 1 femoral nerve block (FNB) in postoperative pain management after total knee arthroplasty (TKA) in a large patient population. This trial analyzes in the early postoperative phase the pain, range of motion, and consumption of pain medications after TKA. METHODS: We conducted a retrospective trial that included all patients who were undergoing primary TKA by one single surgeon in a high-volume arthroplasty center in 2015. Patients who have secondary osteoarthritis due to rheumatoid arthritis or previous knee arthrotomy, as well as revision cases, were excluded. The included patients were divided into 2 groups according to the applied pain management (group 1 FNB, group 2 LIA). Concerning the LIA group, a modified form of composition compared to the first describer without the use of adrenaline was carried out. Post-operative additional pain medications were given on a fixed scheme to the patient. The primary outcome was pain at rest over 7 days after surgery labeled by the numeric pain rating scale (NRS). The secondary outcome measures were the total amount of opioid consumption over the hospital stay and the additional need for non-opioid medication. The conversion of the opiate medications on the morphine preparation was carried out according to the conversion data from the literature. For functional recovery, we compared the range of motion in both groups, which was recorded from the second postoperative day by the attending physiotherapist. RESULTS: In total, 202 patients were assessed for eligibility and included in this clinical trial. Hundred patients were allocated to the continuous FNB group (group 1) and 102 patients to the LIA group (group 2). No statistical difference was found between the two groups regarding demographic data. Primary outcome measurements: The LIA group had a significantly lower NRS score than the continuous FNB group for the measurement in the morning on days 1, 2, and 3 after surgery (day 1, 1.5; day 2, 1.6; day 3, 1.3; p < 0.05). Secondary outcome measurements: The total volume of morphine consumption for the first six postoperative days was significantly lower in the LIA group than the FNB group (FNB 159.8 vs. LIA 96.07). There is also a significant difference between the total morphine consumption of both groups in the direct postoperative course with respect to time and group (two way ANOVA, p < 0.05) On the day of the operation and on the first postoperative day, the intake of additional non-opioids in the LIA group was also significantly reduced compared to the FNB group. No significant difference was observed on the second to sixth postoperative day concerning an additional consumption of non-opioid medications. In terms of range of motion, the LIA group showed a higher active range of motion at the operated extremity than the FNB group during the hospital stay. CONCLUSION: The local intraarticular infiltration therapy (LIA) is a sufficient alternative to regional anesthesia avoiding the known risks of regional procedures. The results of this study reflect the efficiency of this pain management with a lower consumption of analgesics, identical to reduced postoperative pain ratings and an improved ROM in the first postoperative days. LEVEL OF EVIDENCE: Retrospective trial.

Augmentation of plate osteosynthesis for proximal humeral fractures: a systematic review of current biomechanical and clinical studies.

INTRODUCTION: Secondary dislocation due to loss of fixation is the most common complication after plate fixation of proximal humeral fractures. A wide range of different techniques for augmentation has been described to improve the primary and secondary stability. Nevertheless, comparative analyses on the specific advantages and limitations are missing. Therefore, the aim of the present article was to systematically review and evaluate the current biomechanical and clinical studies. MATERIALS AND METHODS: The databases of PubMed and EMBASE were comprehensively searched for studies on augmentation techniques for proximal humeral fractures using defined search terms. Subsequently, all articles identified were screened for eligibility and subdivided in either clinical or biomechanical studies. Furthermore, the level of evidence and study quality were assessed according the Oxford Centre for Evidence-Based Medicine and the Coleman Methodology Score, respectively. RESULTS: Out of 2788, 15 biomechanical and 30 clinical studies were included. The most common techniques were structural allogenic or autologous bone grafting to enhance the medial support, metaphyseal void filling utilizing synthetic bone substitutes or bone grafts, and screw-tip augmentation with bone cement. Biomechanical data were available for structural bone grafting to enhance the medial support, void filling with synthetic bone substitutes, as well as for screw-tip augmentation. Clinical evidence ranged from level II-IV and study quality was 26-70/100 points. Only one clinical study was found investigating screw-tip augmentation. All studies included revealed that any kind of augmentation positively enhances mechanical stability, reduces the rate of secondary dislocation, and improves patients' clinical outcome. None of the studies showed relevant augmentation-associated complication rates. CONCLUSIONS: Augmentation of plate fixation for proximal humeral fractures seems to be a reliable and safe procedure. All common techniques mechanically increase the constructs' stability. Clinically evaluated procedures show reduced complication rates and improved patient outcomes. Augmentation techniques seem to have the highest significance in situations of reduced bone mineral density and in high-risk fractures, such as 4-part fractures. However, more high-quality and comparative clinical trials are needed to give evidence-based treatment recommendations.

Current failure mechanisms after knee arthroplasty have changed: polyethylene wear is less common in revision surgery.

BACKGROUND: The present study was designed to clarify which underlying indications can be currently considered the main reasons for failure after total knee arthroplasty as a function of time. METHODS: We conducted a retrospective study that included all first revisions of total knee replacements during 2005 to 2010 at two high-volume arthroplasty centers. A revision was defined as the replacement of at least one prosthetic component. In the descriptive analysis, polyethylene wear, aseptic loosening, periprosthetic infection, malalignment, instability, arthrofibrosis, extensor mechanism deficiency, periprosthetic fracture, and retropatellar arthritis were given as the failure mechanism associated with an early, intermediate, or late time interval (less than one year, one to three years, and more than three years, respectively) after the index total knee arthroplasty. RESULTS: Three hundred and fifty-eight revision total knee arthroplasties were included. Of those revisions, 19.8% were performed within the first year after the index arthroplasty. The most common indications for revision, besides aseptic loosening (21.8%), were instability (21.8%), malalignment (20.7%), and periprosthetic infection (14.5%). Revisions due to polyethylene wear (7%) rarely occurred. In the early failure group, the primary causes of revision were periprosthetic infection (26.8%) and instability (23.9%). In the intermediate group, instability (23.3%) and malalignment (29.4%) required revision surgery, whereas late failure mechanisms were aseptic loosening (34.7%), instability (18.5%), and polyethylene wear (18.5%). CONCLUSIONS: Aseptic loosening, instability, malalignment, and periprosthetic infection continue to be the primary failure mechanisms leading to revision surgery. Contrary to previous literature, the results in the present study showed a substantial reduction in implant-associated revisions such as those due to polyethylene wear. Failure mechanisms that occur persistently early and in the intermediate term, such as periprosthetic infection, instability, and malalignment, remain common causes of revision surgery. LEVEL OF EVIDENCE: Therapeutic Level IV. See Instructions for Authors for a complete description of levels of evidence.

Indications for and results of arthroscopy in the arthritic knee: a European survey.

PURPOSE: The place of arthroscopic treatment in osteoarthritis of the knee has generated much controversy. A survey was initiated to collect the opinion of experienced surgeons. METHODS: Of the 211 surgeons interviewed, 170 (80.6%) replied to the electronic questionnaire. Respondents had at least ten years of experience in arthroscopy and currently perform more than 100 arthroscopies per year. Various indications and treatment modalities for arthroscopy in osteoarthritis of the knee had to be evaluated on a scale from "excellent" to "no indication". RESULTS: The respondents generally believe that an improvement is more likely in low-grade osteoarthritis (p < 0.001) and in neutral leg axis (p < 0.001). The outcome was rated better if symptoms had persisted for less than six months (p < 0.001) and for patients that were younger than 60 years (p < 0.001). Partial meniscectomy and notchplasty in cases of extension deficit were considered as successful treatment options. Debridement was an accepted indication, with an outcome mainly rated as fair. A majority saw no indication for joint lavage, arthroscopic treatment of arthrofibrosis and removal of osteophytes. The outcome appears to be poor if a bone edema is diagnosed on magnetic resonance imaging prior to arthroscopy. Only 55.9% of respondents were comfortable with the current definition of osteoarthritis. CONCLUSIONS: Experienced arthroscopic surgeons all over Europe believe arthroscopy in osteoarthritis is appropriate, under certain conditions. The major task for surgeons is to select the right patients who are likely to benefit from this intervention.

Rehabilitation results following anterior cruciate ligament reconstruction using a hard brace compared to a fluid-filled soft brace.

The purpose of this study was to compare the clinical outcomes of rehabilitation after ACL reconstruction using a water-filled soft brace to those using a hard brace. The method used in this study was a prospective randomised clinical trial including 36 patients wearing a hard brace and 37 patients wearing a water-filled soft brace for 6 weeks after surgery. Preoperative and postoperative (seven examinations) clinical evaluation within a follow-up period of 1 year including effusion status, swelling and range of motion (ROM), IKDC 2000, KT1000 Arthrometer, Lysholm knee scoring scale and Tegner activity score. Mean values are presented with standard deviations. Data was analysed using descriptive statistics and Student's t-test for unpaired samples. Significantly less effusion was found in the soft brace group from 5 days (p=0.002) to 12 weeks (p<0.024) postoperative. Hard brace patients presented with significantly more extension deficit from 5 days (p=0.036) to 12 months (p=0.014) postoperative but no significant difference was detected in complete ROM, laxity or thigh atrophy at any follow-up examination. Patients treated with a soft brace had significantly higher IKDC subjective ratings at 6 weeks (p=0.02) up to 12 months after operation (p=0.002) and rated significantly higher in Tegner activity score (p=0.004) and Lysholm knee scoring scale (p=0.006) 6 and 12 months (p<0.001 for both scores) postoperatively. The water-filled soft brace was superior regarding effusion, swelling, extension deficit and patient-measured midterm outcome. The soft brace presents a safe, easy-to-use and effective alternative to the hard brace.

Simultaneous 3D assessment of glenohumeral shape, humeral head centering, and scapular positioning in atraumatic shoulder instability: a magnetic resonance-based in vivo analysis.

BACKGROUND: Success rates in the treatment of atraumatic shoulder instability differ, and in vivo identification of the individual insufficient stabilizers is difficult. HYPOTHESIS: Atraumatic shoulder instability is an inhomogeneous entity with varying alterations of the active and passive stabilizers. This might be a reason for inferior treatment results. STUDY DESIGN: Case control study; Level of evidence, 3. METHODS: Shoulders of 28 healthy volunteers and both shoulders of 14 patients with atraumatic instability and multidirectional laxity were examined in different arm positions using open magnetic resonance imaging. Three-dimensional postprocessing techniques were applied to determine 3D glenoid size and retroversion, radius of the humeral head, and curvature of the glenoid. The results of static stabilizers were compared with those of glenohumeral and scapular positioning in the same patients for identification of the individual insufficient stabilizers. RESULTS: The atraumatic unstable shoulders showed an increased mean retroversion on both sides, the difference being significant on the affected side (9.4 degrees +/- 4.8 degrees vs healthy 3.9 degrees +/- 1.3 degrees ; P < .05) with a range of 2.6 degrees to 16.6 degrees . The curvature analysis demonstrated a pronounced flatness of the glenoid with a significantly increased mean radius (103.8 mm vs healthy 41.7 mm). The extent of these changes varied widely among patients. Comparison of the static stabilizers with glenohumeral and scapular positioning revealed that isolated changes of the active stabilizers exist in some patients, whereas no isolated changes of passive stabilizers were found. CONCLUSION: All active and passive stabilizers need to be analyzed in patients with atraumatic instability because the magnitude of alteration varied widely among individuals. Different combinations of alterations of the stabilizers were found. The presented technique allows for in vivo identification of the specific alterations. This is necessary for a better understanding of individual pathomechanics and for initiating a specific causal treatment.

[The mini-midvastus approach for total knee arthroplasty]. / Der Mini-Midvastus-Zugang zur Implantation von Kniegelenkendoprothesen.

OBJECTIVE: Minimally invasive approach to the knee for total knee arthroplasty to reduce soft-tissue trauma. INDICATIONS: Total knee replacements. Revision surgery after total knee arthroplasty. CONTRAINDICATIONS: Severe obesity. Revision surgery with preoperative flexion<90 degrees. SURGICAL TECHNIQUE: Anterior midline incision, blunt separation of the distal part of the oblique fibers of the vastus medialis over a length of 1-3 cm. The muscle split ends at the proximal medial corner of the patella. The incision is continued medially of the patella ending at the tibial tuberosity. After approaching the joint, the patella is shifted laterally without dislocating it, thus exposing the articular surfaces. Surgery is performed in maximal knee flexion of 90 degrees . After insertion of the components, stepwise wound closure and only superficial adaptation of the muscle split. POSTOPERATIVE MANAGEMENT: Mobilization with weight bearing and range of motion as tolerated. RESULTS: In a prospective study, 267 knee prostheses were implanted between 2005 and 2007 using the mini-midvastus approach. All patients (160 female, 107 male, average age 69.3 years [46-89 years]) were examined clinically and radiologically prior to and 6 weeks after surgery. The clinical results were based on the American Knee Society Score, which increased from a preoperative value of 48.9 (32-68) to 86.5 (75-100) at follow-up. Radiologically, 92.1% of the knees showed a malposition<3 degrees.