Ultracompact, completely implantable permanent use electromechanical ventricular assist device and total artificial heart

An ultracompact, completely implantable permanent use electromechanical ventricular assist device (VAD) and total artificial heart (TAH) intended for 50-60 kg size patients have been developed. The TAH and VAD share a miniature electromechanical actuator that comprises a DC brushless motor and a planetary roller screw. The rotational force of the motor is converted into the rectilinear force of the roller screw to actuate the blood pump. The TAH is a one piece design with left and right pusher plate type blood pumps sandwiching an electromechanical actuator. The VAD is one half of the TAH with the same actuator but a different pump housing and a backplate. The blood contacting surfaces, including those of the flexing diaphragm and pump housing, of both the VAD and TAH were made of biocompatible polyurethane. The diameter, thickness, volume, and weight of the VAD are 90 mm, 56 mm, 285 cc, and 380 g, respectively, while those of the TAH are 90 mm, 73 mm, 400 cc, and 440 g, respectively. The design stroke volume of both the VAD and TAH is 60 cc with the stroke length being 12 mm. The stroke length and motor speed are controlled solely based on the commutation signals of the motor. An in vitro study revealed that a maximum pump flow of 7.5 L/min can be obtained with a pump rate of 140 bpm against a mean afterload of 100 mm Hg. The power requirement ranged from 4 to 6 W to deliver a 4-5 L/min flow against a 100 mm Hg afterload with the electrical-to-hydraulic efficiency being 19-20%. Our VAD and TAH are the smallest of the currently available devices and suitable for bridge to transplant application as well as for permanent circulatory support of 50-60 kg size patients.     

The use of a Bayesian forecasting model in the management of warfarin therapy after total hip arthroplasty

This study was performed to compare the computer-based and physician-based management of warfarin therapy after total hip arthroplasty (THA). The computer-assisted and control groups of patients were placed on warfarin postoperatively and followed for a 1-month period. A significant difference (P<.05) was found between the mean number of days needed to reach therapeutic anticoagulation in the control group (4.7+/-3.0 days) and the experimental group (2.8+/-1.4 days) and the proportion of patients in each group who were discharged with a subtherapeutic international normalized ratio (INR) (INR <1.5). The computer-based management of warfarin therapy was more efficient than unaided physician-based management and therefore may lead to improved, cost-effective patient care by reducing length of hospital stay and complications attributable to nontherapeutic anticoagulation in THA patients.     

全髋关节置换术后脱位21例临床分析

目的分析全髋关节置换术后脱位的影响因素,探讨术中如何准确置人髋关节假体以减少髋关节脱位。方法分析我科2005年1月—2012年12月全髋关节置换术后脱位病例的影响因素。结果本组病人脱位发生率为1．3％。女性占脱位人数的比例为62％,男性占38％。早期脱位占脱位人数的比例为90％,晚期脱位占10％。前方脱位占脱位人数的比例为19％,后方脱位占81％。假体位置不良占脱位人数的比例为52％,精神神经功能不全者占29％,术后活动范围过度者占脱位人数的比例为19％。结论患者因素、术者因素及髋关节假体因素都对人工髋关节置换术后脱位产生影响,术中准确置人髋关节假体是影响髋关节脱位的关键因素。     

Unstable versus stable uncemented femoral stems: a radiological study of periprosthetic bone changes in two types of uncemented stems with different concepts of fixation

Introduction Uncemented stems in total hip arthroplasty (THA) are used increasingly often because they are believed to offer a reliable long-term fixation. However, periprosthetic bone remodelling has been a worrying issue. A proximal demineralization has been noted in femurs with well-fixed stems, and it has been explained as by-passing of mechanical forces along the fixed implant (stress-shielding). Aseptic loosening has been a major problem in several uncemented series with earlier designs. The objective for this study was to investigate how the host bone adapts to a loose stem compared with a well-fixed stem after a long time.Materials and methods An investigation with dual-energy X-ray absorptiometry (DEXA), scintimetry and radiological assessment was carried out in 20 patients 8 years after a THA for arthrosis with two different uncemented stems. Ten patients received a stem coated with polytetrafluoroethylene (Anaform); all prostheses showed migration and were considered unstable. Ten patients received a hydroxyapatite-coated stem (Bi-Metric); no prosthesis migrated.Results Different remodelling patterns were seen. In the unstable group, the periprosthetic bone mineral density (BMD) was significantly reduced along the entire stem, while in the stable group only proximal bone loss was seen. The scintigraphic uptake was increased under the stem tip in both groups, and among unstable stems uptake was also increased in the calcar region.Conclusion The assessment of periprosthetic bone remodelling after uncemented THA with long-term observation shows a different host-bone response in stable versus unstable femoral implants. Prior to a femoral revision, measurement of the BMD could be beneficial; it may guide the surgeon when deciding which surgical technique to use.     

Bone Mineral Density in the Proximal Femur and Contralateral Knee After Total Knee Arthroplasty

Osteoarthrosis (OA) is often associated with pain and disability, which are relieved after total knee arthroplasty (TKA), but the nature of bone changes associated with OA is controversial. We examined preoperative hip and contralateral knee bone mineral density (BMD) in patients requiring TKA and monitored the BMD changes postoperatively. Sixty-nine patients, scheduled to have TKA for osteoarthrotic knees, had both hips and contralateral knee BMD measured by dual-energy X-ray absorptiometry (DXA) at the time of operation (baseline) and at 1 yr after operation. X-rays of the knee joints were also taken to evaluate the severity of OA. Preoperatively, 27% and 38% of the patients had total hip BMD Z-score more than 1 SD in the operated side and contralateral hips, respectively. In all regions of interest (ROI), the mean baseline BMD of the affected side proximal femur was significantly lower than that of the contralateral side (p < 0.0005-0.019). The severity of OA was not associated with BMD. During 1-yr follow-up, the postoperative knee status and the physical activity of the patients (AKS score) improved. However, neither the hip nor the nonoperated knee BMDs increased. Knee OA is associated with significantly lower BMD values in the affected side compared with the contralateral hip, and these levels remained similar or decreased during a 1-yr follow-up. We conclude that improved mobility after TKA does not improve the effects of preoperative disuse-associated bone loss in the short term.     

Two-incision technique for minimally invasive total hip arthroplasty

Recently, there has been considerable interest and debate over the application of minimally invasive surgical approaches to primary total hip arthroplasty. The 2-incision technique employs intermuscular and internervous planes to gain access to the hip joint while minimizing the disruption of muscles and tendons. Through the anterior incision, the femoral neck is osteotomized and the head removed, followed by preparation and cementless reconstruction of the acetabulum. The posterior incision permits femoral preparation and reconstruction with a cementless stem. The potential benefits of this technique include decreased perioperative blood loss and pain, more rapid recovery of hip function and return to normal activity, a reduced length of hospital stay, and cosmetically appealing small scars. Other essential considerations include appropriate patient selection, adherence to surgical principles, and familiarity with specialized instruments and implants.     

全直肠系膜切除术治疗直肠癌--附168例报告

目的　探讨全直肠系膜切除术在预防直肠癌术后局部复发中的作用 ,以及同该操作相关的一些并发症。方法　回顾性分析 16 8例直肠癌的临床资料。结果　全组无手术死亡 ,术后随访1～ 36月 ,局部复发 6例 (3.6 % ) ,术后吻合口漏 13例 (10 .7% ) ,多数保肛患者出现便频、便急等症状。结论　全直肠系膜切除术能有效降低直肠癌术后局部复发率 ,提高保肛率 ,但存在吻合口漏 ,控便功能等问题需进一步解决。     

Biomaterials,Part I: Symposium organized by the Scandinavian Orthopedic Association

Background and purpose A questionnaire was introduced by the New Zealand Arthroplasty Registry for use when evaluating the outcome of total ankle replacement surgery. We evaluated the reliability, validity, and responsiveness of the modified Swedish version of the questionnaire (SEFAS) in patients with osteoarthritis or inflammatory arthritis before and/or after their ankle was replaced or fused.

Patients and methods The questionnaire was translated into Swedish and cross-culturally adapted according to a standardized procedure. It was sent to 135 patients with ankle arthritis who were scheduled for or had undergone surgery, together with the foot and ankle outcome score (FAOS), the short form 36 (SF-36) score, and the EuroQol (EQ-5D) score. Construct validity was evaluated with Spearman’s correlation coefficient when comparing SEFAS with FAOS, SF-36, and EQ-5D, content validity by calculating floor and ceiling effects, test-retest reliability with intraclass correlation coefficient (ICC), internal consistency with Cronbach’s alpha (n = 62), agreement by Bland-Altman plot, and responsiveness by effect size and standardized response mean (n = 37).

Results For construct validity, we correlated SEFAS with the other scores and 70% or more of our predefined hypotheses concerning correlations could be confirmed. There were no floor or ceiling effects. ICC was 0.92 (CI 95%: 0.88–0.95), Cronbach’s alpha 0.96, effect size was 1.44, and the standardized response mean was 1.00.

Interpretation SEFAS is a self-reported foot and ankle score with good validity, reliability and responsiveness, indicating that the score can be used to evaluate patients with osteoarthritis or inflammatory arthritis of the ankle and outcome of surgery.     

A Comparison of Classical and Anatomical Total Knee Alignment Methods in Robotic Total Knee Arthroplasty : Classical and Anatomical Knee Alignment Methods in TKA

The purpose of this study was to compare the clinical and radiological outcomes achieved using classical and anatomical alignment methods in primary total knee arthroplasty (TKA). One hundred and seventeen patients were randomly assigned to undergo robotic-assisted TKA using either the classical (56 patients) or the anatomical alignment method (61 patients). Clinical outcomes including varus and valgus laxities, ROM, HSS and WOMAC scores and radiological outcomes were evaluated after a minimum follow-up of 2 years. Varus and valgus laxity assessments showed no significant inter-group differences (P > 0.05). Moreover, no significant differences were observed in ROM, HSS and WOMAC scores (P > 0.05). We could not find any significant difference in mechanical alignment of the lower limb. The results of this study show that two alignment methods provide comparable clinical and radiological outcomes after primary TKA.