Patient-Specific Design and Biomechanical Evaluation of a Novel Bipolar Femoral Hemi-Knee Prosthesis

While total knee replacement is successful, hemiarthroplasty is necessary for some young, obese and active patients who are especially not suitable for unicompartmental or total knee prostheses. Hemiarthroplasty also provides an opportunity for children with bone tumors. The design ofhemiarthroplasty should be patient-specific to reduce contact stress and friction as well as instability, compared to conventional hemi-knee prosthesis. A novel bipolar hemi-knee prosthesis with two flexion stages was developed according to a healthy male＇s knee morphological profile. The motion mode of the bipolar hemi-knee prosthesis was observed through roentgenoscopy in vitro experiment. The biomechanical properties in one gait cycle were evaluated though finite element simulation. The bipolar hemi-knee prosthesis was found to produce knee flexion at two stages through X-ray images. The first stage is the motion from upright posture to a specified 60~ flexion, followed by the second stage of motion subsequently to deep flexion. The finite element simulation results also show that the designed hemi-knee prosthesis has the ability to reduce stresses on the joint contact surfaces. Therefore, it is possible for the bipolar hemi-knee prosthesis to provide better biotribological performances because it can reduce stresses and potentially wear on the opposing contacting surface during a gait cycle, orovidin~ a t~romisin~ treatment strate~v in future Joint renair znd renlneement     

关节置换前后髌骨高度对膝关节功能的影响

目的:研究全膝关节置换术前、术后Insall-Salvati指数和改良Insall-Salvati指数与术后膝关节活动度的关系。方法:采用HSS评分系统对患者全膝关节置换术后半年至一年的关节功能、活动度、肌力、屈曲畸形、稳定性等进行评价。测量81例(106膝)患者术前、术后X线片Insall-salvati指数及改良Insall-salvati指数。结果:术后HSS评分为(89±10)分,术前Insall-salvati指数及改良Insall-salvati指数分别为(1.00±0.13)、(1.61±0.21),术后Insall-salvati指数及改良Insall-salvati指数分别为(0.94±0.19)、(1.67±0.34)。关节置换术后Insall-salvati指数较置换前显著降低(P0.05),改良Insall-salvati指数显著提高(P0.05)。术后低位髌骨组(Insall-salvati指数0.8)HSS评分、活动度和屈曲畸形分值均较正常髌骨组(0.8Insall-salvati指数1.5)显著降低(P0.05)(P0.05)。高位髌骨组(Insall-salvati指数1.5)和正常髌骨组各项评分均无显著差异(P0.05)。术前改良Insall-salvati指数小于1.8的患者术后膝关节HSS评分、功能、活动度、肌力、屈曲畸形、稳定性显著高于大于1.8的患者(P0.05)。结论:术前改良Insall-salvati指数和术后Insall-salvati指数可作为评价术后膝关节功能的参考指标。术前、术后的膝关节高度均会影响术后关节功能,全膝关节置换术中精确截骨对术后关节功能十分重要。     

Histochemistry as a Unique Approach for Investigating Normal and Osteoarthritic Cartilage

In this review article, we describe benefits and disadvantages of the established histochemical methods for studying articular cartilage tissue under normal, pathological and experimental conditions. We illustrate the current knowledge on cartilage tissue based on histological and immunohistochemical aspects, and in conclusion we provide a short overview on the degeneration of cartilage, such as osteoarthritis. Adult articular cartilage has low capacity to repair itself, and thus even minor injuries may lead to progressive damage and osteoarthritic joint degeneration, resulting in significant pain and disability. Numerous efforts have been made to implement the knowledge in the study of cartilage in the last years, and histochemistry proved to be an especially powerful tool to this aim.     

Estimating total knee replacement joint load ratios from kinematics

Accurate prediction of loads acting at the joint in total knee replacement (TKR) patients is key to developing experimental or computational simulations which evaluate implant designs under physiological loading conditions. In vivo joint loads have been measured for a small number of telemetric TKR patients, but in order to assess device performance across the entire patient population, a larger patient cohort is necessary. This study investigates the accuracy of predicting joint loads from joint kinematics. Specifically, the objective of the study was to assess the accuracy of internal–external (I–E) and anterior–posterior (A–P) joint load predictions from I–E and A–P motions under a given compressive load, and to evaluate the repeatability of joint load ratios (I–E torque to compressive force (I–E:C), and A–P force to compressive force (A–P:C)) for a range of compressive loading profiles. A tibiofemoral finite element model was developed and used to simulate deep knee bend, chair-rise and step-up activities for five patients. Root-mean-square (RMS) differences in I–E:C and A–P:C load ratios between telemetric measurements and model predictions were less than 1.10e–3 Nm/N and 0.035 N/N for all activities. I–E:C and A–P:C load ratios were consistently reproduced regardless of the compressive force profile applied (RMS differences less than 0.53e–3 Nm/N and 0.010 N/N, respectively). When error in kinematic measurement was introduced to the model, joint load predictions were forgiving to kinematic measurement error when conformity between femoral and tibial components was low. The prevalence of kinematic data, in conjunction with the analysis presented here, facilitates determining the scope of A–P and I–E joint loading ratios experienced by the TKR population.     

Patellar mechanics during simulated kneeling in the natural and implanted knee

Kneeling is required during daily living for many patients after total knee replacement (TKR), yet many patients have reported that they cannot kneel due to pain, or avoid kneeling due to discomfort, which critically impacts quality of life and perceived success of the TKR procedure. The objective of this study was to evaluate the effect of component design on patellofemoral (PF) mechanics during a kneeling activity. A computational model to predict natural and implanted PF kinematics and bone strains after kneeling was developed and kinematics were validated with experimental cadaveric studies. PF joint kinematics and patellar bone strains were compared for implants with dome, medialized dome, and anatomic components. Due to the less conforming nature of the designs, change in sagittal plane tilt as a result of kneeling at 90° knee flexion was approximately twice as large for the medialized-dome and dome implants as the natural case or anatomic implant, which may result in additional stretching of the quadriceps. All implanted cases resulted in substantial increases in bone strains compared with the natural knee, but increased strains in different regions. The anatomic patella demonstrated increased strains inferiorly, while the dome and medialized dome showed increases centrally. An understanding of the effect of implant design on patellar mechanics during kneeling may ultimately provide guidance to component designs that reduces the likelihood of knee pain and patellar fracture during kneeling.     

Does Isolated Unilateral Hip or Knee Osteoarthritis Lead to Adverse Changes in Extremity Composition?

BackgroundWhile muscle atrophy is a function of normal aging, loss of muscle in the setting of hip and knee osteoarthritis (OA) has been observed using radiographic studies. There is limited data available regarding changes in extremity composition using bioimpedance (BIA). The purpose of this study was to assess the changes in extremity composition in patients with isolated, unilateral hip or knee OA using BIA.MethodsPatients presenting to our institution’s adult reconstruction clinic from February 2020 to April 2021 were retrospectively reviewed to identify those with isolated, unilateral hip and knee OA. The InBody 770 Body Composition Analyzer (InBody USA, Cerritos, California) was used to perform a complete body composition assessment, per protocol. Lean extremity mass (LEM), fat mass (FM), intracellular water (ICW), extremity body water (EBW = ICW + extracellular water (ECW)) and phase angle (PA) were determined. Differences between the affected (OA) and unaffected (no OA) extremities were compared using t-tests.Results38 patients had isolated hip OA. The mean age was 60.8 (±11.7) years, mean BMI was 31.7 (±6.8) kg/m2, and 39.5% were female. LEM, FM, EBW, ICW, and PA were significantly decreased in the hip OA extremity (LEM: 20.0 vs. 20.4 kg, p=0.0008, FM: 8.8 vs. 8.9 kg, p=0.0049, EBW: 15.7 vs 16.0, p=0.0011, ICW: 9.5 vs. 9.7 L, p=0.0004, PA: 4.5 vs 4.9º, p<0.0001). There were 25 patients with isolated knee OA. Mean age was 62.8 (±11.3) years, mean BMI was 33.6 (±6.9) kg/m2, and 52.0% were female. FM and PA were significantly lower in the knee OA extremity (11.3 vs 11.4 kg, p=0.0291, 4.5 vs 4.9º, p<0.0001). There were no significant differences in LEM, EBW, and ICW between the knee OA extremity and the unaffected extremity.ConclusionPatients with isolated, unilateral hip OA had decreased LEM, FM, EBW, and ICW in the affected extremity. Both unilateral hip and knee OA was associated with decreased PA, suggestive of greater underlying dysfunction in muscle or cellular performance. Further study is needed to better define when these abnormalities develop, how they progress over time, and the impact of targeted interventions in reversing these changes. Level of Evidence: III     

Simultaneous tissue profiling of eicosanoid and endocannabinoid lipid families in a rat model of osteoarthritis

We describe a novel LC method for the simultaneous and quantitative profiling of 43 oxylipins including eicosanoids, endocannabinoids, and structurally related bioactive lipids with modified acyl groups. The LC-MS/MS method uses switching at a defined time between negative and positive electrospray ionization modes to achieve optimal detection sensitivity for all the lipids. The validated method is linear over a range of 0.01–5 nmol/g (0.1–50 nmol/g for 2-arachidonoyl glycerol) with intra- and interday precision and accuracy between 1.38 and 26.76% and 85.22 and 114.3%, respectively. The method successfully quantified bioactive lipids in different tissue types in the rat, including spinal cord, dorsal root ganglia (DRGs), knee joint, brain, and plasma. Distinct regional differences in the pattern of lipid measured between tissue types were observed using principle component analysis. The method was applied to analyze tissue samples from an established preclinical rat model of osteoarthritis (OA) pain and showed that levels of 12-hydroxyeicosatetraenoic acid were significantly increased in the OA rat knee joint compared with controls, and that 15-hydroxyeicosatetraenoic acid was significantly increased in the DRGs in the model of OA compared with controls. The developed LC-MS/MS method has the potential to provide detailed pathway profiling in tissues and biofluids where the disruption of bioactive oxylipins may be involved in disease states.