Changes in knee extensor strengths before and after medial patellofemoral ligament reconstruction

Objective: Quadriceps dysfunction has been suggested as a complication after medial patellofemoral ligament (MPFL) reconstruction. The purpose of this study was to investigate changes in knee extensor strength before and after MPFL reconstruction.

Methods: Twenty patients who underwent MPFL reconstruction for unilateral recurrent patellar dislocation (18 females and 2 males; mean age 20.8 ± 7.6 years) were examined. The peak isometric torque at 60° and 90° of knee flexion and isokinetic knee extensor strength at speeds of 60°/s and 90°/s in operated and non-operated legs were measured using a dynamometer preoperatively and 6 months, 1 year, and 2 years postoperatively. The following parameters were evaluated: (1) body weight-adjusted muscle strength, (2) improvement index (post-/preoperative value × 100) (%), and (3) extensor strength ratio (operated/non-operated value × 100) (%).

Results: The mean knee extensor strength in both operated and non-operated legs significantly increased 2 years after surgery compared with that before surgery. At 2 years postoperatively, the improvement indexes of the isometric knee extensor strength at 60° and 90° and of the isokinetic knee extensor strength at 60°/s and 90°/s were 237%, 192%, 318%, and 186%, respectively, in the operated legs and 144%, 124%, 140%, and 140%, respectively, in the non-operated legs. At 2 years postoperatively, the mean isometric knee extensor strength ratios at 60° and 90° and the isokinetic knee extensor strength ratios at 60°/s and 180°/s were 81%, 84%, 81%, and 82%, respectively.

Conclusions: Knee extensor strength was improved in most patients after MPFL reconstruction, at least compared with that before surgery, although an approximately 20% deficit against the non-operated legs remained even 2 years after surgery.     

Rate of torque development is the primary contributor to quadriceps avoidance gait following total knee arthroplasty

BackgroundFollowing rehabilitation for total knee arthroplasty, “quadriceps avoidance gait”, defined by limited knee flexion angle excursion during walking, persists and contributes to poor long-term outcomes. Given the presence of several post-surgical impairments, identifying the contribution of multiple factors to knee flexion angle excursion is important to developing targeted interventions to improve recovery after total knee arthroplasty.Research questionsWhich outcomes continue to improve following rehabilitation for total knee arthroplasty? What are the primary contributors to impaired knee flexion angle excursion during walking following total knee arthroplasty?MethodsPeak muscle strength and rate of torque development of the quadriceps, hip abductors, and hip external rotators, five-time sit-to-stand test, Knee Injury & Osteoarthritis Outcome Score, and gait mechanics were assessed in 24 participants at three and six months post-surgery. Paired sample t-tests or Wilcoxon Signed-Rank tests were used to compare outcomes between assessments. Stepwise multiple linear regression were used to assess the contribution of each measure to knee flexion angle excursion.ResultsSignificant improvements were noted in all outcomes except hip external rotation rate of torque development, gait speed, and knee flexion angle excursion. Quadriceps rate of torque development and knee pain significantly contributed to knee flexion angle excursion at three months (Adjusted R² = 0.342), while quadriceps rate of torque development and peak hip external rotation strength significantly contributed at six months (Adjusted R² = 0.436).SignificanceWhile higher pain levels at three months and greater peak hip external rotation muscle strength at six months contribute to impaired knee flexion angle excursion, quadriceps rate of torque development was the primary contributor to knee flexion angle excursion at both three and six months after surgery. Implementing strategies to maximize quadriceps rate of torque development during rehabilitation may help to reduce quadriceps avoidance gait after total knee arthroplasty.     

Mechanical and morphological determinants of peak power output in elite cyclists

Mechanical peak power output (PPO) is a determinant of performance in sprint cycling. The purpose of this study was to examine the relationship between PPO and putative physiological determinants of PPO in elite cyclists, and to compare sprint performance between elite sprint and endurance cyclists. Thirty-five elite cyclists (18 endurance; 17 sprint) performed duplicate sprint cycling laboratory tests to establish PPO and its mechanical components. Quadriceps femoris (Q_VOL) and hamstring muscle volume (HAM_VOL) were assessed with MRI, vastus lateralis pennation angle (Pθ_VL) and fascicle length (FL_VL) were determined with ultrasound imaging, and neuromuscular activation of three muscles was assessed using EMG at PPO during sprint cycling. For the whole cohort, there was a wide variability in PPO (range 775-2025 W) with very large, positive, bivariate relationships between PPO and Q_VOL (r = .87), HAM_VOL (r = .71), and Pθ_VL (r = .81). Step-wise multiple regression analysis revealed that 87% of the variability in PPO between cyclists was explained by two variables Q_VOL (76%) and Pθ_VL (11%). The sprint cyclists had greater PPO (+61%; P < .001 vs endurance), larger Q_VOL (P < .001), and BF_VOL (P < .001) as well as more pennate vastus lateralis muscles (P < .001). These findings emphasize the importance of quadriceps muscle morphology for sprint cycling events.     

深蹲动作下三连杆模型的对比分析

目的 探讨三连杆模型用于深蹲动作互动动力学分析的合理性，明确三连杆模型与Visual 3D计算关节力矩的差异来源。方法 选取8名受试者，通过Vicon获取深蹲动作运动学数据，采用拉格朗日第二类方程建立三连杆动力学方程，基于Mathematica编程计算获取关节力矩，与Visual 3D下肢链节段模型计算结果进行对比分析，并采用复相关系数（coefficient of multiple correlation, CMC）评价两者的相似程度。结果 8名受试者髋、膝关节CMC均大于0.85，踝关节CMC在0.50～0.85之间，三连杆动力学方程和Visual 3D计算的关节力矩在髋、膝关节处高度相似，在踝关节处仅呈现中度相似性。结论 三连杆模型可用于深蹲动作的关节力矩分析以及进一步的环节互动动力学分析，但应当考虑由地面反作用力引起的互动力矩（外力矩）对踝关节力矩的影响。     

Evaluation of the surface damage of dental implants caused by different surgical protocols: an in vitro study

The implant surface must withstand high insertion torque during implant insertion. The aim of this study was to investigate the damage to implant surfaces caused by two different insertion protocols in vitro. Fifteen titanium implants per group were inserted in standardized polyurethane foam models, group 1 according to a non-threaded surgical protocol and group 2 according to a threaded surgical protocol. Before and after insertion, the surfaces were visualized by scanning electron microscopy (SEM) and non-contact laser profilometry. Different surface area parameters were evaluated and maximum torque during insertion was determined. SEM detected topographical changes such as deposition of the test block and smoothening of the surface in the region of the thread crests in both groups. The laser profilometry analysis revealed significant changes in the surface topography of the implants in both groups, but no differences between the groups. Insertion torque was significantly decreased in the threaded group. Both types of surgical intervention resulted in surface damage. Less damage was detected to the thread crests with the use of a thread cutter, and most of the surface was not visibly affected by the surgical protocol at the microscopic level. The surgical protocol seems to have a minor influence on preservation of the implant surface.     

Positional difference of malleoli-midpoint from three-dimensional geometric centre of rotation of ankle and its effect on ankle joint kinetics

Backgrounds: Joint kinetic calculations are sensitive to joint centre locations. Although geometric hip and knee joint centre/axis are generally developed, the ankle joint centre (AJC) is conventionally defined as the midpoint between the malleolus lateralis and medialis (AJC_MID) in most gait analyses.Research question: We examined the positional difference of the AJC_MID from the geometric centre of rotation (AJC_FUN) and its effect on the ankle joint kinetics in representative human gaits.Methods: In the first experiment, we calculated the AJC_FUN and indicated its location on the ankle MRI in 14 (seven male and seven female) participants. In the second experiment, we compared ankle kinematics/kinetics based on AJC_FUN and AJC_MID during walking and hopping at 2.6 Hz in 17 (nine male and eight female) participants.Results: In both experiments, AJC_FUN was located at positions significantly medial (-9.2 ± 5.4 mm and -10.1 ± 4.4 mm) and anterior (17.0 ± 7.4 mm and 15.3 ± 5.2 mm) from the AJC_MID. Furthermore, the AJC_MID underestimated peak dorsiflexion (AJC_MID/AJC_FUN: 52.6 ± 17.1%) and inversion (AJC_MID/AJC_FUN: 62.2 ± 11.5%) torques and their durations in walking. Additionally, AJC_MID overestimated the plantar flexion torque in both gait modes [AJC_MID/AJC_FUN: 111.3 ± 4.8% (walking) and 112.7 ± 6.3% (hopping)].Significance: We therefore concluded that the positional difference between the geometric and landmark-based AJC definitions significantly affected ankle kinetics, thereby indicating that the functional method should be used for defining AJC for gait analysis.     

Physiological properties of periodontal mechanosensitive neurones in the posteromedial ventral nucleus of rat thalamus

Unitary discharges of periodontal mechanosensitive (PM) neurones responding to mechanical tooth stimulation were recorded from the posteromedial ventral nucleus (VPM) of rat thalamus. PM neurones are distributed in the ventromedial area in the rostral two-thirds of the VPM nucleus. Maxillary and mandibular tooth-sensitive neurones are arranged in dorsoventral sequence. Of the PM neurones, 36% were slowly adapting to pressure applied to the tooth and 67% were rapidly adapting. The majority of PM units were sensitive to the contralateral incisor tooth. Response magnitudes of the slowly adapting neurones varied with stimulus direction and were directionally selective to mechanical tooth stimulation. The optimal stimulus direction was labiolingual or linguolabial. Rapidly adapting neurones were directionally non-selective to tooth stimulation. The threshold for mechanical stimulation was <0.05 N. Mean response latencies evoked by electrical stimulation of the peripheral receptive fields were 4.6 ms in the slowly adapting neurones and 5.8 ms in the rapidly adapting neurones.     

Implant design and intraosseous stability of immediately placed implants: a human cadaver study

Objective: The objective of this study was to explore effects of implant macrodesign and diameter on initial intraosseous stability and interface mechanical properties of immediately placed implants. Material and method: Mandibular premolars of four fresh‐frozen human cadavers were extracted. Ø 4.1/4.8 mm ITI® TE®, Ø 4.1 and 4.8 mm solid screw synOcta® ITI® implants were placed into freshly prepared extraction sockets. Resonance frequency analysis was conducted to quantify primary implant stability quotient (ISQ). Installation torque value (ITV) and removal torque value (RTV) of the implants were measured using a custom‐made strain‐gauged torque wrench connected to a data acquisition system at a sample rate of 10,000 Hz. The vertical defect depth around the collar of each implant was measured directly by an endodontic spreader. The bone–implant contact was determined in digitalized images of periapical radiographs and expressed as percentage bone contact. Results: The ISQ values of the TE® implant was higher than the Ø 4.1 mm implant (P<0.01), and comparable with the Ø 4.8 mm implants (P>0.05). ITVs and RTVs of TE® and Ø 4.8 mm implants were higher than the Ø 4.1 mm implant, although the differences between groups were statistically insignificant (P>0.05). The vertical defect depths around all types of implants were similar. In the radiographic analyses, percentage bone–implant contact of the TE® and Ø 4.8 mm implants were comparable at the marginal bone region and both were higher than that of the Ø 4.1 mm ITI® implant. Nonparametric correlations between groups revealed a significant correlation between ITV and RTV (r=0.838; P<0.001), but not between ISQ values and ITVs and RTVs (P>0.05). Conclusion: Immediately placed ITI® TE® implant leads to initial intraosseous stability and interface mechanical properties comparable with a wide diameter implant.