Hip muscle and joint contact forces before, 6 and 12 months after minimally invasive periacetabular osteotomy.

BACKGROUND: Previous studies on different periacetabular osteotomy approaches for correction of hip dysplasia disagree on the time course of normalisation of muscle function postoperatively, some stating that especially hip flexor function is not fully normalised after 12 months. PURPOSE: The purpose of this study was to evaluate hip function during walking before, and 6 and 12 months after minimally invasive periacetabular osteotomy. METHODS: Using conventional 3D inverse dynamics followed by static optimisation, we calculated hip net joint moment and angular impulse, as well as individual muscle forces and hip joint contact force, during walking for 32 patients with hip dysplasia and 32 matched controls. RESULTS: None of the extensor and abductor measures were significantly different between controls and patients tested preoperatively, nor between any of the 3 time points patients were tested. For all of the flexor measures, patients' preoperative values were lower than controls', but had increased to values above the controls 6 months postoperatively. CONCLUSION: Hip muscle function during walking seemed normalised after 6 months after minimally invasive periacetabular osteotomy, while joint contact force did not fully normalise until 12 months postoperatively, perhaps because the hip joint structures need a longer time to heal than the muscles and a potential pain alleviating strategy was still in effect. TRIAL REGISTRY: Movement pattern in patients with hip dysplasia https://clinicaltrials.gov/ct2/show/NCT01344421, NCT01344421.

A review of computed tomography and manual dissection for calibration of devices for pig carcass classification - Evaluation of uncertainty.

Online pig carcass classification methods require calibration against a reference standard. More than 30years ago, the first reference standard in the EU was defined as the total amount of lean meat in the carcass obtained by manual dissection. Later, the definition was simplified to include only the most important parts of the carcass to obtain a better balance between accuracy and cost. Recently, computed tomography (CT) obtained using medical X-ray scanners has been proposed as a reference standard. The error sources of both traditional (manual) dissection methods and the new methods based on images from CT scanning of pig carcasses are discussed in this paper. The uncertainty resulting from the effect of various error sources is estimated. We conclude that, without standardisation, the uncertainty is considerable for all the methods. However, methods based on volume estimation using CT and image analysis might lead to higher accuracy if necessary precautions are taken with respect to measuring protocol and reference materials.

Three-dimensional kinematic and kinetic analysis of knee rotational stability in ACL-deficient patients during walking, running and pivoting.

BACKGROUND: Anterior cruciate ligament (ACL) deficiency leads to altered stability of the knee. The purpose of this study was to compare the dynamic, rotational stability of the knee, expressed as rotational stiffness, between anterior cruciate ligament-deficient (ACLD) knees, their contralateral intact knees (ACLI) and a knee healthy control group during walking, running and 90° pivoting. We hypothesized a larger tibial internal rotation, a smaller knee joint external moment and a lower rotational stiffness in the ACLD group compared to the ACLI and the control group. METHODS: Kinematic and kinetic data were collected from both legs of 44 ACLD patients and 16 healthy controls during walking, running and a pivoting maneuver (descending a staircase and immediately pivoting 90° on the landing leg). Motion data were captured using 8 high-speed cameras and a force-plate. Reflective markers were attached to bony landmarks of the lower limb and rigid clusters on the shank and thigh (CASH model). Maximum internal tibial rotation and the corresponding rotational moment were identified for all tasks and groups and used to calculate rotational stiffness (= Δmoment /Δrotation) of the knee. RESULTS: The tibial internal rotation of the ACLD knee was not significantly different from the ACLI knee during all three tasks. During walking and running, the tibial rotation of the control group was significantly different from both legs of the ACL-injured patient. For pivoting, no difference in tibial rotation between knees of the ACLD, ACLI and the control group was found. Knee joint external moments were not significantly different between the three groups during walking and pivoting. During running, the moments of the ACLI group were significantly higher than both the knees of the ACLD and the control group. Rotational stiffness did not differ significantly between groups in any of the three tasks. CONCLUSION: A high-intensity activity combining stair descent and pivoting produces similar angular rotations, knee joint external moments and rotational stiffness in ACLD knees compared to ACLI knees and the control group. During running, the ACLI knee displayed a higher external moment than the ACLD and the healthy control group. This could indicate some type of protective strategy or muscular adaptation in the ACL-injured patients.

Walking patterns and hip contact forces in patients with hip dysplasia.

INTRODUCTION: Several studies have investigated walking characteristics in hip dysplasia patients, but so far none have described all hip rotational degrees of freedom during the whole gait cycle. This descriptive study reports 3D joint angles and torques, and furthermore extends previous studies with muscle and joint contact forces in 32 hip dysplasia patients and 32 matching controls. METHODS: 3D motion capture data from walking and standing trials were analysed. Hip, knee, ankle and pelvis angles were calculated with inverse kinematics for both standing and walking trials. Hip, knee and ankle torques were calculated with inverse dynamics, while hip muscle and joint contact forces were calculated with static optimisation for the walking trials. RESULTS: No differences were found between the two groups while standing. While walking, patients showed decreased hip extension, increased ankle pronation and increased hip abduction and external rotation torques. Furthermore, hip muscle forces were generally lower and shifted to more posteriorly situated muscles, while the hip joint contact force was lower and directed more superiorly. CONCLUSION: During walking, patients showed lower and more superiorly directed hip joint contact force, which might alleviate pain from an antero-superiorly degenerated joint.

Gait Deviation Index, Gait Profile Score and Gait Variable Score in children with spastic cerebral palsy: Intra-rater reliability and agreement across two repeated sessions.

The Gait Deviation Index (GDI) and Gait Profile Score (GPS) are the most used summary measures of gait in children with cerebral palsy (CP). However, the reliability and agreement of these indices have not been investigated, limiting their clinimetric quality for research and clinical practice. The aim of this study was to investigate the intra-rater reliability and agreement of summary measures of gait (GDI; GPS; and the Gait Variable Score (GVS) derived from the GPS). The intra-rater reliability and agreement were investigated across two repeated sessions in 18 children aged 5-12 years diagnosed with spastic CP. No systematic bias was observed between the sessions and no heteroscedasticity was observed in Bland-Altman plots. For the GDI and GPS, excellent reliability with intraclass correlation coefficient (ICC) values of 0.8-0.9 was found, while the GVS was found to have fair to good reliability with ICCs of 0.4-0.7. The agreement for the GDI and the logarithmically transformed GPS, in terms of the standard error of measurement as a percentage of the grand mean (SEM%) varied from 4.1 to 6.7%, whilst the smallest detectable change in percent (SDC%) ranged from 11.3 to 18.5%. For the logarithmically transformed GVS, we found a fair to large variation in SEM% from 7 to 29% and in SDC% from 18 to 81%. The GDI and GPS demonstrated excellent reliability and acceptable agreement proving that they can both be used in research and clinical practice. However, the observed large variability for some of the GVS requires cautious consideration when selecting outcome measures.

Forward lunge knee biomechanics before and after partial meniscectomy.

BACKGROUND: Patients following meniscectomy are at increased risk of developing knee osteoarthritis in the tibiofemoral compartment and at the patellofemoral joint. As osteoarthritis is widely considered a mechanical disease, it is important to understand the potential effect of arthroscopic partial meniscectomy (APM) on knee joint mechanics. The purpose of this study was to evaluate changes in knee joint biomechanics during a forward lunge in patients with a suspected degenerative meniscal tear from before to three months after APM. METHODS: Twenty-two patients (35-55 years old) with a suspected degenerative medial meniscal tear participated in this study. Three dimensional knee biomechanics were assessed on the injured and contralateral leg before and three months after APM. The visual analogue scale was used to assess knee pain and the Knee Injury Osteoarthritis Outcome Score was used to assess sport/recreation function and knee-related confidence before and after APM. RESULTS: The external peak knee flexion moment reduced in the APM leg compared to the contralateral leg (mean difference (95% CI)) -1.08 (-1.80 to -0.35) (Nm/(BW × HT)%), p = 0.004. Peak knee flexion angle also reduced in the APM leg compared to the contralateral leg -3.94 (-6.27 to -1.60) degrees, p = 0.001. There was no change in knee pain between the APM leg and contralateral leg (p=0.118). Self-reported sport/recreation function improved (p = 0.004). CONCLUSIONS: Although patients self-reported less difficulty during strenuous tasks following APM, patients used less knee flexion, a strategy that may limit excessive patellar loads during forward lunge in the recently operated leg.

Effects of an unstable shoe construction on balance in women aged over 50 years.

BACKGROUND: Shoes with an unstable sole construction are commonly used as a therapeutic tool by physiotherapists and are widely available from shoe and sporting goods retailers. The aim of this study was to investigate the effects of using an unstable shoe (Masai Barefoot Technology) on standing balance, reactive balance and stability limits. METHODS: Thirty-one subjects agreed to participate in the study and underwent balance tests on three different occasions. After test occasion one (baseline) 20 subjects received Masai Barefoot Technology shoes and were requested to wear them as much as possible for the remaining eight weeks of the study. Three specific balance tests were administered on each test occasion using a Pro Balance Master (NeuroCom International Inc., Oregon, USA). Tests included; a modified sensory organization test, reactive balance test and limits of stability test. FINDINGS: Subjects in the intervention group significantly improved their performance on elements of all three tests however results on these variables were not demonstrated to be significantly better than the control group. No significant differences were observed across testing occasions in the control group. INTERPRETATION: Results from the present study suggest that, for this group of individuals, use of unstable footwear may improve certain aspects of balance.