Biomechanical comparison of a 3D-printed prosthetic foot with conventional feet in people with transtibial amputation: A prospective cohort study.

INTRODUCTION: The method of 3D printing is increasingly gaining utilization in clinical applications and may support prosthetic fitting. The aim was to compare biomechanical outcomes of people with a transtibial amputation using a novel, individualizable, 3D-printed prosthetic foot (ComfyStep, Mecuris) with two conventional, widely used prosthetic feet during level ground walking using a 3D motion analysis system. METHODS: Ten individuals with an unilateral transtibial amputation were fitted with 3 prosthetic feet (ComfyStep, Assure/Össur, DynamicMotion/Ottobock) using their current, well-fitting socket. They had at least 1 week of familiarization for each foot before gait analyses were conducted. Kinematics and kinetics as well as roll over shape (ROS) length and radius were calculated and compared between feet. RESULTS: The sound side gait parameters of the participants were comparable when using different feet. However, there were differences on the affected side. The statistical analysis revealed that the 3D-printed foot differed significantly compared with the conventional feet in the following aspects: reduced range of motion, increased plantar flexion moment, reduced plantar flexion power, larger ROS radius, less favorable energy ratio, and higher overall stiffness. CONCLUSION: In principle, 3D-printed feet have advantages over conventional "off the shelf" feet, as their biomechanical characteristics could be adjusted more in detail according to the patient needs. Although, differences between conventional feet and the ComfyStep were shown. Whether these differences have a negative clinically relevant effect remains unclear. However, results suggest that commercially available 3D-printed feet should incorporate systematically better adjustments, for example, for stiffness, to enhance prosthetic performance.

Estimation of ankle joint parameters in typically developed adults using functional calibration methods.

BACKGROUND: Despite of many attempts to determine or correct hip and knee joint parameters via non-invasive techniques such as regression or functional methods, in conventional gait models the position of the ankle joint center still is assumed at the center point between malleoli. RESEARCH QUESTION: The aim of this study was to estimate the ankle joint parameters using a functional approach. METHODS: To this aim, we used data of 23 typically developed adults performing two different calibration motions. Subsequently, we applied functional approaches to determine the functional joint center and axis. RESULTS: The results show significant differences for ankle joint parameters in all directions for both calibration motions applied with respect to the malleoli line. Most prominently, we find a shift of the ankle joint center of 7 % of the foot length anteriorly to the malleoli mid-point when applying functional calibration. CONCLUSION: These significant alterations of the ankle joint center and axis indicate the importance of accurate determination of ankle joint parameters and consequently their influence on the clinical outcome.

Benefits of an increased prosthetic ankle range of motion for individuals with a trans-tibial amputation walking with a new prosthetic foot.

BACKGROUND: Individuals with trans-tibial amputation show a greater peak prosthetic ankle power (push- off) when using energy storing and returning (ESAR) prosthetic feet as compared to solid-ankle cushion-heel feet. ESAR feet further contribute to the users' body support and thus limit prosthetic ankle motion. To improve ankle motion, articulating prosthetic feet have been introduced. However, articulating feet may diminish push-off. RESEARCH QUESTION: Does a novel prosthetic foot, with a serial layout of carbon fibre leaf springs, connected by a multi-centre joint construction, have advantages in kinematics and kinetics over a conventional ESAR prosthetic foot?> METHODS: Eleven individuals with unilateral trans-tibial amputation were fitted with the novel foot (NF) and a conventional ESAR Foot (CF) and underwent 3D gait analysis. As an additional power estimate of the prosthetic ankle, a unified, deformable, segment model approach was applied. Eleven matched individuals without impairments served as a reference. RESULTS: The NF shows an effective prosthetic ankle range of motion that is closer to a physiologic ankle range of motion, at 31.6° as compared to 15.2° with CF (CF vs. NF p = 0.003/NF vs. Reference p = 0.171) without reducing the maximum prosthetic ankle joint moment. Furthermore, the NF showed a great increase in prosthetic ankle power (NF 2.89 W/kg vs. CF 1.48 W/kg CF vs. NF p = <0.001) and a reduction of 19% in the peak knee varus moment and 13% in vertical ground reaction forces on the sound side for NF in comparison to CF. SIGNIFICANCE: The NF shows that serial carbon fibre leaf springs, connected by a multi-centre joint construction gives a larger ankle joint range of motion and higher ankle power than a conventional carbon fibre structure alone. Consequently load is taken off the contralateral limb, as measured by the decrease in vertical ground reaction forces and peak knee varus moment.

Sound side joint contact forces in below knee amputee gait with an ESAR prosthetic foot.

The incidence of knee and hip joint osteoarthritis in subjects with below knee amputation (BK) appears significantly higher compared to unimpaired subjects, especially in the intact side. However, it is controversial if constant higher loads on the sound side are one of the major factors for an increased osteoarthritis (OA) incidence in subjects with BK, beside other risk factors, e.g. with respect to metabolism. The aim wasto investigate joint contact forces (JCF) calculated by a musculoskeletal model in the intact side and to compare it with those of unimpaired subjects and to further elucidate in how far increased knee JCF are associated with increased frontal plane knee moments. A group of seven subjects with BK amputation and a group of ten unimpaired subjects were recruited for this study. Gait data were measured by 3D motion capture and force plates. OpenSim software was applied to calculate JCF. Maximum joint angles, ground reaction forces, and moments as well as time distance parameters were determined and compared between groups showing no significant differences, with some JCF components of knee and hip even being slightly smaller in subjects with BK compared to the reference group. This positive finding may be due to the selected ESAR foot. However, other beneficial factors may also have influenced this positive result such as the general good health status of the subjects or the thorough and proper fitting and alignment of the prosthesis.

The influence of timing of knee recurvatum on surgical outcome in cerebral palsy.

Recent reports have shown that timing of genu recurvatum (GR) might be caused by different underlying factors and that equinus leads to GR especially during early stance. The purpose of this study was to investigate the reduction of GR after surgical correction of equinus in children with bilateral spastic cerebral palsy and whether the children with early and late type GR show differences in reduction of knee hyperextension after a surgery. In 24 limbs (mean age 10.3 years, GMFCS I-III) showing equinus and GR the kinematics of the knee and ankle as well as the kinetics of the knee were evaluated before and one year (mean follow up period: 12.8 months) after surgical correction of equinus. The study was approved by the local ethical committee. Limbs with early type GR showed a reduction by 11.1° (p<0.001) and those with late type GR by 6.0° (p<0.049) in GR after surgery. Before surgery limbs with early type GR showed increased external extending moments, which decreased significantly after surgery. In contrast limbs with late GR did not show a significant reduction of those moments. The findings of this study underline the influence of equinus on early GR as an underlying factor. As equinus is attributed to early knee hyperextension and proximal factors are more important as underlying factors in late type GR, a classification into early and late onset GR is useful to identify underlying factors and to choose adequate treatment.

Force-controlled dynamic wear testing of total ankle replacements.

Currently, our knowledge of wear performance in total ankle replacements is limited. The aim of this study is to develop a scenario for force-controlled testing and wear testing of total ankle replacements. A force-controlled wear test was developed: based on cadaver measurements, the passive stabilization (ligaments and soft tissue) of the ankle joint was characterized and a restraint model for ankle stabilization was developed. Kinematics and kinetics acting at the replaced ankle joint were defined based on literature data and gait analysis. Afterwards, force-controlled wear testing was carried out on a mobile, three-component, total ankle replacement design. Wear was assessed gravimetrically and wear particles were analyzed. Wear testing resulted in a mean wear rate of 18.2±1.4mm(3)/10(6) cycles. Wear particles showed a mean size of 0.23µm with an aspect ratio of 1.61±0.96 and a roundness of 0.62±0.14. Wear testing of total ankle replacement shows that a relevant wear mass is generated with wear particles in a biologically relevant size range. The developed wear test provides a basis for future wear testing of total ankle replacements.

Hard-on-hard lubrication in the artificial hip under dynamic loading conditions.

The tribological performance of an artificial hip joint has a particularly strong influence on its success. The principle causes for failure are adverse short- and long-term reactions to wear debris and high frictional torque in the case of poor lubrication that may cause loosening of the implant. Therefore, using experimental and theoretical approaches models have been developed to evaluate lubrication under standardized conditions. A steady-state numerical model has been extended with dynamic experimental data for hard-on-hard bearings used in total hip replacements to verify the tribological relevance of the ISO 14242-1 gait cycle in comparison to experimental data from the Orthoload database and instrumented gait analysis for three additional loading conditions: normal walking, climbing stairs and descending stairs. Ceramic-on-ceramic bearing partners show superior lubrication potential compared to hard-on-hard bearings that work with at least one articulating metal component. Lubrication regimes during the investigated activities are shown to strongly depend on the kinematics and loading conditions. The outcome from the ISO gait is not fully confirmed by the normal walking data and more challenging conditions show evidence of inferior lubrication. These findings may help to explain the differences between the in vitro predictions using the ISO gait cycle and the clinical outcome of some hard-on-hard bearings, e.g., using metal-on-metal.

Gait patterns in twins with cerebral palsy: similarities and development over time after multilevel surgery.

To examine gait patterns and gait quality, 7 twins with cerebral palsy were measured preoperatively and after surgical intervention. The aim was to study differences and/or similarities in gait between twins, the influence of personal characteristics and birth conditions, and to describe the development of gait over time after single event multilevel surgery. A standardized clinical exam and a three-dimensional gait analysis were performed. Gait patterns were classified according to Sutherland and Davids, and the Gillette Gait Index was calculated as a global measure of the gait impairment. Next to subject characteristics at time of first measurement, and at time of birth, birth conditions were collected. Gait patterns were determined as crouch gait in 13 legs, as stiff gait in 6 legs and as jump gait in 8 legs. One leg showed a normal gait pattern. The knee flexion-extension angle correlated most constant with the knee flexion-extension angle of the contralateral leg (range 0.91-0.99). Correlations with the legs of the sibling showed variable correlations (range 0.44-0.99); with all other legs medium to high correlations of 0.73-0.91 were found. The Gillette Gait Index was found to initially decrease after surgical intervention. Similar correlations were found between twins or between legs for the gait pattern expressed by the knee flexion-extension angle, and the Gillette Gait Index improved after surgery. It seems that gait quality in twins with cerebral palsy is characterized predominantly by the traumatic disorder: genetic dispositions and personal characteristics only play a negligible role.

Integrating strength tests of amputees within the protocol of conventional clinical gait analysis: a novel approach.

Clinical experience tells us that the lower-limb amputees are one of the patient groups who clearly suffer from a strength deficit in their involved side. However, there is no obvious evidence for the relation between the residual limb strength and walking ability in this population. Correlating the results of the conventional clinical gait analysis (CGA) with strength tests could help to find out how deficits in strength impact the amputees' gait. In this contribution, a new device for measuring the isometric muscle strength of the hip and the knee was tested for feasibility. Three groups were tested: one group of 11 healthy subjects (29±5 years) to test the repeatability of the device, two unilateral amputees (one transfemoral for 56 years, one transtibial for 65 years), and a reference group of 17 healthy subjects (55±10 years). The new method presents an adequate technique to integrate strength testing within a standard protocol of the CGA. Results showed to be repeatable within sessions [i.e., within-day, intraclass correlation coefficient (ICC)>0.972] and between repeated measurements (i.e., day-to-day, ICC>0.765). The tested amputees showed clear deficits in maximum isometric joint moments in their most distal joint. The first results suggest evidence for a relation between the maximum isometric joint moments and gait deviations in amputees.

The influence of hip abductor weakness on frontal plane motion of the trunk and pelvis in patients with cerebral palsy.

Trendelenburg walking pattern is a common finding in various disorders, including cerebral palsy (CP), where it is seen in children and adults. Clinically, this deviation is viewed as a consequence of hip abductor weakness resulting in pelvic obliquity. Trunk lean to the ipsilateral side is a common compensatory mechanism to counteract pelvic obliquity and to maintain gait stability. However, no published investigations objectively address pelvic and trunk motions in the frontal plane or examine the correlation with hip abductor weakness in patients with CP. We selected 375 ambulatory (GMFCS I-III) patients with spastic bilateral CP and 24 healthy controls from our gait laboratory database. They had all undergone a standardized three-dimensional analysis of gait, including trunk motion, and a clinical examination including hip abductor strength testing. Selected frontal plane kinematic and kinetic parameters were investigated and statistically tested for correlation (Spearman rank) with hip abductor strength. Only a weak (r=0.278) yet highly significant correlation between trunk lean and hip abductor strength was found. Hip abductor weakness was accompanied by decreased hip abduction moment. However, no significant differences in pelvic position were found between the different strength groups, indicating that the pelvis remained stable regardless of the patients' strength. Our findings indicate that weak hip abductors in patients with CP are accompanied by increased trunk lean to the ipsilateral side while pelvic position is preserved by this compensatory mechanism. However, since this correlation is weak, other factors influencing lateral trunk lean should be considered. In patients with severe weakness of the hip abductors compensatory trunk lean is no longer fully able to stabilize the pelvis, and frontal pelvic kinematics differs from normal during loading response. The results indicate that the stable pelvic position seems to be of greater importance than trunk position for patients with CP. Further studies are needed to investigate other factors influencing lateral trunk lean.

Acute and chronic avulsive injuries.

Avulsive injuries are common traumatic lesions, especially in young athletes. They can be acute, resulting from excessive tensile forces, or chronic, due to overuse. Avulsion injuries can resemble osteomyelitis or neoplasm and, therefore, familiarity with the radiographic patterns as well as the different muscle attachments is helpful for the clinician to arrive at the correct diagnosis. This article discusses acute and chronic avulsive injuries in the pelvis, knee, elbow, shoulder, and foot.

Hand and wrist.

Some basic principles of orthopedic management of common conditions of the hand and wrist have been presented. These basic principles and an awareness of the potential complications should aid radiologists in evaluation of postoperative films. The interested reader is referred to Green's Operative Hand Surgery and Chapman's Operative Orthopaedics for more detailed information.

Imaging of acute injuries of the cervical spine: value of plain radiography, CT, and MR imaging.

Imaging of injuries of the cervical spine has undergone substantial changes in the past 10 years. The use of CT and MR imaging has been emphasized by many authors. Other studies have stressed the proper use and interpretation of plain radiographs in the emergency setting. There is confusion about whether plain films, CT, or MR imaging is best used to evaluate specific injuries. This review explores the usefulness of CT and MR imaging in the diagnosis and management of acute injuries of the cervical spine and emphasizes the continued importance of conventional radiography. Specific examples that illustrate the relative merits of plain radiography, CT, and MR imaging are shown.

Radiographic assessment of disease progression in rheumatoid arthritis patients enrolled in the cooperative systematic studies of the rheumatic diseases program randomized clinical trial of methotrexate, auranofin, or a combination of the two.

OBJECTIVE: To determine the radiographic progression of disease in rheumatoid arthritis (RA) patients from the Cooperative Systematic Studies of the Rheumatic Diseases clinical trial of auranofin (AUR) versus methotrexate (MTX) versus a combination of the two. METHODS: Baseline (week-0) and study-end (week-48) hand/wrist radiographs in 200 of the 211 patients who completed this multicenter trial (95%) were scored blindly by 2 readers for the presence of erosions and joint space narrowing (JSN). Both intraobserver reliability and interobserver reliability were 0.80 for erosions (P < or = 0.001); intraobserver reliability and interobserver reliability were both 0.75 for JSN (P < or = 0.001). RESULTS: Worsening erosion and JSN scores occurred in all 3 treatment groups, but the difference from baseline reached significance only in the AUR group. CONCLUSION: Clinical improvement has been clearly documented in all 3 treatment groups in this trial. Radiographic deterioration occurs in RA even when clinical features improve, but progression of disease as determined radiographically may be slowed by treatment with MTX.

MR imaging of bone marrow edema pattern: transient osteoporosis, transient bone marrow edema syndrome, or osteonecrosis.

The bone marrow edema (BME) pattern of signal intensity changes on magnetic resonance (MR) images (decreased on T1-weighted and increased on T2-weighted) is a nonspecific finding encountered with several entities, including transient osteoporosis of the hip, transient BME syndrome, osteonecrosis, trauma, infection, and infiltrative neoplasm. Transient osteoporosis, an unusual but distinct syndrome characterized by self-limited pain and radiographically evident osteopenia, can be distinguished from other causes of the BME pattern, particularly osteonecrosis, on the basis of clinical findings and the development of radiographically evident focal osteopenia within 8 weeks after the onset of pain. This is an important distinction, since all patients with transient osteoporosis recover completely, without intervention. The term transient BME syndrome can be used to describe any patient in whom a reversible BME pattern is seen on MR images. Although the transient BME syndrome is also self-limited and quite likely related to transient osteoporosis, the authors believe that to avoid confusion, this nonspecific term should be reserved only for patients who do not develop radiographically evident osteopenia.

Prosthetic above-knee femoropopliteal bypass for intermittent claudication.

There is no consensus about the most appropriate management of the patient with intermittent claudication due to a superficial femoral artery occlusion. To evaluate the natural history of prosthetic above-knee femoropopliteal (AKFP) bypass, 200 operations for intermittent claudication were reviewed. One hundred AKFP bypasses were done with PTFE and 100 with dacron. In the 30 day postoperative period, four PTFE and three dacron grafts occluded without consequence and only one patient died. Analysis of results by the life-table method demonstrated statistically similar primary graft patency rates at five years (PTFE 65% SE +/- 6.5, dacron 57% +/- 6.2) and ten years (PTFE 31% +/- 18/9, dacron 32% +/- 13.2) (p greater than 0.10). Redo procedures (e.g., thrombectomy, angioplasty) were necessary on 21 grafts (12 PTFE, 9 dacron) and "secondary" patency rates at five years were 76% PTFE and 62% dacron; no grafts which required a redo procedure were patent at ten year follow-up. Major amputations during ten year follow-up were necessary in 16 (8%) patients; all amputations were in diabetic patients. Survival rates were 79% at five and 42% at ten years. An anticipated, the leading cause of death was cardiac related (25 patients); 28 (14%) patients underwent aortocoronary bypass during follow-up. A prosthetic AKFP bypass graft is a safe and durable operation which provides relief from the symptoms of intermittent claudication while allowing for the preservation of the saphenous vein for use later in the coronary or infrapopliteal circulations, should the need arise. These results indicate that the risk of amputation after AKFP is no greater than the natural history of untreated claudication; however, AKFP offers a significant improvement in life-style.