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The effect of neutral-cushioned running shoes on the intra-articular force in the haemophilic ankle
Clinical Biomechanics 28 (2013) 672–678
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The effect of neutral-cushioned running shoes on the intra-articular force in the haemophilic ankle Paul McLaughlin a,⁎, Pratima Chowdary a, Roger Woledge b, Ann McCarthy c, Ruth Mayagoitia b a b c
Katharine Dormandy Haemophilia Centre and Thrombosis Unit, Royal Free London NHS Foundation Trust, Pond St, London NW3 2QG, UK School of Biomedical Sciences, King's College London, London, UK Clinical Research Centre for Health Professions, University of Brighton, Brighton, UK
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Article history: Received 6 December 2012 Accepted 20 May 2013 Keywords: Haemophilia Ankle Ankle joint force Footwear
a b s t r a c t Background: The ankle continues to be one of the most affected joints in the haemophilia patient, and as cartilage damage progresses, the joint can feel unstable, painful and stiff. Anecdotally, patients often report that sports trainers can improve their pain and daily function, however the actual mechanism for this remains unclear. Methods: Nine patients with ankle haemarthropathy and three controls were examined using ‘CODAmotion’ analysis and a force plate. Kinematic and kinetic variables of the hip, knee and ankle were recorded. Data was imported from CODA to Excel, where a programme using 2D modelling of the ankle joint forces was employed. This calculated intra-articular force from heel strike to toe-off. Findings: The haemophilia group at midstance showed an increase in intra-articular force in the ankle when wearing the trainer compared to the shoe (P = b 0.05). Overall the haemophilia cohort had an increased joint force in both the trainers and shoes, compared to controls. Interpretation: The type of footwear worn by individuals with ankle arthropathy has a significant effect on the amount of force acting at the joint surface. Sports shoes, in providing better comfort and foot support, may facilitate an increased muscular activity around the ankle and therefore improved dynamic joint stability, accounting for why some patients with ankle arthropathy report less pain. Further research is needed to establish levels of acceptable force and the combined effects of orthotics and footwear. © 2013 Elsevier Ltd. All rights reserved.
1. Introduction Haemophilia is an inherited bleeding disorder characterised by a deficiency or complete absence of clotting factors VIII (Haemophilia A) or IX (Haemophilia B). They are X-linked disorders, thus affecting only males and the worldwide prevalence is estimated to be one in 5000 males for Haemophilia A and one in 25,000 males for Haemophilia B (Bolton-Maggs and Pasi, 2003). The baseline factor VIII or IX determines the severity of the disorder, and the classification in most common use is the one recommended by the International Society on Thrombosis and Haemostasis (ISTH). Those with procoagulant factor levels below 1% are severe, 1–5% moderate and mild being >5% (White et al., ISTH communication, 2000). Patients with severe Haemophilia A or B are characterised by spontaneous bleeding into joints, muscles and other internal organs, and the latter can be fatal. Modern management is regular infusion of the deficient factor, with either recombinant or plasma-derived factor VIII or IX two to three times a week to prevent spontaneous bleeding (termed prophylaxis.) Recurrent joint bleeds cause synovial hypertrophy and subsequent destruction of articular cartilage resulting in haemophilic arthropathy (Jansen ⁎ Corresponding author. E-mail address: [email protected] (P. McLaughlin). 0268-0033/$ – see front matter © 2013 Elsevier Ltd. All rights reserved. http://dx.doi.org/10.1016/j.clinbiomech.2013.05.008
et al., 2007). Bleeding into the knees, elbows and ankles account for almost 80% of episodes (Rodriguez-Merchan, 1996) with the ankle now accepted as being the most affected joint (Stephensen et al., 2009). Ankle cartilage is relatively uniform in thickness ranging from 1 to 1.7 mm whilst the knee having variations anywhere from 1 to 6 mm thick (Shepherd and Seedhom, 1999). The thinness of the ankle articular cartilage and the high peak contact stresses to which it is submitted may make it less adaptable to incongruity, decreased stability, or increased stresses that may follow a traumatic event (Daniels and Thomas, 2008). It still remains unclear what effect poor articular geometry may have on ankle intra-articular forces and indeed the actual transmission of the force across the talar surface. Tochigi et al. (2008) reported that ankle instability events involved distinctly abrupt increases or decreases in local articular contact stresses, and that the degree of abruptness had an almost linear correlation with the abnormality in the kinematics, concluding that ankle instability resulted primarily from loss of contact between the anterior distal tibial surface and the talar dome. The above is of clinical value as many patients in the authors treatment centre empirically report symptoms of ankle instability and pain secondary to established joint arthropathy. However, a recurring theme with some patients is the positive effect footwear, in particular
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trainers and softer soled shoes have on such symptoms, although the mechanism remains unclear. Relatively little has been done previously in gait assessment in Haemophilia. Studies done on young boys with haemophilia reported statistically significant increases in swing, stance, single and double support time in the asymptomatic individuals, suggesting a possible contribution of these gait changes to lower limb dysfunction (Bladen et al., 2007; Stephensen et al., 2009). Another study analysing the effect on gait with and without silicon heel cups highlighted that even with no clinical evidence of motion restriction in the ankle joint with a low degree of haemarthropathy, a distinct difference in comparison with normal gait could be detected (Seuser et al., 1997). More recently it has been highlighted that 3-dimensionl gait analysis is useful for assessing the abnormal gait patterns secondary to arthropathy in people with haemophilia (Lobet et al., 2010) and the same authors have described how the metabolic energy cost in gait is higher in such individuals because of a decrease in muscle efficiency (Lobet et al., 2012). Interestingly, a further study looking at gait changes with custom made foot orthoses with the haemophilic ankle reported that rocker bottom shoes improved ankle propulsion, postulating that this may be secondary to improved comfort and decreasing ankle pain (Lobet et al., 2012). Multiple studies have investigated the effects of footwear on ground reaction force and shock attenuation, and the vast majority of these have been related to sport and running. Light et al. (1980) compared the effect of walking barefoot, with conventional and shock absorbing footwear and concluded that the shock absorbing shoe moderated deceleration of the leg and produced a longer and lower shock wave in the tibia, with similar outcomes reported by LaFortune and Hennig (1992). Wegener et al. (2008) compared in-shoe plantar pressure loading and comfort in running in three shoe types and found sports training shoes significantly decreased peak pressures and force at the forefoot. They suggested also that comfort was an important issue and was multifactorial. The notion of comfort has been proposed to be primarily associated with the cushioning aspect of running shoes, as well as fit, anatomical characteristics of the foot inside the shoe and foot sensitivity; it may affect pressure distribution and above all is a subjective experience (Nigg and Segesser, 1992; Reinschmidt and Nigg, 2000). Conversely, Kersting and Bruggemann (2006) found no consistent relationship between in-shoe force and impact when examining subjects running with similar findings reported by McNair and Marshall (1994) and Hardin et al. (2004). These studies imply that footwear simply acts as a buffer to peak forces at heel strike and that the motor programme responsible for the pattern of the lower limb was unaffected by footwear. They postulate that this was due to highly individual adaptation strategies employed by each subject and that individuals use these strategies of mechanical and neuromuscular adaptation to make the most of the characteristics of the footwear. There is paucity in work to look at the intra-articular forces at the ankle joint, and researchers have relied on the application of mathematical models, usually based on cadaveric studies. Scott and Winter (1990) examined the internal forces at chronic running injury sites using a two-dimensional mathematical model. They reported a peak ankle compressive force of 5700 N (11.2 times Body weight [BW]) and noted that 82% of the peak compressive force is created by the muscles crossing the joint, whilst the reaction force accounts for only 18%. However in this model, it was acknowledged that no account was taken of the dampening effect of soft tissue or footwear, therefore values could be overestimated. Burdett (1982) utilised a 3D mathematical model to predict forces that occur in the stance phase of running. They reported that the compressive forces on the foot reached values of between 8 and 13 BW for all three subjects, with the largest tendon forces occurring in the plantar flexion group. Procter and Paul (1982) attempted to quantify
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muscle and joint loads in the ankle using a 3D modelling system, based on cadaveric studies of five specimens. They found a talocrural compressive joint force peak of approximately 4 BW, with a muscle force peak of the calf group of around 2.5 BW. Stauffer et al. (1977) proposed a very simple 2D hinge model of the ankle to calculate forces within the ankle joint as well as the calf and anterior shin muscles. In comparing the compressive joint forces in normal and diseased ankles in stance phase, they found a maximum peak force of 4.5–5.5 BW in normals, but in the diseased ankles this force rose only to 3 BW. From the literature it remains unclear what effect footwear has on shock absorbency and forces acting at the ankle. Specifically, it is not clear what the effect is of poor joint congruency from degenerative disease on these forces. In an attempt to ascertain force without the additional cofounding factor of foot posture alteration, this study aims to examine the effect of a neutral sports trainer on the forces acting on the talocrural joint of adult haemophiliacs with haemarthropathy as compared to conventional footwear. 2. Methods This study used kinematic and kinetic data supplied by a CODA motion analysis system applied to a two-dimensional model in the sagittal plane of ankle motion. The model assumes that from the point of initial contact, the main moment force is that of plantarflexion (from the Gastrocnemius complex) and that the forces from ligaments and capsule restraints are negligible in the sagittal plane of movement of the ankle. This method of modelling is similar to the studies mentioned previously. Also Burdett (1982) on comparing a 2D model with a 3D model, found both to be similar in predicting compressive forces in the ankle joint. 20 patients were identified from attendance at a Haemophilia review clinic according to inclusion/exclusion criteria (Table 1) and subsequent physiotherapy assessment and joint scoring (Manco-Johnson et al., 2000) as appropriate for participation in this study. Nine agreed to take part (Table 2). A control group (n = 3) of normal male population was recruited locally from within the hospital. A same-subject experimental design was used to compare measurements between using a shoe and a trainer, as appropriate for this study (Hicks, 1995). Ethical approval was obtained from Moorfields and Whittington NHS Research Ethics Committee (Reference number: 08/H0721/30). Permission was also gained from the Research and Development Departments at the Royal Free Hospital Hampstead and The Royal National Orthopaedic Hospital (RNOH), Stanmore, UK. The anthropometric data of each participant was recorded (height, weight, thigh and shank length, knee and ankle joint width, foot length and ASIS width). Length measures were ascertained with an anthropometric counter recording instrument (‘Harpenden’ Anthropometer, Holtain Ltd, Pembrokeshire, UK). As per lab protocol, the markers were attached to the following anatomical landmarks (bilaterally) using double sided tape: lateral knee joint line, lateral tip of the lateral malleolus, over the point of the postero-inferior calcaneus and 5th metatarsal whilst the footwear (shoe or trainer) was in situ. Wands with anterior and posterior markers were attached to the pelvis, thigh and shank. Markers and battery packs were attached to the wands Table 1 Participant inclusion/exclusion criteria. Inclusion criteria
Exclusion criteria
• • • •
• • • •
Male Aged 18–60 Haemophilia A or B Only ankle joint affected with arthropathy on physical assessment (unilateral or bilateral)
Multiple joint damage Chronic synovitis Any other acute illness Lower limb bleed in previous four weeks • Active joint or muscle bleed • Significant/gross joint abnormality
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Table 2 General characteristics of participants and controls. Age (years)
Height (m)
Weight (kg)
Haemophilia type and severity
Target joint
Subject 1 34 2 47 3 43
1.64 1.7 1.82
58.2 66.1 83.9
A — Severe B — Severe A — Severe
4 5 6 7 8 9
1.72 1.85 1.87 1.74 1.73 1.76
76.8 96.8 80.5 79.5 73.5 75.9
A — Severe A — Severe A — Severe A — Severe A — Severe B — Severe
Left ankle Bilateral ankle Bilateral ankle Right > left Right ankle Right ankle Left ankle Left ankle Left ankle Bilateral ankle Left > right
1.9 1.82 1.85
86.7 93.3 84.7
No joint pathology
39 28 28 27 49 42
Controls 1 29 2 31 3 31
with double sided tape. The pelvic wand was aligned with the participant's natural pelvic tilt position. The thigh wand was aligned perpendicular to the knee joint line, and the shank (tibial wand) was aligned perpendicular to the ankle joint line. Each of the lower limb wands was secured in place with Velcro bands around the participant's limb. On the day of each test procedure, the CODA (CODA Mpx30, Charnwood Dynamics Motion Analysis, Leicestershire, UK, 1996) and the force plate (Bertec Force Plate, Type 4060-10, Bertec Corporation, Ohio, USA) were calibrated as per laboratory protocol. Each participant wore a pair of shorts with their T-shirt tucked into the shorts to allow unobstructed view of the markers about the pelvis (Fig. 1). Each participant was shown the gait lab and a standardised explanation of the CODA motion equipment was given. Participants were instructed to walk at their ‘self selected normal speed’ along the walkway when given the command by the lead investigator. The participant group was randomised in regard to the order of assessment between the trainer and shoe. One group (n = 5) were assessed with the shoe first and then trainer, and a second group (n = 4) used the trainer first. The shoe used was a hard soled worn-in shoe belonging to each patient. The trainer used was a new neutral Asics ‘Gel Nimbus 11’ (Fig. 1). Sagittal, frontal and transverse motions of the hip, knee and ankle joints were recorded alongside force plate data for each trial. Participants were encouraged to walk repeatedly along the walkway until eight clean cycles were recorded. At this point, participants changed their footwear (to the shoe or trainer, depending on group). The markers on the foot and ankle were removed from the footwear
and then replaced again by the lead investigator. The shank and thigh wands were rechecked for positioning. The participant was then asked to repeat the walking trials along the walkway, again until at least another eight clean trials had been recorded. Fatigue was avoided by a rest period when shoes were changed. 2.1. Data analysis The way CODA motion collects and presents movement data has been previously described (Maynard et al., 2003; Monaghan et al., 2007). This section will explain how the movement data from CODA was utilised in the 2D model of the ankle to ascertain ankle joint force (Fig. 2). Using the anatomical markers, CODA collected the appropriate kinetic and kinematic information to be used to present force information about the right and left ankles (Fig. 3). This data produced a graph using the following numerical values from CODA; - Marker positions for the 5th metatarsal head, heel and ankle in the x and y axes - Segment reference point for the knee and ankle joint centre in the x and y axes - Force vector position of the force point of application in the x and y axes - Force of the foot in the x and y axes - Moment of plantarflexion of the ankle on the y axis. (Segmental reference points are calculated from the surface marker positions using the standard CODA model provided by the manufacturer). This data allowed a graphical display of the force acting at the ankle joint. The calculation considered the joint centre to be between the midpoints of the malleoli. Direction and magnitude of forces were calculated on the distance from the ankle to the knee, ankle to the Achilles tendon and the ankle moment. This established Achilles tendon and ankle joint forces alongside the ground reaction forces, which in turn calculated an estimate of the intra-articular force at the ankle. Joint forces were normalised to body weight (BW) for each individual. Each data set for each footwear variable in each participant was then analysed at the peak force value of mid-stance (as this initial force plateau was considered clinically important for joint loading and control) and terminal stance. With each participant, mean values and SD of footwear variable were recorded. Fig. 3a and b are examples of the diagrams and graphs produced for each participant at mid-stance for each data trial collected from CODA. Line (A) represents ground reaction force, Line (B) represents the Achilles force, Line (C) represents the resultant plantarflexion
Fig. 1. Asics neutral soled ‘Gel Nimbus 11’ and location of markers used.
P. McLaughlin et al. / Clinical Biomechanics 28 (2013) 672–678
a
675
690 590 E
Force (N)
490 C
390 290
A
190
B D
90 -10
0
1000
500
Time (ms)
b 2500 Fig. 2. Simplified free body diagram of the foot and ankle at heel strike. Compressive force (FN), tangential force (FT) and Achilles tendon force (FK) are calculated from CODA data to give ankle intra-articular force.
3. Results The mean and SD for the ankle force (BW) in each footwear variable at midstance and terminal stance are presented in Tables 3 and 4. Comparing the footwear conditions in midstance, the haemophilic group had an increase in ankle joint force on both the right and left ankle when wearing the trainer compared to the shoe. The left ankle force increased by 12.4%, 1.37 → 1.54 BW (P = b 0.01) whilst in the trainer, the right ankle force increased by 15.6%, 1.41 → 1.63 BW (P = b 0.0001). In five of the haemophilia group (subjects 5–9, Table 2), the target joint experienced less force in both the shoe and trainer than the contralateral ankle, and it was significant in 4 of these individuals (P = b 0.001 for subjects 5–8 in the shoe, 5–7 in the trainer and 0.013 for subject 9 in the trainer). However two subjects had a significant increase of force in the target ankle compared to the contralateral joint, subject one (P = 0.02 shoe, P = b 0.001 in trainer), and subject 3 (P = b 0.01 in the shoe and P = b 0.0001 in the trainer). In the control group, the force at the ankle also increased in the trainer compared to the shoe. On the left there was an increase of 16% BW (P = b 0.01), and the right had a smaller increase of 6.4% BW (P = 0.225). On comparing footwear conditions in terminal stance the haemophilia group had a small decrease in the force acting at the ankle whilst wearing the trainers. The mean force whilst wearing the left shoe was 3.6 BW (± 0.33) compared to that of the left trainer which was 3.5 BW (± 0.29), a decrease of 2.85% which was significant (P = 0.043). The mean force in the right shoe was 3.79 BW (±0.35) compared to that in the right trainer of 3.74 BW (±0.29), a decrease of 1.34% (P = 0.402). Similar findings were recorded in the control group. There was a minimal decrease in the left ankle force whilst wearing the trainer, 3.75 BW (± 0.3) to 3.66 BW (±0.28), and on the right the decrease
Joint force (N)
moment, and Line (D) represents the resultant moment between the tibia and the Achilles tendon. (E) is the line representing the tibia. A Paired T-test was used to determine any difference in the calculated peak force at the ankle between participant shoe of choice and the sports trainer within the groups. A Wilcoxon matched pairs signed rank sum test was used to compare between the groups. The level of significance was set at P = b 0.05 for all tests.
2000
1500
Peak at mid stance
1000
500
0 0
0.2
0.4
0.6
0.8
Time (s) Fig. 3. a. Stick diagram of forces acting around the ankle at midstance. ([A] Ground reaction force, [B] Achilles Force, [C] Plantarflexion moment, [D] moment between tibia and Achilles tendon, [E] line representing tibia). b. Graph highlighting the point of maximum force of 1228.4 N at 0.19 s at midstance.
was from 3.68 BW (±0.19) to 3.48 BW (± 0.21). Neither of these decreases were significant (left P = 0.126, right P = 0.179). When comparing within the group, comparison of the right ankle with the left ankle of the haemophilia cohort did not highlight any significant difference in the forces (shoes: P = 0.72, trainers: P = 0.38). The same was found in the control group (shoes: P = 0.08, trainers: P = 0.39). There were no significant differences when comparing the subgroup randomised to wear the trainers first for gait analysis (n = 4) versus the shoe first group. 4. Discussion The results show a significant increase in the joint force acting on a haemophilic ankle when wearing a pair of neutral sports trainers compared to harder soled shoes in both the right and left ankles in midstance. Previous studies by Procter and Paul (1982) and Stauffer et al. (1977) studied the forces at one ankle at the push-off phase of terminal stance. The current study recorded the forces of both ankles in both footwear types at midstance and terminal stance; therefore comparison can only be done with terminal stance. In the control
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Table 3 Mean and SD of peak ankle forces at midstance. Type of footwear
Left shoe Left trainer Right shoe Right trainer
Midstance Haemophilia group Mean ankle force (xBW)
Control Mean ankle force (xBW)
Paired T-test Haemophilia group (both shoes) (P = b 0.05)
Paired T-test Control (both shoes) (P = b 0.05)
1.37 1.54 1.41 1.63
1.124 1.35 1.49 1.4
b0.007
b0.003
(SD (SD (SD (SD
0.4) 0.35) 0.37) 0.41)
(SD 0.11) (SD 0.12) (SD 0.29) (SD 0.2)
b0.0001
group the mean peak forces were calculated at 3.75 BW and 3.68 BW in the left and right shoes respectively and 3.66 and 3.48 BW in the left and right trainers respectively. These figures are less than that found by Procter and Paul (4 BW) and Stauffer (4.5–5.5 BW). However the mean peak forces in the haemophilic group of 3.6 BW and 3.79 BW in the left and right shoes respectively, and 3.5 BW and 3.74 BW in the left and right trainers respectively, are greater than that reported by Stauffer et al. (1977) in their study with diseased ankles (3 BW). This study found significant differences between shoes and trainers in force at mid-stance, no previous study has reported this. The results of the current study indicate that intra-articular joint force at mid-stance increases when wearing a sports trainer and in the haemophilic group this is significant. These findings may suggest increased muscle activity at the haemophilic ankle whilst wearing trainers that was not seen in the control group. It is possible that the force difference between the groups may be associated with impaired proprioceptive awareness in damaged joints, thus leading to increased muscle activity. The effect of haemarthropathy on joint proprioceptive abilities is unknown and further studies should aim to compare balance and joint position sense between controls and haemophiliacs. The increase in joint force recorded with the present study may in part be representative of an increase in the concentric activity of the gastrocnemius–soleus complex throughout the stance phase. Empirically, the author has had subjective reports from patients who use sports trainers with a decrease feeling of instability and less pain. Improved fit and support offered to the foot by the trainer may provide a biomechanical advantage to the Achilles tendon, which in turn allows an increase in muscle activity to actively dissipate force arising from walking. Increased muscle activity has a direct effect on forces crossing the joint. The increase in intra-articular force indicates an increased compressive force in the joint. As the ankle is designed to weight-bear, an increase in compressive force in mid-stance would be a positive outcome to enhance stability, particularly in a haemophilic ankle, which may have joint instability from synovitis and arthropathy. Tochigi et al. (2008) reported that ankle instability resulted in the loss of congruity between the tibia and talus, and Potthast et al. (2008) demonstrated the importance of the posterior calf muscles in maintaining physiologic ankle joint contact stress. It is plausible that the trainers have enabled the joint to become more dynamically stable and at less risk of subluxation, as the risk of a potentially damaging shear force is reduced with increased compression. It has been suggested that individuals feel more comfortable in a softer shoe (Mündermann et al., 2002), and sensory feedback from
0.225
the feet may be influenced by changing the characteristic of a shoe sole (Nurse et al., 2005). This may allow an improved feedback–feed forward mechanism and so facilitate an appropriate muscle response to joint loading. The increase in force seen here may be attributable to an improved sensory feedback from the plantar aspect of the foot, and the softer-soled trainers used here may have provided a comfortable environment, as well as potentially lowering and spreading plantar pressures. This concept, regarded as muscle tuning, suggests that the body reacts to different inputs to control soft tissue vibrations, and that it is the dominant response of the human locomotor system to impact loading (Nigg, 2001). Each shoe provides a specific impact input into the locomotor system (Boyer and Nigg, 2004), and an increase in muscle activity may improve damping of vibrations, providing safer attenuation of shock forces following loading in the stance phase. Five of the haemophilia cohort displayed significant decreases in force in the target joint in both footwear conditions, although these were still higher than those seen in the control group. This may reflect a gait adaptation in an attempt to reduce loading through that joint. It is unclear if this is a learned effect, or indeed if articular surface changes in the joint or muscle weakness is partly responsible. It would be interesting for further studies to compare radiological and joint scores of ankles, with kinetic and kinematic data, as well as functional activity scores for each individual. The 2D model employed by the current study is similar to those used by previous authors (Procter and Paul, 1982; Scott and Winter, 1990; Stauffer et al., 1977), although the present study only utilised posterior calf muscles. All cited authors acknowledge the same limitation with using such a modelling system with the ankle joint. The fact that it is two-dimensional highlights the oversimplified nature of ‘ignoring’ or combining other joint structures and forces. This is a consequence of modelling, as it is impossible to allow for all the permutations of forces and structures involved in creating a workable model. The current model ignores the effect of the muscle anterior to the ankle (Tibialis anterior) as it was felt that the largest force would be that of the gastrocnemius–soleus complex, which has been shown to bear a considerable amount of load during the stance phase in walking (Glitsch and Baumann, 1997). However this omission may explain why the figures found in this study are higher than those of Stauffer et al. who included tibialis anterior in their force calculations. There may be an overestimation of the forces as no account is made for potential coupling of muscle action. The mean age of participants was lower in this study (37 years) compared to Stauffer et al. (1977) at 43 years, who also described their ankle
Table 4 Mean and SD of peak forces at terminal stance. Type of footwear
Left shoe Left trainer Right shoe Right trainer
Terminal stance Haemophilia group Mean ankle force (xBW)
Control Mean force (xBW)
Paired T-test Haemophilia group (P = b 0.05)
Paired T-test Control (P = b 0.05)
3.6 (SD 3.5 (SD 3.79 (SD 3.74 (SD
3.75 3.66 3.68 3.48
0.043
0.126
0.402
0.179
0.33) 0.29) 0.35) 0.29)
(SD 0.3) (SD 0.28) (SD 0.19) (SD 0.21)
P. McLaughlin et al. / Clinical Biomechanics 28 (2013) 672–678
participants as having disabling disease. The degree of joint degeneration may also then have an effect on results. The current model is based on two cylindrical, frictionless segments, moving in a single plane of movement of concave on convex. However individual patient presentations and varying levels of joint disease may make modelling for this difficult. It therefore remains unclear if the current results could suffer from underestimating intra-articular joint forces as no account is taken of friction between the tibial and talar surfaces. With previous studies using 2D models, all (apart from Stauffer et al., 1977) have examined normal ankle joints. Further work is required to establish if these models are of any clinical use with individuals with affected joints. 4.1. Methodological limitations The author acknowledges that the numbers in the sample group are low. However given the size of this haemophilic population they constitute a good pilot cohort. It may have been useful to standardise the harder soled shoe worn by the groups, although it was felt at the time to be more clinically applicable to assess participants in the shoe of their choice, as empirically, footwear is a concern for many people with haemophilia who attend clinics. Another limitation is that there was no account taken for the potential movement of the foot in the shoe, due to the markers being placed on the shoe itself. This has been acknowledged previously in similar previous studies (Nigg et al., 2003). 5. Conclusion The current study highlights that neutral soled trainers appear to have an effect on peak midstance force acting at the ankle joint in a sample of haemophiliacs. What constitutes an acceptable joint force remains unclear and requires further investigation. These findings may provide some indication for care when prescribing insoles or orthotics with haemophiliacs. This is particularly relevant if patients will be using prescribed orthotics in different shoe types, as there is some suggestion from the literature that foot orthoses may enhance coupling effects between the leg and rearfoot (Hatton et al., 2008). An appreciation of potential force generation at a joint surface and its effects needs to be recognized. In conclusion, it is clear that neutral cushioned trainers have a significant effect on the forces acting at a haemophilic ankle at midstance. The results may help to explain the subjective reports of some patients who find sports trainers helpful and comfortable. The longterm effects of footwear on pain and function in individuals with haemophilic arthropathy of the ankle require further investigation. Contributions Matt Thornton — Provided expert advice on the use of CODA at the Gait Lab, Royal National Orthopaedic Hospital, Stanmore, Middlesex. Runner's Need Shop, King's Cross, London — With kindness provided the trainers used in the study. Acknowledgements The authors state that they had no interests that may be perceived as posing conflict or bias. There was no external funding used for this study. Paul McLaughlin — contributed to the conception, design, data collection, analysis and writing of the paper. Dr Pratima Chowdary — critically appraised the paper and approved the final version. Prof Roger Woledge — contributed to the design of the paper and created the 2-Dimensional mathematical model in which the data from CODA was utilised.
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Ann McCarthy — critically appraised the paper. Dr Ruth Mayagoitia — contributed to the design and data analysis of the paper and critically appraised the paper.
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Lobet, S., Detrembleur, C., Francq, B., Hermans, C., 2010. Natural progression of bloodinduced joint damage in patients with haemophilia: clinical relevance and reproducibility of three-dimensional gait analysis. Haemophilia 16, 813–821. Lobet, S., Detrembleur, C., Lantin, A., Haemecour, l, Hermans, C., 2012a. Functional impact of custom-made foot orthoses in patients with haemophilic ankle arthropathy. Haemophilia 18, e227–e235. Lobet, S., Hermans, C., Bastien, G.J., Massaad, F., Detrembleur, C., 2012b. Impact of ankle osteoarthritis on the energetics and mechanics of gait: the case of haemophilic arthropathy. Clin. Biomech. 27 (6), 625–631. Manco-Johnson, M.J., Nuss, R., Funk, S., Murphy, J., 2000. Joint evaluation instruments for children and adults with haemophilia. Haemophilia 6, 649–657. Maynard, V., Bakheit, A.M.O., Oldham, J., Freeman, J., 2003. Intra-rater and inter-rater reliability of gait measurements with CODA mpx30 motion analysis system. Gait Posture 17, 59–67. McNair, P.J., Marshall, R.N., 1994. Kinematic and kinetic parameters associated with running in different shoes. Br. J. Sports Med. 28 (4), 256–260. Monaghan, K., Delahunt, E., Caulfield, B., 2007. Increasing the number of gait trial recordings maximises intra-rater reliability of the CODA motion analysis system. Gait Posture 25, 303–315. Mündermann, A., Nigg, B.M., Stefanyshyn, D.J., Humble, R.N., 2002. Development of a reliable method to assess footwear comfort during running. Gait Posture 16, 38–45. Nigg, B.M., 2001. The role of impact forces and foot pronation: a new paradigm. Clin. J. Sports Med. 11, 2–9. Nigg, B.M., Segesser, B., 1992. Biomechanical and orthopaedic concepts in sport shoe construction. Med. Sci. Sports Exerc. 24 (5), 595–602. Nigg, B.M., Stergiou, P., Cole, G., Stefanyshan, D., Mündermann, A., Humble, N., 2003. Effects of shoe inserts on kinematics, center of pressure, and leg joint movements during running. Med. Sci. Sports Exerc. 35 (2), 314–319. Nurse, M.A., Hulliger, H., Wakeling, J.M., Nigg, B.M., Stefanyshyn, D.J., 2005. Changing the texture of footwear can alter gait patterns. J. Electromyogr. Kinesiol. 15, 496–506. Potthast, W., Lersch, C., Segesser, B., Koebke, J., Brüggemann, G.P., 2008. Intraarticular pressure distribution in the talocrural joint is related to lower leg muscle forces. Clin. Biomech. 23, 632–639. Procter, P., Paul, J.P., 1982. Ankle joint biomechanics. J. Biomech. 15 (9), 627–634. Reinschmidt, C., Nigg, B.M., 2000. Current issues in the design of running and court shoes. Sportverletz. Sportschaden 14, 71–81. Rodriguez-Merchan, E.C., 1996. Effects of haemophilia on articulations of children and adults. Clin. Orthop. Relat. Res. 328, 7–13. Scott, S.H., Winter, D.A., 1990. Internal forces at chronic running injury sites. Med. Sci. Sports Exerc. 22 (3), 357–369. Seuser, A., Wallny, T., Klein, H., Ribbans, W.J., Schumpe, G., Brackman, H.H., 1997. Gait analysis of the hemophilic ankle with silicon heel cushion. Clin. Orthop. Relat. Res. 343, 74–80. Shepherd, D.E.T., Seedhom, B.B., 1999. Thickness of human articular cartilage in joints in the lower limb. Ann. Rheum. Dis. 58, 27–34. Stauffer, R.N., Chao, E.Y.S., Brewster, R.C., 1977. Force and motion analysis of the normal, diseased, and prosthetic ankle joint. Clin. Orthop. Relat. Res. 127, 189–196.
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Stephensen, D., Drechsler, W., Winter, M., Scott, O., 2009a. Comparison of biomechanical gait parameters of young children with haemophilia ad those of age-matched peers. Haemophilia 15, 509–518. Stephensen, D., Tait, R.C., Brodie, N., Collins, P., Cheal, R., Keeling, D., et al., 2009b. Changing patterns of bleeding in patients with severe haemophilia A. Haemophilia 15 (6), 1210–1214. Tochigi, Y., Rudert, M.J., McKinley, T.O., Pedersen, D.R., Brown, T.D., 2008. Correlation of dynamic cartilage contact stress aberrations with severity of instability in ankle incongruity. J. Orthop. Res. 26, 1186–1193.
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Clinical Biomechanics journal homepage: www.elsevier.com/locate/clinbiomech
The effect of neutral-cushioned running shoes on the intra-articular force in the haemophilic ankle Paul McLaughlin a,⁎, Pratima Chowdary a, Roger Woledge b, Ann McCarthy c, Ruth Mayagoitia b a b c
Katharine Dormandy Haemophilia Centre and Thrombosis Unit, Royal Free London NHS Foundation Trust, Pond St, London NW3 2QG, UK School of Biomedical Sciences, King's College London, London, UK Clinical Research Centre for Health Professions, University of Brighton, Brighton, UK
a r t i c l e
i n f o
Article history: Received 6 December 2012 Accepted 20 May 2013 Keywords: Haemophilia Ankle Ankle joint force Footwear
a b s t r a c t Background: The ankle continues to be one of the most affected joints in the haemophilia patient, and as cartilage damage progresses, the joint can feel unstable, painful and stiff. Anecdotally, patients often report that sports trainers can improve their pain and daily function, however the actual mechanism for this remains unclear. Methods: Nine patients with ankle haemarthropathy and three controls were examined using ‘CODAmotion’ analysis and a force plate. Kinematic and kinetic variables of the hip, knee and ankle were recorded. Data was imported from CODA to Excel, where a programme using 2D modelling of the ankle joint forces was employed. This calculated intra-articular force from heel strike to toe-off. Findings: The haemophilia group at midstance showed an increase in intra-articular force in the ankle when wearing the trainer compared to the shoe (P = b 0.05). Overall the haemophilia cohort had an increased joint force in both the trainers and shoes, compared to controls. Interpretation: The type of footwear worn by individuals with ankle arthropathy has a significant effect on the amount of force acting at the joint surface. Sports shoes, in providing better comfort and foot support, may facilitate an increased muscular activity around the ankle and therefore improved dynamic joint stability, accounting for why some patients with ankle arthropathy report less pain. Further research is needed to establish levels of acceptable force and the combined effects of orthotics and footwear. © 2013 Elsevier Ltd. All rights reserved.
1. Introduction Haemophilia is an inherited bleeding disorder characterised by a deficiency or complete absence of clotting factors VIII (Haemophilia A) or IX (Haemophilia B). They are X-linked disorders, thus affecting only males and the worldwide prevalence is estimated to be one in 5000 males for Haemophilia A and one in 25,000 males for Haemophilia B (Bolton-Maggs and Pasi, 2003). The baseline factor VIII or IX determines the severity of the disorder, and the classification in most common use is the one recommended by the International Society on Thrombosis and Haemostasis (ISTH). Those with procoagulant factor levels below 1% are severe, 1–5% moderate and mild being >5% (White et al., ISTH communication, 2000). Patients with severe Haemophilia A or B are characterised by spontaneous bleeding into joints, muscles and other internal organs, and the latter can be fatal. Modern management is regular infusion of the deficient factor, with either recombinant or plasma-derived factor VIII or IX two to three times a week to prevent spontaneous bleeding (termed prophylaxis.) Recurrent joint bleeds cause synovial hypertrophy and subsequent destruction of articular cartilage resulting in haemophilic arthropathy (Jansen ⁎ Corresponding author. E-mail address: [email protected] (P. McLaughlin). 0268-0033/$ – see front matter © 2013 Elsevier Ltd. All rights reserved. http://dx.doi.org/10.1016/j.clinbiomech.2013.05.008
et al., 2007). Bleeding into the knees, elbows and ankles account for almost 80% of episodes (Rodriguez-Merchan, 1996) with the ankle now accepted as being the most affected joint (Stephensen et al., 2009). Ankle cartilage is relatively uniform in thickness ranging from 1 to 1.7 mm whilst the knee having variations anywhere from 1 to 6 mm thick (Shepherd and Seedhom, 1999). The thinness of the ankle articular cartilage and the high peak contact stresses to which it is submitted may make it less adaptable to incongruity, decreased stability, or increased stresses that may follow a traumatic event (Daniels and Thomas, 2008). It still remains unclear what effect poor articular geometry may have on ankle intra-articular forces and indeed the actual transmission of the force across the talar surface. Tochigi et al. (2008) reported that ankle instability events involved distinctly abrupt increases or decreases in local articular contact stresses, and that the degree of abruptness had an almost linear correlation with the abnormality in the kinematics, concluding that ankle instability resulted primarily from loss of contact between the anterior distal tibial surface and the talar dome. The above is of clinical value as many patients in the authors treatment centre empirically report symptoms of ankle instability and pain secondary to established joint arthropathy. However, a recurring theme with some patients is the positive effect footwear, in particular
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trainers and softer soled shoes have on such symptoms, although the mechanism remains unclear. Relatively little has been done previously in gait assessment in Haemophilia. Studies done on young boys with haemophilia reported statistically significant increases in swing, stance, single and double support time in the asymptomatic individuals, suggesting a possible contribution of these gait changes to lower limb dysfunction (Bladen et al., 2007; Stephensen et al., 2009). Another study analysing the effect on gait with and without silicon heel cups highlighted that even with no clinical evidence of motion restriction in the ankle joint with a low degree of haemarthropathy, a distinct difference in comparison with normal gait could be detected (Seuser et al., 1997). More recently it has been highlighted that 3-dimensionl gait analysis is useful for assessing the abnormal gait patterns secondary to arthropathy in people with haemophilia (Lobet et al., 2010) and the same authors have described how the metabolic energy cost in gait is higher in such individuals because of a decrease in muscle efficiency (Lobet et al., 2012). Interestingly, a further study looking at gait changes with custom made foot orthoses with the haemophilic ankle reported that rocker bottom shoes improved ankle propulsion, postulating that this may be secondary to improved comfort and decreasing ankle pain (Lobet et al., 2012). Multiple studies have investigated the effects of footwear on ground reaction force and shock attenuation, and the vast majority of these have been related to sport and running. Light et al. (1980) compared the effect of walking barefoot, with conventional and shock absorbing footwear and concluded that the shock absorbing shoe moderated deceleration of the leg and produced a longer and lower shock wave in the tibia, with similar outcomes reported by LaFortune and Hennig (1992). Wegener et al. (2008) compared in-shoe plantar pressure loading and comfort in running in three shoe types and found sports training shoes significantly decreased peak pressures and force at the forefoot. They suggested also that comfort was an important issue and was multifactorial. The notion of comfort has been proposed to be primarily associated with the cushioning aspect of running shoes, as well as fit, anatomical characteristics of the foot inside the shoe and foot sensitivity; it may affect pressure distribution and above all is a subjective experience (Nigg and Segesser, 1992; Reinschmidt and Nigg, 2000). Conversely, Kersting and Bruggemann (2006) found no consistent relationship between in-shoe force and impact when examining subjects running with similar findings reported by McNair and Marshall (1994) and Hardin et al. (2004). These studies imply that footwear simply acts as a buffer to peak forces at heel strike and that the motor programme responsible for the pattern of the lower limb was unaffected by footwear. They postulate that this was due to highly individual adaptation strategies employed by each subject and that individuals use these strategies of mechanical and neuromuscular adaptation to make the most of the characteristics of the footwear. There is paucity in work to look at the intra-articular forces at the ankle joint, and researchers have relied on the application of mathematical models, usually based on cadaveric studies. Scott and Winter (1990) examined the internal forces at chronic running injury sites using a two-dimensional mathematical model. They reported a peak ankle compressive force of 5700 N (11.2 times Body weight [BW]) and noted that 82% of the peak compressive force is created by the muscles crossing the joint, whilst the reaction force accounts for only 18%. However in this model, it was acknowledged that no account was taken of the dampening effect of soft tissue or footwear, therefore values could be overestimated. Burdett (1982) utilised a 3D mathematical model to predict forces that occur in the stance phase of running. They reported that the compressive forces on the foot reached values of between 8 and 13 BW for all three subjects, with the largest tendon forces occurring in the plantar flexion group. Procter and Paul (1982) attempted to quantify
673
muscle and joint loads in the ankle using a 3D modelling system, based on cadaveric studies of five specimens. They found a talocrural compressive joint force peak of approximately 4 BW, with a muscle force peak of the calf group of around 2.5 BW. Stauffer et al. (1977) proposed a very simple 2D hinge model of the ankle to calculate forces within the ankle joint as well as the calf and anterior shin muscles. In comparing the compressive joint forces in normal and diseased ankles in stance phase, they found a maximum peak force of 4.5–5.5 BW in normals, but in the diseased ankles this force rose only to 3 BW. From the literature it remains unclear what effect footwear has on shock absorbency and forces acting at the ankle. Specifically, it is not clear what the effect is of poor joint congruency from degenerative disease on these forces. In an attempt to ascertain force without the additional cofounding factor of foot posture alteration, this study aims to examine the effect of a neutral sports trainer on the forces acting on the talocrural joint of adult haemophiliacs with haemarthropathy as compared to conventional footwear. 2. Methods This study used kinematic and kinetic data supplied by a CODA motion analysis system applied to a two-dimensional model in the sagittal plane of ankle motion. The model assumes that from the point of initial contact, the main moment force is that of plantarflexion (from the Gastrocnemius complex) and that the forces from ligaments and capsule restraints are negligible in the sagittal plane of movement of the ankle. This method of modelling is similar to the studies mentioned previously. Also Burdett (1982) on comparing a 2D model with a 3D model, found both to be similar in predicting compressive forces in the ankle joint. 20 patients were identified from attendance at a Haemophilia review clinic according to inclusion/exclusion criteria (Table 1) and subsequent physiotherapy assessment and joint scoring (Manco-Johnson et al., 2000) as appropriate for participation in this study. Nine agreed to take part (Table 2). A control group (n = 3) of normal male population was recruited locally from within the hospital. A same-subject experimental design was used to compare measurements between using a shoe and a trainer, as appropriate for this study (Hicks, 1995). Ethical approval was obtained from Moorfields and Whittington NHS Research Ethics Committee (Reference number: 08/H0721/30). Permission was also gained from the Research and Development Departments at the Royal Free Hospital Hampstead and The Royal National Orthopaedic Hospital (RNOH), Stanmore, UK. The anthropometric data of each participant was recorded (height, weight, thigh and shank length, knee and ankle joint width, foot length and ASIS width). Length measures were ascertained with an anthropometric counter recording instrument (‘Harpenden’ Anthropometer, Holtain Ltd, Pembrokeshire, UK). As per lab protocol, the markers were attached to the following anatomical landmarks (bilaterally) using double sided tape: lateral knee joint line, lateral tip of the lateral malleolus, over the point of the postero-inferior calcaneus and 5th metatarsal whilst the footwear (shoe or trainer) was in situ. Wands with anterior and posterior markers were attached to the pelvis, thigh and shank. Markers and battery packs were attached to the wands Table 1 Participant inclusion/exclusion criteria. Inclusion criteria
Exclusion criteria
• • • •
• • • •
Male Aged 18–60 Haemophilia A or B Only ankle joint affected with arthropathy on physical assessment (unilateral or bilateral)
Multiple joint damage Chronic synovitis Any other acute illness Lower limb bleed in previous four weeks • Active joint or muscle bleed • Significant/gross joint abnormality
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Table 2 General characteristics of participants and controls. Age (years)
Height (m)
Weight (kg)
Haemophilia type and severity
Target joint
Subject 1 34 2 47 3 43
1.64 1.7 1.82
58.2 66.1 83.9
A — Severe B — Severe A — Severe
4 5 6 7 8 9
1.72 1.85 1.87 1.74 1.73 1.76
76.8 96.8 80.5 79.5 73.5 75.9
A — Severe A — Severe A — Severe A — Severe A — Severe B — Severe
Left ankle Bilateral ankle Bilateral ankle Right > left Right ankle Right ankle Left ankle Left ankle Left ankle Bilateral ankle Left > right
1.9 1.82 1.85
86.7 93.3 84.7
No joint pathology
39 28 28 27 49 42
Controls 1 29 2 31 3 31
with double sided tape. The pelvic wand was aligned with the participant's natural pelvic tilt position. The thigh wand was aligned perpendicular to the knee joint line, and the shank (tibial wand) was aligned perpendicular to the ankle joint line. Each of the lower limb wands was secured in place with Velcro bands around the participant's limb. On the day of each test procedure, the CODA (CODA Mpx30, Charnwood Dynamics Motion Analysis, Leicestershire, UK, 1996) and the force plate (Bertec Force Plate, Type 4060-10, Bertec Corporation, Ohio, USA) were calibrated as per laboratory protocol. Each participant wore a pair of shorts with their T-shirt tucked into the shorts to allow unobstructed view of the markers about the pelvis (Fig. 1). Each participant was shown the gait lab and a standardised explanation of the CODA motion equipment was given. Participants were instructed to walk at their ‘self selected normal speed’ along the walkway when given the command by the lead investigator. The participant group was randomised in regard to the order of assessment between the trainer and shoe. One group (n = 5) were assessed with the shoe first and then trainer, and a second group (n = 4) used the trainer first. The shoe used was a hard soled worn-in shoe belonging to each patient. The trainer used was a new neutral Asics ‘Gel Nimbus 11’ (Fig. 1). Sagittal, frontal and transverse motions of the hip, knee and ankle joints were recorded alongside force plate data for each trial. Participants were encouraged to walk repeatedly along the walkway until eight clean cycles were recorded. At this point, participants changed their footwear (to the shoe or trainer, depending on group). The markers on the foot and ankle were removed from the footwear
and then replaced again by the lead investigator. The shank and thigh wands were rechecked for positioning. The participant was then asked to repeat the walking trials along the walkway, again until at least another eight clean trials had been recorded. Fatigue was avoided by a rest period when shoes were changed. 2.1. Data analysis The way CODA motion collects and presents movement data has been previously described (Maynard et al., 2003; Monaghan et al., 2007). This section will explain how the movement data from CODA was utilised in the 2D model of the ankle to ascertain ankle joint force (Fig. 2). Using the anatomical markers, CODA collected the appropriate kinetic and kinematic information to be used to present force information about the right and left ankles (Fig. 3). This data produced a graph using the following numerical values from CODA; - Marker positions for the 5th metatarsal head, heel and ankle in the x and y axes - Segment reference point for the knee and ankle joint centre in the x and y axes - Force vector position of the force point of application in the x and y axes - Force of the foot in the x and y axes - Moment of plantarflexion of the ankle on the y axis. (Segmental reference points are calculated from the surface marker positions using the standard CODA model provided by the manufacturer). This data allowed a graphical display of the force acting at the ankle joint. The calculation considered the joint centre to be between the midpoints of the malleoli. Direction and magnitude of forces were calculated on the distance from the ankle to the knee, ankle to the Achilles tendon and the ankle moment. This established Achilles tendon and ankle joint forces alongside the ground reaction forces, which in turn calculated an estimate of the intra-articular force at the ankle. Joint forces were normalised to body weight (BW) for each individual. Each data set for each footwear variable in each participant was then analysed at the peak force value of mid-stance (as this initial force plateau was considered clinically important for joint loading and control) and terminal stance. With each participant, mean values and SD of footwear variable were recorded. Fig. 3a and b are examples of the diagrams and graphs produced for each participant at mid-stance for each data trial collected from CODA. Line (A) represents ground reaction force, Line (B) represents the Achilles force, Line (C) represents the resultant plantarflexion
Fig. 1. Asics neutral soled ‘Gel Nimbus 11’ and location of markers used.
P. McLaughlin et al. / Clinical Biomechanics 28 (2013) 672–678
a
675
690 590 E
Force (N)
490 C
390 290
A
190
B D
90 -10
0
1000
500
Time (ms)
b 2500 Fig. 2. Simplified free body diagram of the foot and ankle at heel strike. Compressive force (FN), tangential force (FT) and Achilles tendon force (FK) are calculated from CODA data to give ankle intra-articular force.
3. Results The mean and SD for the ankle force (BW) in each footwear variable at midstance and terminal stance are presented in Tables 3 and 4. Comparing the footwear conditions in midstance, the haemophilic group had an increase in ankle joint force on both the right and left ankle when wearing the trainer compared to the shoe. The left ankle force increased by 12.4%, 1.37 → 1.54 BW (P = b 0.01) whilst in the trainer, the right ankle force increased by 15.6%, 1.41 → 1.63 BW (P = b 0.0001). In five of the haemophilia group (subjects 5–9, Table 2), the target joint experienced less force in both the shoe and trainer than the contralateral ankle, and it was significant in 4 of these individuals (P = b 0.001 for subjects 5–8 in the shoe, 5–7 in the trainer and 0.013 for subject 9 in the trainer). However two subjects had a significant increase of force in the target ankle compared to the contralateral joint, subject one (P = 0.02 shoe, P = b 0.001 in trainer), and subject 3 (P = b 0.01 in the shoe and P = b 0.0001 in the trainer). In the control group, the force at the ankle also increased in the trainer compared to the shoe. On the left there was an increase of 16% BW (P = b 0.01), and the right had a smaller increase of 6.4% BW (P = 0.225). On comparing footwear conditions in terminal stance the haemophilia group had a small decrease in the force acting at the ankle whilst wearing the trainers. The mean force whilst wearing the left shoe was 3.6 BW (± 0.33) compared to that of the left trainer which was 3.5 BW (± 0.29), a decrease of 2.85% which was significant (P = 0.043). The mean force in the right shoe was 3.79 BW (±0.35) compared to that in the right trainer of 3.74 BW (±0.29), a decrease of 1.34% (P = 0.402). Similar findings were recorded in the control group. There was a minimal decrease in the left ankle force whilst wearing the trainer, 3.75 BW (± 0.3) to 3.66 BW (±0.28), and on the right the decrease
Joint force (N)
moment, and Line (D) represents the resultant moment between the tibia and the Achilles tendon. (E) is the line representing the tibia. A Paired T-test was used to determine any difference in the calculated peak force at the ankle between participant shoe of choice and the sports trainer within the groups. A Wilcoxon matched pairs signed rank sum test was used to compare between the groups. The level of significance was set at P = b 0.05 for all tests.
2000
1500
Peak at mid stance
1000
500
0 0
0.2
0.4
0.6
0.8
Time (s) Fig. 3. a. Stick diagram of forces acting around the ankle at midstance. ([A] Ground reaction force, [B] Achilles Force, [C] Plantarflexion moment, [D] moment between tibia and Achilles tendon, [E] line representing tibia). b. Graph highlighting the point of maximum force of 1228.4 N at 0.19 s at midstance.
was from 3.68 BW (±0.19) to 3.48 BW (± 0.21). Neither of these decreases were significant (left P = 0.126, right P = 0.179). When comparing within the group, comparison of the right ankle with the left ankle of the haemophilia cohort did not highlight any significant difference in the forces (shoes: P = 0.72, trainers: P = 0.38). The same was found in the control group (shoes: P = 0.08, trainers: P = 0.39). There were no significant differences when comparing the subgroup randomised to wear the trainers first for gait analysis (n = 4) versus the shoe first group. 4. Discussion The results show a significant increase in the joint force acting on a haemophilic ankle when wearing a pair of neutral sports trainers compared to harder soled shoes in both the right and left ankles in midstance. Previous studies by Procter and Paul (1982) and Stauffer et al. (1977) studied the forces at one ankle at the push-off phase of terminal stance. The current study recorded the forces of both ankles in both footwear types at midstance and terminal stance; therefore comparison can only be done with terminal stance. In the control
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Table 3 Mean and SD of peak ankle forces at midstance. Type of footwear
Left shoe Left trainer Right shoe Right trainer
Midstance Haemophilia group Mean ankle force (xBW)
Control Mean ankle force (xBW)
Paired T-test Haemophilia group (both shoes) (P = b 0.05)
Paired T-test Control (both shoes) (P = b 0.05)
1.37 1.54 1.41 1.63
1.124 1.35 1.49 1.4
b0.007
b0.003
(SD (SD (SD (SD
0.4) 0.35) 0.37) 0.41)
(SD 0.11) (SD 0.12) (SD 0.29) (SD 0.2)
b0.0001
group the mean peak forces were calculated at 3.75 BW and 3.68 BW in the left and right shoes respectively and 3.66 and 3.48 BW in the left and right trainers respectively. These figures are less than that found by Procter and Paul (4 BW) and Stauffer (4.5–5.5 BW). However the mean peak forces in the haemophilic group of 3.6 BW and 3.79 BW in the left and right shoes respectively, and 3.5 BW and 3.74 BW in the left and right trainers respectively, are greater than that reported by Stauffer et al. (1977) in their study with diseased ankles (3 BW). This study found significant differences between shoes and trainers in force at mid-stance, no previous study has reported this. The results of the current study indicate that intra-articular joint force at mid-stance increases when wearing a sports trainer and in the haemophilic group this is significant. These findings may suggest increased muscle activity at the haemophilic ankle whilst wearing trainers that was not seen in the control group. It is possible that the force difference between the groups may be associated with impaired proprioceptive awareness in damaged joints, thus leading to increased muscle activity. The effect of haemarthropathy on joint proprioceptive abilities is unknown and further studies should aim to compare balance and joint position sense between controls and haemophiliacs. The increase in joint force recorded with the present study may in part be representative of an increase in the concentric activity of the gastrocnemius–soleus complex throughout the stance phase. Empirically, the author has had subjective reports from patients who use sports trainers with a decrease feeling of instability and less pain. Improved fit and support offered to the foot by the trainer may provide a biomechanical advantage to the Achilles tendon, which in turn allows an increase in muscle activity to actively dissipate force arising from walking. Increased muscle activity has a direct effect on forces crossing the joint. The increase in intra-articular force indicates an increased compressive force in the joint. As the ankle is designed to weight-bear, an increase in compressive force in mid-stance would be a positive outcome to enhance stability, particularly in a haemophilic ankle, which may have joint instability from synovitis and arthropathy. Tochigi et al. (2008) reported that ankle instability resulted in the loss of congruity between the tibia and talus, and Potthast et al. (2008) demonstrated the importance of the posterior calf muscles in maintaining physiologic ankle joint contact stress. It is plausible that the trainers have enabled the joint to become more dynamically stable and at less risk of subluxation, as the risk of a potentially damaging shear force is reduced with increased compression. It has been suggested that individuals feel more comfortable in a softer shoe (Mündermann et al., 2002), and sensory feedback from
0.225
the feet may be influenced by changing the characteristic of a shoe sole (Nurse et al., 2005). This may allow an improved feedback–feed forward mechanism and so facilitate an appropriate muscle response to joint loading. The increase in force seen here may be attributable to an improved sensory feedback from the plantar aspect of the foot, and the softer-soled trainers used here may have provided a comfortable environment, as well as potentially lowering and spreading plantar pressures. This concept, regarded as muscle tuning, suggests that the body reacts to different inputs to control soft tissue vibrations, and that it is the dominant response of the human locomotor system to impact loading (Nigg, 2001). Each shoe provides a specific impact input into the locomotor system (Boyer and Nigg, 2004), and an increase in muscle activity may improve damping of vibrations, providing safer attenuation of shock forces following loading in the stance phase. Five of the haemophilia cohort displayed significant decreases in force in the target joint in both footwear conditions, although these were still higher than those seen in the control group. This may reflect a gait adaptation in an attempt to reduce loading through that joint. It is unclear if this is a learned effect, or indeed if articular surface changes in the joint or muscle weakness is partly responsible. It would be interesting for further studies to compare radiological and joint scores of ankles, with kinetic and kinematic data, as well as functional activity scores for each individual. The 2D model employed by the current study is similar to those used by previous authors (Procter and Paul, 1982; Scott and Winter, 1990; Stauffer et al., 1977), although the present study only utilised posterior calf muscles. All cited authors acknowledge the same limitation with using such a modelling system with the ankle joint. The fact that it is two-dimensional highlights the oversimplified nature of ‘ignoring’ or combining other joint structures and forces. This is a consequence of modelling, as it is impossible to allow for all the permutations of forces and structures involved in creating a workable model. The current model ignores the effect of the muscle anterior to the ankle (Tibialis anterior) as it was felt that the largest force would be that of the gastrocnemius–soleus complex, which has been shown to bear a considerable amount of load during the stance phase in walking (Glitsch and Baumann, 1997). However this omission may explain why the figures found in this study are higher than those of Stauffer et al. who included tibialis anterior in their force calculations. There may be an overestimation of the forces as no account is made for potential coupling of muscle action. The mean age of participants was lower in this study (37 years) compared to Stauffer et al. (1977) at 43 years, who also described their ankle
Table 4 Mean and SD of peak forces at terminal stance. Type of footwear
Left shoe Left trainer Right shoe Right trainer
Terminal stance Haemophilia group Mean ankle force (xBW)
Control Mean force (xBW)
Paired T-test Haemophilia group (P = b 0.05)
Paired T-test Control (P = b 0.05)
3.6 (SD 3.5 (SD 3.79 (SD 3.74 (SD
3.75 3.66 3.68 3.48
0.043
0.126
0.402
0.179
0.33) 0.29) 0.35) 0.29)
(SD 0.3) (SD 0.28) (SD 0.19) (SD 0.21)
P. McLaughlin et al. / Clinical Biomechanics 28 (2013) 672–678
participants as having disabling disease. The degree of joint degeneration may also then have an effect on results. The current model is based on two cylindrical, frictionless segments, moving in a single plane of movement of concave on convex. However individual patient presentations and varying levels of joint disease may make modelling for this difficult. It therefore remains unclear if the current results could suffer from underestimating intra-articular joint forces as no account is taken of friction between the tibial and talar surfaces. With previous studies using 2D models, all (apart from Stauffer et al., 1977) have examined normal ankle joints. Further work is required to establish if these models are of any clinical use with individuals with affected joints. 4.1. Methodological limitations The author acknowledges that the numbers in the sample group are low. However given the size of this haemophilic population they constitute a good pilot cohort. It may have been useful to standardise the harder soled shoe worn by the groups, although it was felt at the time to be more clinically applicable to assess participants in the shoe of their choice, as empirically, footwear is a concern for many people with haemophilia who attend clinics. Another limitation is that there was no account taken for the potential movement of the foot in the shoe, due to the markers being placed on the shoe itself. This has been acknowledged previously in similar previous studies (Nigg et al., 2003). 5. Conclusion The current study highlights that neutral soled trainers appear to have an effect on peak midstance force acting at the ankle joint in a sample of haemophiliacs. What constitutes an acceptable joint force remains unclear and requires further investigation. These findings may provide some indication for care when prescribing insoles or orthotics with haemophiliacs. This is particularly relevant if patients will be using prescribed orthotics in different shoe types, as there is some suggestion from the literature that foot orthoses may enhance coupling effects between the leg and rearfoot (Hatton et al., 2008). An appreciation of potential force generation at a joint surface and its effects needs to be recognized. In conclusion, it is clear that neutral cushioned trainers have a significant effect on the forces acting at a haemophilic ankle at midstance. The results may help to explain the subjective reports of some patients who find sports trainers helpful and comfortable. The longterm effects of footwear on pain and function in individuals with haemophilic arthropathy of the ankle require further investigation. Contributions Matt Thornton — Provided expert advice on the use of CODA at the Gait Lab, Royal National Orthopaedic Hospital, Stanmore, Middlesex. Runner's Need Shop, King's Cross, London — With kindness provided the trainers used in the study. Acknowledgements The authors state that they had no interests that may be perceived as posing conflict or bias. There was no external funding used for this study. Paul McLaughlin — contributed to the conception, design, data collection, analysis and writing of the paper. Dr Pratima Chowdary — critically appraised the paper and approved the final version. Prof Roger Woledge — contributed to the design of the paper and created the 2-Dimensional mathematical model in which the data from CODA was utilised.
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Ann McCarthy — critically appraised the paper. Dr Ruth Mayagoitia — contributed to the design and data analysis of the paper and critically appraised the paper.
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