The findings of this study appear to confirm the hypothesis that mean cross sectional area is greater in FDB associated with claw toes than rectus toes. This however is a simplistic analysis, and several issues should be considered to ensure that this finding is viewed within the appropriate context. Further investigation revealed there was a significant difference in the mean cross sectional area of the two rectus feet and the two claw feet. The difference between the means of the two claw feet was 151 μ2, whilst the difference of the means between claw and rectus feet was only 3 μ2 greater at 154 μ2. When the mean cross sectional area for each of the anatomical sites of the four feet were contrasted, as displayed in Figure 3 it was noted that not all anatomical sites of the claw feet were greater than the same anatomical site in the rectus feet.
The two rectus feet followed a similar pattern of cross sectional area at each anatomical site within the muscle, whereas the two claw feet did not. Foot 4 was greater at each anatomical site than both rectus feet, but apart from the sites of Belly and Proximal to Division of Foot 2, the measurements from this claw foot were similar in size and pattern to the two rectus feet. It is therefore not entirely accurate to conclude that the cross sectional area is greater in claw feet than rectus feet.
One of the major influences on these results, is the age of the sample. The youngest was 71 years, with the other three aged 83, 84 and 88 years. Inokuci  concluded that muscle tissue is marked by an increase in fat and connective tissue in the elderly, especially those in advance of 80 years. During dissection, it was noted in the 88 year old that visually, there appeared to be a greater amount of fat surrounding and impregnating the muscle. Additionally, under microscopic conditions, an increase in the endomysial spaces was visually apparent. Hooper  recorded that one characteristic of ageing muscle is an increased variation in fibre size due to atrophy and compensatory hypertrophy. Table 1 displays the maximum and minimum measurements, and indicates an exceptionally large range of fibre sizes, giving credence to this theory. There appear to be two theories as to why there is fibre atrophy with compensatory hypertrophic changes. Firstly, as age increases above 60 years, neurogenic alterations occur, resulting in cycles of denervation and reinnervation of motor neurons. With each cycle, some fibres are permanently denervated, resulting in atrophy and are eventually replaced by connective tissue . Secondly, a reduction in the effectiveness of the peripheral arterial supply due to arteriosclerosis is a physiological process that occurs with advancing age . This reduces the healing properties in any muscle fibres which are injured, even during moderate physical activity, resulting in eventual muscle loss. As a consequence of either occurrence, a reduced number of fibres would be required to maintain the same activity, resulting in hypertrophic changes. Grimby and Saltin  suggest that neurogenic changes affecting muscle fibres, are directly related to the length of the peripheral nerve, thereby implying there is a likely risk of these changes affecting muscles of the foot. Atrophic changes will also arise from muscle disuse , due to reduction in ambulation as age increases. In the light of age related changes to muscle tissue, the 83 year old rectus and 84 year old claw (both female) feet were compared. A two-way ANOVA confirmed a significant difference between claw and rectus toes, with the cross sectional area of all corresponding anatomical sites greater in the foot with claw toes (Table 2).
It would also be prudent to observe five other limitations associated with this study. Firstly, the study was carried out on muscle tissue from cadavers treated with a Formaldehyde based embalming fluid as per Glasgow University embalming protocols. This may result in the tissues becoming hard, rigid and often difficult to dissect . MacBride  also suggested that studies using embalmed cadavers were often avoided because the fixation process was poor, making tissues less suitable for histological examination. In examining the effects of various fixatives on bovine muscle, Stickland  observed that Formaldehyde based solutions were amongst those most likely to cause shrinkage to the muscle fibre. However, it should also be considered that the effects of shrinkage on skeletal muscle of cadaveric fixation was marked when muscle tissue was fixed in isolation from the skeleton, but not when fixed in situ on the skeleton . Apart from the effects of the embalming solution, the subsequent stages of dehydrating and clearing have also been implicated in muscle fibre shrinkage. It has been concluded by Stickland  that these processes cause shrinkage to a greater degree than fixation. Histological processing can also cause fragmentation of tissue , and this was evident in some of the tissues under microscopic examination, occasionally making measurement difficult. In addition to the effects of fixation, dehydrating and clearing, muscle fibres taken from cadavers differ architecturally  from in vivo muscle. Living muscle fibres are either in an extreme of relaxation or contraction, whereas cadaveric muscle is in a state between relaxation and contraction . This is thought to be a result of fixation occurring whilst the muscle fibres are in the partially contracted state seen in rigor mortis. Due to the alterations of fixation, histological processing and rigor mortis, results of cadaveric studies cannot reflect exactly what would be found in a living specimen. One final problem in conducting this cadaveric study was that no medical history was available that may have indicated an aetiological influence on fibre atrophy, hypertrophy or development of claw toes.
The second major limitation is that this investigation has only looked at the muscle fibre cross sectional area, but has not accounted for any differences associated with the other two components of muscle contraction, namely, fibre length and fibre type. Although fibre length was not investigated, observation of Figure 3 demonstrates that the mean cross sectional area varies at each of the various sections along the muscle. It is not known whether the fibre lengths or their origins and insertions to connective tissue varies between claw and rectus toes. Length of fibres from FDB would be observations in the sagittal plane, the same plane on which claw toe deformity occurs. Many biomechanical abnormalities associated with the development of claw toes are also associated with elongation of the medial longitudinal arch of the foot . In such conditions, chronic stretching of muscle fibres could occur in FDB. As a result the fibre may increase in length, causing the muscle velocity, excursion and ability to generate force to increase . This would be consistent with the theory that there is excessive pull of FDB associated with claw toes.
There was no possible means of making any observations relating to fibre type during this study, as H&E does not reveal any difference. Serrano et al.  illustrated not only the potential of muscle fibre to change fibre type, but the existence of "hybrid fibres" which can quickly undergo transitions from one fibre type to another, in response to changes of muscle activity. Fibre types have been seen to change in response to force, duration and velocity of muscle activity, all of which are relevant within the context of gait. It would be of extreme interest to note if there is a difference in proportion of fibre type between claw and rectus toes, and if the hypertrophic changes affect one fibre type more than another. Any findings from such a study would give great indication as to whether FDB is involved in active gait or postural stability.
The third major limitation is that this was a morphological study, which has investigated a functional pathology. In order to fully understand muscle function, especially within the foot, muscle activity requires to be studied during gait. The options for obtaining quantitative data from muscle activity from the foot are limited due to both the restrictions of the instrumentation and the anatomical positioning of foot muscles. EMG studies have been used, but possible limitations have already been documented. Magnetic resonance imaging has been extremely successful in the study of cadaveric muscle, but less successful when used for in vivo muscle activity . Ultrasonographic studies have been documented as the method to provide a better understanding of the dynamic nature of skeletal muscle, and could be used to elucidate the biomechanics of muscle contraction .
Fourthly, it should be recognised that this study has only made observations regarding FDB in isolation from other muscles that may be implicated in the development of claw toes. In order to gain a true understanding of atrophic and hypertrophic changes, a comprehensive study of all muscles attaching to the lesser toes is required. This would facilitate a comparison not only of individual muscles and their differences in claw and rectus toes, but how muscles of the same foot compare between the two conditions.
A fifth point to note is that the sample used was small, with only four feet being analysed. Although a larger sample would give a clearer picture, conclusions have been drawn from previous cadaver studies using a similar sample size [31, 34].
In order to gain more data, further studies in this field are required and should endeavour to select a larger sample with similar specimen ages to obtain a more meaningful comparison. It is also necessary to investigate all muscles which are potentially involved in the development of claw toes. To advance the understanding of muscle differences between claw and rectus toes at a morphological level, the investigation of fibre type would be advantageous. A high proportion of Type IIA and IIB fibres would indicate an active functional role in gait, as they produce high power output, but a high proportion of Type I fibres would indicate a link to postural stability. It is possible there may be a difference in proportion of fibre types between muscles associated with rectus toes, and those with claw toes. The study of fibre type using sigma antibodies to fast myosin is required.