Sixty healthy individuals (33 males and 27 females) above the age of 21 years (to allow for completion of ossification), were selected randomly for the study by adopting convenience sampling. The study was conducted between December 2008 and October 2009, after obtaining Institutional Ethical Committee approval and consent from the participants. They were healthy adults of the teaching institute in which the study was conducted. Subjects with history of major and/or long term injuries to the feet, past surgeries on the feet or those with long standing pain in the feet were excluded from the study.

Standardized Antero-Posterior (AP) radiographs of both feet of the individuals were taken. AP radiographs of both feet were taken one at a time. Subject was seated, foot was placed flat on the cassette and X-ray beam was centred on the base of third metatarsal which was identified by palpation. Source- Image receiver distance was fixed at 100 cm. Exposure factors were 46 kV and 6.5 mAS. The radiographic projection and positioning of the foot was strictly determined and adhered to, in order to minimize the influence of pronation and supination of the foot on the radiograph. Radiographic exposures of all the subjects were done by the same technician for uniformity. The radiographs were screened for readability.

Measurement technique- Measurements were conducted on the radiographs using Vernier calipers (Mitutoyo, Japan, Least count - 0.01). Reference points for taking length and width measurements were fixed as described. Measurements for length were taken from the most distal point on the heads of metatarsals to the midpoint of the shadow of the articular surface on the bases. For the fifth metatarsal base, the midpoint of the articular surface excluding the styloid process was considered. Measurements for lengths of phalanges were taken from the middle of the articular surfaces both proximally and distally. Measurements for widths of all the bones were taken at mid-shaft level [Table/Fig-1].

[Table/Fig-1]:

An Antero-Posterior radiograph of the foot showing the position of points of reference for taking measurements of the lengths and widths of metatarsals and lengths of phalanges.

The mean, range and Standard Deviations (SD) of different measurements were calculated. Correlation analysis was done to assess the association between different variables. The significance threshold was set at 0.05.

The mean age of males was 27.78 (21–36) years and that for females was 27.96 (21-37) years. Lengths of metatarsals and phalanges on standardized radiographs of both feet were measured and tabulated. The mean, SD and range were calculated [Table/Fig-2,3]. Correlation of the lengths of the bones amongst their own group were calculated, i.e., metatarsals within themselves [Table/Fig-4], proximal phalanges within themselves [Table/Fig-5], middle phalanges within themselves [Table/Fig-6] and distal phalanges within themselves [Table/Fig-7]. There was strong correlation in these groups within themselves.

The second and the first metatarsals were the longest and shortest metatarsals, respectively. The mean lengths of these were; first metatarsal- 56.42±4.41 mm and 50.09±3.06 mm; second metatarsal - 67.61±3.49 mm and 62.46±3.45 mm, in males and females respectively.

The longest phalanx in both the sexes was the first proximal phalanx (28.0±2.40 mm in males and 25.8±2.21 mm in females). The fifth distal phalanx (5.2±1.33 mm in males and 4.4±1.03 mm in females) was the shortest.

Widths of all metatarsals were measured and tabulated. The mean and SD and range were calculated [Table/Fig-8]. The widest metatarsal in the present study was the first metatarsal (13.7±1.00 mm in males and 11.7±0.91 mm in females). The narrowest metatarsal was the third metatarsal (6.8±0.65 mm in males and 5.9±0.57 mm in females). The correlation of the widths of metatarsals amongst themselves was not significant in most [Table/Fig-9].

Measurements of the dimensions of the forefoot bones help in assessment of the severity of the disorder, planning of surgery, choosing one corrective procedure over another and also in postoperative assessments.

Morphometric studies of metatarsals and phalanges involve conducting measurements either directly on dry macerated bones or on radiographic films. Radiographic studies have been mainly on angle measurements for formulating theories of hallux valgus development, its preoperative assessment, the surgical techniques to be used for correction [9] and assessment of results of surgeries [10]. Researchers, in their review of the principles of osteotomies of the first metatarsal indicate the need for length measurements to choose the correct procedure [11]. Our study involves measurements of the dimensions of the bones of the foot on standardized radiographs in healthy adults.

Dogan A et al., found that the longest metatarsal was the fifth (72.10±5.55 mm in males and 68.56±3.19 mm in females) followed by second, third, fourth. In our study we found the second metatarsal to be the longest (67.61±3.49 mm in males and 62.46±3.45 mm in females) [5]. This difference is probably because we have not taken the styloid process of the fifth metatarsal into consideration. Dogan A et al., have not mentioned about the styloid process of the fifth metatarsal [5]. The shortest was the first metatarsal in the study by Dogan A et al., (8.89±0.79 mm in males and 7.83±0.72 mm in females) and this is in agreement with our findings [5]. In another study by Abdel Moneim WM et al., the lengths of the metatarsals (in centimeters) in males and females respectively was, first - 6.4±0.22 cm and 5.1±0.12 cm, second - 7.0±0.38 cm and 6.1±0.12 cm, third - 7.0±0.12 cm and 6.4±0.09 cm, fourth - 6.9±0.88 cm and 6.6±0.13 cm and fifth - 7.5±0.25 cm and 6.4±0.10 cm [12]. In this study, the points of reference for measurement of lengths of each metatarsal bone were the highest and the lowest points [12].

The widest metatarsal in studies by Dogan A et al., and Abdel Moneim WM et al., was the first metatarsal, which is the same as in our study [5,12]. The third was the narrowest metatarsal in the study by Dogan et al., (15.60±1.49 mm in males and 13.14±1.03 mm in females) and ours [5]. However, in the study by Abdel Moneim et al., the narrowest in males was the fifth metatarsal (0.89±0.1 cm) and that in females was the second metatarsal (0.57±0.08 cm) [5,12].

In our study, the longest of the phalanges, were first proximal phalanx and the shortest was the fifth distal phalanx. In the study by Dogan A et al., the longest and shortest phalanges were first proximal phalanx (31.81±2.76 mm in males and 28.29±2.56 mm in females) and fifth middle phalanx (7.78±1.46 mm in males and 6.59±0.90 mm in females) respectively [5].

Conversion factors to quantify the amount of magnification imparted on a radiograph have been calculated using radiographic and direct measurements on preserved bone specimens. These factors are of value in the preoperative assessment of patients. Opposition to use radiographic measurements as the sole criterion for formulating treatment plans has been advanced by a few surgeons [18]. Some researchers prefer basing surgical corrections on intraoperative assessments rather than radiographic measurements. Even so, for assessing the outcomes of surgeries, they have relied on radiographic measurements in addition to clinical scoring systems [19]. The utility of using radiographic assessment of the feet in diagnosis and treatment of foot pathologies thus cannot be denied.

Metatarsals may need either lengthening or shortening for correction of disabilities. Osteotomies of the forefoot are some of the most common procedures performed by both orthopaedic surgeons and podiatrists. One of the three criteria to achieve an ideal osteotomy is to maintain adequate length [20]. Hallux valgus, metatarsalgia and dislocations of the lesser metatarsophalangeal joints are some of the indications for surgeries. In such cases, preoperative measurement of all metatarsals and correlation between metatarsal lengths can be utilized.

The primary aim of surgeries on the metatarsals for correction of brachymetatarsia, metatarsalgia etc., is to restore the lengths of metatarsals according to the formula 1=2>3>4>5 [21,22].

Preoperative assessment of lengths of metatarsals is important in estimation: (i) of length of osteotomy required for a normal metatarsal parabola; (ii) of amount of shortening required (old 6=new10); (iii) for proper alignment of the lengthened metatarsal [23,24]; and (iv) to decide upon a particular technique of correction to be utilized. In multiple metatarsal surgeries [25] a lengthening of not more than 50% of the original length led to completely satisfactory clinical follow up with no serious or severe complications [22]. To avoid potential complications such as metatarsophalangeal joint subluxation, cavus foot and hallux valgus, the postoperative first metatarsal length should not exceed 40%-50% of the original length [26].

Preoperative and postoperative measurements of dimensions of metatarsals have been used in assessing the outcome of shortening osteotomies for plantar callosities, for assessing effectiveness of osteotomies and for information of the patient regarding risk of postoperative metatarsalgia in case a short metatarsal is already existing [27,28].

It is possible to arrive at a fixed correlation amongst the measurements of the bones of the forefoot. In our view, measurements of the metatarsals and phalanges both preoperatively and postoperatively when carried out on standardized AP radiographs will be helpful in: (a) clinical assessment of the forefoot disorders; (b) choice of surgical procedure to be employed; and in (c) evaluating the outcome of such a surgical procedure. If the lengths and widths of a forefoot bone are known, then the dimensions of the others can be calculated by using the correlation.