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hind-foot arthrodesis procedures in a cadaveric model
Clinical Biomechanics 29 (2014) 170–176
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Maintenance of longitudinal foot arch after different mid/hind-foot arthrodesis procedures in a cadaveric model Yanxi Chen ⁎, Kun Zhang, Minfei Qiang, Yini Hao Department of Orthopedic Trauma, East Hospital, Tongji University School of Medicine, 150 Jimo Rd, 200120 Shanghai, China
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Article history: Received 19 April 2013 Accepted 20 November 2013 Keywords: Flatfoot Longitudinal foot arch Mid/hind foot arthrodesis Biomechanical measurement Cadaver
a b s t r a c t Background: Currently, the optimal treatment of flatfoot remains inconclusive. Our objectives were to understand the effect of different arthrodeses on maintenance of foot arch and provide experimental basis for rational selection in treatment of flatfoot. Methods: Sixteen fresh-frozen cadaver feet amputated above the ankle along with a section of leg were studied from ten males and six females. We used standard clinical techniques and hardware for making the arthrodeses. Plantar pressure in the medial and lateral longitudinal arch distribution was measured with a plantar pressure mapping system under different loading conditions. Findings: Values of plantar pressure reaction, mean and maximum dynamic peak pressure between all group pairs were statistically significant (P b 0.05). The plantar pressure reaction appeared at the load of 960 N in the medial arch of the unoperated foot, compared with 1080 N after subtalar arthrodesis, 1200 N after talonavicular arthrodesis, 1080 N after calcaneocuboid arthrodesis, 1320 N after double arthrodesis, and 1560 N after triple arthrodesis. The plantar pressure reaction appeared at the load of 360 N in the lateral arch of the unoperated foot, compared with 600 N after subtalar arthrodesis, 600 N after talonavicular arthrodesis, 840 N after calcaneocuboid arthrodesis, 960 N after double arthrodesis, and 1440 N after triple arthrodesis. Interpretation: The triple arthrodesis provided the highest support to both arches; the double arthrodesis appeared to be similar to talonavicular arthrodesis in supporting the medial arch and similar to calcaneocuboid arthrodesis in supporting the lateral arch; subtalar arthrodesis was less effective in supporting both arches. © 2013 Elsevier Ltd. All rights reserved.
1. Introduction Flatfoot is characterized by depression or absence of medial longitudinal arch. The prevalence was 6.6% (Kohls-Gatzoulis et al., 2009) for flatfoot deformity. Development of flatfoot may result in further joint and soft-tissue disorders and thus cause pain, lower limb weakness, and difficulty in mobility. Treatments for flatfoot aim to correct the deformity and eliminate the associated symptoms. A successful treatment should restore the biomechanical characteristics of a normal arch. Currently, the optimal treatment remains inconclusive. Among various options, selective mid/hind foot arthrodesis is widely performed because of its advantages in alleviating pain and maintaining the arch stability (O'Malley et al., 1995; Zaret and Myerson, 2003). Commonly performed mid/hind foot arthrodesis procedures include subtalar, talonavicular, calcaneocuboid, double (talonavicular and calcaneocuboid), and triple (subtalar, talonavicular, and calcaneocuboid) arthrodesis. Subtalar arthrodesis was reported to be primarily suitable
⁎ Corresponding author. E-mail address: [email protected] (Y. Chen). 0268-0033/$ – see front matter © 2013 Elsevier Ltd. All rights reserved. http://dx.doi.org/10.1016/j.clinbiomech.2013.11.016
for medium to severe adult flatfoot accompanied by stage-3 or more advanced posterior tibial tendon dysfunction (PTTD), and especially effective for patients who experience lateral ankle pain and diagnosed by radiography to have osteoarthritis but generally confined to the subtalar joint (Cohen and Johnson, 2001; Johnson et al., 2000; Kitaoka and Patzer, 1997; Stephens et al., 1999). The procedure can normalize the connection between bones of the mid- and hind foot, correct the deformity without bone grafting, and has a high bone union rate. Talonavicular arthrodesis is suitable for flexible flatfoot deformity accompanied by talonavicular osteoarthritis (Fortin, 2001; Harper and Tisdel, 1996; Mothershed et al., 1999). It can correct forefoot abduction, elevate the arch, stabilize the medial column, prevent excessive intorsion of the subtalar joint, and alleviate pain. Calcaneocuboid distraction arthrodesis also can elevate the arch and correct flatfoot deformity (Hintermann et al., 1999; Phillips, 1983). Double arthrodesis can increase the midfoot stability and avoid the development of lateral column pain following talonavicular arthrodesis alone; it is particularly suitable for obese patients and patients with talonavicular or calcaneocuboid osteoarthritis (Mann et al., 1998). Triple arthrodesis is suitable for rigid flatfoot, flexible flatfoot accompanied by stage-3 or more advanced PTTD, and also flatfoot accompanied by severe osteoarthritis of the hindfoot (Graves et al.,
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1993; Jarde et al., 2002; Sullivan and Aronow, 2002). It can correct subtalar eversion, talonavicular collapse, and forefoot abduction at the midtarsal joint. It can also prevent the development of joint osteoarthritis adjacent to the fused joints as a potential side-effect after a singlejoint arthrodesis. Although effective, these procedures inevitably result in reduced mobility of the mid/hind foot. The reduced mobility results in degenerative changes of the unfused joints, which can progress into osteoarthritis and cause pain and impaired foot function due to rigidity. To date, most studies on flatfoot treatment investigated only one arthrodesis procedure. Moreover, the measurement of arch height and marker points varied among studies: the height measured dynamically or statically, and the marker points placed on the navicular or medial cuneiform. These limitations have prevented reliable comparisons among different studies. The outcomes of these arthrodesis procedures have been systematically examined and their indications and key points have been analyzed. It was found that the chief disadvantage associated with these procedures is the loss of mid/hind foot mobility. The loss of mobility can induce the unfused joints to undergo degenerative changes, which may develop osteoarthritis and cause foot pain and loss of foot function due to rigidity (Astion et al., 1997; Deland et al., 1995; Fortin, 2001; Harper and Tisdel, 1996; Mann et al., 1998; Savory et al., 1998). Therefore, an optimum arthrodesis procedure that can maintain the arch stability and minimize the loss in mid/hind foot mobility remains to be investigated. In this study, we simulated these popular arthrodesis procedures in human cadaveric models. In the model, a load was applied along the tibial diaphysis and the plantar pressure in the medial and lateral longitudinal arch distributions was measured after the foot was treated by each procedure. Our objectives were to understand the effect of different arthrodesis procedures on the maintenance of the foot arch and thereby provide experimental basis for rational selection of arthrodesis procedures in the clinic treatment of flatfoot. 2. Methods 2.1. Materials Sixteen fresh-frozen cadaver feet amputated above the ankle along with a section of leg were studied from ten male and six female patients. Specimens had no evidence of previous injury, operations, osteoarthritis, or severe deformity by visual inspection and X-ray examination. Five were left and eleven were right feet. The mean age at the time of death was 37 years (range, 18–58 years). The tibia and fibula were amputated at the junction of the middle third and distal third. The skin, subcutaneous tissues, and muscle were dissected from the most proximal portion. The interosseus and ligaments of foot and ankle were kept intact. Specimens were stored frozen at −80 °C before the experiment and thawed to room temperature at the beginning of the experiment. 2.2. Ethics statement Institutional Ethical Approval was obtained prospectively, and conforms to the provisions of the Declaration of Helsinki (Tongji Hospital Ethics Committee, Ethics number LL (H)-08-02). The subjects gave informed consent and patient anonymity has been preserved. All consent was written in nature, and where deceased, written consent was obtained from the next of kin of the deceased.
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with the exception that the articular surfaces were left intact. The arthrodesis procedures included: I) Subtalar arthrodesis: The calcaneus was everted relative to the talus by 5°–10°. Three half-threaded cancellous screws (diameter: all 6.5 mm; length: 75 mm, 75 mm, and 70 mm) were inserted from the calcaneus, across the subtalar joint and into the talus. II) Talonavicular arthrodesis: The deep fascia was dissected and the tibial anterior tendon and the extensor hallucis longus were exposed. After elevating the muscles, three full-thread cancellous screws were inserted through the navicular bone, across the talonavicular joint and into the talus without opening the joint capsule. III) Calcaneocuboid arthrodesis: After dissecting the deep fascia, the peroneus brevis was retracted postero-laterally. The belly of the extensor digitorum brevis was bluntly separated and retracted superiorly without opening the joint capsule. With the foot maintained at a neutral position, the calcaneocuboid joint was fixed with a butterfly-shaped titanium plate and fully threaded cancellous screws. IV) Double and triple arthrodesis: These procedures were performed simply by combining the corresponding procedures described above (Fig. 1). 2.4. Biomechanical measurement Plantar pressure distribution was measured with a plantar pressure mapping system (F-Scan Mobile, Tekscan, Boston, MA, USA). Considering that the pressure sensed in this system may be influenced by the actual pressure as well as the rate and duration of loading, a consistent loading profile was used in this study to ensure the comparability of the results. Specimens were mounted in a universal mechanical testing machine (CSS-44010, Changchun, China) which was fixed in a horizontal position to apply repeatable axial loads with the load downward along the tibial diaphysis. The foot was orientated in neutral position. The tibial diaphysis was vertical and parallel to the plumb line and perpendicular to the plantar plane as well as the platform surface. The line connecting the calcaneal tuberosity and the medial margin of the intermediate cuneiform bone was coronal. The loads were applied at a constant rate of 60 N/s to 1800 N in 30 s and released at the same rate in 30 s. During both loading and unloading, the horizontal displacement of tibial diaphysis was set and monitored by the built-in software to be restricted within 0–2 mm automatically; moreover, the sensor matt was placed on a laboratory-made fixture to prevent the matt from slipping during experiment. With the fixture, no matt slippage could be observed during any experiment. In addition, several pins were inserted to the bones near the fused joint(s). A threedimensional coordinate measurement system (MicroScribe G2X, Immersion USA) was set up on the table near the specimen. The tips of the pins were touched by the stylus of the digitizer handled by the examiner. And rotation angles (Cardan angles, also called Tait–Bryan angles) of the joints were calculated. Application program was made for easy calculating and was hooked up to the software (Matlab 7.01, Mathworks Inc., Natick, MA, USA). The system has an accuracy of up to 0.2 mm to ensure the absence of abnormal joint movement during loading/unloading (Fig. 2). Before experimenting with the arthrodesis procedures, the operated foot was loaded–unloaded and the resulting plantar pressures were measured. Then, the foot was sequentially treated by the arthrodesis procedures, and the corresponding pressure distributions were subsequently measured. During all experiments, the room temperature was maintained between 18 and 20 °C and the relative humidity was maintained at 40–50% to keep the cadavers moist. 2.5. Pressure data collection
2.3. Arthrodesis procedures There were normal conditions and five arthrodesis procedures at the hind foot to be studied were based on minimizing the damage to soft tissues in the mid/hind foot. We used standard clinical techniques and hardware (Kanghui Ltd, Changzhou, China) for making the arthrodesis,
After treatment with each arthrodesis procedure, the foot underwent three cycles of loading/unloading and the maximum peak pressures under the medial and lateral longitudinal arches were monitored during each cycle and averaged. For each measurement, the midfoot was divided into two regions representing the medial and
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Fig. 1. X-ray images of feet after arthrodesis. We used standard clinical techniques and hardware for making the arthrodesis, including: talonavicular (A), calcaneocuboid + talonavicular (B), subtalar (C), calcaneocuboid (D) and triple arthrodesis (E).
lateral arches. The regions were chosen by visual identification using maximum peak pressure optimal marquee of the F-Scan system. The change of peak pressure with time was plotted and the differences in static peak pressure and mean/maximum dynamic peak pressures after different procedures were analyzed (Fig. 3).
2.6. Statistical analyses All data were expressed as mean (standard deviation) and analyzed by SAS 12.0 (SAS Institute Inc., SAS Campus Drive, Cary, North Carolina, USA). Differences within the same group were analyzed by repeated measure ANOVA. Differences among groups were analyzed by oneway ANOVA followed by Scheffe tests for pair-wise comparisons. A P b 0.05 was considered statistically significant.
Fig. 2. Working environment of measuring plantar pressure distribution before and after arthrodesis procedures.
Fig. 3. Maximum peak pressure under the medial and lateral longitudinal arches. We use maximum peak pressure optimal marquee of the F-Scan system to figure out the maximum peak pressure of each time node during loading. (A) Plantar pressure before loading. (B) Plantar pressure after loading.
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Fig. 4. Pressure–time curve of medial longitudinal arches in normal feet and feet after arthrodesis procedures.
Fig. 5. Pressure–time curve of lateral longitudinal arches in normal feet and feet after arthrodesis procedures.
3. Results All 16 cadaveric feet were successfully studied and the displacement was confirmed to be b2 mm in all experiments. No abnormal joint movement was detected during any experiment. All cadavers showed similar creep behaviors before and after the study. All data followed the normal distribution. Dynamic and static pressure data were successfully measured and visualized as two- and three-dimensional images. During loading, the maximum static peak pressures on the medial and lateral longitudinal arches were measured every 2 s (i.e. load increment of 120 N). It was found that the peak pressures recorded under the medial arch of unoperated feet (F = 113.6, P b 0.001) and feet treated by subtalar arthrodesis (F = 147.8, P b 0.001), talonavicular arthrodesis (F = 156.9, P b 0.001), calcaneocuboid arthrodesis (F = 197.4, P b 0.001), double arthrodesis (F = 240.5, P b 0.001) and triple arthrodesis (F = 367.3, P b 0.001) all have statistical significance within each group. Fig. 4 shows the pressure profiles measured during loading. It can be seen that, all arthrodesis procedures stabilized the medial arches to different degrees. The plantar pressure reaction appeared at the load of 960 N in the medial arch of the unoperated foot, compared with 1080 N after subtalar arthrodesis, 1200 N after talonavicular arthrodesis, 1080 N after calcaneocuboid arthrodesis, 1320 N after double arthrodesis, and 1560 N after triple arthrodesis. The peak pressures recorded on the lateral longitudinal arches of unoperated feet (F = 154.3, P b 0.001) and feet treated by subtalar arthrodesis (F = 198.6, P b 0.001), talonavicular arthrodesis (F = 142.5, P b 0.001), calcaneocuboid arthrodesis (F = 264.3, P b 0.001), double arthrodesis (F = 222.5, P b 0.001) and triple arthrodesis (F = 98.7, P b 0.001) all have statistical significance within each group. Fig. 5 shows the pressure files during loading. Similarly, all arthrodesis procedures were able to stabilize the lateral arch to different degrees. The plantar pressure reaction appeared at the load of 360 N in the lateral arch of unoperated foot, compared with 600 N after subtalar arthrodesis, 600 N after talonavicular
arthrodesis, 840 N after calcaneocuboid arthrodesis, 960 N after double arthrodesis, and 1440 N after triple arthrodesis. During unloading, a load of 600 N was assumed as the static peak pressure under physiological conditions (neutral standing position). The pressures on the medial and lateral arches measured at the
Table 1 Comparisons of static peak pressures and mean/maximum dynamic peak pressures under medial longitudinal arches of normal feet and feet after different arthrodesis procedures (mean values and standard deviations). Grouping
Normal feet (KPa) Subtalar (KPa) Talonavicular (KPa) Calcaneocuboid (KPa) Double arthrodesis (KPa) Triple arthrodesis (KPa) F value P value Pairwise comparison (P value) Normal feet: subtalar Normal feet: talonavicular Normal feet: calcaneocuboid Normal feet: double arthrodesis Normal feet: triple arthrodesis Subtalar: talonavicular Subtalar: calcaneocuboid Subtalar: double arthrodesis Subtalar: triple arthrodesis Talonavicular: calcaneocuboid Talonavicular: double arthrodesis Talonavicular: triple arthrodesis Calcaneocuboid: double arthrodesis Calcaneocuboid: triple arthrodesis Double arthrodesis: triple arthrodesis
Static peak pressure (600 N)
Dynamic(1800 N) Mean pressure
Maximum peak pressure
0 0 0 0 0 0 0 0
41.2 (4.3) 25.54 (3.1) 13.1 (2.8) 33.3 (4.5) 11.8 (2.4) 7.3 (1.5) 19.95 0.001
130.6 (23.6) 107.8 (16.5) 66.4 (8.9) 119.5 (18.6) 63.0 (6.2) 52.3 (5.6) 75.32 0.001
0 0 0 0 0 0 0 0 0 0 0 0 0 0 0
0.001 0.001 0.001 0.001 0.001 0.001 0.001 0.001 0.001 0.001 0.018 0.001 0.001 0.001 0.001
0.001 0.001 0.029 0.001 0.001 0.001 0.008 0.001 0.001 0.001 0.045 0.023 0.001 0.001 0.012
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Table 2 Comparisons of static peak pressures and mean/maximum dynamic peak pressures under lateral longitudinal arches of normal feet and feet after different arthrodesis procedures (mean values and standard deviations). Grouping
Normal feet (KPa) Subtalar (KPa) Talonavicular (KPa) Calcaneocuboid (KPa) Double arthrodesis (KPa) Triple arthrodesis (KPa) F value P value Pairwise comparison (P value) Normal feet: subtalar Normal feet: talonavicular Normal feet: calcaneocuboid Normal feet: double arthrodesis Normal feet: triple arthrodesis Subtalar: talonavicular Subtalar: calcaneocuboid Subtalar: double arthrodesis Subtalar: triple arthrodesis Talonavicular: calcaneocuboid Talonavicular: double arthrodesis Talonavicular: triple arthrodesis Calcaneocuboid: triple arthrodesis Calcaneocuboid: triple arthrodesis Double arthrodesis: triple arthrodesis
Static peak pressure (600 N)
Dynamic (1800 N) Mean pressure
Maximum peak pressure
36.3 (6.4) 3.6 (1.2) 12.5 (3.1) 0 0 0 12.53 0.001
231.4 (25.2) 125.3 (16.8) 197.8 (22.3) 68.2 (8.5) 56.6 (6.1) 21.4 (3.5) 19.95 0.001
570.0 (32.5) 404.3 (26.4) 505.6 (28.9) 240.7 (21.6) 213.7 (16.5) 126.8 (11.6) 156.43 0.001
0.001 0.001 0.001 0.001 0.001 0.001 0.001 0.001 0.001 0.001 0.001 0.001 0 0 0
0.001 0.001 0.001 0.001 0.001 0.001 0.001 0.001 0.001 0.001 0.001 0.001 0.035 0.001 0.001
0.001 0.001 0.001 0.001 0.001 0.001 0.001 0.001 0.001 0.001 0.001 0.001 0.024 0.001 0.001
maximum load (1800 N) were input into the Timing Analysis Module (TAM) of the F-Scan system to simulate the dynamic peak pressures under the corresponding arches. (See Tables 1and 2) (See Figs. 6 and 7) All data and results of statistical analyses are shown in Tables 1, 2 and Figs. 6, 7. 4. Discussion Flatfoot can result in misalignment of foot joints, which may appear as forefoot abduction, hindfoot eversion, and arch collapse (Brodsky et al., 2004). It can also lead to subluxation of the subtalar and talonavicular joints, reduction in contact area between the talus and the anterior/middle/posterior calcaneal articular surfaces, navicular eversion/extorsion/plantar flexion relative to the talus, and separation or plantar flexion of the medial cuneiform relative to the navicular (Ellis et al., 2010). The various conditions may combine and cause arch instability and abnormal plantar pressure distribution. Selective arthrodesis reconstructs connection between bones in a flatfoot to fix the lax joints, restore the normal interaction between the midfoot and hindfoot during locomotion, and maintain the arch stability. Therefore, it can correct subtalar/talonavicular subluxation and foot extorsion/eversion, and eliminate the associated symptoms such as pain caused by mid- or hindfoot osteoarthritis (O'Malley et al., 1995; Zaret and Myerson, 2003). In this study, we compared the arch support of five popular arthrodesis procedures under identical loading/unloading conditions using a modern 3D plantar pressure measurement system (Mueller and Strube, 1996; Sumiya et al., 1998; Chau, 2001; Wearing et al., 2000;
Fig. 6. Comparisons of different pressures in medial arches. We compared static pressures and mean/maximum dynamic peak pressures under medial longitudinal arches of normal feet and feet after different procedures.
Fig. 7. Comparisons of different pressures in lateral arches. We compared static pressures and mean/maximum dynamic peak pressures under lateral longitudinal arches of normal feet and feet after different procedures.
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Woodburn and Helliwell, 1997; Young, 1993). Loading of fresh cadaveric feet with dynamic stresses simulating physiological weight bearing is an important method in studying the dynamic mechanic properties of joints and tendons. In physiological conditions, the body weight is transferred via the tibial diaphyses, the ankle joints, to the tali, and then further conducted along three stress lines (posterior, anterolateral, and anteromedial). Accordingly, perpendicular loading along the tibial diaphysis has been extensively used in simulating dynamic loading of the human body. In this study, we adopted this loading mode and carefully monitored (visually and with the computer control system equipped with the mechanical testing machine) the loading/unloading processes and the resulting tibial diaphyseal displacement to ensure the absence of foot slipping or destruction. During all experiments, the loading/unloading cycles were confirmed to be linear and the displacements b2 mm. However, in this loading mode, the position of the tibial diaphysis and the direction of the load were fixed regardless of the position of the foot. Comparatively, in physiological conditions (e.g. plantar flexion movement of the ankle), the upper tibial diaphysis moves along the sagittal axis together with the knee joint. Thus, it remains difficult to simulate the load applied on the ankle and foot during real physiological movement (Martinelli et al., 2012). It was reported that the maximum pressure on an ankle can reach five times that of the body weight. In this study, we aimed to investigate the plantar pressure distribution and arch stability after different arthrodesis procedures, therefore it is important to keep the loading conditions unchanged before and after arthrodesis as well as close to the physiological conditions. Based on repeated pre-tests, a maximum load of 1800 N chosen to ensure the applied load was constantly below the destructive threshold of the cadaveric specimens. The result indicated that these arthrodesis procedures all provided stable support to the medial and lateral arch under physiological condition. Specifically, original reaction pressure, measurement of mean and maximum dynamic peak pressure all revealed that the triple arthrodesis provided the highest support, followed by double arthrodesis. However, the talonavicular and calcaneocuboid arthrodesis presented a different order in the support of medial and lateral arches. The talonavicular arthrodesis provided better support to the medial arch and appeared to be similar to double arthrodesis. According to previous studies, motion of the talonavicular joint is the key to motion of the triple joint complex, and talonavicular arthrodesis limits motion of calcaneocuboid and subtalar joint as well as double arthrodesis does, so isolated talonavicular arthrodesis is an effective alternative to double arthrodesis (Astion et al., 1997; Thelen et al., 2010) while double arthrodesis is suitable for obese patients and patients with talonavicular and calcaneocuboid osteoarthritis (Mann et al., 1998). The arthrodesis of calcaneocuboid joint had the least effect on the motion of the other joints (Astion et al., 1997). Nevertheless, arthrodesis of calcaneocuboid joint offers the least support on the maintenance of medial arch. The subtalar arthrodesis also provided enough support to both arches. Meanwhile, about 25 to 56% of the motion of the talonavicular joint and more than 50% of the motion of the calcaneocuboid joint remained after subtalar arthrodesis (Astion et al., 1997; Mann et al., 1998). So it was also a choice to treat medium to severe adult flatfoot (Cohen and Johnson, 2001; Johnson et al., 2000; Kitaoka and Patzer, 1997; Stephens et al., 1999). Triple arthrodesis is suitable for the most severe cases (Graves et al., 1993; Jarde et al., 2002; Sullivan and Aronow, 2002). Taken together, our results show that the five arthrodesis procedures were all able to provide some degree of support to both lateral and medial arches. The triple arthrodesis was found to provide the highest support to both arches; the double arthrodesis appeared to be similar to talonavicular arthrodesis in supporting the medial arch and similar to calcaneocuboid arthrodesis in supporting the lateral arch; subtalar arthrodesis was less effective in supporting both arches compared with both talonavicular and calcaneocuboid arthrodesis. The method that consecutive procedures applied on the same cadaver may influence the accuracy in assessing the result of single
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arthrodesis. However, the method was used widely (Astion et al., 1997; Jung et al., 2005). In this research, tendon injury was prevented and soft tissue damage was minimized. The procedures were standardized and the data are consistent within the study. Therefore, the feet could have stable properties throughout the procedures. It remains difficult in podiatry to develop a biomechanical model maximally close to the normal physiological conditions based on fresh cadaveric lower limb specimens. Despite this difficulty, our results allowed reliable comparison among the effects of different arthrodesis procedures and thus provide valuable information for a rational selection of procedures in clinics. Although the plantar pressures were not measured in truly physiological conditions, the measurement conditions were kept consistent in this study, which ensured a comparability of results. 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Maintenance of longitudinal foot arch after different mid/hind-foot arthrodesis procedures in a cadaveric model Yanxi Chen ⁎, Kun Zhang, Minfei Qiang, Yini Hao Department of Orthopedic Trauma, East Hospital, Tongji University School of Medicine, 150 Jimo Rd, 200120 Shanghai, China
a r t i c l e
i n f o
Article history: Received 19 April 2013 Accepted 20 November 2013 Keywords: Flatfoot Longitudinal foot arch Mid/hind foot arthrodesis Biomechanical measurement Cadaver
a b s t r a c t Background: Currently, the optimal treatment of flatfoot remains inconclusive. Our objectives were to understand the effect of different arthrodeses on maintenance of foot arch and provide experimental basis for rational selection in treatment of flatfoot. Methods: Sixteen fresh-frozen cadaver feet amputated above the ankle along with a section of leg were studied from ten males and six females. We used standard clinical techniques and hardware for making the arthrodeses. Plantar pressure in the medial and lateral longitudinal arch distribution was measured with a plantar pressure mapping system under different loading conditions. Findings: Values of plantar pressure reaction, mean and maximum dynamic peak pressure between all group pairs were statistically significant (P b 0.05). The plantar pressure reaction appeared at the load of 960 N in the medial arch of the unoperated foot, compared with 1080 N after subtalar arthrodesis, 1200 N after talonavicular arthrodesis, 1080 N after calcaneocuboid arthrodesis, 1320 N after double arthrodesis, and 1560 N after triple arthrodesis. The plantar pressure reaction appeared at the load of 360 N in the lateral arch of the unoperated foot, compared with 600 N after subtalar arthrodesis, 600 N after talonavicular arthrodesis, 840 N after calcaneocuboid arthrodesis, 960 N after double arthrodesis, and 1440 N after triple arthrodesis. Interpretation: The triple arthrodesis provided the highest support to both arches; the double arthrodesis appeared to be similar to talonavicular arthrodesis in supporting the medial arch and similar to calcaneocuboid arthrodesis in supporting the lateral arch; subtalar arthrodesis was less effective in supporting both arches. © 2013 Elsevier Ltd. All rights reserved.
1. Introduction Flatfoot is characterized by depression or absence of medial longitudinal arch. The prevalence was 6.6% (Kohls-Gatzoulis et al., 2009) for flatfoot deformity. Development of flatfoot may result in further joint and soft-tissue disorders and thus cause pain, lower limb weakness, and difficulty in mobility. Treatments for flatfoot aim to correct the deformity and eliminate the associated symptoms. A successful treatment should restore the biomechanical characteristics of a normal arch. Currently, the optimal treatment remains inconclusive. Among various options, selective mid/hind foot arthrodesis is widely performed because of its advantages in alleviating pain and maintaining the arch stability (O'Malley et al., 1995; Zaret and Myerson, 2003). Commonly performed mid/hind foot arthrodesis procedures include subtalar, talonavicular, calcaneocuboid, double (talonavicular and calcaneocuboid), and triple (subtalar, talonavicular, and calcaneocuboid) arthrodesis. Subtalar arthrodesis was reported to be primarily suitable
⁎ Corresponding author. E-mail address: [email protected] (Y. Chen). 0268-0033/$ – see front matter © 2013 Elsevier Ltd. All rights reserved. http://dx.doi.org/10.1016/j.clinbiomech.2013.11.016
for medium to severe adult flatfoot accompanied by stage-3 or more advanced posterior tibial tendon dysfunction (PTTD), and especially effective for patients who experience lateral ankle pain and diagnosed by radiography to have osteoarthritis but generally confined to the subtalar joint (Cohen and Johnson, 2001; Johnson et al., 2000; Kitaoka and Patzer, 1997; Stephens et al., 1999). The procedure can normalize the connection between bones of the mid- and hind foot, correct the deformity without bone grafting, and has a high bone union rate. Talonavicular arthrodesis is suitable for flexible flatfoot deformity accompanied by talonavicular osteoarthritis (Fortin, 2001; Harper and Tisdel, 1996; Mothershed et al., 1999). It can correct forefoot abduction, elevate the arch, stabilize the medial column, prevent excessive intorsion of the subtalar joint, and alleviate pain. Calcaneocuboid distraction arthrodesis also can elevate the arch and correct flatfoot deformity (Hintermann et al., 1999; Phillips, 1983). Double arthrodesis can increase the midfoot stability and avoid the development of lateral column pain following talonavicular arthrodesis alone; it is particularly suitable for obese patients and patients with talonavicular or calcaneocuboid osteoarthritis (Mann et al., 1998). Triple arthrodesis is suitable for rigid flatfoot, flexible flatfoot accompanied by stage-3 or more advanced PTTD, and also flatfoot accompanied by severe osteoarthritis of the hindfoot (Graves et al.,
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1993; Jarde et al., 2002; Sullivan and Aronow, 2002). It can correct subtalar eversion, talonavicular collapse, and forefoot abduction at the midtarsal joint. It can also prevent the development of joint osteoarthritis adjacent to the fused joints as a potential side-effect after a singlejoint arthrodesis. Although effective, these procedures inevitably result in reduced mobility of the mid/hind foot. The reduced mobility results in degenerative changes of the unfused joints, which can progress into osteoarthritis and cause pain and impaired foot function due to rigidity. To date, most studies on flatfoot treatment investigated only one arthrodesis procedure. Moreover, the measurement of arch height and marker points varied among studies: the height measured dynamically or statically, and the marker points placed on the navicular or medial cuneiform. These limitations have prevented reliable comparisons among different studies. The outcomes of these arthrodesis procedures have been systematically examined and their indications and key points have been analyzed. It was found that the chief disadvantage associated with these procedures is the loss of mid/hind foot mobility. The loss of mobility can induce the unfused joints to undergo degenerative changes, which may develop osteoarthritis and cause foot pain and loss of foot function due to rigidity (Astion et al., 1997; Deland et al., 1995; Fortin, 2001; Harper and Tisdel, 1996; Mann et al., 1998; Savory et al., 1998). Therefore, an optimum arthrodesis procedure that can maintain the arch stability and minimize the loss in mid/hind foot mobility remains to be investigated. In this study, we simulated these popular arthrodesis procedures in human cadaveric models. In the model, a load was applied along the tibial diaphysis and the plantar pressure in the medial and lateral longitudinal arch distributions was measured after the foot was treated by each procedure. Our objectives were to understand the effect of different arthrodesis procedures on the maintenance of the foot arch and thereby provide experimental basis for rational selection of arthrodesis procedures in the clinic treatment of flatfoot. 2. Methods 2.1. Materials Sixteen fresh-frozen cadaver feet amputated above the ankle along with a section of leg were studied from ten male and six female patients. Specimens had no evidence of previous injury, operations, osteoarthritis, or severe deformity by visual inspection and X-ray examination. Five were left and eleven were right feet. The mean age at the time of death was 37 years (range, 18–58 years). The tibia and fibula were amputated at the junction of the middle third and distal third. The skin, subcutaneous tissues, and muscle were dissected from the most proximal portion. The interosseus and ligaments of foot and ankle were kept intact. Specimens were stored frozen at −80 °C before the experiment and thawed to room temperature at the beginning of the experiment. 2.2. Ethics statement Institutional Ethical Approval was obtained prospectively, and conforms to the provisions of the Declaration of Helsinki (Tongji Hospital Ethics Committee, Ethics number LL (H)-08-02). The subjects gave informed consent and patient anonymity has been preserved. All consent was written in nature, and where deceased, written consent was obtained from the next of kin of the deceased.
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with the exception that the articular surfaces were left intact. The arthrodesis procedures included: I) Subtalar arthrodesis: The calcaneus was everted relative to the talus by 5°–10°. Three half-threaded cancellous screws (diameter: all 6.5 mm; length: 75 mm, 75 mm, and 70 mm) were inserted from the calcaneus, across the subtalar joint and into the talus. II) Talonavicular arthrodesis: The deep fascia was dissected and the tibial anterior tendon and the extensor hallucis longus were exposed. After elevating the muscles, three full-thread cancellous screws were inserted through the navicular bone, across the talonavicular joint and into the talus without opening the joint capsule. III) Calcaneocuboid arthrodesis: After dissecting the deep fascia, the peroneus brevis was retracted postero-laterally. The belly of the extensor digitorum brevis was bluntly separated and retracted superiorly without opening the joint capsule. With the foot maintained at a neutral position, the calcaneocuboid joint was fixed with a butterfly-shaped titanium plate and fully threaded cancellous screws. IV) Double and triple arthrodesis: These procedures were performed simply by combining the corresponding procedures described above (Fig. 1). 2.4. Biomechanical measurement Plantar pressure distribution was measured with a plantar pressure mapping system (F-Scan Mobile, Tekscan, Boston, MA, USA). Considering that the pressure sensed in this system may be influenced by the actual pressure as well as the rate and duration of loading, a consistent loading profile was used in this study to ensure the comparability of the results. Specimens were mounted in a universal mechanical testing machine (CSS-44010, Changchun, China) which was fixed in a horizontal position to apply repeatable axial loads with the load downward along the tibial diaphysis. The foot was orientated in neutral position. The tibial diaphysis was vertical and parallel to the plumb line and perpendicular to the plantar plane as well as the platform surface. The line connecting the calcaneal tuberosity and the medial margin of the intermediate cuneiform bone was coronal. The loads were applied at a constant rate of 60 N/s to 1800 N in 30 s and released at the same rate in 30 s. During both loading and unloading, the horizontal displacement of tibial diaphysis was set and monitored by the built-in software to be restricted within 0–2 mm automatically; moreover, the sensor matt was placed on a laboratory-made fixture to prevent the matt from slipping during experiment. With the fixture, no matt slippage could be observed during any experiment. In addition, several pins were inserted to the bones near the fused joint(s). A threedimensional coordinate measurement system (MicroScribe G2X, Immersion USA) was set up on the table near the specimen. The tips of the pins were touched by the stylus of the digitizer handled by the examiner. And rotation angles (Cardan angles, also called Tait–Bryan angles) of the joints were calculated. Application program was made for easy calculating and was hooked up to the software (Matlab 7.01, Mathworks Inc., Natick, MA, USA). The system has an accuracy of up to 0.2 mm to ensure the absence of abnormal joint movement during loading/unloading (Fig. 2). Before experimenting with the arthrodesis procedures, the operated foot was loaded–unloaded and the resulting plantar pressures were measured. Then, the foot was sequentially treated by the arthrodesis procedures, and the corresponding pressure distributions were subsequently measured. During all experiments, the room temperature was maintained between 18 and 20 °C and the relative humidity was maintained at 40–50% to keep the cadavers moist. 2.5. Pressure data collection
2.3. Arthrodesis procedures There were normal conditions and five arthrodesis procedures at the hind foot to be studied were based on minimizing the damage to soft tissues in the mid/hind foot. We used standard clinical techniques and hardware (Kanghui Ltd, Changzhou, China) for making the arthrodesis,
After treatment with each arthrodesis procedure, the foot underwent three cycles of loading/unloading and the maximum peak pressures under the medial and lateral longitudinal arches were monitored during each cycle and averaged. For each measurement, the midfoot was divided into two regions representing the medial and
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Fig. 1. X-ray images of feet after arthrodesis. We used standard clinical techniques and hardware for making the arthrodesis, including: talonavicular (A), calcaneocuboid + talonavicular (B), subtalar (C), calcaneocuboid (D) and triple arthrodesis (E).
lateral arches. The regions were chosen by visual identification using maximum peak pressure optimal marquee of the F-Scan system. The change of peak pressure with time was plotted and the differences in static peak pressure and mean/maximum dynamic peak pressures after different procedures were analyzed (Fig. 3).
2.6. Statistical analyses All data were expressed as mean (standard deviation) and analyzed by SAS 12.0 (SAS Institute Inc., SAS Campus Drive, Cary, North Carolina, USA). Differences within the same group were analyzed by repeated measure ANOVA. Differences among groups were analyzed by oneway ANOVA followed by Scheffe tests for pair-wise comparisons. A P b 0.05 was considered statistically significant.
Fig. 2. Working environment of measuring plantar pressure distribution before and after arthrodesis procedures.
Fig. 3. Maximum peak pressure under the medial and lateral longitudinal arches. We use maximum peak pressure optimal marquee of the F-Scan system to figure out the maximum peak pressure of each time node during loading. (A) Plantar pressure before loading. (B) Plantar pressure after loading.
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Fig. 4. Pressure–time curve of medial longitudinal arches in normal feet and feet after arthrodesis procedures.
Fig. 5. Pressure–time curve of lateral longitudinal arches in normal feet and feet after arthrodesis procedures.
3. Results All 16 cadaveric feet were successfully studied and the displacement was confirmed to be b2 mm in all experiments. No abnormal joint movement was detected during any experiment. All cadavers showed similar creep behaviors before and after the study. All data followed the normal distribution. Dynamic and static pressure data were successfully measured and visualized as two- and three-dimensional images. During loading, the maximum static peak pressures on the medial and lateral longitudinal arches were measured every 2 s (i.e. load increment of 120 N). It was found that the peak pressures recorded under the medial arch of unoperated feet (F = 113.6, P b 0.001) and feet treated by subtalar arthrodesis (F = 147.8, P b 0.001), talonavicular arthrodesis (F = 156.9, P b 0.001), calcaneocuboid arthrodesis (F = 197.4, P b 0.001), double arthrodesis (F = 240.5, P b 0.001) and triple arthrodesis (F = 367.3, P b 0.001) all have statistical significance within each group. Fig. 4 shows the pressure profiles measured during loading. It can be seen that, all arthrodesis procedures stabilized the medial arches to different degrees. The plantar pressure reaction appeared at the load of 960 N in the medial arch of the unoperated foot, compared with 1080 N after subtalar arthrodesis, 1200 N after talonavicular arthrodesis, 1080 N after calcaneocuboid arthrodesis, 1320 N after double arthrodesis, and 1560 N after triple arthrodesis. The peak pressures recorded on the lateral longitudinal arches of unoperated feet (F = 154.3, P b 0.001) and feet treated by subtalar arthrodesis (F = 198.6, P b 0.001), talonavicular arthrodesis (F = 142.5, P b 0.001), calcaneocuboid arthrodesis (F = 264.3, P b 0.001), double arthrodesis (F = 222.5, P b 0.001) and triple arthrodesis (F = 98.7, P b 0.001) all have statistical significance within each group. Fig. 5 shows the pressure files during loading. Similarly, all arthrodesis procedures were able to stabilize the lateral arch to different degrees. The plantar pressure reaction appeared at the load of 360 N in the lateral arch of unoperated foot, compared with 600 N after subtalar arthrodesis, 600 N after talonavicular
arthrodesis, 840 N after calcaneocuboid arthrodesis, 960 N after double arthrodesis, and 1440 N after triple arthrodesis. During unloading, a load of 600 N was assumed as the static peak pressure under physiological conditions (neutral standing position). The pressures on the medial and lateral arches measured at the
Table 1 Comparisons of static peak pressures and mean/maximum dynamic peak pressures under medial longitudinal arches of normal feet and feet after different arthrodesis procedures (mean values and standard deviations). Grouping
Normal feet (KPa) Subtalar (KPa) Talonavicular (KPa) Calcaneocuboid (KPa) Double arthrodesis (KPa) Triple arthrodesis (KPa) F value P value Pairwise comparison (P value) Normal feet: subtalar Normal feet: talonavicular Normal feet: calcaneocuboid Normal feet: double arthrodesis Normal feet: triple arthrodesis Subtalar: talonavicular Subtalar: calcaneocuboid Subtalar: double arthrodesis Subtalar: triple arthrodesis Talonavicular: calcaneocuboid Talonavicular: double arthrodesis Talonavicular: triple arthrodesis Calcaneocuboid: double arthrodesis Calcaneocuboid: triple arthrodesis Double arthrodesis: triple arthrodesis
Static peak pressure (600 N)
Dynamic(1800 N) Mean pressure
Maximum peak pressure
0 0 0 0 0 0 0 0
41.2 (4.3) 25.54 (3.1) 13.1 (2.8) 33.3 (4.5) 11.8 (2.4) 7.3 (1.5) 19.95 0.001
130.6 (23.6) 107.8 (16.5) 66.4 (8.9) 119.5 (18.6) 63.0 (6.2) 52.3 (5.6) 75.32 0.001
0 0 0 0 0 0 0 0 0 0 0 0 0 0 0
0.001 0.001 0.001 0.001 0.001 0.001 0.001 0.001 0.001 0.001 0.018 0.001 0.001 0.001 0.001
0.001 0.001 0.029 0.001 0.001 0.001 0.008 0.001 0.001 0.001 0.045 0.023 0.001 0.001 0.012
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Table 2 Comparisons of static peak pressures and mean/maximum dynamic peak pressures under lateral longitudinal arches of normal feet and feet after different arthrodesis procedures (mean values and standard deviations). Grouping
Normal feet (KPa) Subtalar (KPa) Talonavicular (KPa) Calcaneocuboid (KPa) Double arthrodesis (KPa) Triple arthrodesis (KPa) F value P value Pairwise comparison (P value) Normal feet: subtalar Normal feet: talonavicular Normal feet: calcaneocuboid Normal feet: double arthrodesis Normal feet: triple arthrodesis Subtalar: talonavicular Subtalar: calcaneocuboid Subtalar: double arthrodesis Subtalar: triple arthrodesis Talonavicular: calcaneocuboid Talonavicular: double arthrodesis Talonavicular: triple arthrodesis Calcaneocuboid: triple arthrodesis Calcaneocuboid: triple arthrodesis Double arthrodesis: triple arthrodesis
Static peak pressure (600 N)
Dynamic (1800 N) Mean pressure
Maximum peak pressure
36.3 (6.4) 3.6 (1.2) 12.5 (3.1) 0 0 0 12.53 0.001
231.4 (25.2) 125.3 (16.8) 197.8 (22.3) 68.2 (8.5) 56.6 (6.1) 21.4 (3.5) 19.95 0.001
570.0 (32.5) 404.3 (26.4) 505.6 (28.9) 240.7 (21.6) 213.7 (16.5) 126.8 (11.6) 156.43 0.001
0.001 0.001 0.001 0.001 0.001 0.001 0.001 0.001 0.001 0.001 0.001 0.001 0 0 0
0.001 0.001 0.001 0.001 0.001 0.001 0.001 0.001 0.001 0.001 0.001 0.001 0.035 0.001 0.001
0.001 0.001 0.001 0.001 0.001 0.001 0.001 0.001 0.001 0.001 0.001 0.001 0.024 0.001 0.001
maximum load (1800 N) were input into the Timing Analysis Module (TAM) of the F-Scan system to simulate the dynamic peak pressures under the corresponding arches. (See Tables 1and 2) (See Figs. 6 and 7) All data and results of statistical analyses are shown in Tables 1, 2 and Figs. 6, 7. 4. Discussion Flatfoot can result in misalignment of foot joints, which may appear as forefoot abduction, hindfoot eversion, and arch collapse (Brodsky et al., 2004). It can also lead to subluxation of the subtalar and talonavicular joints, reduction in contact area between the talus and the anterior/middle/posterior calcaneal articular surfaces, navicular eversion/extorsion/plantar flexion relative to the talus, and separation or plantar flexion of the medial cuneiform relative to the navicular (Ellis et al., 2010). The various conditions may combine and cause arch instability and abnormal plantar pressure distribution. Selective arthrodesis reconstructs connection between bones in a flatfoot to fix the lax joints, restore the normal interaction between the midfoot and hindfoot during locomotion, and maintain the arch stability. Therefore, it can correct subtalar/talonavicular subluxation and foot extorsion/eversion, and eliminate the associated symptoms such as pain caused by mid- or hindfoot osteoarthritis (O'Malley et al., 1995; Zaret and Myerson, 2003). In this study, we compared the arch support of five popular arthrodesis procedures under identical loading/unloading conditions using a modern 3D plantar pressure measurement system (Mueller and Strube, 1996; Sumiya et al., 1998; Chau, 2001; Wearing et al., 2000;
Fig. 6. Comparisons of different pressures in medial arches. We compared static pressures and mean/maximum dynamic peak pressures under medial longitudinal arches of normal feet and feet after different procedures.
Fig. 7. Comparisons of different pressures in lateral arches. We compared static pressures and mean/maximum dynamic peak pressures under lateral longitudinal arches of normal feet and feet after different procedures.
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Woodburn and Helliwell, 1997; Young, 1993). Loading of fresh cadaveric feet with dynamic stresses simulating physiological weight bearing is an important method in studying the dynamic mechanic properties of joints and tendons. In physiological conditions, the body weight is transferred via the tibial diaphyses, the ankle joints, to the tali, and then further conducted along three stress lines (posterior, anterolateral, and anteromedial). Accordingly, perpendicular loading along the tibial diaphysis has been extensively used in simulating dynamic loading of the human body. In this study, we adopted this loading mode and carefully monitored (visually and with the computer control system equipped with the mechanical testing machine) the loading/unloading processes and the resulting tibial diaphyseal displacement to ensure the absence of foot slipping or destruction. During all experiments, the loading/unloading cycles were confirmed to be linear and the displacements b2 mm. However, in this loading mode, the position of the tibial diaphysis and the direction of the load were fixed regardless of the position of the foot. Comparatively, in physiological conditions (e.g. plantar flexion movement of the ankle), the upper tibial diaphysis moves along the sagittal axis together with the knee joint. Thus, it remains difficult to simulate the load applied on the ankle and foot during real physiological movement (Martinelli et al., 2012). It was reported that the maximum pressure on an ankle can reach five times that of the body weight. In this study, we aimed to investigate the plantar pressure distribution and arch stability after different arthrodesis procedures, therefore it is important to keep the loading conditions unchanged before and after arthrodesis as well as close to the physiological conditions. Based on repeated pre-tests, a maximum load of 1800 N chosen to ensure the applied load was constantly below the destructive threshold of the cadaveric specimens. The result indicated that these arthrodesis procedures all provided stable support to the medial and lateral arch under physiological condition. Specifically, original reaction pressure, measurement of mean and maximum dynamic peak pressure all revealed that the triple arthrodesis provided the highest support, followed by double arthrodesis. However, the talonavicular and calcaneocuboid arthrodesis presented a different order in the support of medial and lateral arches. The talonavicular arthrodesis provided better support to the medial arch and appeared to be similar to double arthrodesis. According to previous studies, motion of the talonavicular joint is the key to motion of the triple joint complex, and talonavicular arthrodesis limits motion of calcaneocuboid and subtalar joint as well as double arthrodesis does, so isolated talonavicular arthrodesis is an effective alternative to double arthrodesis (Astion et al., 1997; Thelen et al., 2010) while double arthrodesis is suitable for obese patients and patients with talonavicular and calcaneocuboid osteoarthritis (Mann et al., 1998). The arthrodesis of calcaneocuboid joint had the least effect on the motion of the other joints (Astion et al., 1997). Nevertheless, arthrodesis of calcaneocuboid joint offers the least support on the maintenance of medial arch. The subtalar arthrodesis also provided enough support to both arches. Meanwhile, about 25 to 56% of the motion of the talonavicular joint and more than 50% of the motion of the calcaneocuboid joint remained after subtalar arthrodesis (Astion et al., 1997; Mann et al., 1998). So it was also a choice to treat medium to severe adult flatfoot (Cohen and Johnson, 2001; Johnson et al., 2000; Kitaoka and Patzer, 1997; Stephens et al., 1999). Triple arthrodesis is suitable for the most severe cases (Graves et al., 1993; Jarde et al., 2002; Sullivan and Aronow, 2002). Taken together, our results show that the five arthrodesis procedures were all able to provide some degree of support to both lateral and medial arches. The triple arthrodesis was found to provide the highest support to both arches; the double arthrodesis appeared to be similar to talonavicular arthrodesis in supporting the medial arch and similar to calcaneocuboid arthrodesis in supporting the lateral arch; subtalar arthrodesis was less effective in supporting both arches compared with both talonavicular and calcaneocuboid arthrodesis. The method that consecutive procedures applied on the same cadaver may influence the accuracy in assessing the result of single
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arthrodesis. However, the method was used widely (Astion et al., 1997; Jung et al., 2005). In this research, tendon injury was prevented and soft tissue damage was minimized. The procedures were standardized and the data are consistent within the study. Therefore, the feet could have stable properties throughout the procedures. It remains difficult in podiatry to develop a biomechanical model maximally close to the normal physiological conditions based on fresh cadaveric lower limb specimens. Despite this difficulty, our results allowed reliable comparison among the effects of different arthrodesis procedures and thus provide valuable information for a rational selection of procedures in clinics. Although the plantar pressures were not measured in truly physiological conditions, the measurement conditions were kept consistent in this study, which ensured a comparability of results. 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