Midtarsal Joint Research Articles

Subtalar and Naviculocuneiform Arthrodesis for the Treatment of Hindfoot Valgus With Collapse of the Medial Arch

In many cases of acquired flatfoot deformity, the sagging of the joint line originates in the naviculocuneiform joint with collapse of the medial arch. Posterior tibial tendon function may or may not be preserved. The commonly held treatment option with triple or double arthrodesis fails to address the instability of the naviculocuneiform joint. To achieve a stable correction of the deformity, the authors, therefore, started to combine an arthrodesis of the subtalar joint with a fusion of the naviculocuneiform joint. In case of residual valgus malalignment after preliminary correction, a medial sliding osteotomy of the calcaneus is necessary to achieve full correction of the hindfoot. Sparing the Chopart joint may enable the foot to accommodate better to the ground while walking, particularly on uneven ground. Despite excellent short-term results, longer term outcome studies are necessary to validate the benefit of this technique.

Midtarsal joint locking: New perspectives on an old paradigm

We investigated the existence of a midtarsal joint locking mechanism using cadaveric simulations of normal gait. Previous descriptions of this phenomenon led us to hypothesize that non-coupled rotations of the calcaneocuboid and talonavicular (i.e., midtarsal) joints and cubonavicular and talocalcaneal joints occur at heel strike and during weight acceptance, after which joint rotations cease with all bone-to-bone orientations remaining constant during the latter portions of stance phase. Three-dimensional kinematics of the talus, calcaneus, cuboid, and navicular were recorded along with muscle and ground reaction forces. Finite helical axis parameters and joint angles of directly articulating bones were subsequently derived and examined. During weight acceptance, the midtarsal joints everted with obvious changes in the relative orientation of their helical axes. The relative non-parallel orientation of these axes then remained constant until late in stance when these joints inverted and dorsiflexed toward their original pre-stance orientation. The cubonavicular and talocalcaneal joints demonstrated complimentary behavior. Contrary to our hypothesis, the midtarsal joints remained compliant during foot flat and even more so during push-off, despite divergent joint axes. Joint rotations were present after weight acceptance, thereby challenging the concept that midtarsal joint locking produces a rigid lever during push-off. © 2013 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 32:110-115, 2014.

Fracture of the talar neck associated with a compression fracture of the calcaneocuboid joint in a 5-year-old child: a case report

The objectives of this present case study are to report a rare combination of a displaced talar neck fracture with a compression fracture of the calcaneocuboid joint in a 5-year-old child and to describe its radiological features, surgical treatment and clinical outcome. A 5-year-old male boy was injured in a car accident in which his left foot underwent one of the tires. On arrival at the hospital, a displaced talar neck fracture associated both with a cuboid fracture and compression of the articular surface of the cuboid at the calcaneocuboid join was identified. Fractures were fixed surgically. Leg was protected with a below-knee plaster split immobilization and non-weight-bearing for 5weeks. After that period, the patient initiated a rehabilitation protocol with active and passive motion exercises. Fractures and fracture dislocations at the mid-tarsal joint have an important impact on the global foot function because malunion can result in post-traumatic arthritis and three-dimensional deformities of the foot. If a cuboid compression fracture is not reduced properly, it can result in the shortening of the lateral column with the development of an abduction, pronation and flat foot deformity. A talar neck fracture, if unreduced, can result in medial column displacement and rotational dislocation of the talar head, leading to a subluxation in the talonavicular joint with severe restriction of foot function. With early surgical treatment and open reduction and internal fixation, our patient recovered from the accident without having symptoms of pain, avascular necrosis, postoperative foot deformities or neurovascular deficits. The combination of a displaced talar neck fracture with a compression fracture of the calcaneocuboid joint in children usually requires correct diagnoses and early treatment with anatomic reduction and internal fixation to prevent severe post-traumatic deformities. V.

Brief communication: A midtarsal (midfoot) break in the human foot

The absence of a midtarsal break has long been regarded as a derived feature of the human foot. Humans possess a rigid midfoot that acts as an efficient lever during the propulsive phase of bipedal gait. Non-human primates, in contrast, have a more mobile midfoot that is adaptive for tree climbing. Here, we report plantar pressure and video evidence that a small percentage of modern humans (n = 32/398) possess both elevated lateral midfoot pressures and even exhibit midfoot dorsiflexion characteristic of a midtarsal break. Those humans with a midtarsal break had on average a significantly flatter foot than those without. Midtarsal breakers also had significantly more medial weight transfer (pronation) during the stance phase of gait than those without this midfoot mobility. These data are in accordance with Elftman (Clin Orthop 16 (1960) 41-45) who suggested that pronation aligns the axes of the transverse tarsal joint, permitting elevated midfoot mobility.

Kinetics and kinematics after the Bridle procedure for treatment of traumatic foot drop

BackgroundThe Bridle procedure restores active ankle dorsiflexion through a tri-tendon anastomosis of the tibialis posterior, transferred to the dorsum of the foot, with the peroneus longus and tibialis anterior tendon. Inter-segmental foot motion after the Bridle procedure has not been measured. The purpose of this study is to report kinetic and kinematic variables during walking and heel rise in patients after the Bridle procedure. Methods18 Bridle and 10 control participants were studied. Walking and heel rise kinetic and kinematic variables were collected and compared using an ANOVA. FindingsDuring walking the Bridle group, compared with controls, had reduced ankle power at push-off [2.3 (SD 0.7) W/kg, 3.4 (SD 0.6) W/kg, respectively, P<.01], less hallux extension during swing [−13 (SD 7)°, 15 (SD 6)°, respectively, P<.01] and slightly less ankle dorsiflexion during swing [6 (SD 4)°, 9 (SD 2)°, respectively, P=.03]. During heel rise the Bridle group had 4 (SD 6)° of forefoot on hindfoot dorsiflexion compared to 8 (SD 3)° of plantarflexion in the controls (P<.01). InterpretationThis study provides evidence that the Bridle procedure restores the majority of dorsiflexion motion during swing. However, plantarflexor function during push-off and hallux extension during swing were reduced during walking in the Bridle group. Abnormal mid-tarsal joint motion, forefoot on hindfoot dorsiflexion instead of plantarflexion, was identified in the Bridle group during the more challenging heel rise task. Intervention after the Bridle procedure must maximize ankle plantarflexor function and midfoot motion should be examined during challenging tasks.

Charcot neuroarthropathy triggered and complicated by osteomyelitis. How limb salvage can be achieved

Charcot neuroarthropathy is a severe complication in the feet of patients with diabetes, which can lead to a major amputation. Osteomyelitis and surgery for osteomyelitis have been reported as trigger mechanisms of developing Charcot neuroarthropathy. However, the development of acute Charcot neuroarthropathy triggered by osteomyelitis during conservative antibiotic treatment is not well outlined in the medical literature. Two patients apparently developed mid and rear foot Charcot neuroarthropathy, which was clinically suspected while being treated with antibiotics for osteomyelitis. One of them presented osteomyelitis of the navicular bone and subsequently developed acute Charcot neuroarthropathy of the tarsometatarsal joints. The other presented calcaneal osteomyelitis with pathological fracture and developed Charcot neuroarthropathy of the transverse tarsal joint. No offloading had been implemented in either case. A major amputation had been indicated in both cases in their teaching hospitals. Limb salvage was achieved in both cases by means of surgery, culture-guided post-operative antibiotics, intraosseus instillation of super-oxidized solution, bed rest before placing a total contact cast and stabilization of the unstable foot with a total contact cast with an opening for checking the healing course and to detect any complications. The mechanisms of the development of acute Charcot neuroarthropathy in a patient with osteomyelitis are discussed. Osteomyelitis in the feet of patients with diabetes and neuropathy may trigger the development of acute Charcot neuroarthropathy. Fractures and dislocated joints may subsequently become infected from the index focus, producing a severe infected and unstable foot that may require a major amputation. Limb salvage can be achieved in specialized departments.

Die Arthrodese des oberen Sprunggelenks – klinische, radiologische und biomechanische Aspekte unter besonderer Berücksichtigung des unteren Sprunggelenkkomplexes

Arthrodesis as well as total arthroplasty are well established but controversially discussed treatment options for end-stage osteoarthritis of the ankle joint. For guidance concerning the significance of both surgical procedures we have correlated our clinical, radiological and biomechanical data with an up-to-date literature review. 15 patients after arthrodesis because of an isolated end-stage osteoarthritis of the ankle joint were followed clinically and radiologically 4 (1.9-8.8) years after surgery. To evaluate the outcome, different scores (AOFAS, Kellgren and Lawrence) were used. In the second part of the study a dynamic foot model was implemented to simulate a foot strike in vitro utilising a cadaver foot. By controlling 6 extrinsic tendons via steel cables, a hydraulic force application and a moving ground plate, a foot strike was simulated. Intraarticular compression load was measured in the talonavicular and calcaneocuboid joints with pressure-sensitive foils. The mean AOFAS score for the subcategory pain was 28 ± 12 points. In the subcategory function the patients had a mean score of 38 ± 9 points summing up to a mean total AOFAS score of 66 ± 18 points. Six patients showed radiological evidence of degeneration of the talonavicular joint. For these patients the Kellgren and Lawrence score was 2.3 (1-4) points higher than for the opposite side. Concerning the subtalar joint in 6 patients the Kellgren and Lawrence score was 1.6 (1-3) points higher compared to the non-surgery side. In contrast we noted only one case with degeneration of the calcaneocuboid joint. The native trial utilising the foot model revealed a continuous rise of load transmission in both parts of the Chopart joint. After performing an arthrodesis, load transmission rose significantly in the second half of the foot strike concerning the talonavicular joint whereas the calcaneocuboid joint showed a decreased transmission of load. Referring to published data complication rates after ankle arthrodesis are lower compared to total ankle arthroplasty whilst adjacent joint degeneration of the subtalar and talonavicular joints is more common.

Biometry of the calcaneocuboid joint: Biomechanical implications

Precise biometric data of calcaneus, cuboid bones and calcaneocuboid joint are not alluded to in textbooks of anatomy. This study focussed on the biometry of 50 calcanei, 30 cuboid dry bones, and anatomical specimens of 21 transverse tarsal joints. Measurement of the length, width, angular orientation, contact surface and radius of curvature, rolling band of the joints surfaces according to the main axes were performed. The results focussed on biometric variations with several morphological types never identified previously. Measurements obtained on dry bones and anatomical specimens with the functions of ligaments were distinguished. The morphology of the calcaneus could explain the results of osteotomy procedures for the treatment of adult flatfoot. A better knowledge of the joint surfaces and biometric data would generate a modeling of the calcaneocuboid joint and function in locking the transverse tarsal joint.

Flatfoot in Müller-Weiss syndrome: a case series

IntroductionSpontaneous osteonecrosis of the navicular bone in adults is a rare entity, known as Müller-Weiss syndrome. We report here on our experience with six patients with Müller-Weiss syndrome accompanied by flatfoot deformity, but on a literature search found no reports on this phenomenon. Because the natural history and treatment are controversial, an understanding of how to manage this deformity may be helpful for surgeons when choosing the most appropriate operative procedure.Case presentationSix patients (five women, one man; average age, 54 years) with flatfoot caused by osteonecrosis of the navicular bone were followed up between January 2005 and December 2008 (mean follow-up period, 23.2 months). Conservative treatment, such as physical therapy, and non-steroidal anti-inflammatory drugs were used, but failed. Physical examinations revealed flattening of the medial arch of the involved foot and mild tenderness at the mid-tarsal joint. Weight-bearing X-rays (anterior-posterior and lateral views), computed tomography, and MRI scans were performed for each case. Talonavicular joint arthrodesis was performed in cases of single talonavicular joint arthritis. Triple arthrodesis was performed in cases of triple joint arthritis to reconstruct the medial arch. Clinical outcomes were assessed using the American Orthopaedic Foot and Ankle Society ankle-hindfoot scale; the scores were 63.0 pre-operatively and 89.8 post-operatively. All patients developed bony fusion.ConclusionsThe reason for the development of flatfoot in patients with Müller-Weiss syndrome is unknown. Surgical treatment may achieve favorable outcomes in terms of deformity correction, pain relief, and functional restoration. The choice of operative procedure may differ in patients with both flatfoot and posterior tibial tendon dysfunction.

Intramedullary Foot Fixation for Midfoot Charcot Neuroarthropathy

Midfoot Charcot collapse commonly occurs through the tarsometatarsal and/or midtarsal joints, which creates the characteristic “rocker bottom” deformity. Intramedullary metatarsal fixation spanning the tarsus into the talus and/or calcaneus is a recently developed method for addressing unstable midfoot Charcot deformity. The intramedullary foot fixation technique has various advantages when addressing midfoot Charcot deformity in the neuropathic patient. These advantages include anatomical realignment, minimally invasive fixation technique, formal multiple joint fusion, adjacent joint fixation beyond the level of Charcot collapse, rigid interosseus fixation, and preservation of foot length. The goals of the intramedullary foot fixation procedure are to create a stable, plantigrade, and ulcer-free foot, which allows the patient to ambulate with custom-molded orthotics and shoes.

The Effect of Goniometric Alignment on Passive Ankle Dorsiflexion Range of Motion among Patients Following Ankle Arthrodesis or Arthroplasty

Goniometric measurement is a standard method used to quantify limited ankle dorsiflexion (DF). However, compensatory motion at the subtalar and midtarsal joints might also contribute to the amount of ankle DF obtained by goniometric measurements. The purpose of this study was to examine the effect of goniometric alignment on DF range of motion measurement among patients following ankle arthrodesis or arthroplasty and age- and gender-matched controls. A total of 22 participants were recruited to participate in this observational cohort study, including 7 patients following total ankle arthroplasty (2 male, 5 female; mean age = 67.5 years, standard deviation [SD] = 9.6 years), 4 patients following ankle arthrodesis (2 male, 2 female; mean age = 70.5 years, SD = 5.2 years), and 11 age- and gender-matched controls (4 male, 7 female; mean age 67.5 years, SD = 9.0 years). Two investigators measured and recorded ankle DF passive range of motion (PROM) using a randomly determined sequence of 2 alignment methods: (1) the distal aspect of the lateral calcaneus, and (2) the fifth metatarsal. One-sample t tests were performed to assess differences in ankle DF between the 2 different alignment methods. Significantly greater degrees of DF were obtained when aligning with the fifth metatarsal versus the lateral calcaneus on the patients' uninvolved sides and the randomly selected side of matched controls (P < .05) but not on the patients' operative side (P > .05). This study found that more degrees of DF PROM are measured when aligning a goniometer with the fifth metatarsal versus the calcaneus on the uninvolved side of patients and matched controls. Diagnostic, Level IV.

Rotational Stiffness of Football Shoes Influences Talus Motion during External Rotation of the Foot

Shoe-surface interface characteristics have been implicated in the high incidence of ankle injuries suffered by athletes. Yet, the differences in rotational stiffness among shoes may also influence injury risk. It was hypothesized that shoes with different rotational stiffness will generate different patterns of ankle ligament strain. Four football shoe designs were tested and compared in terms of rotational stiffness. Twelve (six pairs) male cadaveric lower extremity limbs were externally rotated 30 deg using two selected football shoe designs, i.e., a flexible shoe and a rigid shoe. Motion capture was performed to track the movement of the talus with a reflective marker array screwed into the bone. A computational ankle model was utilized to input talus motions for the estimation of ankle ligament strains. At 30 deg of rotation, the rigid shoe generated higher ankle joint torque at 46.2 ± 9.3 Nm than the flexible shoe at 35.4 ± 5.7 Nm. While talus rotation was greater in the rigid shoe (15.9 ± 1.6 deg versus 12.1 ± 1.0 deg), the flexible shoe generated more talus eversion (5.6 ± 1.5 deg versus 1.2± 0.8 deg). While these talus motions resulted in the same level of anterior deltoid ligament strain (approxiamtely 5%) between shoes, there was a significant increase of anterior tibiofibular ligament strain (4.5± 0.4% versus 2.3 ± 0.3%) for the flexible versus more rigid shoe design. The flexible shoe may provide less restraint to the subtalar and transverse tarsal joints, resulting in more eversion but less axial rotation of the talus during foot∕shoe rotation. The increase of strain in the anterior tibiofibular ligament may have been largely due to the increased level of talus eversion documented for the flexible shoe. There may be a direct correlation of ankle joint torque with axial talus rotation, and an inverse relationship between torque and talus eversion. The study may provide some insight into relationships between shoe design and ankle ligament strain patterns. In future studies, these data may be useful in characterizing shoe design parameters and balancing potential ankle injury risks with player performance.

Isolated Tarsal Navicular Fracture Dislocation

Injuries to the midtarsal joints are rare. They occur in the form of various combinations such as fracture, fracture subluxation, and fracture dislocation. The largest series of 71 cases has been reported by Main and Jowett in 1975. Isolated tarsal navicular dislocations are rare injuries. Being rare, these injuries remain poorly understood. Only few case reports exist, which describe the probable mechanism of injury and optimal treatment. Of the few case reports, only one describes closed reduction with external fixator and percutaneous fixation as the treatment modality. This case report emphasizes the use of external fixation with pins in the calcaneum and not in talus as described by the earlier report. Therapeutic, Level IV.

Deformity of talus and calcaneous in congenital clubfoot

Clubfoot is a complex congenital deformity. Midtarsal joint is a key point to understand the deformity in clubfoot as a consequence of the malalignment of the osseous columns. Talar and calcaneal deformities affecting the normal alignment of the medial and lateral osseous columns in the foot can be the factors that determine the difficulty in the management of clubfoot. We report observations of two clubfeet of one stillborn. Our observations in the head of the talus report two different articular areas: the histological section of medial area facing the navicular shows active articular cartilage and the lateral area shows an atrophic articular cartilage suggesting a difference between the anatomical declination angles of the talus from a functional declination angle. Observing the calcaneous, we report a twisting rotational deformity along the longitudinal axis of the calcaneous. These observations may contribute to a better understanding of the clubfoot relapse, and also the treatment of complicated cases of clubfeet.

Analysis of a kinetic multi-segment foot model part II: Kinetics and clinical implications

Kinematic multi-segment foot models have seen increased use in clinical and research settings, but the addition of kinetics has been limited and hampered by measurement limitations and modeling assumptions. In this second of two companion papers, we complete the presentation and analysis of a three segment kinetic foot model by incorporating kinetic parameters and calculating joint moments and powers. The model was tested on 17 pediatric subjects (ages 7–18years) during normal gait. Ground reaction forces were measured using two adjacent force platforms, requiring targeted walking and the creation of two sub-models to analyze ankle, midtarsal, and 1st metatarsophalangeal joints. Targeted walking resulted in only minimal kinematic and kinetic differences compared with walking at self selected speeds. Joint moments and powers were calculated and ensemble averages are presented as a normative database for comparison purposes. Ankle joint powers are shown to be overestimated when using a traditional single-segment foot model, as substantial angular velocities are attributed to the mid-tarsal joint. Power transfer is apparent between the 1st metatarsophalangeal and mid-tarsal joints in terminal stance/pre-swing. While the measurement approach presented here is limited to clinical populations with only minimal impairments, some elements of the model can also be incorporated into routine clinical gait analysis.

Pigmented Villonodular Synovitis of the Ankle

Because of its high recurrence rate, complete excision with total synovectomy is crucial for diffuse pigmented villonodular synovitis (DPVNS). Regardless of location, surgical approach requires meticulous soft tissue management and full joint exposure to assure complete tumor excision. In the ankle, PVNS can be present in the medial and lateral gutters, as well as extend along the syndesmotic ligament, flexor and peroneal tendon sheaths, and adjacent joints (ie, subtalar and midtarsal joints). The authors describe an open, anterior-posterior technique for excision of DPVNS lesions from the ankle joint with erosive lesions of the tibia and talus, as well as from the flexor hallucis longus and peroneal tendon sheaths. Whereas previously described dual-incision techniques have focused on posteromedial and posterolateral approaches to the ankle, the authors' posterior exposure, in particular, uses a midline skin incision and a longitudinal split of the Achilles tendon. This provides an excellent exposure and minimizes potential wound healing complications.

The Convergent Evolution of Suspensory Posture and Locomotion in Tree Sloths

Recent phylogenetic analyses imply a distant relationship and long separated evolution of two-toed sloths (Choloepus) and three-toed sloths (Bradypus). No known fossil sloth is interpreted to have been suspensory. As a consequence, the suspensory posture and locomotion of the extant genera likely evolved convergently in both lineages, forming a new framework for the analysis of functional aspects of the locomotor apparatus of extant tree sloths. The suspensory posture and locomotion has altered functional demands from the phylogenetically plesiomorphic non-suspensory pronograde situation. Here, anatomical traits that have been argued to be of adaptive significance for quadrupedal suspensory locomotion are reviewed and the evolution of these traits is discussed in light of the new framework. Experimental data are largely limited to Choloepus, but help to deduce functional aspects of the anatomy in Bradypus as well. The most important adaptive traits are hands and feet modified into relatively rigid hook-like appendages, great mobility of all joints proximal to the midcarpal and transverse tarsal joints, relatively long arms with a relatively short scapula, a rounded thorax with a small diameter, a highly mobile sterno-clavicular articulation, and emphasis on powerful flexion in the proximal limb joints via advantageous lever arms. Despite these changes, patterns of limb kinematics remained conservative during the course of evolution in the lineages leading to extant tree sloths, and it is suggested here that this also applies to the pattern of neuromuscular control of limb movements during locomotion. Morphological ‘solutions’ to altered functional demands posed by inversed orientation of the body differ in the two genera of extant tree sloths, thereby corroborating the proposed diphyly. Convergent evolution in tree sloths may be attributed to functional constraints posed by fossorial adaptations in early Xenarthra that canalized sloths to adopt a suspensory posture and locomotion in the arboreal habitat.

Excision of Extensive Midfoot Pigmented Villonodular Synovitis With Microvascular Anastamosis of Iliac Crest Bone Graft Using External Fixation

Pigmented villonodular synovitis (PVNS) is a relatively rare lesion in the foot and ankle, most commonly involving the ankle joint and atypically, the subtalar and midtarsal joints. It is a benign proliferative disease characterized by an increase in villous or nodular synovium in joints. Resection of the tumor is often indicated in most cases because of the potentially aggressive joint destructive nature of this lesion. This report presents a case of chronic enlarging pervasive midtarsal and metatarsal-cuneiform joint PVNS in a 28-year-old male. This patient had a midtarsal mass that enlarged over a period of 2 years, causing increased pain, deformity, and difficulty with ambulation. Cross-sectional imaging studies identified evidence of erosive disease through much of the midfoot articulations, with biopsy confirming the mass as PVNS. The dimensions of the mass approximated 5.5 cm × 4.1 cm × 2.8 cm. Simple resection was problematic because of the size and multiple joints involved. Amputation was most commonly advised by multiple consultants. The patient preferred attempt at limb salvage. En bloc resection and placement of a revascularized iliac crest bone graft was used to fill the defect. The graft was microvascularly anastamosed and fixated with standard external fixation. Pathologic and histologic specimens from surgical biopsy reconfirmed the diagnosis of PVNS postoperatively. Second-stage arthrodesis was performed when the patient was stable and disease free. The patient was followed postoperatively for 10 years without recurrence and was able to return to full function and partake in moderate athletic activity at last visit. This case describes a retrospective review of the procedure and reconstruction, as well as an overview of current surgical management of PVNS.

Stabilization of Joint Forces of the Subtalar Complex via HyProCure Sinus Tarsi Stent

The foot is the foundation of the body. The stability of the osseous hindfoot structure is crucial in bipedal locomotion. The subtalar joint is responsible for conversion of the rotatory forces of the lower extremities and dictates the movements of the midtarsal joints and the forefoot. In a hyperpronated foot, excessive abnormal pronation results in partial to full obliteration of the sinus tarsi. The hypothesis is that the HyProCure device will prevent obliteration of the sinus tarsi, thereby stabilizing the subtalar joint complex and eliminating the excessive forces to the proximal and distal musculoskeletal system that occur with every step. Five fresh-frozen human foot cadaver specimens that represented pathologic hindfoot and midfoot instability and partial to full obliteration of the sinus tarsi were axially compressed to 2,000 N and internally rotated by 15° to produce maximum pronation of the subtalar joint using a biaxial materials testing machine. The forces were measured across the posterior and anterior talocalcaneal joint facets before and after placement of the HyProCure stent. The subtalar joint stabilized after placement of the HyProCure sinus tarsi stent. The mean ± 1 SD forces in the posterior talocalcaneal joint increased from 795.88 ± 106 N to 1,004.86 ± 72.41 N (P < 0.05, two-tailed paired t test). The mean ± SD forces at the anterior talocalcaneal joint decreased from 520.15 ± 127.18 N to 394.56 ± 73.83 N (P < 0.05), shifting the contact area posteriorly. Placement of the HyProCure subtalar stabilization stent in a hyperpronated foot prevents excessive talar subluxation and assists in proper distribution of the axial loads on the subtalar facet joints.

(i) Understanding the gait cycle, as it relates to the foot

Abstract The gait cycle is outwardly something complex, which seems difficult to grasp. This really isn't the case and with a few relatively simple facts to understand it can be easily understood. The purpose of this article is to try and break this complex process into a series of comprehensible steps. The gait cycle is defined and its major components are then described. The key is understanding how the foot can be both a flexible and then a rigid structure in different parts of the gait cycle. This is a function of the subtalar and especially the midtarsal joints. We also look at how the plantar fascia plays a part too. Finally we look at how the cycle may be altered in various clinical scenarios. Which we hope will be of general use but especially to trainees taking final professional examinations.