Biomechanical effects of an articulating prosthetic toe joint during stair navigation for individuals with unilateral, below-knee limb loss.

Stair navigation is an essential and demanding form of locomotion. During stair ascent and descent, persons with lower limb loss exhibit gait characteristics which may increase their risk of falls and joint degeneration of the intact limb. To reduce deviations from typically-able-bodied gait and overloading of the intact limb for this population, one potential intervention involves modifying passive prosthetic feet by incorporating a flexible toe joint that simulates the biological metatarsophalangeal joint. In this study, we aimed to assess the user preferences and biomechanical effects of a flexible prosthetic toe joint during stair ascent and descent for persons with unilateral lower-limb loss. Nine participants with unilateral lower-limb loss were recruited (Male; Medicare Functional Classification Level: eight K4, one K3; age: 41 ± 11 years; mass: 95 ± 13 kg; height: 1.84 ± 0.05 m; mean ± SD). No significant changes in lower-limb joint mechanics were identified. Five of nine participants preferred the unmodified prosthesis with a standard carbon fiber keel for both stair ascent and descent. Varied user preferences and inconsistent changes in lower-limb joint parameters between participants highlight the importance of subject-specific analyses and individualized device prescription.

Vascularized Origami Medial Femoral Condyle Flap for Finger Joint Reconstruction.

SUMMARY: Total finger joint reconstruction is challenging. Vascularized toe joint transfer is currently used for reconstruction, but it is difficult to perform, fails to achieve maximal joint flexibility, and is associated with donor-site complications. As an alternative, the authors developed a vascularized medial femoral condyle flap technique, wherein the vascularized corticoperiosteum is shaped via origami, with the donor tissue folded to fit the recipient site. In this article, the authors describe the use of this method for reconstruction of interphalangeal and metacarpophalangeal joints with a reduced range of motion. The mean age of the patients (three men and four women) was 51 years (range, 36 to 68 years), and the mean follow-up period was 3 years 1 month (range, 4 months to 5 years). In the reconstructed joints, the mean range of motion; Disabilities of the Arm, Shoulder, and Hand score; and pinch strength of the unaffected side were 55 degrees (range, 24 to 90 degrees), 2.3 (range, 0 to 6), and 98% (range, 70% to 38%), respectively. No donor-site morbidities were observed. Radiography and computed tomography scans revealed joint-like grafted tissue remodeling. The study findings suggest that the origami medial femoral condyle flap is useful for functional finger joint reconstruction. The procedure requires fabrication before grafting, but tissue harvest is relatively easy.

Late-Diagnosed Dislocation of the Proximal Interphalangeal Joint of the Fifth Toe in a 7-Year-Old Boy: A Case Report.

Dislocation of the proximal interphalangeal joint of the fifth toe is an uncommon injury. When it is diagnosed in the acute phase, closed reduction is commonly an adequate treatment option. We describe a rare case of a 7-year-old patient who presented with late-diagnosed isolated dislocation of the proximal interphalangeal joint of the fifth toe. Although there are a few reported cases of late-diagnosis combined fracture-dislocation of the toes in both adult and pediatric age groups in the literature, belatedly diagnosed dislocation of the fifth toe without accompanying fracture in the pediatric population, to our knowledge, has not yet been reported. This patient achieved good clinical outcomes after treatment via open reduction and internal fixation.

Minimally Invasive Arthrodesis of the Equine Proximal Interphalangeal Joint: A Biomechanical Comparison of Three 5.5-mm Cortical Screws Inserted in Lag Fashion and Two 7.0-mm Headless Cannulated Dual-Pitch Compression Screws.

OBJECTIVE: The aim of this study was to compare the biomechanical properties of two minimally invasive arthrodesis techniques of the equine proximal interphalangeal (PIP) joint (three transarticular 5.5-mm cortical screws [AO-3TLS] vs. two transarticular 7.0-mm headless cannulated multi-use compression screws [MUC-2TS]) in dynamic non-destructive testing and compression testing to failure. STUDY DESIGN: The experimental study included six pairs of cadaveric adult equine forelimbs; one limb from each horse was randomly assigned to one of the treatments, and the contralateral limb was submitted to the remaining treatment. The dynamic test was performed alternating non-destructive compression tests at a displacement rate of 5 mm/min up to 5,000 N and sinusoidal compressive cyclic tests at 6 Hz, using a 3,600-N amplitude for 8,550 cycles. Construct stiffness and maximum sagittal plane rotation about the PIP joint markers were determined during the dynamic test. After the dynamic test reached 136,800 cycles, the monotonic compressive test until failure was performed on each construct: load, displacement and sagittal plane rotation about the PIP joint marker at failure were analysed. RESULTS: The evaluated biomechanical properties showed no statistical difference between the AO-3TLS and MUC-2TS treatment groups in any of the ramps of the dynamic non-destructive test and in the compression loading until failure test. CONCLUSION: The MUC-2TS treatment produced biomechanical properties equivalent to the AO-3TLS treatment for PIP joint arthrodesis.

Metacarpophalangeal Joint Reconstruction by Vascularized Partial Metatarsophalangeal Joint Transplantation: A Case Report.

CASE: A 27-year-old man underwent metacarpophalangeal joint reconstruction of his right middle finger using vascularized tissue from the distal component of the metatarsophalangeal joint of the right second toe. The donor site was reconstructed using a portion of the iliac bone and overlying tendinous fiber. The reconstructed metacarpophalangeal joint was stable 2 years postoperatively, and the arc of active motion was 80°. The reconstructed metatarsophalangeal joint did not interfere with walking. Radiography revealed the satisfactory condition of these joints. CONCLUSION: Depending on the type of defective joint and soft tissue injuries, vascularized partial joint transplantation could be considered for reconstruction.

Metatarsophalangeal and interphalangeal joint angle measurements on weight-bearing CT images.

BACKGROUND: The aim of this study was to present and evaluate methods of measuring toe joint angels using joint-surface based and inertial axes approaches. METHODS: Nine scans of one frozen human cadaveric foot were obtained using weight-bearing CT. Two observers independently segmented bones in the forefoot and measured metatarsalphalangeal joint (MTPJ) angles, proximal and distal interphalangeal joint (PIPJ and DIPJ) angles and interphalangeal angles of the hallux (IPJ) using 1) inertial axes, representing the long anatomical axes, of the bones and 2) axes determined using centroids of articular joint surfaces. RESULTS: The standard deviations (SD) of the IPJ/PIPJ and DIPJ angles were lower using joint-surface based axes (between 1.5˚ and 4.1˚) than when the inertial axes method was used (between 3.3˚ and 16.4˚), for MTPJ the SD's were similar for both methods (between 0.5˚ and 2.6˚). For the IPJ/PIPJ and DIPJ angles, the width of the 95% CI and the range were also lower using the joint-surface axes method (95% CI: 2.0˚-4.1˚ vs 3.2˚-16.3˚; range: 3.1˚-7.4˚ vs 3.8˚-35.8˚). Intra-class correlation coefficients (ICC) representing inter- and intra-rater reliability were good to excellent regarding the MTPJ and IPJ/PIPJ angles in both techniques (between 0.85 and 0.99). For DIPJ angles, ICC's were good for the inertial axes method (0.78 and 0.79) and moderate for the joint-surface axes method (0.60 and 0.70). CONCLUSION: The joint-surface axes method enables reliable and reproducible measurements of MTPJ, IPJ/PIPJ and DIPJ angles. For PIPJ and DIPJ angles this method is preferable over the use of inertial axes.

A lightweight robotic leg prosthesis replicating the biomechanics of the knee, ankle, and toe joint.

Robotic leg prostheses promise to improve the mobility and quality of life of millions of individuals with lower-limb amputations by imitating the biomechanics of the missing biological leg. Unfortunately, existing powered prostheses are much heavier and bigger and have shorter battery life than conventional passive prostheses, severely limiting their clinical viability and utility in the daily life of amputees. Here, we present a robotic leg prosthesis that replicates the key biomechanical functions of the biological knee, ankle, and toe in the sagittal plane while matching the weight, size, and battery life of conventional microprocessor-controlled prostheses. The powered knee joint uses a unique torque-sensitive mechanism combining the benefits of elastic actuators with that of variable transmissions. A single actuator powers the ankle and toe joints through a compliant, underactuated mechanism. Because the biological toe dissipates energy while the biological ankle injects energy into the gait cycle, this underactuated system regenerates substantial mechanical energy and replicates the key biomechanical functions of the ankle/foot complex during walking. A compact prosthesis frame encloses all mechanical and electrical components for increased robustness and efficiency. Preclinical tests with three individuals with above-knee amputation show that the proposed robotic leg prosthesis allows for common ambulation activities with close to normative kinematics and kinetics. Using an optional passive mode, users can walk on level ground indefinitely without charging the battery, which has not been shown with any other powered or microprocessor-controlled prostheses. A prosthesis with these characteristics has the potential to improve real-world mobility in individuals with above-knee amputation.

Selected hallmarks of hallux valgus in older women with symptomatic hallux valgus compared to middle-aged women with and without deformation of the forefoot.

The aim of the study was to compare the shape of the feet, the mobility of the metatarsophalangeal and interphalangeal joints and the flexibility of the calf muscles in older women with hallux valgus versus middle-aged women with and without this deformation to identify the presence of features which correlate particularly strongly with hallux valgus, and on which prophylaxis and conservative treatment should focus. The study involved 201 women: 92 aged 60-84 years with hallux valgus of both toes, 78 aged 38-59 with hallux valgus of both toes, and 31 aged 38-57 years with correctly shaped feet. The intensity of pain in the foot, the valgus angle of the big toe and fifth toe, the longitudinal and transverse arches of the foot, the symmetry of foot load with body weight, toe joint mobility and muscle flexibility were analysed. Both groups of women with hallux valgus differed from women with normal feet in the height of the transverse arch, the extent of dorsal extension in the first metatarsophalangeal joint and plantar flexion in the first interphalangeal joint. Older women were additionally characterised by reduced plantar flexion in the metatarsophalangeal joint of the big toe, limited flexibility of the soleus and gastrocnemius muscles as well as less pain in the toe area than in the foot itself. The most characteristic changes which were observed in older women with hallux valgus are a limited range of motion in the MTP and IP joints of the big toe, a reduced transverse arch and increased restriction of calf muscle flexibility.

A Passive Three Degree of Freedom Transtibial Prosthesis With Adjustable Coronal Compliance and Independent Toe Joint.

The effects of including lateral compliance or a toe joint in transtibial prostheses have been studied independently, showing the potential to improve the gait biomechanics in terms of stability, walking speed, and metabolic cost. However, both of these features are not commonly found in commercial prostheses despite their importance in human gait. In this work, we present a multi-axis passive transtibial prosthesis with three degrees of freedom (DOF). The prosthesis includes a compliant and adjustable coronal articulation using beam springs, an independent 3D-printed flexible forefoot as a toe joint, and sagittal dorsiflexion-plantarflexion stiffness using a helicoidal spring. We mechanically characterize each degree of freedom in terms of the provided stiffness. The measured stiffness values were 3.26Nm/deg, 4.94, or 5.63 Nm/deg in the sagittal plane (with different springs), and 2.54 Nm/deg, 2.79 Nm/deg, 2.94 Nm/deg, or 3.72 Nm/deg in the coronal plane (by adjusting the mechanism). Finally, the effect of different types of infill and infill levels for the 3D printed toes were explored, showing stiffness varying from 2.05 N/mm to 350 N/mm. The obtained sagittal stiffness is beneath the ones found in able-bodied persons; in contrast, the lateral stiffness values are comparatively higher than that of the able-bodied persons. However, the current design is simple to rearrange and modify the stiffness values. Lastly, the wide range of stiffness achievable in the 3D printed toes can be useful to achieve proper torque requirements in the forefoot for a broad range of users.

Does Inclination of the Toe Proximal Phalangeal Head Affect the Outcomes of Vascularized Joint Transfers? Retrospective Study of 22 Joint Transfers.

BACKGROUND: Different shapes of the proximal phalangeal head of toe proximal interphalangeal joints (e.g., oval and circular) are observed in vascularized joint transfers. The difference in shape implies the varying degrees of inclination of the articular surfaces between toes. This study investigated the impact of articular inclination on outcomes after toe joint transfers for finger proximal interphalangeal joint reconstruction. METHODS: Twenty-one patients who underwent vascularized joint transfer from May of 2009 to May of 2018 were included. Their mean age was 33.4 years and mean follow-up period was 28.9 months. All patients had a type I central slip according to the Te classification. Articular surface inclination was measured on lateral radiographic views. RESULTS: Passive range of motion of the toe proximal interphalangeal joint before vascularized joint transfer was 71.1 ± 9.6 degrees. The functional range of motion of the reconstructed proximal interphalangeal joint was 60.0 ± 17.0 degrees. The extensor lag after the joint transfer was 9.4 ± 19.6 degrees. The articular inclination of the toe joint was 71.9 ± 9.7 degrees. A Pearson correlation analysis of all variables, including age, preoperative range of motion of the toe joint, postoperative range of motion of the reconstructed joint, articular inclination of the toe joint, and extensor lag of the reconstructed joint with toe articular inclination, was performed. There was no significant correlation between articular inclination of the toe joint and extensor lag of the reconstructed joint ( p = 0.226). CONCLUSION: The articular surface inclination of the toe did not affect the functional range of motion after joint transfer. CLINICAL QUESTION/LEVEL OF EVIDENCE: Risk, III.

Fiber-reinforced fixation implant for proximal interphalangeal joint arthrodesis shows advanced implant bio-integration at 2-year follow-up.

BACKGROUND: A bio-integrative fiber-reinforced implant (OSSIOfiber® Hammertoe Fixation Implant, OSSIO Ltd., Caesarea, Israel) for proximal interphalangeal joint (PIPJ) correction-arthrodesis showed partial bio-integration at 1-year follow-up (1FU) in a previous study. The study was prolonged to assess the bio-integration at 2-year-follow-up (2FU). METHODS: Twenty-four patients with proximal interphalangeal joint (PIPJ) correction-arthrodesis using the fiber-reinforced implant and analysed at 1FU, completed 2FU. Follow-up included clinical examination, patient reported outcomes, radiographs, MRI and bio-integration scoring. Results were compared between the 1FU and 2FU (paired t-test). RESULTS: Radiographs confirmed fusion in 96 % (n = 23) at 2FU (1FU, 92 % (n = 22)). Implant was no longer visible in 21 % (n = 5), partially visible in 33 % (n = 8), and fully visible in 46 % (n = 11)(1FU, fully visible 100 % (n = 24)). The border between implant and surrounding bone was scored not visible in 88 % (n = 21) and partially visible in 12 % (n = 3) (1FU, border partially visible 100 % (n = 24)). There were no cyst formation or fluid accumulation findings 1FU/2FU. Mild bone edema was detected in 4 % (n = 1) (1FU, 29 % (n = 7)). None of the edema findings were considered as adverse implant related. The mean bio-integration score was 9.71 ± 0.69 at 2FU (1FU, 7.71 ± 0.46). The parameters of border between implant and bone and bone edema further improved at the 2FU compared to the 1FU, total bio-integration score was also higher at 2FU than 1FU (each p < 0.05). CONCLUSIONS: This study demonstrates 96 % PIPJ fusion rate and increased bio-integration from 1FU to 2FU, reaching advanced bio-integration of the fiber-reinforced implant at 2FU.

Unilateral below-knee prosthesis users walking on uneven terrain: The effect of adding a toe joint to a passive prosthesis.

Lower limb prosthesis users cite uneven terrain as a challenging surface to walk on. We sought to determine whether adding a Flexible toe joint to a prosthetic foot would be preferred by unilateral below-knee prosthesis users relative to a Locked (non-articulating) toe joint for walking on uneven terrain. We also quantified lower limb joint kinetics for the Locked and Flexible toe joint configurations. Five of our nine participants preferred the Flexible toe joint when walking on uneven terrain, yet from a biomechanical standpoint, the reason for this is unclear. All participants exhibited reductions in prosthetic limb net positive hip joint work when walking with a Flexible toe joint (11%; p < 0.05). For other parameters (e.g., prosthetic side knee joint moments) we observed high inter-subject variation, which adds to a growing body of literature highlighting the need for subject-specific data analyses in lower limb prosthetics research.

Nonvascularized Toe Joint Transfers to the Hand in Young Children: Technique Revisited.

BACKGROUND: Small joint reconstruction of the hand poses a significant challenge, especially in children where both functional motion and preservation of the epiphysis are desired. Auto-transplantation of whole joints is the only way to reconstruct a functional joint that maintains growth potential. Historically, nonvascularized toe-to-finger joint transfer has been criticized for high rates of avascular necrosis and joint dissolution, while vascularized transfers seemingly resulted in increased durability of the joint space and epiphysis. However, certain populations remain poor candidates for microvascular reconstruction, such as those with congenital deformities or sequelae from trauma or infection. In our case series, we demonstrate that a simplified nonvascularized surgical technique and careful patient selection can produce stable, functional joints. METHODS: Nonvascularized toe-to-finger joint transfer was performed in 3 children between the ages of 4 and 6. Reconstructed joints included 2 proximal interphalangeal (PIP) joints and 1 metacarpophalangeal (MCP) joint. Donor grafts consisted of second toe PIP joints harvested en bloc to include the epiphysis of the middle phalanx, collateral ligaments, volar plate, and a diamond-shaped island of extensor tendon with its central slip attachment. RESULTS: Follow-up ranged from 7 to 29 months. Each patient demonstrated functional improvements in joint motion and stability. Postoperative radiographs confirmed adequate joint alignment and persistence of the joint spaces. Epiphyseal closure was observed in 1 patient as early as 25 months postoperatively. CONCLUSIONS: Nonvascularized joint transfer should remain a practical consideration for small joint reconstruction of the hand in certain pediatric patients.

Toe-to-Finger Vascularized Joint Transfers for Proximal Interphalangeal Joint Reconstruction: A Systematic Review.

Vascularized joint transfer (VJT) from the proximal interphalangeal joint (PIPJ) of the toe is an attractive reconstructive option in cases of nonsalvageable finger PIPJ but is limited by equivocal functional outcomes. This systematic review aims to provide an update on vascularized toe-to-finger PIPJ transfers, examining functional outcomes, complications, and the latest refinements in operative technique. A systematic review of the available literature was performed according to Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines. Studies examining vascularized toe-to-finger PIPJ transfer for post-traumatic indications were included for analysis. Outcomes assessed included postoperative active range of motion, extension lag, and complications. Thirteen studies examining 210 VJTs were analyzed. Five VJTs experienced microsurgical failure giving an overall survival rate of 97.6%. Average postoperative PIPJ active range of motion (ROM) was 40.3° ± 12.9°, with an average extensor lag of 29° ± 10.5° and mean flexion of 68.9° ± 10.9°. For studies reporting complication outcomes, 59/162 complications were seen. No significant differences were seen between studies published prior to 2013 and after 2013 when comparing digital ROM (P = .123), flexion (P = .602), and extensor lag (P = .280). Studies using a reconstructive algorithm based on prior assessment of the donor toe central slip and recipient finger anatomy had significantly improved ROM outcomes (P = .013). Although VJT provides a reliable option for autologous reconstruction in posttraumatic joints, it is limited by impaired postoperative ROM. Careful assessment of the donor toe and recipient finger anatomy followed by systematic and meticulous reconstruction may lead to improved functional outcomes.

Fiber-reinforced fixation implant for proximal interphalangeal joint arthrodesis shows implant bio-integration at 1-year follow-up.

BACKGROUND: A new bio-integrative fiber-reinforced implant (OSSIOfiber® Hammertoe Fixation Implant, OSSIO Ltd., Caesarea, Israel) was developed for proximal interphalangeal joint (PIPJ) correction-arthrodesis. The main purpose of this clinical study was to assess implant bio-integration at 1-year follow-up. METHODS: Twenty-four patients, previously treated for a Hammertoe deformity using the bio-integrative, fiber-reinforced implant, were enrolled in this follow-up study. One-year follow-up included clinical examination, patient reported outcomes, radiographs, Magnetic Resonance Imaging (MRI) and bio-integration scoring. RESULTS: Proximal interphalangeal joint (PIPJ) radiographic fusion rate was 92% (n = 22). MRI was analyzed for 24 (100%) patients. In 100% of patients (n = 24), the border between implant and surrounding tissue was scored as partially visible. There were no cyst formation or fluid accumulation findings. Mild bone edema was detected in 29% (n = 7) and is attributed to the chronic distribution of forces due to chronic abnormal gait and pasture. None of the edema findings were considered as adverse implant-related finding. The mean bio-integration score was 7.71 ± 0.46. CONCLUSIONS: This study demonstrates safe bio-integration of the newly developed fiber-reinforced implant at 1-year follow-up without negative side effects.

Design of 3D printable prosthetic foot to implement nonlinear stiffness behavior of human toe joint based on finite element analysis.

Toe joint is known as one of the critical factors in designing a prosthetic foot due to its nonlinear stiffness characteristic. This stiffness characteristic provides a general feeling of springiness in the toe-off and it also affects the ankle kinetics. In this study, the toe part of the prosthetic foot was designed to improve walking performance. The toe joint was implemented as a single part suitable for 3D printing. The various shape factors such as curved shape, bending space, auxetic structure, and bending zone were applied to mimic human foot characteristics. The finite element analysis (FEA) was conducted to simulate terminal stance (from heel-off to toe-off) using the designed prosthetic foot. To find the structure with characteristics similar to the human foot, the optimization was performed based on the toe joint geometries. As a result, the optimized foot showed good agreement with human foot behavior in the toe torque-angle curve. Finally, the simulation conditions were validated by comparing with human walking data and it was confirmed that the designed prosthetic foot structure can implement the human foot function.