Biomechanical comparison of metatarsal head designs in first metatarsophalangeal joint arthroplasty

Displacement of the Metatarsal Sesamoids in Relation to First Metatarsophalangeal Joint Extension

Background:

Quantifying normal sesamoid movement in relation to first metatarsophalangeal joint (MTPJ1) motion is essential to identifying aberrant kinematics and understanding how they may contribute to forefoot pain and dysfunction. The present study aims to report sesamoid displacement in relation to MTPJ1 extension and to compare sesamoid displacement with MTPJ1 range of motion (ROM) from several imaging modalities.

Methods:

Using 10 fresh frozen cadaveric feet, sesamoid displacement was evaluated during simulated MTPJ1 extension. The ability of 3 MTPJ1 measurement techniques (goniometry, fluoroscopy, and unloaded cone beam computed tomography [CBCT]) in predicting sesamoid displacement were compared. Kinematics were expressed in a coordinate frame based on the specimen-specific first metatarsal anatomy, and descriptive statistics are reported.

Results:

In the sagittal plane in both neutral and maximally extended positions, the tibial sesamoid was located on average more anteriorly than the fibular sesamoid. The angular displacement of the tibial and fibular sesamoids in the sagittal plane were 30.2 ± 14.3 degrees and 35.8 ± 10.6 degrees, respectively. In the transverse plane, both sesamoids trended toward the body midline from neutral to maximum extension. The intersesamoidal distance remained constant throughout ROM. Of the 3 measurement techniques, MTPJ1 ROM from CBCT correlated best (R² = 0.62 and 0.81 [P < .05] for the tibial and fibular sesamoid, respectively) with sagittal plane sesamoid ROM.

Conclusion:

The sesamoids were displaced anteriorly and medially in relation to increasing MTPJ1 extension. CBCT was the most correlated clinical imaging technique in relating MTPJ1 extension with sesamoid displacement.

Clinical Significance:

This study advances our understanding of the biomechanical function of the sesamoids, which is required for both MTPJ1 pathology interventions and implant design. These findings support the use of low-dose CBCT as the information gathered provides more accurate detail about bone position compared with other imaging methods.

Structural assessment of pre-flexion in silicone implants for arthroplasty of the first metatarsophalangeal joint

The development of numerical models to analyze pathologies and implants related to the first metatarsophalangeal joint of the foot remains an issue for attention. The structural effects of implants pre-flexion have been discarded in several finite elements analyses due to complexities to achieve these positions. This work aims to evaluate if the pre-flexion stress state should be included or could be discarded when only flexion is applied in two different silicone commercial implants, Swanson and Tornier, during a gait cycle. Finite element models were created for silicone implants. Both models were discretized using high-order finite elements. The hyperelasticity constitutive material model of Arruda-Boyce was used, based on experimental data; its behavior was compared with linear elastic models reported and used frequently assuming small and large deformations and applying to the Swanson and Tornier implants a flexion angle of 64°, which corresponds to in vivo measurements reported after implantation. Comparison between models, regarding hyperelastic model, showed mean variations of up to 32.5% for stresses and 14.01% for bending moment in Swanson implant, while for Tornier implant mean variations of 29.73% and 632.55% was obtained for stress and bending moment respectively. The maximum stress value obtained for the hyperelastic model in the Swanson implant reached a value of 22.82% of the tensile strength of the implant material while in the Tornier implant reached a value of 25.92%, the above values were evaluated at a flexion angle of 64°. The results suggest considering in finite element analyses not only the stress state generated to achieve critical flexion position in pleflexed implants models but also the hyperelastic material behavior of silicone for implants to avoid dismissing the non-linear structural behavior of hyperelastic materials.

Management of high-grade hallux rigidus: a narrative review of the literature

Hallux rigidus is a disease characterized by an osteoarthritic degeneration of the first metatarsophalangeal joint. Aetiology of hallux rigidus is not clear in the literature. History of trauma is considered one of the most common causes of unilateral hallux rigidus. Also, repetitive microtraumas or inflammatory and metabolic causes such as gout, rheumatoid arthritis and seronegative arthropathy can cause degeneration of the joint. The aim of this literature narrative overview is to summarize and expose the great amount of management concepts and information, including the well-codified main operative procedures to treat of hallux rigidus. This may provide current information for med-school students, researchers and physicians. A comprehensive literature search using PubMed database has been performed. The management for hallux rigidus can involve a variety of therapeutic interventions, conservative or operative. High-grade hallux rigidus represents a complex disease characterized by several clinical and pathological findings, and to achieve optimal results, surgical treatment should be chosen between several surgical techniques depending on the degree of arthritis and other different clinical conditions.

Biomechanical Comparison of the Influences of 2 Proximal Metatarsal Osteotomies on First Ray Articular Contact Characteristics

Background:

An understudied area of proximal first metatarsal osteotomies is the effect on articular contact properties following the surgeries. Potential long-term risks include altered joint mechanics and possible arthritic progression. A biomechanical comparison of articular characteristics of the proximal opening wedge and Ludloff osteotomies was performed in this study. It was hypothesized that the proximal opening wedge osteotomy (POWO) would lead to greater alterations in articular contact properties along the first ray.

Methods:

Seven paired fresh-frozen below-knee cadaveric limbs with hallux valgus were selected. Specimens in each pair were tested in the intact state and then randomized to receive either a Ludloff or POWO. A 4-mm opening wedge osteotomy was used in all cases. Loading of the flexor hallucis longus was to 100 N using an instrumented tensioner. A 28-N load was added at the distal phalanx to simulate the ground reaction force. First metatarsophalangeal (MTP) and tarsometatarsal (TMT) articular properties were recorded simultaneously using 2 pressure sensors. For each state, a pressure map was generated and contact area, peak pressure, and center of pressure were calculated. Wilcoxon signed-rank test was used to assess statistical significance.

Results:

Average peak pressure was noted to be elevated at the MTP (4.6 vs 6.9 mPa, P = .04) and TMT (3.3 mPa vs 5.1 mPa, P = .30) joints when comparing the Ludloff and the POWO, respectively. Contact area was also noted to be lower in the POWO relative to the Ludloff for the MTP (86.6 vs 69.1 mm², P = .30) but not the TMT joints (89.1 vs 88.5 mm², P = .97). There was a slight plantar-lateral and dorsomedial shift in pressure at the MTP and TMT articulations, respectively, of the POWO relative to the Ludloff. A trend toward decreased contact force within the TMT joint was noted following opening wedge osteotomy relative to the intact state (103.8 vs 113.9 N, P = .31), while forces were elevated at the MTP joint (104.3 vs 96.0 N, P = .63), although not statistically significant. Smaller increases in TMT and MTP joint forces were noted following the Ludloff when compared to the intact state (95.6 vs 93.3 N at TMT and 109.2 vs 103.2 N at MTP).

Conclusion:

POWO can potentially change articular contact characteristics along the TMT and MTP articulations of the first ray. This could possibly lead to altered loading patterns and possible long-term damage vs other osteotomies.

Clinical Relevance:

While it is unlikely that the changes observed with the sizes of the osteotomy commonly used would lead to long-term significant clinical consequences, further study with larger group sizes would be beneficial.

Implant Arthroplasty versus Arthrodesis for the Treatment of Advanced Hallux Rigidus: A Meta-analysis of Comparative Studies

Implant arthroplasty and arthrodesis of the first metatarsophalangeal joint are the main surgical treatment options for advanced hallux rigidus. The superiority of each modality continues to be debated, because there are few high-quality evidence-based studies, such as randomized controlled clinical trials or meta-analyses of comparative studies. The purpose of this study was to identify whether implant arthroplasty or arthrodesis is superior for the treatment of advanced hallux rigidus through meta-analysis of comparative studies. A comprehensive search of the MEDLINE, EMBASE, and Cochrane library databases was conducted. Only retrospective or prospective comparative studies were included in this meta-analysis. The literature search, data extraction, and quality assessment were conducted by 2 independent reviewers. The primary outcomes were clinical scores and patient satisfaction. The rate of reoperation and complication were also investigated. Seven comparative studies were included (2 prospective and 5 retrospective studies). There were no significant differences between the 2 groups in the American Orthopedic Foot and Ankle Society-Hallux Metatarsophalangeal Interphalangeal score, patient satisfaction rate, reoperation rate, or complication rate. The visual analogue scale for pain was significantly lower in the arthrodesis group than the implant arthroplasty group. This meta-analysis revealed that implant arthroplasty and arthrodesis of the first metatarsophalangeal joint led to similar clinical outcomes, patient satisfaction, reoperation rates, and complication rates, whereas pain was significantly lower in arthrodesis. Further studies of high methodological quality are required to confirm these conclusions.

First Metatarsophalangeal Contact Properties Following Proximal Opening Wedge and Scarf Osteotomies for Hallux Valgus Correction: A Biomechanical Study

BACKGROUND

Proximal opening wedge osteotomy (POWO) is an established procedure for moderate to severe hallux valgus. A common concern of this procedure is that it results in lengthening of the first metatarsal, which could cause increased intra-articular pressure of the first metatarsophalangeal joint (MTP) and may ultimately lead to arthritis because of these altered mechanics. The purpose of this study was to use a cadaveric model to compare intra-articular pressures and articulating contact properties of the MTP joint following either scarf osteotomy or POWO.

METHODS

Fresh-frozen cadaveric below-knee specimens with pre-existing hallux valgus (n = 12) and specimens without hallux valgus (n = 6, control group) were used. The hallux valgus specimens were stratified into 2 groups (n = 6 each): POWO or scarf osteotomy. The groups were matched based on the degree of deformity. Peak intra-articular pressure, force, and area were measured in all normal, preoperative, and postoperative specimens with a simulated weightbearing model. These measurements were made with a pressure transducer placed within the first MTP joint.

RESULTS

Postoperatively POWO group had slightly higher contact forces and pressures compared to the scarf group and lower contact forces and pressures than those of the normal group but were not statistically significant ( P > .05). Normal specimens had higher intra-articular force, pressure, and area than postoperative specimens but the difference was not found to be significant. First metatarsal lengthening was found in both the scarf and POWO specimens; however, neither increase was found to be significant ( P > .05).

CONCLUSION

The results from this study show that after operative correction, contact properties of the fist MTP joint among normal, POWO, and scarf osteotomy groups revealed no significant differences. First MTP joints in those with hallux valgus had significantly lower contact force and pressure compared to those without hallux valgus.

CLINICAL RELEVANCE

With little long-term outcomes of proximal opening wedge osteotomy, this study will help predict the possibility of future MTP joint arthritis.

Total Arthroplasty of the Metatarsophalangeal Joint of the Hallux

BACKGROUND

The current gold standard in the treatment of severe hallux rigidus is arthrodesis of the first metatarsophalangeal (MTP-I) joint. We present the results of a new 3-component MTP-I prosthesis. We determined (1) the intraoperative and perioperative complications; (2) survivorship of prosthesis components and rate of secondary surgeries for any reason; (3) prosthetic component stability and radiographic alignment; (4) the degree of pain relief; and (5) the midterm functional outcomes including radiographic range of motion (ROM).

METHODS

From 2008 to 2010, we prospectively included 29 MTP-I prostheses in 25 patients. The average age of the patients was 63.1 years (range, 48-87 years). The average follow-up was 49.5 months (range, 36-62 months). We observed complications and reoperations. A visual analog scale for pain and the American Orthopaedic Foot & Ankle Society (AOFAS) forefoot score were obtained pre- and postoperation. Component stability and alignment were assessed using weight-bearing radiographs. Fluoroscopy was used to determine radiographic MTP-I ROM.

RESULTS

Seven (24.1%) patients underwent 1 or more secondary surgeries. Four cases (13.7%) eventually had a conversion to MTP-I arthrodesis. Two patients (3 cases) died from causes not related to the procedure. This left 22 feet in 19 patients for final follow-up. All but 3 remaining prostheses showed stable osteointegration and no migration, but MTP-I alignment showed high variability. The average pain score decreased from 5.9 (range, 3-9) to 1.2 (range, 0-5). The average AOFAS forefoot score increased from 55 (range, 0-80) to 83.5 (range, 58-95). Range of motion initially increased from 37.8 degrees (range, 0-60 degrees) to 88.6 degrees (range, 45-125 degrees) intraoperatively and decreased to 29.0 degrees (range, 11-52 degrees) at latest follow-up.

CONCLUSION

Our data suggest that total arthroplasty of MTP-I leads to a high amount of revision surgeries, but the remaining patients had significant pain relief at midterm follow-up. However, we observed high variability regarding the prosthesis component alignment and poor range of motion.

LEVEL OF EVIDENCE

Level IV, prospective cohort study.

Total Toe Replacement in the United States: What Is Known and What Is on the Horizon

Arthritis of the first metatarsophalangeal is a common problem of the forefoot. The gold standard surgical treatment has been fusion of the first metatarsophalangeal joint. Many patients are unwilling to accept pain relief at the expense of loss of motion and the corresponding loss of shoe wear choices and activities requiring dorsiflexion of the hallux. Early implants were plagued with loosening and continued pain but implants have evolved. Current implants use modern bearing surfaces with press-fit fixation. These implants have renewed optimism for total toe arthroplasty. This article reviews the literature for implants currently available and describes the surgical techniques.

Comparison of 2D-3D Measurements of Hallux and First Ray Sagittal Motion in Patients With and Without Hallux Valgus

BACKGROUND

Clinicians base treatment decisions on measures of hallux and first ray motion in the management of first metatarsophalangeal joint disorders. Women account for a majority of the patients. This study assessed the reliability of a 2D approach for the measurements of sagittal motion, and compared the result to a Cardan (3D) angle criterion standard and evaluated how hallux valgus (bunion) deformity affected the comparisons.

METHODS

Twenty-nine women (controls n = 10; bunion n = 19) were examined using a retrospective repeated measures design. Weightbearing magnetic resonance (MR) images were acquired to replicate the position of the foot during the stance phase of gait. The images were reconstructed into virtual bone models using computer processes, whereby measures of hallux and first ray motion were represented by 2D and 3D methods of measurement. An examiner measured 2D motion on the image data sets using a goniometer, and reliability was assessed. The 3D Cardan angle result was derived from a matrix calculation. The 2D-3D comparison of measurements was evaluated with an analysis of variance (ANOVA) model across gait conditions, run separate for groups.

RESULTS

The 2D measurement was reliable (ICC ≥ 0.98, SEM ≤ 0.89 degrees). There was no method-by-condition interaction (F ≤ 1.37, P ≥ .25) between variables. No significant difference was detected between the 2D-3D measurements in the control group (F ≤ 1.24, P ≥ .30), but the measurements were statistically different (F ≥ 4.46, P ≤ .049) in the bunion group.

CONCLUSION

This study described a reliable 2D approach for measuring hallux and first ray sagittal motion from weightbearing images. The 2D measurements were comparable to a Cardan angle component motion result in controls, but not in women with bunion.

CLINICAL RELEVANCE

Joint motion measurements may augment clinical decision making. These results suggest that a 2D image-based approach may be adequate to estimate hallux and first ray sagittal motion, although bunion deformity creates out-of-plane motions that may require 3D methods to accurately quantify. Further clinical study is required to assess the differences in clinical outcomes between measurement techniques.

An in vitro and finite element study of load redistribution in the midfoot

A good knowledge of midfoot biomechanics is important in understanding the biomechanics of the entire foot, but it has never been investigated thoroughly in the literature. This study carried out in vitro experiments and finite element analysis to investigate the midfoot biomechanics. A foot-ankle finite element model simulating the mid-stance phase of the normal gait was developed and the model validated in in vitro experimental tests. Experiments used seven in vitro samples of fresh human cadavers. The simulation found that the first principal stress peaks of all midfoot bones occurred at the navicular bone and that the tensile force of the spring ligament was greater than that of any other ligament. The experiments showed that the longitudinal strain acting on the medial cuneiform bone was -26.2±10.8 μ-strain, and the navicular strain was -240.0±169.1 μ-strain along the longitudinal direction and 65.1±25.8 μ-strain along the transverse direction. The anatomical position and the spring ligament both result in higher shear stress in the navicular bone. The load from the ankle joint to five branches of the forefoot is redistributed among the cuneiforms and cuboid bones. Further studies on the mechanism of loading redistribution will be helpful in understanding the biomechanics of the entire foot.