Hybrid Fixation Restores Tibiofibular Kinematics for Early Weightbearing After Syndesmotic Injury.

BACKGROUND: Disruption of the anterior inferior tibiofibular ligament (AITFL), posterior inferior tibiofibular ligament (PITFL), and interosseous membrane (IOM) is a predictive measure of residual symptoms after an ankle injury. Controversy remains regarding the ideal fixation technique for early return to sport, which requires restoration of tibiofibular kinematics with early weightbearing. PURPOSE: To quantify tibiofibular kinematics after syndesmotic fixation with different tricortical screw and suture button constructs during simulated weightbearing. STUDY DESIGN: Controlled laboratory study. METHODS: A 6 degrees of freedom robotic testing system was used to test 9 fresh-frozen human cadaveric specimens (mean age, 65.1 ± 17.3 years). A 200-N compressive load was applied to the ankle, while a 5-N·m external rotation and a 5-N·m inversion moment were applied independently to the ankle at 0° of flexion, 15° and 30° of plantarflexion, and 10° of dorsiflexion. Fibular medial-lateral translation, anterior-posterior translation, and internal-external rotation relative to the tibia were tracked by use of an optical tracking system in the following states: (1) intact ankle; (2) AITFL, PITFL, and IOM transected ankle; (3) single-screw fixation; (4) double-screw fixation; (5) hybrid fixation; (6) single suture button fixation; and (7) divergent suture button fixation. Repeated-measures analysis of variance with Bonferroni correction was performed for statistical analysis. RESULTS: In response to the external rotation moment and axial compression, single tricortical screw fixation resulted in significantly higher lateral translation of the fibula compared with that of the intact ankle at 10° of dorsiflexion (P < .05). Suture button fixation resulted in significantly higher posterior translation of the fibula at 0° of flexion and 10° of dorsiflexion, whereas divergent suture button fixation resulted in higher posterior translation at only 0° of flexion (P < .05). In response to the inversion moment and axial compression, single tricortical screw and hybrid fixation significantly decreased lateral translation in plantarflexion, whereas double tricortical screw fixation and hybrid fixation significantly decreased external rotation of the fibula compared with that of the intact ankle at 15° of plantarflexion (P < .05). CONCLUSION: Based on the data in this study, hybrid fixation with 1 suture button and 1 tricortical screw may most appropriately restore tibiofibular kinematics for early weightbearing. However, overconstraint of motion during inversion may occur, which has unknown clinical significance. CLINICAL RELEVANCE: Surgeons may consider this data when deciding on the best algorithm for syndesmosis repair and postoperative rehabilitation.

Sagittal instability with inversion is important to evaluate after syndesmosis injury and repair: a cadaveric robotic study.

PURPOSE: Disruption of the syndesmosis, the anterior-inferior tibiofibular ligament (AITFL), the posterior-inferior tibiofibular ligament (PITFL), and the interosseous membrane (IOM), leads to residual symptoms after an ankle injury. The objective of this study was to quantify tibiofibular joint motion with isolated AITFL- and complete syndesmotic injury and with syndesmotic screw vs. suture button repair compared to the intact ankle. METHODS: Nine fresh-frozen human cadaveric specimens (mean age 60 yrs.; range 38-73 yrs.) were tested using a six degree-of-freedom robotic testing system and three-dimensional tibiofibular motion was quantified using an optical tracking system. A 5 Nm inversion moment was applied to the ankle at 0°, 15°, and 30° plantarflexion, and 10° dorsiflexion. Outcome measures included fibular medial-lateral translation, anterior-posterior translation, and external rotation in each ankle state: 1) intact ankle, 2) AITFL transected (isolated AITFL injury), 3) AITFL, PITFL, and IOM transected (complete injury), 4) tricortical screw fixation, and 5) suture button repair. RESULTS: Both isolated AITFL and complete injury caused significant increases in fibular posterior translation at 15° and 30° plantarflexion compared to the intact ankle (p < 0.05). Tricortical screw fixation restored the intact ankle tibiofibular kinematics in all planes. Suture button repair resulted in 3.7 mm, 3.8 mm, and 2.9 mm more posterior translation of the fibula compared to the intact ankle at 30° and 15° plantarflexion and 0° flexion, respectively (p < 0.05). CONCLUSION: Ankle instability is similar after both isolated AITFL and complete syndesmosis injury and persists after suture button fixation in the sagittal plane in response an inversion stress. Sagittal instability with ankle inversion should be considered when treating patients with isolated AITFL syndesmosis injuries and after suture button fixation. LEVEL OF EVIDENCE: Controlled laboratory study, Level V.

Influence of knee position and examiner-induced motion on the kinematics of the pivot shift.

BACKGROUND: Grading of the pivot shift test varies significantly depending on the examiner's technique. Thus, the purpose of this study was to determine the influence of knee starting position and the magnitude of motion during the reduction event on the magnitude of the pivot shift test. METHODS: Twenty-five clinical providers each performed a total of twenty pivot shift tests on one of two fresh-frozen cadaveric full lower extremity specimens with different grades of rotatory knee laxity. By means of ACL transection and lateral meniscectomy, one specimen was prepared to have a high-grade pivot shift and one to have a low-grade pivot shift. Six-degree-of-freedom kinematics were recorded during each pivot shift test using an electromagnetic-tracking-system. Successful pivot shift tests were defined and selected using an automated, mathematical algorithm based on the exceeding of a threshold value of anterior translation of the lateral knee compartment. The kinematics were correlated with the magnitude of anterior translation of the lateral knee compartment based on varying degrees of rotatory knee laxity using the Pearson correlation coefficient. RESULTS: Only mild correlations between anterior translation of the lateral knee compartment and internal tibial rotation at the start of the reduction event were observed in both specimens. The ability to generate a successful reduction event was significantly dependent on the rotatory knee laxity, with a 54% success rate on the high-laxity specimen compared to a 30% success rate on the low-laxity specimen (p < 0.001). Nearly 80% of the variability of the anterior translation of the lateral knee compartment in both specimens was accounted for by external rotation during the reduction event (r = 0.847; p < 0.001). Varus rotation during the reduction event also showed a strong correlation with the anterior translation of the lateral knee compartment in the low-laxity specimen (r = 0.835; p < 0.001). CONCLUSION: Magnitude of motion during the reduction event affected the magnitude of anterior translation of the lateral knee compartment more than the starting position. External rotation during the reduction event accounted for most of the variability in the pivot shift test. More uniform maneuvers and improved teaching are essential to generate repeatable quantitative results of the pivot shift test.

Education and repetition improve success rate and quantitative measures of the pivot shift test.

PURPOSE: Clinicians have different techniques and varying levels of experience with the pivot shift test, introducing variability into its performance. The purpose of this study was to evaluate the influence of teaching and repetition on the success rate and anterior translation of the lateral knee compartment during the pivot shift test in a cadaveric ACL injury model. METHODS: Twenty-five participants (five each of medical students, orthopaedic surgery residents, physical therapists, athletic trainers, sports medicine fellows) were recruited and a senior orthopaedic surgeon served as gold standard examiner. Each participant performed 20 pivot shift tests on lower extremity cadaveric specimens with ACL deficiency and lateral meniscectomy: 5 prior to education (baseline), 10 after watching an instructional video (passive teaching), and 5 after an interactive education session (active teaching). The anterior translation of the lateral knee compartment was recorded during each pivot shift test using electromagnetic tracking system. RESULTS: For medical students and orthopaedic surgery residents, significant improvement in success rate was found when compared to baseline (12% and 24%, respectively) after both passive (36% and 60%, respectively) and active teaching (52% and 72%, respectively) (p < 0.5). Medical students and residents were the only participants that independently achieved significant increases in anterior translation of the lateral knee compartment, each tripling the respective baseline value (p < 0.5). In the entire study population, significant increases in anterior translation of the lateral knee compartment and success rate of the pivot shift test were seen with continuous repetition (p < 0.5). However, the standard deviation of anterior translation of the lateral knee compartment was more than twice the gold standard examiner's standard deviation, indicating a high degree of variability. CONCLUSION: Teaching of the pivot shift test plays a major role in the development of a proper technique. However, variability persisted despite teaching and repetition. New methods may be needed to improve the teaching of the pivot shift test.

Radiographic Analysis of National Football League Players' Fifth Metatarsal Morphology Relationship to Proximal Fifth Metatarsal Fracture Risk.

BACKGROUND:: Fractures of the proximal fifth metatarsal are one of the most common foot injuries in athletes. Repetitive stresses endured by the fifth metatarsal can lead to stress fracture, delayed union, and refracture, making optimal treatment challenging. A radiographic analysis of fifth metatarsal morphology and foot type in National Football League (NFL) players was performed to investigate morphologic risk factors for these injuries. METHODS:: This was a case-control study that looked at NFL players treated between 1992 and 2012, as well as participants at the NFL Combine. Ninety-six feet (51 athletes) were included. Fractures were present in 15 feet. Two reviewers assessed fifth metatarsal morphology and foot type on anteroposterior, lateral, and oblique radiographs. Differences in foot type and metatarsal morphology between athletes with and without fractures were determined. RESULTS:: On anteroposterior radiographs, significant differences in apex medullary canal width, 4-5 intermetatarsal angle, fifth metatarsal angle, and talar head uncovering were observed between fractured and non-fractured feet ( P = .001, .003, .004, .008, respectively). On lateral radiographs, significant differences in the fifth metatarsal length, distance to apex, apex height, fifth metatarsal angle, and talocalcaneal angle were observed between fractured and nonfractured feet ( P = .04, .01, .02, .01, .01, respectively). On oblique radiographs, a significant difference was observed in apex height between fractured and nonfractured feet ( P = .002). CONCLUSION:: Individuals with long, narrow, and straight fifth metatarsals with an adducted forefoot were most at risk for fifth metatarsal fractures. With this insight, attempts at fracture prevention can be implemented via footwear modifications, orthoses, and off-loading braces that account for those aforementioned morphologic attributes that place athletes at risk. LEVEL OF EVIDENCE:: Level III, retrospective comparative study.

Syndesmotic Injury Assessment With Lateral Imaging During Stress Testing in a Cadaveric Model.

BACKGROUND: External rotation, lateral, and sagittal stress tests are commonly used to diagnose syndesmotic injuries, but their efficacy remains unclear. The purpose of this study was to characterize applied stresses with fibular motion throughout the syndesmotic injury spectrum. We hypothesized that sagittal fibular motion would have greater fidelity in detecting changes in syndesmotic status compared to mortise imaging. METHODS: Syndesmotic instability was characterized using motion analysis during external rotation, lateral, and sagittal stress tests on cadaveric specimens (n = 9). A progressive syndesmotic injury was created by sectioning the tibiofibular and deltoid ligaments. Applied loads and fibular motion were synchronously measured using a force transducer and motion capture, respectively, while mortise and lateral radiographs were acquired to quantify clinical measurements. Fibular motion in response to these 3 stress tests was compared between the intact, complete lateral syndesmotic injury and lateral injury plus a completely sectioned deltoid condition. RESULTS: Stress tests performed under lateral imaging detected syndesmotic injuries with greater sensitivity than the clinical-standard mortise view. Lateral imaging was twice as sensitive to applied loads as mortise view imaging. Specifically, half as much linear force generated 2 mm of detectable syndesmotic motion. In addition, fibular motion increased linearly in response to sagittal stresses (Pearson's r [ρ] = 0.91 ± 0.1) but not lateral stresses (ρ = 0.29 ± 0.66). CONCLUSION: Stress tests using lateral imaging detected syndesmotic injuries with greater sensitivity than a typical mortise view. In addition to greater diagnostic sensitivity, reduced loads were required to detect injuries. CLINICAL RELEVANCE: Syndesmotic injuries may be better diagnosed using stress tests that are assessed using lateral imaging than standard mortise view imaging.

Biomechanical Analysis of Suture Anchor vs Tenodesis Screw for FHL Transfer.

BACKGROUND: Chronic Achilles injury is often treated with flexor hallucis longus (FHL) tendon transfer to the calcaneus using 1 or 2 incisions. A single incision avoids the risks of extended dissections yet yields smaller grafts, which may limit fixation options. We investigated the required length of FHL autograft and biomechanical profiles for suture anchor and biotenodesis screw fixation. METHODS: Single-incision FHL transfer with suture anchor or biotenodesis screw fixation to the calcaneus was performed on 20 fresh cadaveric specimens. Specimens were cyclically loaded until maximal load to failure. Length of FHL tendon harvest, ultimate load, stiffness, and mode of failure were recorded. RESULTS: Tendon harvest length needed for suture anchor fixation was 16.8 ± 2.1 mm vs 29.6 ± 2.4 mm for biotenodesis screw ( P = .002). Ultimate load to failure was not significantly different between groups. A significant inverse correlation existed between failure load and donor age when all specimens were pooled (ρ = -0.49, P < .05). Screws in younger specimens (fewer than 70) resulted in significantly greater failure loads ( P < .03). No difference in stiffness was found between groups. Modes of failure for screw fixation were either tunnel pullout (n = 6) or tendon rupture (n = 4). Anchor failure occurred mostly by suture breakage (n = 8). CONCLUSION: Adequate FHL tendon length could be harvested through a single posterior incision for fixation to the calcaneus with either fixation option, but suture anchor required significantly less graft length. Stiffness, fixation strength, and load to failure were comparable between groups. An inverse correlation existed between failure load and donor age. Younger specimens with screw fixation demonstrated significantly greater failure loads. CLINICAL RELEVANCE: Adequate harvest length for FHL transfer could be achieved with a single posterior incision. There was no difference in strength of fixation between suture anchor and biotenodesis screw.

Effect of Complete Syndesmotic Disruption and Deltoid Injuries and Different Reduction Methods on Ankle Joint Contact Mechanics.

BACKGROUND: Syndesmotic injuries can be associated with poor patient outcomes and posttraumatic ankle arthritis, particularly in the case of malreduction. However, ankle joint contact mechanics following a syndesmotic injury and reduction remains poorly understood. The purpose of this study was to characterize the effects of a syndesmotic injury and reduction techniques on ankle joint contact mechanics in a biomechanical model. METHODS: Ten cadaveric whole lower leg specimens with undisturbed proximal tibiofibular joints were prepared and tested in this study. Contact area, contact force, and peak contact pressure were measured in the ankle joint during simulated standing in the intact, injured, and 3 reduction conditions: screw fixation with a clamp, screw fixation without a clamp (thumb technique), and a suture-button construct. Differences in these ankle contact parameters were detected between conditions using repeated-measures analysis of variance. RESULTS: Syndesmotic disruption decreased tibial plafond contact area and force. Syndesmotic reduction did not restore ankle loading mechanics to values measured in the intact condition. Reduction with the thumb technique was able to restore significantly more joint contact area and force than the reduction clamp or suture-button construct. CONCLUSION: Syndesmotic disruption decreased joint contact area and force. Although the thumb technique performed significantly better than the reduction clamp and suture-button construct, syndesmotic reduction did not restore contact mechanics to intact levels. CLINICAL RELEVANCE: Decreased contact area and force with disruption imply that other structures are likely receiving more loads (eg, medial and lateral gutters), which may have clinical implications such as the development of posttraumatic arthritis.

Bracing versus casting in ankle fractures.

Casting and splinting techniques for treating patients with fractures have been used for centuries. Functional bracing after ankle fracture has recently been utilized in an effort to avoid the atrophy and stiffness sometimes associated with casting; functional bracing allows for early mobilization of the ankle joint during recovery. Our review investigated the published literature comparing bracing with casting after ankle fracture. Studies examining both operatively and nonoperatively treated ankle fractures were included. There is minimal evidence supporting the use of functional bracing over cast immobilization to improve functional outcome, range of motion, swelling, or post-traumatic arthrosis after ankle fracture in the long term. The primary benefits of functional bracing are the potential to return to work earlier and bracing may facilitate activities of daily living, such as bathing and dressing. In addition, there may be a decreased patient risk of developing deep vein thrombosis due to immobilization. However, there is an increased risk of wound infection when using a brace after open reduction and internal fixation of an unstable ankle fracture. Functional bracing can be used for treating stable and postoperative ankle fractures in compliant patients to potentially expedite and facilitate the recovery process.