Pedal Musculovenous Pump Activation Effectively Counteracts Negative Impact of Knee Flexion on Human Popliteal Venous Flow.

Knee scooters are commonly used for mobility instead of other devices. However, passive popliteal venous flow impedance has been observed with knee scooter usage ostensibly as a result of deep knee flexion. This study aimed to characterize the magnitude of impact knee flexion has on popliteal venous flow in relation to the degree of knee flexion when walking boot immobilized. Furthermore, the countervailing effect of standardized pedal musculovenous pump (PMP) activation was observed. Popliteal venous diameter and flow metrics were assessed with venous ultrasonography in 24 healthy individuals. Straight leg, crutch, and knee scooter positioning while wearing a walking boot and non-weight-bearing were compared. Flow was assessed with muscles at rest and with PMP activation. Of 24 participants, 16 (67%) were female. Twelve limbs (50%) were right sided. The mean age was 21.9 (SD = 3.0) years, and the mean body mass index was 21.9 (SD 1.9) kg/m2. Observer consistencies were excellent (intraclass correlation range = 0.93 to 0.99). No significant differences in mean vessel diameter, time-averaged mean velocity, and total volume flow occurred (all P > .01). Corresponding knee flexion effect sizes were small (range = -0.04 to -0.26). A significant decrease (-24%) in active median time-averaged peak velocity occurred between upright and crutch positions (20.89 vs 15.92 cm/s; P < .001) with a medium effect size (-0.51). PMP activation increased all flow parameters (all P < .001), and effect sizes were comparatively larger (>0.6) across all knee flexion positions.Clinical Significance: Knee flexion has a small to medium impact on popliteal venous return in healthy patients. Active toe motion effectively counters the negative effects of gravity and knee flexion when the ankle is immobilized.Levels of Evidence: Therapeutic, Level IV.

Intraoperative Assessment of Reduction of the Ankle Syndesmosis.

PURPOSE OF REVIEW: Postoperative malreduction of the ankle syndesmosis is common, poorly defined, and its assessment is controversial. In the absence of a gold standard method to evaluate the ankle syndesmosis, a variety of techniques have been described. As the knowledgebase expands, data illustrating caveats for such techniques has become available. The purpose of this review is to highlight literature-sourced technical pearls and their related caveats for the intraoperative assessment of the ankle syndesmosis. RECENT FINDINGS: Although numerical criteria are commonly used to assess syndesmotic reduction, anatomical variation in the healthy population frequently exceeds proposed cutoffs. Patient-specific uninjured anatomy can be defined by comparing to the uninjured contralateral ankle; however, side-to-side variation is present for many anatomical relationships. Advanced imaging (e.g., lateral radiographs, 3-dimensional radiography) can influence intraoperative surgeon decision-making and improve syndesmosis reduction, but minute improvements in syndesmosis reduction may not outweigh increased operating time and costs. Intraoperative imaging is an adjunct, not a replacement for direct visualization or palpation when reducing the syndesmosis. Arthroscopy may benefit younger patients with high physical demands by improving identification of intra-articular pathology absent on MRI. Although anatomical reduction is important to restore pre-injury biomechanics, it is unclear whether differences in reduction quality influence patient-reported outcomes. In the absence of a gold standard, awareness of the options for intraoperative assessment of the syndesmosis and their respective accuracy and limitations reported herein could enhance surgeons' ability to intraoperatively reduce the syndesmosis with the tools currently available.

Grafting of massive tibial subchondral bone defects in a caprine model using beta-tricalcium phosphate versus autograft.

OBJECTIVE: This study evaluated the ability of beta-tricalcium phosphate particles (beta-TCP) and autograft (AUTO) to maintain joint surface morphology when used to supplement massive subchondral bone defects in a caprine model. DESIGN: This was a prospective, parallel arm study with 2 experimental arms and a control group. METHODS: Unilateral, 11 mm diameter, 25 mm deep cylindrical defects were created in tibial subchondral bone of anesthetized goats (n = 16) and filled with autograft or beta-tricalcium phosphate particles. The contralateral limbs served as internal controls. Goats were killed at 3 months and both tibiae harvested. Molds made of the tibial plateau surface were used to create positive casts from which medial and lateral tibial plateau surfaces of both experimental (beta-tricalcium phosphate particles, autograft) and control limbs were digitized in 3 dimensions. Mirror images of the medial condyle surface contours from the controls were superimposed onto the experimental surfaces and deviations were compared using a Student t test (alpha = 0.05). Tibiae were then cut sagittally into medial (biomechanics) and lateral (histology) halves. Compressive modulus within the defect area was assessed by indentation to 2.0 mm at 0.2 mm per second using a 6-mm diameter pin. Specimens from the lateral tibial plateau were processed for undecalcified histology and the area of bone within the defect region measured. The articular surface of 86% of the autograft and 0% of the beta-tricalcium phosphate particles group had degenerative changes, with 29% of autograft goats exhibiting large-scale plateau collapse. Mean surface deviation for autograft was significantly greater than for beta-tricalcium phosphate particles (2.19 +/- 1.49 mm versus 0.78 +/- 0.19 mm), as was maximum surface deviation (11.19 +/- 8.02 mm versus 4.39 +/- 1.33 mm) (P < 0.05). The compressive modulus within the defect area for control animals was significantly higher than the experimental groups (P < 0.05). Significantly more bone was regenerated within beta-tricalcium phosphate particle-grafted defects compared to autograft (P < 0.05). These results indicated that beta-tricalcium phosphate particles might be a useful graft material for local repair of load bearing skeletal sites such as depressed tibial plateau fractures.

Popliteal sciatic perineural local anesthetic infusion: a comparison of three dosing regimens for postoperative analgesia.

BACKGROUND: This randomized, double-blind study investigated the efficacy of continuous and patient-controlled ropivacaine infusion via a popliteal sciatic perineural catheter in ambulatory patients undergoing moderately painful orthopedic surgery of the foot or ankle. METHODS: Preoperatively, patients (n = 30) received a posterior popliteal sciatic perineural catheter and nerve block. Postoperatively, patients were discharged home with a portable infusion pump delivering 0.2% ropivacaine (500 ml) in one of three dosing regimens: the basal group (12-ml/h basal rate, 0.05-ml patient-controlled bolus dose), the basal-bolus group (8-ml/h basal rate, 4-ml bolus dose), or the bolus group (0.3-ml/h basal rate, 9.9-ml bolus dose). RESULTS: The bolus group experienced an increase in baseline pain, breakthrough pain incidence and intensity, and sleep disturbances compared with the other two groups (P < 0.05 for all comparisons). Compared with the basal-bolus group, the basal group experienced an increase in these outcome measures only after local anesthetic reservoir exhaustion, which occurred earlier than in the other two groups (P < 0.05 for all comparisons). Satisfaction scores did not differ among the three groups. CONCLUSIONS: This study demonstrates that when providing analgesia with 0.2% ropivacaine via a popliteal sciatic perineural catheter after moderately painful surgery of the foot or ankle, a continuous infusion is required to optimize infusion benefits. Furthermore, adding patient-controlled bolus doses allows for a lower continuous basal rate and decreased local anesthetic consumption and thereby increases the duration of infusion benefits when in an ambulatory environment with a limited local anesthetic reservoir.

Quantitative assessment of mechanical laxity in the functionally unstable ankle.

PURPOSE: Delineating between functional and mechanical instability in those with chronic ankle dysfunction is a challenging task. Current methods of assessing ankle ligamentous laxity are subjective in nature and limit our ability to identify the site and extent of instability; therefore, a need exists for objective laxity measurements. The purpose of this study was to determine whether subjects with self-reported, functional ankle instability (FAI) demonstrated increased mechanical laxity when tested with instrumented arthrometry and stress radiography. METHODS: Both ankles were tested in 51 subjects with self-reported unilateral FAI. An instrumented ankle arthrometer measured ankle-subtalar joint motion for total anteroposterior (AP) displacement (mm) during loading at 125 N and total inversion-eversion (I-E) rotation (degrees of ROM) during loading at 4 N x m. The Telos GA-II/E device provided either anterior or lateral stress (15 kp) while fluoroscopic radiographs were recorded for anterior displacement (mm) and talar tilt (degrees). RESULTS: The arthrometry measurements of anterior and total AP displacement and the radiographic measurements of anterior displacement were greater (P < 0.05) in the FAI ankles when compared with the uninjured ankles. There were no differences in total I-E rotation, inversion rotation, or talar tilt between ankles when analyzed with either measurement technique. CONCLUSION: The ability to objectively measure mechanical instability in the functionally unstable ankle is important to understanding the nature and cause of the instability. Ankle arthrometry and stress radiographic measurements are objective assessment tools for mechanical laxity. Despite finding greater laxity in the functionally unstable ankle, the clinical significance of the observed displacement remains unanswered. Further research is needed to determine the amount of laxity that constitutes mechanical instability and how this relates to FAI.