Ipsilateral Hindfoot Research Articles

Association of Timing of Hindfoot Arthrodesis and Early Reoperation Rates for Total Ankle Arthroplasty.

Prior literature has demonstrated that ipsilateral hindfoot arthrodesis may increase the risk for reoperation after total ankle arthroplasty (TAA) and that simultaneous hindfoot arthrodesis with TAA could result in short-term clinical and radiologic improvements. The purpose of this study is to compare the reoperation rates after TAA with prior hindfoot arthrodesis vs simultaneous arthrodesis and TAA. Patients who underwent primary TAA were identified in the PearlDiver database. Patients were sorted into 2 study cohorts: hindfoot arthrodesis prior to TAA and simultaneous arthrodesis and TAA. Propensity matched control cohorts were identified for each study group. Multivariate analysis was conducted to account for any confounding variables and covariates when identifying differences in complications between cohorts. 297 patients underwent TAA with prior hindfoot arthrodesis and 174 underwent TAA and hindfoot arthrodesis concurrently. The incidence of reoperation (13.8% vs 5.2%, P < .001) and infection (12.6% vs 5.9%, P = .011) for the simultaneous cohort was higher when compared to the matched control cohort. In contrast, there was no statistically significant difference when comparing the prior arthrodesis cohort to the matched control cohort in reoperation rates (5.1% vs 4.7%, P = .787) or infection rates (4.4% vs 4.8%, P = .734). Those undergoing simultaneous procedures had increased incidences of reoperation, wound complications, infection, and emergency department visits (P < .0167) when compared to the TAA with prior arthrodesis cohort. Patients undergoing TAA and hindfoot arthrodesis concurrently were found to have higher rates of reoperation and infection when compared to the matched control cohort . In contrast, there was no difference in these rates in patients undergoing TAA with prior hindfoot arthrodesis compared with their matched control cohort. Patients undergoing simultaneous procedures had increased rates of reoperations, wound complications, infection, and emergency department visits compared to the TAA with prior arthrodesis cohort. Level III, retrospective comparative database study.

Does Timing of Subtalar Arthrodesis Affect Reoperation or Revision Rates for Total Ankle Arthroplasty?

Introduction/Purpose: The incidence of primary total ankle arthroplasty (TAA) in the treatment of end-stage ankle arthritis has increased substantially over the last decade. TAA may be performed alone or in conjunction with additional procedures including subtalar (ST) or triple arthrodesis as end-stage ankle arthritis is often associated with degenerative disease affecting neighboring joints. Prior literature has demonstrated that the ipsilateral hindfoot arthrodesis may increase the risk for revision after TAA and that simultaneous ST arthrodesis with TAA could result in significant short term clinical and radiologic improvements. However, there is limited research comparing staged versus simultaneous hindfoot arthrodesis with concomitant TAA. The purpose of this study is to compare the reoperation rates after TAA with simultaneous hindfoot arthrodesis versus staged hindfoot arthrodesis followed by TAA. Methods: Patients who underwent primary TAA from 2015-2022 were identified in the PearlDiver database using international classification of diseases (ICD) and current procedural (CPT) codes. Patients were only selected if they contained 1-year database follow-up after the index TAA. Patients were sorted into three cohorts: (1) primary TAA without any history of hindfoot arthrodesis (control), (2) those with staged hindfoot arthrodesis prior to TAA, and (3) those with hindfoot arthrodesis at the same time as TAA. Demographic characteristics including age, gender, and Charlson Comorbidity Index (CCI) were assessed for each cohort. The 1-year rate of reoperation and revision were the primary outcomes of this study. Univariate analysis using chi- square tests and student T-tests were performed to analyze any differences in patient demographics, comorbidities, and complications. Multivariate analysis using logistic regression was subsequently conducted to account for any confounding variables and covariates. Results: 9,912 patients underwent TAA without prior hindfoot arthrodesis, 297 patients underwent TAA with prior hindfoot arthrodesis and 174 with hindfoot arthrodesis concurrently with TAA. The incidences of reoperation (OR 3.52, 12.6% vs. 3.9%, P&lt;0.001) and revision (OR 3.66, 4.0% vs. 1.1%, P=0.001) were higher in the simultaneous cohort when compared to the control. However, there were no statistically significant differences in rates of reoperation (OR 0.96, 4.0% vs. 3.9%, P= 0.891) or revision (OR 1.94, 2.4% vs. 1.1 %, P= 0.095) when comparing staged hindfoot arthrodesis to the control. Conclusion: Patients undergoing concurrent hindfoot arthrodesis with TAA had a 3.5 times higher odds of reoperation and revision when compared to the control. Patients undergoing staged procedures did not demonstrate a difference in revision or reoperation rates when compared to the control. Staged hindfoot arthrodesis and TAA may be an effective option in treating complex end-stage ankle and hindfoot arthritis whereas a simultaneous approach may lead to higher rates of complications.

After Total Ankle Arthroplasty, When Does Bone Perfusion and Metabolic Activity at the Bone-Implant Interface Normalize? A PET/CT Study

Category: Ankle Arthritis Introduction/Purpose: Radionuclide bone scintigraphy in combination with computed tomography (CT) has been used to evaluate painful total hip and knee arthroplasties, and has also been used in the evaluation of the painful total ankle arthroplasty (TAA). Increased tracer uptake around implants may indicate loosening, but uptake characteristics of bone-seeking radiopharmaceuticals in asymptomatic total ankle patients have not been clarified. While findings of increased metabolic activity may prompt surgical intervention, there has been no work performed to define when postoperatively periprosthetic activity normalizes, if at all. In this study, we plan to establish normative data on 18F sodium fluoride (18F-NaF) positron emission tomography/CT (PET/CT) uptake ratios around TAA implants at various time intervals after surgery in asymptomatic TAA patients. Methods: The majority of the arthroplasty literature has investigated use of SPECT/CT performed with 99mTc-labeled bisphosphonates. However, data suggest that 18F-NaF PET/CT may be superior for this indication, with more favorable pharmacokinetics and similar sensitivity to detect aseptic loosening. In the present study, asymptomatic patients who underwent TAA with a modern fixed-bearing TAA prosthesis (either the Wright Infinity Adaptis or Exactech Vantage prosthesis) for posttraumatic arthritis were eligible for inclusion. Patients with ipsilateral hindfoot fusion and with any periprosthetic lucencies or cysts were excluded. Patients were enrolled at one of four time intervals following TAA: 6, 12, 18, or 24 months. Standard uptake values were measured at the bone-implant interface for the tibial and talar components on static PET, in regions of interest defined on axial CT scan slices. Periprosthetic bone blood flow (K1) and bone turnover (flux) were assessed at each time interval in each periprosthetic region using dynamic PET. Results: Sixteen asymptomatic patients underwent PET/CT: 4 patients at 6 months postoperatively, 6 at 12 months, and 6 at 24 months. We are currently still in data collection and at this time only 2 patients at 18 months have completed the scan, therefore their data were excluded. The average age was 65 years (range, 55 to 80) and 6 patients were female (38%), with individual patient data shown in the Table. Talar K1 and flux both appeared to increase from 6 to 12 months, and decrease between 12 and 24 months, although there was no statistically significant difference between timepoints. Overall tibial K1 and flux appeared to decrease slightly from 6 to 12 months, and stayed relatively stable between 12 and 24 months, again with no significant difference between timepoints (Figure). Conclusion: There is currently no normative data to help guide interpretation of radionuclide bone scintigraphy for the painful TAA. The present study utilizing 18F-NaF PET/CT scans demonstrates that even in asymptomatic patients, periprosthetic bone blood flow and bone turnover remain elevated up to 24 months following modern fixed-bearing TAA. Not only do these values remain elevated at 24 months, but we found that there does not appear to be any significant decrease in either measurement over time from 6 to 24 months postoperatively. Our findings suggest that radionuclide bone scintigraphy should be cautiously interpreted when performed within 2 years of TAA.

Risk Factors for Early Mechanical Failure and Revision in Modern Total Ankle Replacements

Category: Ankle Arthritis; Ankle Introduction/Purpose: Total ankle replacements (TAR) have rapidly advanced in terms of volume, technique, design, and indications. However, they are still at risk for failure and need for revision, even early in the postoperative period. Although recently there has been extensive research on TAR, many studies are limited in their power and sample size to assess risk factors for failure/revision. Using a large multi-surgeon retrospective database, we sought to describe the incidence and etiology of mechanical failure across modern implants. We also aimed to identify risk factors for early mechanical failure. We hypothesized that greater body mass index (BMI) and ipsilateral hindfoot fusion would be predictors of mechanical failure, and that implants with greater extent of tibial fixation (stems and keels) would be protective against mechanical failure. Methods: This is a single-center retrospective review of TAR patients in a prospective database. Adults undergoing primary TAR using any implant (Cadence, Inbone, Infinity, Invision, Salto, STAR, Vantage, Zimmer) who were minimum 2 years post-surgery were included. Exclusion criteria included revision TAR or patients undergoing ankle fusion takedown and conversion to TAR. Five surgeons contributed patients. Demographics, etiology of arthritis, operative data, and postoperative complications, reoperations, and revisions were collected. Revisions and reoperations were classified by standard criteria. Cause of revision was recorded. There were 560 TARs eligible for 2-year follow-up (mean 3.9 +- 1.1 years postoperative), with mean follow-up of 2.2 +- 1.4 years (range 1-71 months). The cohort had mean age 63.8 +- 9.1 years, BMI 29.4 +- 5.2 kg/m2, and 57% were male. Kaplan- Meier survival plots were created. Risk factors for revision due to mechanical failure were analyzed using multivariable logistic regression with partial Wald chi square statistics. Results: Most implants were low-profile (n=444, 79.3%), with 28 implants having tibial keels (5%) and 88 with tibial/talar stems (15.7%). There were 25 (4.5%) revisions of tibial and/or talar components at mean 1.6 years after index surgery (Figure). Preoperative coronal deformity did not impact revision rates (p=0.433). Patients who underwent revision for mechanical failure had significantly higher rates of concomitant hindfoot fusion (20% vs. 8.4%, p=0.047) and greater BMI (31.4 kg/m2 vs. 29.3 kg/m2, p=0.04). In multivariable logistic regression, hindfoot fusion was just short of statistical significance (odds ratio [OR] 2.96, p=0.056), and BMI was not significant (OR 1.05, p=0.417). Stemmed or keeled implants did not significantly decrease revision rates compared to low-profile implants, although the revision rate of stemmed implants was substantially low (1/88, 1.1%). Conclusion: Among 560 modern TAR implants, short-term survivorship was 95% at 2-year follow-up, which is consistent with existing studies. Patients who underwent revision for early mechanical failure had significantly higher BMI and rates of hindfoot arthrodesis. However, these variables fell short of statistical significance in multivariable regression, suggesting that there are either additional factors contributing to revision, or a larger cohort is needed. In addition, these results are likely biased by surgeons' tendencies to use stemmed implants in patients with hindfoot fusions. Further research is warranted to determine if stemmed implants provide a protective effect in these high-risk patients.

Transfibular Approach for Ankle Arthrodesis

Background: Ankle arthritis is a highly frequent condition and treatment choice in young individuals may be a difficulty. Fifty percent of older people get some sort of foot or ankle arthrosis. The most prevalent cause is post-traumatic arthritis, comprising 70 percent of people with osteoarthritis. Ankle fusion gives a solid foot that is painless, plantigrade. Several various procedures for ankle fusion were documented, although, including external fixators, internal binding and intramedullary nailing, this is a rescue treatment that leads to lasting abnormalities in gait and there is a danger of worsening owing to the danger of developing ipsilateral hind foot arthritis. There are several operational procedures including open or arthroscopic methods for ankle arthrodesis. Following both techniques, successful clinical outcomes may be attained. The major purpose of this research was to assess the clinical impact of arthrodesis of the knee with transfibular fastening. Methods: Methods: This is a study of 20 patients operated on a transfibular basis at university hospitals Benha and El helal. Results and findings: Compared to the pre-operative values, the post-operative AOFAS rear foot score has been significantly improved. In 20 patients, 95% bone union was accomplished which demonstrates that ankle arthrodesis with transfibular fixation results in good clinical results. This method guarantees high bone union rate and strong stability, removes ankle discomfort, corrects deformation and enhances the ankle function substantially.

Clinical Faceoff: The Complex Tibial Plafond Fracture: ORIF or Circular External Fixation?

Clinical Faceoff: The Complex Tibial Plafond Fracture: ORIF or Circular External Fixation?

Risk Factors for Early Failure of Fourth Generation Total Ankle Arthroplasty Prostheses

A number of 2-component, fourth generation total ankle arthroplasty (TAA) prostheses have been introduced to the market in the past few years, as the popularity and indications for TAA have continued to expand. The purpose of the present study was to identify independent risk factors for the early failure of fourth generation TAA prostheses. A total of 97 ankles underwent TAA with a fourth generation prostheses (INFINITY, CADENCE) between August 2015 and June 2018 at a single institution and were at least 6 months postoperative (mean 18.3 months, range 6-43). The primary outcome assessed was the need for revision surgery, defined as removal of 1 or both metal components for any reason, excluding infection. Baseline patient demographics, characteristics, radiographic alignment parameters, and distal tibia cortical bone thickness (CBT) were assessed. Revisions, reoperations, and complications were classified according to the criteria established by Vander Griend et al and Glazebrook et al, respectively. Univariate and multivariate analyses were performed. Three ankles (3.1%) underwent revision surgery for aseptic loosening at a mean of 24.3 (range, 16-31) months; all had a CBT <4 mm. Independent predictors for reoperation were CBT <4 mm, presence of diabetes, and ipsilateral hindfoot fusion (p = .04). No associations were identified for purported risk factors (age, body mass index, and coronal deformity). The present study is the first to suggest a potential relationship between reduced CBT of the distal tibia, and TAA failure. Additional studies are warranted to better understand the role of bone density in TAA survivorship.

Risk Factors for Early Failure of 4th Generation Total Ankle Arthroplasty Prostheses

Category:Ankle Arthritis; Ankle; OtherIntroduction/Purpose:A number of two-component, 4th generation total ankle arthroplasty (TAA) prostheses have been introduced to the market in the past few years, as the popularity and indications for TAA have continued to expand. The purpose of the present study was to identify independent risk factors for the early failure of 4th generation TAA prostheses.Methods:A total of 97 ankles underwent TAA with a 4th generation prostheses (INFINITY, CADENCE) between August 2015 and June 2018 at a single institution and were at least 6 months postoperative (mean 18.3 months, range 6-43). The primary outcome assessed was the need for revision surgery, defined as removal of 1 or both metal components for any reason, excluding infection. Baseline patient demographics, characteristics, radiographic alignment parameters, and distal tibia cortical bone thickness (CBT) were assessed. Revisions, reoperations, and complications were classified according to the criteria established by Vander Griend et al. and Glazebrook et el., respectively. Univariate and multivariate analyses were performed.Results:Three ankles (3.1%) underwent revision surgery for aseptic loosening at a mean of 24.3 (range, 16-31) months; all had a CBT <4mm. Independent predictors for reoperation were a CBT < 4mm, the presence of diabetes, and ipsilateral hindfoot fusion (p=0.04). No associations were identified for purported risk factors (age, BMI, and coronal deformity).Conclusion:The present study is the first to suggest a potential relationship between CBT of the distal tibia and TAA failure. Additional studies are warranted to better understand the role of bone density in TAA survivorship.

Risk Factors for Failure of Total Ankle Arthroplasty With a Minimum Five Years of Follow-up

As the popularity of total ankle arthroplasty (TAA) increases and indications expand, surgeons require a better understanding of which patient factors are associated with implant failure. In this study, we aimed to use a large total ankle database to identify independent risk factors for implant failure at mid- to long-term follow-up. A prospectively collected database was used to identify all patients who underwent primary TAA with a minimum 5 years' follow-up. The primary outcome was revision, defined as removal of one or both metal components; failures due to infection were excluded. Patient and clinical factors analyzed included age, sex, body mass index (BMI), smoking status, presence of diabetes, indication for TAA, implant, tourniquet time, and presence of ipsilateral hindfoot fusion. Preoperative coronal deformity and sagittal talar translation were assessed, as were postoperative coronal and sagittal tibial component alignment. Univariable and multivariable analyses were performed to identify predictors of implant failure. After excluding 5 ankles that failed because of deep infection, 533 ankles with a mean 7 (range, 5-11) years of follow-up met the inclusion criteria. Four implants were used: INBONE I, INBONE II, STAR, and Salto-Talaris. Thirty-four ankles (6.4%) were revised or removed a mean 4 (range, 1-9) years postoperatively. The only independent predictors of failure were the INBONE I prosthesis and ipsilateral hindfoot fusion ( P = .006 and P = .023, respectively). This is among the largest studies to analyze the relationship between TAA failure rates and multiple different patient, operative, and radiographic factors. Of note, age, BMI, and amount of deformity were not associated with higher failure rates. Only patients with ipsilateral hindfoot fusion or who received the INBONE I prosthesis were at significantly higher risk of implant failure. Level III, retrospective cohort study.

Increased Early Revision Rate with the INFINITY Total Ankle Prosthesis

Category: Ankle Arthritis Introduction/Purpose: Modern total ankle arthroplasties (TAAs) have demonstrated improved survival rates at early- and mid-term follow-up, with revision rates ranging from 4 to 8% at five years. The INFINITY total ankle system (Wright Medical Technology, Arlington, TN) was first used in the United States in 2014. Its advantages include the ability to use patient-specific instrumentation and the option to choose between talar dome resurfacing and flat-cut talar components. While this implant is currently popular in the United States, clinical outcomes have not yet been reported. Our aim was to identify the rate of early revision among patients receiving the INFINITY prosthesis. Methods: Patients from two prospectively-collected databases at the authors’ institution were screened for inclusion in the present study. All patients who underwent a primary TAA with the INFINITY prosthesis and who were at least one year postoperative were included. All surgeries were performed by one of two orthopaedic foot and ankle surgeons with extensive experience in total ankle arthroplasty. The primary outcome was the need for revision surgery, which was defined as removal of one or both metal components. Peri-implant lucency at most recent follow-up was a secondary outcome. Anteroposterior and lateral radiographs at most recent follow-up were graded for lucency independently by two reviewers, both orthopaedic foot and ankle fellows, for individual peri-implant zones (Figure). Each zone was only considered “lucent” if recorded as such by both reviewers. Results: 160 patients underwent TAA with the INFINITY prosthesis between August 2014 and November 2016 with a mean 20 months of follow-up (range, 12-37). Six patients were lost to follow-up. Sixteen patients (10%) underwent revision a mean 1.2 years postoperatively. Revision was performed most commonly for tibial component loosening (seven patients, 4.4%) and deep infection (five patients, 3.1%). Of cases with tibial loosening, progressive lucency and/or subsidence was obvious radiographically in four patients; one patient had equivocal radiographs but loosening was suggested on single-photon emission computed tomography; and two patients revised for persistent pain had loosening confirmed intraoperatively. Of the 108 patients with retained components and at least one year of radiographic follow-up, eight (7.4%) had global lucency around the tibial component at most recent follow-up. Conclusion: Our initial review of patients undergoing TAA with the INFINITY prosthesis demonstrates an elevated early revision rate due to tibial component loosening. The reasons for this finding remain unclear, but could possibly include inadequate bony purchase of the implant’s three prongs, particularly in patients with large preoperative deformities or with imperfect component alignment. We plan to further investigate the possible reasons for this finding in the future by assessing additional patient factors, including age, sex, arthritis type, tobacco use, pre- and postoperative coronal and sagittal alignment, and presence of ipsilateral hindfoot fusion.

The Silverskold Test, Are We All Doing it the Same?

Category: Pathophysiology Introduction/Purpose: Gastrocnemius eqiunus has been associated with a wide range of foot and ankle pathologies in the literature, however, many still question it’s involvement or existence. A recent response in Foot &amp; Ankle International pointed out an incorrect demonstration of the Silfverskold test in a prior study. With a growing body of literature supporting gastrocnemius equinus as a contributing factor in foot and ankle pain, why do many feel that it still does not exist? It was our hypothesis that unless the examination is performed correctly, the diagnosis can be missed and could be the potential cause for disbelief in its existence or effect on foot and ankle pain. We sought to demonstrate the difference in examination findings when performing the test correctly and incorrectly. Methods: Thirty consecutive patients with conditions associated with gastrocnemius equinus in the literature were included in the study. Each patient was consented and had a Silverskold test performed correctly by inverting and locking the subtalar joint as well as stabilizing the talonavicular joint in order to isolate the ankle joint. We then performed the exam incorrectly without stabilizing the same two joints, allowing motion through the ipsilateral hindfoot and midfoot joints. A long arm goniometer was used to measure the angles with each arm along the length of the fibula and fifth metatarsal. The senior author performed all of the examinations to maintain consistency. The angles were recorded for later review. Results: We found that when the subtalar and talonavicular joints were stabilized, there was almost fifteen degrees less dorsiflexion than when the same joints were not stabilized. The average dorsiflexion when performed in the correct manner was seventy-eight degrees, while the average dorsiflexion with the exam performed incorrectly was ninety-three degrees. Conclusion: We demonstrated that if the examination is not performed correctly, the equinus contracture could go undiagnosed as motion through the hindfoot and midfoot joints can alter the findings. It is important to understand and perform the technique correctly to evaluate for the contracture as it has been shown to be a contributing factor in many foot and ankle problems. If we standardize the examination, there may be less disagreement about its existence or affect on foot and ankle pain.

Evaluation of plantar pressure distributions in patients with anteriorcruciate ligament deficiency: preoperative and postoperative changes.

Anterior cruciate ligament (ACL) deficiency results in several kinematic changes in the lower extremities. The aim of this study is to define the plantar pressure parameters in ACL-deficient patients and to show the effect of ACL reconstruction on dynamic plantar pressure. Forty patients with unilateral ACL rupture and 40 healthy controls were included in this study. Dynamic plantar pressures of both groups were recorded by the EMED SF-2 system during level walking. Thirteen of the patients who had ACL reconstructions with hamstring autografts (HS group) were reevaluated at an average of 14.5 months following the ACL reconstructions. ACL-deficient patients had significantly lower hindfoot (P = 0.007) but higher midfoot pressure values (P = 0.03) on their ipsilateral foot compared to control group subjects. Ipsilateral hindfoot pressures were also found to be significantly lower than those of the contralateral foot (P = 0.001). Hindfoot pressure values of the HS group were increased in postoperative measurements (P = 0.01). ACL-deficient patients have altered plantar pressure distributions and ACL reconstructions restore these changes to normal. Pedobarography might be used as a practical method for dynamic functional assessment of ACL-deficient patients.

Outcomes After Total Ankle Replacement in Association With Ipsilateral Hindfoot Arthrodesis

Ipsilateral hindfoot arthrodesis in combination with total ankle replacement (TAR) may diminish functional outcome and prosthesis survivorship compared to isolated TAR. We compared the outcome of isolated TAR to outcomes of TAR with ipsilateral hindfoot arthrodesis. In a consecutive series of 404 primary TARs in 396 patients, 70 patients (17.3%) had a hindfoot fusion before, after, or at the time of TAR; the majority had either an isolated subtalar arthrodesis (n = 43, 62%) or triple arthrodesis (n = 15, 21%). The remaining 334 isolated TARs served as the control group. Mean patient follow-up was 3.2 years (range, 24-72 months). The SF-36 total, AOFAS Hindfoot-Ankle pain subscale, Foot and Ankle Disability Index, and Short Musculoskeletal Function Assessment scores were significantly improved from preoperative measures, with no significant differences between the hindfoot arthrodesis and control groups. The AOFAS Hindfoot-Ankle total, function, and alignment scores were significantly improved for both groups, albeit the control group demonstrated significantly higher scores in all 3 scales. Furthermore, the control group demonstrated a significantly greater improvement in VAS pain score compared to the hindfoot arthrodesis group. Walking speed, sit-to-stand time, and 4-square step test time were significantly improved for both groups at each postoperative time point; however, the hindfoot arthrodesis group completed these tests significantly slower than the control group. There was no significant difference in terms of talar component subsidence between the fusion (2.6 mm) and control groups (2.0 mm). The failure rate in the hindfoot fusion group (10.0%) was significantly higher than that in the control group (2.4%; p < 0.05). To our knowledge, this study represents the first series evaluating the clinical outcome of TARs performed with and without hindfoot fusion using implants available in the United States. At follow-up of 3.2 years, TAR performed with ipsilateral hindfoot arthrodesis resulted in significant improvements in pain and functional outcome; in contrast to prior studies, however, overall outcome was inferior to that of isolated TAR. Level II, prospective comparative series.

Effects of spinal cord stimulation with “standard clinical” and higher frequencies on peripheral blood flow in rats

Background: It is unclear whether spinal cord stimulation (SCS) at higher frequencies induces further increases in vasodilation and enhances clinical efficacy. Objectives: This study investigated effects of SCS at both a normal frequency (as used clinically) and two higher frequencies on peripheral vasodilation. Methods: A unipolar ball electrode was placed on the left dorsal column at the lumbar 2–3 spinal cord segments (L2–L3) in sodium pentobarbital anesthetized, paralyzed, and artificially ventilated rats. Cutaneous blood flow recordings from both ipsilateral (left) and contralateral (right) hind foot pads were measured with laser Doppler flow perfusion monitors. SCS at frequencies of 50, 200, or 500 Hz was applied at 30%, 60%, and 90% of motor threshold (MT) using standard square waves. Resiniferatoxin (RTX: an ultrapotent analog of capsaicin) and a calcitonin gene-related peptide (CGRP) receptor blocker (CGRP 8–37) was also used to elucidate mechanisms of SCS vasodilation at these higher frequencies. Results: SCS applied with the three frequencies produced similar MT ( n = 22). SCS at 500 Hz significantly increased cutaneous blood flow and decreased vascular resistance compared to changes induced by frequencies of 50 and 200 Hz ( P < 0.05, n = 8). RTX (2 μg/kg, i.v.) as well as CGRP 8–37 (2.37 mg/kg, i.v.) significantly reduced SCS-induced vasodilation at 500 Hz ( P < 0.05, n = 6) as compared to responses prior to administrations of these drugs. Conclusion: SCS at 500 Hz significantly increased SCS-induced vasodilation without influencing MT. Furthermore, effects of SCS at 500 Hz are mediated via activation of TRPV1-containing fibers and a release of CGRP.

Effects of Spinal Cord Stimulation with different frequencies on blood flow in the rat hind paw

Spinal cord stimulation (SCS) at a frequency of ∼50 Hz is used to improve peripheral blood flow. However, it is unclear whether SCS at higher frequencies induces further increases vasodilation and enhances clinical efficacy. This study investigated effects of SCS at different frequencies on peripheral vasodilation. SCS was setup at the lumbar 2–3 spinal cord segments in rats. Cutaneous blood flows from both ipsilateral and contralateral hind foot pads were recorded with laser Doppler flow perfusion monitors. SCS at frequencies of 50, 200 or 500 Hz was applied through the ball electrode at 30%, 60% and 90% of motor threshold (MT). Resiniferatoxin (RTX), an ultra potent analog of capsaicin, was applied to block the transient receptor potential vanilloid receptor (TRPV1); Furthermore, calcitonin gene related peptide (CGRP) 8–37, a CGRP‐1 receptor blocker, was used to elucidate mechanisms of SCS vasodilation at a high frequency. SCS applied with the three frequencies produced similar MT. SCS at the frequency of 500 Hz induced a higher increase of cutaneous blood flow and decreased vascular resistance compared to that with the frequency of 50 and 200 Hz (P&lt;0.05). RTX (2 μg/Kg. i.v.) as well as CGRP8–37 (2.37 mg/Kg. i.v.) significantly reduced SCS‐induced vasodilation at this high frequency (500 Hz) (P&lt;0.05). In conclusion, SCS at a high frequency significantly increased SCS‐induced vasodilation effect without influencing the MT. Furthermore, effects of SCS at high frequency seem to be predominantly mediated via activation of TRPV1 containing fibers including a release of CGRP.

Sensory fibers containing vanilloid receptor-1 (VR-1) mediate spinal cord stimulation-induced vasodilation

Background and aims: Spinal cord stimulation (SCS) is used to improve peripheral blood flow in selected populations of patients with ischemia of the extremities. Previous studies show that antidromic activation of sensory fibers is an important mechanism that contributes to SCS-induced vasodilation. However, the characteristics of sensory fibers involved in vasodilation are not fully known. This study investigated the contribution of vanilloid receptor type 1 (VR-1) containing fibers to SCS-induced vasodilation. Methods: A unipolar ball electrode was placed on the left dorsal column at the lumbar 2–3 spinal cord segments (L2–L3) in sodium pentobarbital anesthetized, paralyzed and ventilated rats. Cutaneous blood flows from both ipsilateral (left) and contralateral (right) hind foot pads were recorded with laser Doppler flow perfusion monitors. SCS (50 Hz; 0.2 ms) was applied through the ball electrode at 30%, 60%, 90% and 300% of motor threshold (MT). Resiniferatoxin (RTX), an ultra potent analog of capsaicin and VR-1 receptor agonist, was used to suppress the activities of VR-1 containing sensory fibers. Results: SCS at 30%, 60%, 90% and also at 300% of MT significantly increased cutaneous blood flow in the ipsilateral foot pad compared to that in the contralateral side. RTX (2 μg/kg, i.v.) significantly attenuated SCS-induced vasodilation of the ipsilateral side ( P < 0.05, n = 7) compared with responses prior to RTX administration. A pledget of cotton soaked with RTX (2 μg/ml) placed on L2–L3 spinal cord significantly decreased SCS-induced vasodilation of the ipsilateral side at 30%, 60%, 90% and 300% of MT ( P < 0.05, n = 7) compared with responses prior to RTX administration. Additionally, topical application of a pledget of cotton soaked with RTX (2 μg/ml) on the sciatic nerve at the middle level of the thigh or on the tibial nerve at the lower level of the lower hindlimb also decreased SCS-induced vasodilation ( n = 5). Conclusion: SCS-induced vasodilation is predominantly mediated via VR-1 containing sensory fibers.

Gait Analysis and Functional Outcomes Following Ankle Arthrodesis for Isolated Ankle Arthritis

The functional outcomes following ankle arthrodesis are not known. The purpose of the present study was to compare the intermediate-term clinical results for a group of patients in whom an ankle arthrodesis had been performed with use of modern surgical techniques with the findings for a group of healthy gender and age-matched controls on the basis of validated outcome measures and gait analysis. Twenty-six patients who had undergone ankle arthrodesis for the treatment of isolated unilateral ankle arthritis were identified and retrospectively assessed clinically and radiographically. The mean age at the time of surgery was fifty-four years, and the mean interval between surgery and assessment was forty-four months. A gender and age-matched control group of twenty-seven individuals was recruited for comparison. All subjects were evaluated with gait analysis, the American Orthopaedic Foot and Ankle Society (AOFAS) Ankle-Hindfoot scale, the Musculoskeletal Outcomes Data Evaluation and Management Systems (MODEMS) questionnaire, and the Ankle Osteoarthritis Scale (AOS). On preliminary review, twenty of the twenty-six patients were completely satisfied or satisfied with their surgical outcome. All patients but one stated that they would undergo the surgery again. Five patients stated that they did not notice a gait abnormality. Twelve patients wore orthotics, and all believed that the use of the orthotics improved their gait. When the functional outcome scores in the arthrodesis group were compared with those in the control group, specific scores assessing hindfoot pain and satisfaction were similar. However, scores focusing on ankle-hindfoot function and disability revealed significant differences. Gait analysis also identified significant differences between the two groups with regard to cadence and stride length. In addition, there was significantly decreased sagittal, coronal, and transverse range of motion of the hindfoot and midfoot during the stance and swing phases of gait in the arthrodesis group. Radiographic review demonstrated that four of the twenty-six patients had development of moderate to severe arthritis of the subtalar joint. In the intermediate term following an arthrodesis for the treatment of end-stage ankle arthritis, pain is reliably relieved and there is good patient satisfaction. However, there are substantial differences between patients and the normal population with regard to hindfoot function and gait. On the basis of these results, patients should be counseled that an ankle fusion will help to relieve pain and to improve overall function; however, it is a salvage procedure that will cause persistent alterations in gait with a potential for deterioration due to the development of ipsilateral hindfoot arthritis.

Characterization of biphasic modulation of spinal nociceptive transmission by neurotensin in the rat rostral ventromedial medulla.

Modulation of spinal nociceptive transmission by neurotensin microinjected in the rostral ventromedial medulla (RVM) was examined in anesthetized, paralyzed rats. Forty-three spinal dorsal horn neurons in the L3-L5 spinal segments responding to mechanical and noxious thermal stimulation (50 degrees C) of the plantar surface of the ipsilateral hind foot were studied. Spinal units were classified as either wide dynamic range or nociceptive specific and were located in spinal laminae I-V. Microinjection of neurotensin (0.03 pmol/0.2 microl) into the RVM produced a significant facilitation (135% of control) of spinal unit responses to noxious thermal stimulation (50 degrees C) that lasted approximately 12 min. In contrast, injection of greater doses of neurotensin (300 or 3,000 pmol) produced an inhibition of spinal unit responses to noxious heat (51.7 and 10.6% of control, respectively) that had a longer duration (60-120 min). The effects of neurotensin on wide-dynamic-range and nociceptive-specific neuron responses to noxious heat were qualitatively and quantitatively similar. Spinal unit responses to graded heating of the skin (42-50 degrees C) were completely inhibited after microinjection of 3,000 pmol of neurotensin into the RVM. Injection of a lesser dose of neurotensin (300 pmol), however, resulted in a partial inhibition of spinal unit responses and significantly reduced the slope of the stimulus-response function to graded heating of the skin. Transection of either the ipsilateral or contralateral dorsolateral funiculus (DLF) significantly reduced the inhibition of spinal nociceptive transmission produced by neurotensin (3,000 pmol) in the RVM, whereas bilateral transection of the DLFs completely blocked the effect. In contrast, bilateral transection of the DLFs had no effect on facilitation of spinal nociception by neurotensin (0.03 pmol) in the RVM. The inhibition of spinal nociceptive transmission by neurotensin (3,000 pmol) in the RVM was completely blocked by injection of the nonpeptide neurotensin receptor antagonist SR48692 (30 fmol) into the RVM 10 min before neurotensin. To confirm a specific block of neurotensin-receptor-mediated effects by the antagonist, a subsequent injection of L-glutamate into the RVM was performed. L-Glutamate (100 nmol) was found to inhibit the nociceptive responses of those spinal units whose responses were no longer inhibited by neurotensin. In contrast, injection of SR48692 (30 fmol) into the RVM failed to block the facilitation of spinal unit responses to noxious heat produced by a subsequent injection of neurotensin (0.03 pmol) into the same site. The present series of experiments demonstrate a specific role for neurotensin in the RVM in the modulation of spinal nociceptive transmission, because the peptide was found to both facilitate and inhibit spinal neuron responses to noxious thermal stimulation. Additionally, the facilitatory and inhibitory effects of neurotensin appear to occur via interaction with multiple neurotensin receptors in the RVM that activate independent systems that descend in the ventrolateral funiculi and DLFs, respectively. The results from these experiments are consistent with prior studies demonstrating that the RVM both facilitates and inhibits spinal nociceptive transmission, and they complement previous work showing that neurotensin in the RVM modulates spinal nociceptive behavioral responses.

Effects of neonatal capsaicin treatment on descending modulation of spinal nociception from the rostral, medial medulla in adult rat

Stimulation-produced modulation from the rostral, medial medulla (RMM) on the spinal nociceptive tail-flick (TF) reflex and on lumbar spinal dorsal horn neuron reponses to noxious cutaneous stimulti was studied in adult rats treated as neonates with capsaicin or vehicle. In vehicle-treated rats ( n = 7), both descending facilitatory and inhibitory influences on the TF reflex were produced from the RMM. At 11/23 sites in the RMM, electrical stimulation produced biphasic modulatory effects. Electrical stimulation facilitated the spinal nociceptive TF reflex at low intensities (5–25 μA) and inhibited the TF reflex at greater intensities (50–200 μA). The mean threshold intensity of stimulation to inhibit the TF reflex (cut-off time= 7.0s) was 66 μA ( n = 11). At 11 of 23 sites, electrical stimulation only inhibited the TF reflex; the mean threshold intensity of stimulation to inhibit the TF reflex was 50 μA ( n = 11). At one stimulation site, electrical stimulation only facilitated the TF reflex at the intensities tested (5–100 μA). In capsaicin-treated rats ( n = 6), the proportion of sites from which electrical stimulation only inhibited the TF reflex was significantly less (3/27sites= 11%) than in vehicle-treated rats (11/23= 48%). The threshold intensity of stimulation to inhibit the TF reflex from these three sites was 50 μA. The number of sites RMM fronm which electrical stimulation only facilitated the TF reflex was significantly greater in capaicin-treated rats (15/27= 56%) than in vehicle-treated rats (1/23= 4%). Neither the number of sites in RMM from which electrical stimulation produced biphasic modulatory effects on the TF reflex (48% and 33%, respectively) nor the intensities of stimulation or magnitudes of facilitation or inhibition of the TF reflex significantly differed between vehicle- and capsaicin-treated rats. In electrophysiological experiments, all units studied responded to non-noxious and noxious intensities of mechanical stimulation applied to the glabrous skin of the plantar surface of the ipsilateral hind foot and also to noxious heating of the skin (50°C). The number of sites where electrical stimulation produced only facilitatory effects on responses of spinal dorsal horn neurons to noxious stimulation (thermal or mechanical) of the skin was significantly increased from 13% of the total sites in vehicle-treated rats to 40% in capsaicin-treated rats. The number of sites where stimulation only produced inhibitory effects on responses of spinal dorsal horn neurons to noxious stimulation was decreased from 47% of the total sites in vehicle-treated rats to 35% in capsaicin-treated rats. The intensity of stimulation for producing inhibitory effects and the magnitude of inhibitory effects produced were not significantly different between vehicle- and capsaicin-treated rats. Immunocytochemical evaluation of the lumbar spinal dorsal horn verified that there were substantial reductions in substance-P and calcitonin gene-related peptide-like immunoreactivity, confirming the effectiveness of neonatal capsaicin treatment. The present study, in support of anatomical studies documenting central effects of capsaicin, suggests that neonatal capsaicin treatment also has significant effects on bulbospinal systems important to the modulation of spinal nociceptive transmission. Specifically, capsaicin treatment of neonates leads to a reduction in inhibitory and an increase in facilitatory influences on spinal nociception descending from the caudal brainstem.

Sensory responses to passive hindlimb joint rotation in the cerebellar cortex of the cat

We recorded from Purkinje cells in the anterior and posterior lobes of the cerebellar vermis in anesthetized cats during passive flexion and extension of the ipsilateral hind foot. Nearly 60% of the 302 cells recorded in lobules I–IV anterior and VII–IX posterior responded to this stimulus. In lobule V, generally considered to be the forelimb projection area, about a third of the 38 cells tested responded to hind foot movement. Cells in the anterior lobe typically exhibited different poststimulus patterns in response to foot flexion and extension while posterior cells usually had the same response to these stimuli. We also noted that cells recorded in the medial vermis (within 2.7 mm of the midline) generally had longer response latencies than cells recorded more laterally (2.7–4.5 mm) in both lobes. The results illustrate a diffuse proprioceptive input to the cerebellar vermis which has different features in various cerebellar areas.