Unilateral Ankle Fracture Research Articles

Patterns of Ankle Fractures Based on Radiographs and CT Images of 1000 Consecutive Patients.

The knowledge of different types of ankle fractures based on plain radiographs and computed tomography (CT) images can help improve patients' management. This cross-sectional study assessed the plain radiographs and CT images of 1,000 consecutive patients observed in an emergency department between March 2015 and March 2020. Fractures were labeled as uni-, bi-, or trimalleolar. Malleolar fractures were classified into medial, lateral, and posterior ones based on Herscovici, Danis-Weber, and Mason and Molloy classifications, respectively. Bi- and trimalleolar fractures, on the other hand, were categorized according to the Lauge-Hansen classification. This study included 1,000 patients with 1,003 ankle fractures. Of them, 901 were adults (mean±SD age: 41.6±16.7, male: 567 [62.9%]) with 904 fractures. In total, 53% of adult patients were 18 to 39 years old. Considering unilateral ankle fractures, the medial malleolar fracture was the most common unimalleolar fracture (62.6%), with Herscovici C being the most frequent subtype (65.3%). On the other hand, the most common type of lateral malleolar fracture was Danis-Weber type B (65.5%). There were also 209 (23.3%) bimalleolar and 114 (12.7%) trimalleolar fractures, 5.8% (16 fractures) of which could not be classified based on the Lauge-Hansen classification. Unimalleolar fractures were also observed in 87 (87.9%) children, with the medial malleolar fracture being the most common type (89.7%). Medial malleolar fractures were the most frequent malleoli in patients observed in the emergency department under study. Among bi- and trimalleolar ankle fractures, supination-external rotation and pronation-external rotation injuries were the most common patterns. The Lauge-Hansen classification was not applicable in 5.8% of bi- and trimalleolar fractures.

Splint versus no splint after ankle fracture fixation; Results from the multi-centre post-operative ankle splint trial (PAST)

BackgroundThere is considerable variation in the rehabilitation of ankle fractures. Ankle fractures treated surgically are often immobilized or splinted in the early post-operative period, despite the lack of robust evidence supporting this intervention. Thus, this randomized controlled trial aims to investigate the anecdote that splinting reduces pain and oedema. MethodsA prospective multi-centre randomized controlled trial was performed in three trauma centres. Eligible patients were over 18 years of age that have sustained an isolated unilateral ankle fracture requiring surgical intervention. Patients were randomized to two groups receiving either; a plaster of Paris posterior back-slab or compressive bandage dressing. The post-operative rehabilitation protocol was standardized across both groups. Baseline demographics and fracture characteristics and classifications were analysed. Primary outcomes included; oedema measured by the figure-of-eight-20 technique and pain at multiple time points. Secondary outcomes included; the American Orthopaedic Foot and Ankle Society (AOFAS) score, satisfaction, unplanned emergency room (ER) visits and complications. ResultsA total of 104 comparable participants were included; 54 in the non-splint group and 50 in the splint group. There was no significance difference in ankle oedema, ankle oedema compared to contralateral ankle and pain scores between the two groups (P = 0.56, P = 0.25, P = 0.39 respectively). Patient satisfaction was higher in the early postoperative period in the non-splint group (P = 0.016). The AOFAS score was not significantly different across any time point (P = 0.534). In the splint group, there was a 46% rate of splint-related complaints and complications. Unplanned ER visits occurred in 46% of the splint group and 7.4% of the non-splint group (P < 0.001). There were 2 wound infections, 1 non-union and 1 deep vein thrombosis in the splint group. There was 1 wound infection and 1 deep vein thrombosis in the no-splint group (P = 0.481) ConclusionThe routine use of a splint does not add any perceivable benefit to the postoperative course of an ankle fracture fixation, particularly in the reduction of oedema and postoperative pain. Another key finding is that the absence of a splint does not appear to result in higher complication rates, instead leads to higher unplanned ER visits and lower early satisfaction rates.

Treatment of perioperative swelling by rest, ice, compression, and elevation (RICE) without and with additional application of negative pressure (RICE+) in patients with a unilateral ankle fracture: study protocol for a monocentric, evaluator-blinded randomized controlled pilot trial

BackgroundEdema is commonly seen after surgical fixation of ankle fractures. Rest, ice, compression, and elevation (RICE) is an established combination to prevent swelling but hardly able to stimulate lymphatic resorption. Recently, an epicutaneously applied negative pressure suction apparatus (LymphaTouch®) has been introduced to stimulate lymphatic flow. While postoperative recovery, soft tissue, and osseous healing as well as functional outcome are probably linked to the amount of postoperative swelling, estimates on this relative to prevention (RICE) or prevention + stimulated resorption (RICE+) of fluid are scarce.Methods and analysisThis is a single-center, evaluator-blinded randomized pilot trial to investigate postoperative swelling in adults requiring surgical fixation of a closed unilateral ankle fracture. A total of 50 patients will be recruited and randomly assigned to RICE or RICE+ prior to surgery. All patients will undergo evaluator-blinded measurements of the ankle volume the day before surgery and subsequently from the evening of the 2nd postoperative day every 24 h until discharge. RICE will be initiated right after surgery and continued until discharge from the hospital in all patients. Additional application of negative pressure therapy (RICE+) will be initiated on the morning of the 2nd postoperative day and repeated every 24 h until the time of discharge from the hospital. Outcome measures are (i) the relative amount and the time course of the postoperative swelling, (ii) the demand for analgesic therapy (type and amount) together with the perception of pain, (iii) the rate of complications, and (iv) mobility of the ankle joint and the recovery of walking abilities during a 12-weeks follow-up period. Serum and urine samples taken prior to sugery and during postoperative recovery will allow to evaluate the ratio of naturally occurring stable calcium isotopes (δ44/42Ca) as a marker of skeletal calcium accrual.Ethics and disseminationThe protocol was approved by the institutional Ethics Committee (Rostock University Medical Center, Rostock, Germany) in accordance with the Declaration of Helsinki (approval number: A 2020-0092). The results of this study will be actively disseminated through scientific publications and conference presentations.Trial registrationDRKS, DRKS00023739. Registered on 14 December 2020

Blood-flow restricted exercise following ankle fractures — A feasibility study

BackgroundThe objective was to investigate the feasibility of blood flow restricted exercise (BFRE) as a rehabilitation modality in patients with a unilateral ankle fracture. MethodsFeasibility study with a prospective cohort design. Inclusion criteria were above 18 years of age and unilateral ankle fractures. Exclusion criteria: history of cardiac or embolic diseases, cancer, diabetes, hypertension and family history of cardio or vascular diseases. The predefined feasibility outcome was based on three criteria regarding patients experience with participating in the BFRE protocol and the absence of any serious adverse events. ResultsEight patients were included. Median age was 33 years (range: 23−60). All eight patients reported maximum satisfaction on the two questions regarding patient’s perception of the overall experience with BFRE training and the feasibility to introduce BFRE as an intervention. ConclusionEarly use of BFRE in patients with unilateral ankle fractures seems feasible in patients without comorbidity.

Pre-operative physiotherapy following unilateral ankle fractures at a tertiary hospital in South Africa: Perceptions of patients and nurses.

BackgroundAnkle fractures are a common injury because of an increase in levels of physical activity, as well as senescence worldwide. Ankle fractures often require surgical management for optimal stabilisation. Pre-operative physiotherapy is necessary to prepare patients for early mobilisation and home discharge. There is a lack of information on the influence of pre-operative physiotherapy on post-operative rehabilitation success, as well as timeous discharge, in patients with ankle fractures.ObjectivesTo explore the perceptions of patients receiving pre-operative physiotherapy care following a unilateral ankle fracture and the perceptions of nursing staff managing these patients at a tertiary hospital in South Africa.MethodA descriptive qualitative design, using semi-structured interviews, including both patients with unilateral ankle fractures and nurses caring for these patients, was adopted. Interviews were recorded and verbatim transcriptions were analysed utilising thematic analysis.ResultsFour overarching themes emerged: the perceived benefits of pre-operative physiotherapy; inhibitors to physiotherapy rehabilitation; hidden enablers to pre-operative physiotherapy and future initiatives for rehabilitation.ConclusionThe perceived benefits included improved functional independence and safety of patients, as well as reduced burden of care for nurses. Patients also believed that pain and fear were two inhibitors to physiotherapy. Furthermore, nurses identified that organisational limitations, such as short-staffing and inadequately trained staff, inhibited pre-operative physiotherapy and continuity of care. Early post-operative discharge was a crucial hidden enabler to the pre-operative physiotherapy protocol. Recommendations included improved health education; the potential role of nursing staff as facilitators in pre-operative rehabilitation and regular, pre-operative in-patient monitoring of physiotherapy intervention.Clinical implicationsHealth education was perceived to have improved patient safety and compliance which subsequently reduced patient safety incidences as well as served as a risk mitigation measure. Furthermore, gait training and muscle strengthening exercises was perceived to have resulted in safe, independent mobility to ensure prompt discharge home. Consequently, a reduced post-operative length of in hospital stay results in major cost savings per patient as well as improved access and bed availability. Future studies may need to explore the effects of pre-operative physiotherapy on post-operative success and return to pre-injury activity.

Comparison of the efficacy of posterior-anterior screws, anterior-posterior screws and a posterior-anterior plate in the fixation of posterior malleolar fractures with a fragment size of\u2009\u2265\u200915 and\u2009

BackgroundDifferent fixation methods have been used to treat posterior malleolar fractures (PMFs), but the clinical efficacy of different fixation methods in the treatment of PMF with different fragmentation has rarely been reported. The purpose of this study was to investigate the efficacy of posterior-anterior (PA), anterior-posterior (AP) screws and PA plate in the fixation of PMFs with a fragment size of ≥15 and < 15%.MethodsThis is a retrospective study of the clinical data of 243 patients with a unilateral ankle fracture involving the posterior malleolar ankle fracture. All patients were divided into two groups based on their fragment size, ≥15% (n = 136) and < 15% (n = 107). After reduction of PMF under direct vision via a posterolateral approach, posterior-anterior (PA), anterior-posterior (AP) screws and PA plate were used for fixation of PMF in the two groups. Briefly, for fixation of PMF with PA screw, two to three 3.5-mm (Depuy Synthes, Switzerland) cannulated screws were placed from the posterior to anterior direction; for fixation with PA plate, a 3.5-mm reconstruction plate (Depuy Synthes, Switzerland) was placed from the posterior to anterior direction, and for fixation of PMF with an AP screw, two to three 3.5-mm screws were placed from the anterior to posterior direction. All patients were followed up at 1, 3, 6, and 12 months after surgery and thereafter at 6-month intervals. The primary outcomes were AOFAS and ROM, which were recorded at the final follow-up.ResultsThe average follow-up time for all patients was 18.9 months (range 12–36 months), and all fractures healed. In fragment size ≥15% group, the average AOFAS score of patients treated with PA, AP screws and posterior plate were 91.5, 91.8, and 90.8, respectively, and the average limited ankle-dorsiflexion ROM was 5.0 °, 5.4 ° and 5.6°, respectively, at the last follow-up, there was no significant difference between the three fixation methods in terms of AOFAS scores and ankle ROM (P > 0.05). In fragment size < 15% group, the average AOFAS score of patients treated with PA, AP screws and posterior plate were 92.3, 91.9, and 84.1, respectively, the average limited ankle-dorsiflexion ROM were 5.1 °, 4.7 °, and 6.3 °, respectively, at the last follow-up. There were statistically significant differences in AOFAS scores and ankle ROM between posterior plate fixation and PA, AP screw fixation (P < 0.05); while no significant difference was found between PA and AP screw fixation (P > 0.05).ConclusionFor PMFs with fragment size ≥15%, there was no significant difference in the outcomes between the three fixation methods. For PMF with fragmentation < 15%, the PA and AP screws both provided good fixation.

Cone-beam CT measurements of distal tibio-fibular syndesmosis in asymptomatic uninjured ankles: does weight-bearing matter?

To evaluate the influence of weight-bearing (WB) load in standard axial ankle syndesmotic measurements using cone beam CT (CBCT) examination of asymptomatic uninjured ankles. In this IRB approved, prospective study, patients with previous unilateral ankle fractures were recruited. We simultaneously scanned the injured ankles and asymptomatic contralateral ankles of 27 patients in both WB and NWB modes. For this study, only asymptomatic contralateral ankles with normal plain radiographs were included. Twelve standardized syndesmosis measurements at two axial planes (10mm above the tibial plafond and 5mm below the talar dome) were obtained by two expert readers using a custom CBCT viewer with the capability for geometric measurements between user-identified anatomical landmarks. Inter-reader reliability between two readers was obtained using the intra-class correlation coefficient (ICC). We compared the WB and NWB measurements using paired t test. Significant agreement was observed between two readers for both WB and NWB measurements (p <0.05). ICC values for WB and NWB measurements had a range of 50-95 and 31-71 respectively. Mean values of the medial clear space on WB images (1.75, 95% confidence interval [95% CI]: 1.6, 1.9) were significantly lower than on NWB images (2.05, 95% CI: 1.8, 2.2) measurements (p <0.001). There was no significant difference between the remaining WB and NWB measurements. Measurements obtained from WB images are reliable. Except for the medial clear space, no significant difference in syndesmotic measurements were observed during the WB mode of CBCT acquisition, implying that the tibio-fibular relationship remains unchanged when the physiological axial weight-bearing load is applied.

A Radiographic Dye Method for Intraoperative Evaluation of Syndesmotic Injuries.

The Chertsey test has been recently defined as an intraoperative test for the detection of the syndesmotic injuries by the application of intra-articular contrast. However, no study has investigated the reliability and comparative analysis of the Chertsey test. The purpose of this study was to explore the diagnostic accuracy of the Chertsey test in predicting syndesmosis instability of the injured ankle, with correlation to preoperative computed tomography (CT) findings. A total of 39 patients who were operated on due to the unilateral ankle fracture and had no complaint on the contralateral ankle joint were included in the study. An intraoperative Chertsey test was performed on all ankle fractures and bilateral ankle CT was obtained preoperatively. Ankles were classified as Chertsey +, Chertsey -, and contralateral control group. The morphology categorization, width, and volume of the syndesmotic region were measured on axial images of the CT. Mann-Whitney U test was used to compare the data. Intraobserver and interobserver agreements were accessed by calculating the intraclass correlation coefficient (ICC) for radiologic parameters and the Chertsey test. The Chertsey test was positive in 13 (33.3%) of 39 ankle fractures. Patients with a positive Chertsey test showed a significant increase in syndesmotic width and volume compared with Chertsey - and control group. However, there was no significant difference between Chertsey - and the control group. All the ICC values were excellent for both radiologic measurements and test. The Chertsey test is a reliable and useful test that can be used intraoperatively in the diagnosis of syndesmotic injuries. III, comparative series.

The American Orthopaedic Foot and Ankle Society Ankle-Hindfoot Scale; translation and validation of the Dutch language version for ankle fractures

ObjectivesThe American Orthopaedic Foot and Ankle Society (AOFAS) Ankle-Hindfoot Scale is among the most commonly used instruments for measuring outcome of treatment in patients who sustained a complex ankle or...

Does a Patient’s Self-Reported Ability to Weightbear Immediately after Injury Predict Stability for Ankle Fractures

Category: Trauma Introduction/Purpose: Determining the stability of ankle fractures, particularly for apparent isolated Weber B fibula fractures, can be difficult. While the ultimate goal remains achieving an anatomic mortise, different techniques to predict ankle stability such as stress and weightbearing radiographs have been utilized with variable results. History of injury and the ability to walk after sustaining ankle trauma may be predictive of stability. Therefore, this study seeks to determine whether a patient’s ability to fully weight bear immediately after injury is an effective indicator for ankle stability following ankle fracture. Methods: A prospective review was conducted of patients sustaining isolated, unilateral ankle fractures presenting to two level I trauma centers. Aside from demographic data and fracture characteristics, a patient’s ability or inability to fully weightbear immediately after injury was elicited by interview at their initial assessment. This information was correlated with their ankle radiographs, which were deemed stable or unstable fractures based on commonly used indices to assess ankle stability. Results: 102 consecutive patients sustaining ankle fractures were included. Mean age was 45. When analyzing the entire cohort, patients who were able to ambulate immediately after injury were 10 times more likely to have a stable ankle fracture than those who could not bear weight (odds ratio (OR) 9.9 (P &lt; 0.001). The positive predictive value (PPV) for being able to fully weightbear as it relates to a stable ankle fracture was 77%. Additionally, inability to weightbear was 89% specific for an unstable fracture. When separately analyzing patients with apparent isolated fibula fractures (n=56), the PPV was 75%, specificity was 83%, while the OR was 5.8 (p=0.003) for those who could fully bear weight having a stable ankle fracture. Conclusion: This study demonstrates that patient’s self-reported ability to fully weightbear immediately after injury is a specific and convenient prognostic indicator for ankle stability across a range of ankle fracture subtypes. Future studies can analyze whether initial weightbearing accurately predicts ultimate management and good outcome.

Intraoperative Assessment of the Stability of the Distal Tibiofibular Joint in Supination-External Rotation Injuries of the Ankle

This study was designed to assess the sensitivity, specificity, and interobserver reliability of the hook test and the stress test for the intraoperative diagnosis of instability of the distal tibiofibular joint following fixation of ankle fractures resulting from supination-external rotation forces. We conducted a prospective study of 140 patients with an unstable unilateral ankle fracture resulting from a supination-external rotation mechanism (Lauge-Hansen SE). After internal fixation of the malleolar fracture, a hook test and an external rotation stress test under fluoroscopy were performed independently by the lead surgeon and assisting surgeon, followed by a standardized 7.5-Nm external rotation stress test of each ankle under fluoroscopy. A positive stress test result was defined as a side-to-side difference of >2 mm in the tibiotalar or the tibiofibular clear space on mortise radiographs. The sensitivity and specificity of each test were calculated with use of the standardized 7.5-Nm external rotation stress test as a reference. Twenty-four (17%) of the 140 patients had a positive standardized 7.5-Nm external rotation stress test after internal fixation of the malleolar fracture. The hook test had a sensitivity of 0.25 (95% confidence interval, 0.12 to 0.45) and a specificity of 0.98 (95% confidence interval, 0.94 to 1.0) for the detection of the same instabilities. The external rotation stress test had a sensitivity of 0.58 (95% confidence interval, 0.39 to 0.76) and a specificity of 0.96 (95% confidence interval, 0.90 to 0.98). Both tests had excellent interobserver reliability, with 99% agreement for the hook test and 98% for the stress test. Interobserver agreement for the hook test and the clinical stress test was excellent, but the sensitivity of these tests was insufficient to adequately detect instability of the syndesmosis intraoperatively.

Effects of long-term immobilization and recovery on human triceps surae and collagen turnover in the Achilles tendon in patients with healing ankle fracture

The aim of the present study was to analyze how human tendon connective tissue responds to an approximately 7-wk period of immobilization and a remobilization period of a similar length, in patients with unilateral ankle fracture, which is currently unknown. Calf muscle cross-sectional area (CSA) decreased by 15% (5,316 to 4,517 mm2) and strength by 54% (239 to 110 N.m) in the immobilized leg after 7 wk. During the 7-wk remobilization, the CSA increased by 9% (to 4,943 mm2) and strength by 37% (to 176 Nm). Achilles tendon CSA did not change significantly during either immobilization or remobilization. Local collagen turnover was measured as the peritendinous concentrations of NH2-terminal propeptide of type I collagen (PINP) and COOH-terminal telopeptide region of type I collagen (ICTP), markers thought to be indexes of type I collagen synthesis and degradation, respectively. Both markers were increased (PINP: 257 vs. 56 ng/ml; ICTP: 9.8 vs. 2.1 microg/l) in the immobilized leg compared with the control leg after the 7 wk of immobilization, and levels decreased again in the immobilized leg during the recovery period (PINP: 103 vs. 44 ng/ml; ICTP: 4.2 vs. 1.9 microg/l). A significant reduction in calf muscle CSA and strength was found in relation to 7 wk of immobilization. Immobilization increased both collagen synthesis and degradation in tendon near tissue. However, it cannot be excluded that the facture of the ankle in close proximity could have affected these data. Remobilization increased muscle size and strength and tendon synthesis and degradation decreased to baseline levels. These dynamic changes in tendon connective tissue turnover were not associated with macroscopic changes in tendon size.

PATHOANATOMY OF POSTERIOR MALLEOLAR FRACTURES OF THE ANKLE

Background: The functional outcome following ankle fractures that involve a posterior malleolar fragment is often not satisfactory, and treatment of this type of fracture remains controversial. Thorough knowledge of the pathologic anatomy of the posterior malleolar fracture is essential for planning appropriate treatment. Thus, we conducted a computed tomographic study to clarify the pathologic anatomy of the posterior malleolar fracture. Methods: Between 1999 and 2003, fifty-seven consecutive patients with a unilateral ankle fracture with one or more posterior fragments were managed at our hospital. We reviewed the patients' preoperative computed tomographic scans to determine (1) the ratio of the posterior fragment area to the total cross-sectional area of the tibial plafond and (2) the angle between the bimalleolar axis and the major fracture line of the posterior malleolus. Each fracture was categorized according to the location of the major fracture line on the computed tomographic image at the level of the tibial plafond. Results: The fifty-seven fractures were categorized into three types: (1) the posterolateral-oblique type (thirty-eight fractures; 67%), (2) the medial-extension type (eleven fractures; 19%), and (3) the small-shell type (eight fractures; 14%). Two of the eleven medial-extension fractures extended to the anterior part of the medial malleolus, and the other nine actually consisted of two fragments. The average area of the fragment comprised 11.7% of the cross-sectional area of the tibial plafond for posterolateral-oblique fractures and 29.8% for medial-extension fractures. In the cases of seven of the nine fractures that comprised >25% of the tibial plafond, the fracture line extended to the medial malleolus. The angles between the bimalleolar axis and the major fracture line of the posterior malleolus varied. Conclusions: The fracture lines associated with posterior malleolar fractures appear to be highly variable. A large fragment extending to the medial malleolus existed in almost 20% of the posterior malleolar fractures in the current study, and some fragments involved almost the entire medial malleolus. Because of the great variation in fracture configurations, preoperative use of computed tomography may be justified. The information obtained from this study will be helpful for conducting basic research of this condition and for determining appropriate surgical approaches.

Pathoanatomy of Posterior Malleolar Fractures of the Ankle

The functional outcome following ankle fractures that involve a posterior malleolar fragment is often not satisfactory, and treatment of this type of fracture remains controversial. Thorough knowledge of the pathologic anatomy of the posterior malleolar fracture is essential for planning appropriate treatment. Thus, we conducted a computed tomographic study to clarify the pathologic anatomy of the posterior malleolar fracture. Between 1999 and 2003, fifty-seven consecutive patients with a unilateral ankle fracture with one or more posterior fragments were managed at our hospital. We reviewed the patients' preoperative computed tomographic scans to determine (1) the ratio of the posterior fragment area to the total cross-sectional area of the tibial plafond and (2) the angle between the bimalleolar axis and the major fracture line of the posterior malleolus. Each fracture was categorized according to the location of the major fracture line on the computed tomographic image at the level of the tibial plafond. The fifty-seven fractures were categorized into three types: (1) the posterolateral-oblique type (thirty-eight fractures; 67%), (2) the medial-extension type (eleven fractures; 19%), and (3) the small-shell type (eight fractures; 14%). Two of the eleven medial-extension fractures extended to the anterior part of the medial malleolus. A total of nine of the eleven medial-extension fractures actually consisted of two fragments [corrected] The conditions are not exclusive of one another; for example, in the case of one of the fractures exhibiting two fragments, the fracture also extended to the anterior part of the medial malleolus [corrected] The average area of the fragment comprised 11.7% of the cross-sectional area of the tibial plafond for posterolateral-oblique fractures and 29.8% for medial-extension fractures. In the cases of seven of the nine fractures that comprised >25% of the tibial plafond, the fracture line extended to the medial malleolus. The angles between the bimalleolar axis and the major fracture line of the posterior malleolus varied. The fracture lines associated with posterior malleolar fractures appear to be highly variable. A large fragment extending to the medial malleolus existed in almost 20% of the posterior malleolar fractures in the current study, and some fragments involved almost the entire medial malleolus. Because of the great variation in fracture configurations, preoperative use of computed tomography may be justified. The information obtained from this study will be helpful for conducting basic research of this condition and for determining appropriate surgical approaches.

Muscle Activation Deficits During Fatigue after Limb Disuse

1890 PURPOSE: To determine the extent of plantarflexor muscle activation deficits during fatigue in patients after immobilization. METHODS: Six patients with surgically stabilized, unilateral ankle fractures and 6 healthy subjects participated. Patients were immobilized for 8 weeks, followed by 10 weeks of rehabilitation. Isometric plantarflexion torque was measured at 1 week (1w-R), 5 weeks (5w-R) and 10 weeks (10w-R) of rehabilitation. Subjects performed maximal voluntary isometric contractions (MVIC) with burst superimposition (100ms; 100pps) to assess muscle activation. Fatigue testing involved a 90 second, sustained MVIC of the plantarflexors, with burst superimposition at the beginning, middle, and end. Muscle activation was quantified using the central activation ratio (CAR), which was calculated by dividing the maximum voluntary force by the maximum force produced with electrical stimulation. A CAR of 1.0 indicates full muscle activation by the central nervous system. A fatigue index (final/initial force) was used quantify the extent of muscle fatigue. T-tests were used for all comparisons. RESULTS: At 1 wk-R, the involved leg fatigued less than 5%, while the uninvolved leg fatigued almost 50% (p<0.05). At 5w-R and 10w-R, the involved leg fatigued between 20 and 25%. During the nonfatigued state at 1wk-R, there were significant differences in muscle activation between the involved and uninvolved limbs (CAR = 0.98 vs. 0.79) (p<0.05), which resolved by 5w-R (0.93) and 10w-R (0.96). Decreases in CAR during the fatigue test were minimal (<0.1) for all subjects for both the involved and uninvolved legs. Torque deficits present in the involved legs at 1w-R, recovered to normal by 10w-R (p<0.05). CONCLUSION: Patients experienced less muscle fatigue in their involved leg, early after limb disuse. Fatigability did not recover to normal levels even after 10 weeks of rehabilitation, despite the complete restoration of torque and muscle activation deficits. Initial muscle activation deficits can only account for some of the decreased fatigue in patients early after limb disuse because activation deficits resolved by 5w-R. Clinically, these results suggest that traditional measures of strength may not completely reflect the resolution of a patient's impairments. Supported by NIH-RO1HD37645, NIHRO1HD40850, 2P41RR02305.

Muscle Activation Deficits During Fatigue after Limb Disuse

1890 PURPOSE: To determine the extent of plantarflexor muscle activation deficits during fatigue in patients after immobilization. METHODS: Six patients with surgically stabilized, unilateral ankle fractures and 6 healthy subjects participated. Patients were immobilized for 8 weeks, followed by 10 weeks of rehabilitation. Isometric plantarflexion torque was measured at 1 week (1w-R), 5 weeks (5w-R) and 10 weeks (10w-R) of rehabilitation. Subjects performed maximal voluntary isometric contractions (MVIC) with burst superimposition (100ms; 100pps) to assess muscle activation. Fatigue testing involved a 90 second, sustained MVIC of the plantarflexors, with burst superimposition at the beginning, middle, and end. Muscle activation was quantified using the central activation ratio (CAR), which was calculated by dividing the maximum voluntary force by the maximum force produced with electrical stimulation. A CAR of 1.0 indicates full muscle activation by the central nervous system. A fatigue index (final/initial force) was used quantify the extent of muscle fatigue. T-tests were used for all comparisons. RESULTS: At 1 wk-R, the involved leg fatigued less than 5%, while the uninvolved leg fatigued almost 50% (p<0.05). At 5w-R and 10w-R, the involved leg fatigued between 20 and 25%. During the nonfatigued state at 1wk-R, there were significant differences in muscle activation between the involved and uninvolved limbs (CAR = 0.98 vs. 0.79) (p<0.05), which resolved by 5w-R (0.93) and 10w-R (0.96). Decreases in CAR during the fatigue test were minimal (<0.1) for all subjects for both the involved and uninvolved legs. Torque deficits present in the involved legs at 1w-R, recovered to normal by 10w-R (p<0.05). CONCLUSION: Patients experienced less muscle fatigue in their involved leg, early after limb disuse. Fatigability did not recover to normal levels even after 10 weeks of rehabilitation, despite the complete restoration of torque and muscle activation deficits. Initial muscle activation deficits can only account for some of the decreased fatigue in patients early after limb disuse because activation deficits resolved by 5w-R. Clinically, these results suggest that traditional measures of strength may not completely reflect the resolution of a patient's impairments. Supported by NIH-RO1HD37645, NIHRO1HD40850, 2P41RR02305.