Dorsiflexion of the Human Ankle as it Relates to Ski Boot Design in Downhill Skiing

1987 ◽  
Vol 31 (10) ◽  
pp. 1128-1132
Author(s):  
Jasper E. Shealy ◽  
David A. Miller
Keyword(s):  
Weight Bearing ◽  
Voluntary Contraction ◽  
Independent Variables ◽  
Safe Level ◽  
Downhill Skiing ◽  
Reasonable Limit ◽  
The Mean ◽  
Forward Falls ◽  
Extended Posture ◽  
Current Standards

This study is part of an on-going series of studies that relate to Alpine or Downhill Ski Boot Design. In current Alpine skiing, the ski boot is an integral part of the ski boot-binding system. One of the roles of the ski boot is to protect the ankle from excessive dorsiflexion during forward falls, as the ski boot is levered out of the heel binding. A boot designer needs to know what the ranges of dorsiflexion are for human ankles so that the allowable forward flex built into the ski boot will not exceed some specified level. That specified level should be such that a large part of the population will not exceed a safe level of dorsiflexion. The stiffening of the ankle by voluntary contraction of the muscles that control the ankle joint cannot be relied upon since the reaction time to contract the muscles will be greater than the time available to the skier under many circumstances. This study looks at the maximum voluntary dorsiflexion of a group of people (n=64) similar to a skiing population. The anatomical and biomechanical posture of the subjects was intended to represent typical skiing situations, therefore the subjects were measured in a weight bearing, flexed knee, upright posture. The age, gender, height, weight and skiing experience of the subjects was recorded as independent variables. The maximum voluntary dorsiflexion of the ankle was the dependent variable. 10 subjects were measured while the knee was kept in a straight or extended posture. The analysis indicates that there is no statistically significant relationship between dorsiflexion and any of the independent variables. The mean dorsiflexion was 42.7 degrees, the 5th% value was 28.5 and the 95th% was 56.7 degrees. The straight knee posture reduces the effective dorsiflexion by 8.5 degrees. Current standards permit as much as 40 to 45 degrees dorsiflexion. The implications are that current standards are excessive, a reasonable limit would be something under 30 degrees. Such a limit, or less, is consistent with the maximum dorsiflexion found in most current ski boots.

scholarly journals Non-locking buttress plate in distal tibial metaphyseal fractures

2018 ◽  
Vol 1 (2) ◽  
pp. 87-91
Author(s):  
Norman Lamichhane ◽  
Bhogendra Bahadur KC ◽  
Chandra Bahadur Mishra ◽  
Sabita Dhakal
Keyword(s):  
Soft Tissue ◽  
Weight Bearing ◽  
Delayed Union ◽  
Full Weight Bearing ◽  
Distal Fibula ◽  
Fibula Fracture ◽  
Group A ◽  
The Mean ◽  
Group B ◽  
Metaphyseal Fractures

Background: Treatment of distal tibial metaphyseal fractures is often challenging and no single technique has been unanimously advocated. Open reduction and internal fixation with plates and screws allows better restoration of anatomical alignment but with more soft tissue complication. Simultaneous fixation of the fibula is not universally carried out. This study aims at evaluation of the outcome of plating technique and the effect of fixation of fibula fracture in treatment of distal tibial metaphyseal fractures. Material and methods: Thirty-one cases (14 cases in Group A with concomitant distal fibula fracture and 17 cases in Group B without distal fibula fracture) were analyzed retrospectively for the mean duration of full weight bearing, mean union time and complications, and compared. Results: The mean time for full weight bearing and radiological union in our study was 14.2 weeks (15.9 in Group A and 13.1 in Group B) and 23.8 weeks (26.6 in Group A and 21.5 in Group B) respectively. 16.1% of cases had post-operative complications including one case of deep infection and malalignment of 6 degree varus (following delayed union) was seen in one case of Group A. Range of motion (ROM) at ankle was not problem in any of the cases except the one delayed union which had 5 degrees of dorsiflexion and 15 degrees of plantiflexion. Conclusion: Open reduction and internal fixation with plate and screws in distal tibial metaphyseal fracture is more economic means of treatment modality with comparable incidence of post-union malalignment and union time,though more soft tissue complications compared to other modalities. Fixation of fibula fracture aids in reducing the incidence of malalignment.

Mean Temperature Difference Charts for Air Coolers

1983 ◽  
Vol 105 (3) ◽  
pp. 592-597 ◽  
Author(s):  
A. Pignotti ◽  
G. O. Cordero
Keyword(s):  
Heat Transfer ◽  
Heat Capacity ◽  
Temperature Difference ◽  
Optimization Technique ◽  
Independent Variables ◽  
Mean Temperature ◽  
Air Cooler ◽  
The Mean ◽  
The One ◽  
Water Ratio

Computer generated graphs are presented for the mean temperature difference in typical air cooler configurations, covering the combinations of numbers of passes and rows per pass of industrial interest. Two sets of independent variables are included in the graphs: the conventional one (heat capacity water ratio and cold fluid effectiveness), and the one required in an optimization technique of widespread use (hot fluid effectiveness and the number of heat transfer units). Flow arrangements with side-by-side and over-and-under passes, frequently found in actual practice, are discussed through examples.

scholarly journals ASSESSMENT OF PHYSICA L ACT IVITY OF MEMBERS OF THE HELICO PTER EMERGENCY MEDICA L SERVICE (HEMS)

2019 ◽  
Vol 7 (2) ◽  
pp. 91-98
Author(s):  
Agata Gaździńska ◽  
Paweł Jagielski ◽  
Robert Gałązkowski
Keyword(s):  
Physical Activity ◽  
Medical Service ◽  
Helicopter Emergency Medical Service ◽  
Team Members ◽  
Winter Sport ◽  
Study Population ◽  
Downhill Skiing ◽  
The Mean ◽  
The Relationship ◽  
Financial Issues

The aim: Assessment of physical activity of members of the Helicopter Emergency Medical Service. Material and methods: The study was conducted in a group of 131 people (65 paramedics, 66 pilots), members of HEMS teams from all bases in Poland, aged 27-59. The characteristics of physical activity was obtained using the author’s questionnaire. Results: The mean age of the study population was 42.73 ± 9.58 years. Pilots were significantly older than paramedics and had significantly higher BMI values (p < 0.05). No significant relationship between the age and BMI in the analyzed groups was found (p > 0.05), while the relationship between the frequency of physical activity and BMI was demonstrated. 70% of subjects undertook physical activity less than three times a week. The most frequently chosen forms were cycling, walking and swimming. Paramedics statistically significant more often than pilots chose wall climbing (p = 0.001). Downhill skiing (61%) was the most common declared winter sport played by pilots, while hiking in the mountains – by paramedics (49%). The most important reason for pilots to take up physical activity was concern for their health (47%), while for paramedics – the pleasure (63%). Paramedics statistically significant more often than pilots indicated a large number of other activities (90.6 vs. 74.2%) and financial issues (18.8 vs. 6.1%) as barriers that prevented more involvement in physical activities. Conclusions: The frequency of physical activity undertaken by HEMS members is insufficient. Low physical activity of HEMS team members has an adverse effect on their nutritional status. It is necessary to take initiatives to promote physical activity in this professional group.

scholarly journals Intercalary reconstruction of femur after tumour resection: is a vascularized fibular autograft plus allograft a long-lasting solution?

2018 ◽  
Vol 100-B (3) ◽  
pp. 378-386 ◽  
Author(s):  
D. A. Campanacci ◽  
F. Totti ◽  
S. Puccini ◽  
G. Beltrami ◽  
G. Scoccianti ◽  
...  
Keyword(s):  
Weight Bearing ◽  
Young Patients ◽  
Bone Tumour ◽  
Full Weight Bearing ◽  
Tumour Resection ◽  
Fibular Graft ◽  
Musculoskeletal Tumor Society ◽  
Long Term Outcome ◽  
The Mean

Aims After intercalary resection of a bone tumour from the femur, reconstruction with a vascularized fibular graft (VFG) and massive allograft is considered a reliable method of treatment. However, little is known about the long-term outcome of this procedure. The aims of this study were to determine whether the morbidity of this procedure was comparable to that of other reconstructive techniques, if it was possible to achieve a satisfactory functional result, and whether biological reconstruction with a VFG and massive allograft could achieve a durable, long-lasting reconstruction. Patients and Methods A total of 23 patients with a mean age of 16 years (five to 40) who had undergone resection of an intercalary bone tumour of the femur and reconstruction with a VFG and allograft were reviewed clinically and radiologically. The mean follow-up was 141 months (24 to 313). The mean length of the fibular graft was 18 cm (12 to 29). Full weight-bearing without a brace was allowed after a mean of 13 months (seven to 26). Results At final follow-up, the mean Musculoskeletal Tumor Society Score of 22 evaluable patients was 94% (73 to 100). Eight major complications, five fractures (21.7%), and three nonunions (13%) were seen in seven patients (30.4%). Revision-free survival was 72.3% at five, ten, and 15 years, with fracture and nonunion needing surgery as failure endpoints. Overall survival, with removal of allograft or amputation as failure endpoints, was 94.4% at five, ten, and 15 years. Discussion There were no complications needing surgical revision after five years had elapsed from surgery, suggesting that the mechanical strength of the implant improves with time, thereby decreasing the risk of complications. In young patients with an intercalary bone tumour of the femur, combining a VFG and massive allograft may result in a reconstruction that lasts a lifetime. Cite this article: Bone Joint J 2018;100-B:378–86.

scholarly journals Dynamic Pedobarography Shows Pain Avoidance Gait of Symptomatic Severe Flatfoot Patient

2018 ◽  
Vol 3 (2) ◽  
pp. 2473011418S0001
Author(s):  
Woo-Chun Lee ◽  
Chihoon Ahn ◽  
Ji-Beom Kim ◽  
Mu Hyun Kim
Keyword(s):  
Plantar Pressure ◽  
Weight Bearing ◽  
Metatarsal Head ◽  
Assessment System ◽  
Medial Longitudinal Arch ◽  
Head Elevation ◽  
Radiographic Parameters ◽  
Longitudinal Arch ◽  
Bearing Load ◽  
The Mean

Category: Basic Sciences/Biologics, Midfoot/Forefoot Introduction/Purpose: In the flatfoot patients, collapsed medial longitudinal arch during gait induced pain and it results decreased center of progression excursion index(CPEI) in dynamic pedobarography. Although the CPEI decreased is pathologic gait of flatfoot patients, range of the CPEIs is wide even in similar severity of flatfoot patients. We hypothesized that some flatfoot patients inverted forefoot or elevated first metatarsal head during gait for avoiding the pain from collapsed medial longitudinal arch, which resulted wide range of the CPEIs in flatfoot patients. The purposes of this study were to investigate the incidence of forefoot inversion and 1st metatarsal head elevation during gait in severe symptomatic flatfoot patients, and to confirm whether forefoot inversion and 1st metatarsal head elevation increases the CPEI, by using the dynamic pedobarography. Methods: We retrospectively evaluated patients who underwent surgery for flatfoot in our clinic from January, 2017 to May, 2017. Before surgery, all patients underwent plain weight-bearing radiographs and dynamic pedobarography by using in-shoe plantar pressure assessment system (Tekscan, Inc., South Boston, MA). Radiographic parameters, talonavicular coverage angle, Meary angle and moment arm, and the CPEI in dynamic pedobarogrpahy were measured. The forefoot inversion and the 1st metatarsal head elevation were defined when sum of 3rd-4th and 5th submetatarsal plantar pressure was higher than sum of 1st and 2nd submetatarsal plantar pressure, and when 2nd submetatarsal plantar pressure was higher than 1st submetatarsal plantar pressure, respectively. Correlations between the radiographic parameters and the CPEI were investigated. Incidence of the forefoot inversion and the 1st metatarsal head elevation was investigated. The CPEIs in flatfeet with forefoot inversion or 1st metatarsal head elevation were compared with those in flatfeet without these pain avoidance gait. Results: Twenty-eight flatfeet from 28 patients were included in the present study. The average age of patients was 42.3 years (range: 19-71). Means of the three radiographic parameters and the CPEI of the 28 flatfeet were listed at table.1. There was no significant correlation between the CPEI and the three radiographic parameters.(Table.2) The incidence of forefoot inversion and 1st metatarsal head elevation were 11%(3 feet), 54%(15 feet) respectively. The mean CPEI of the flatfeet with forefoot inversion or 1st metatarsal head elevation was 8(range: -10 – 18), and the mean CPEI of the flatfeet without these two compensations was 5 (range: -3 – 12). The CPEI in the flatfeet with the two compensations was significant larger than that of the flatfeet without the two compensations. (P=0.027) Conclusion: In the present study, forefoot inversion or 1st metatarsal head elevation were happened in 65% of symptomatic flatfoot patients. These two pain avoidance gait shifts weight-bearing load laterally, which decreases collapsing medial longitudinal arch and pain on the flatfoot. Because lateral shifting of weight-bearing load increases the CPEI, flatfoot patients with these two gaits showed high the CPEI. Therefore, the degree of the CPEIs are various even in similar severity of flatfoot and are not correlated with the severity of the flatfoot. Clinicians should consider these pain avoidance gait of flatfoot patients when they interpret a dynamic pedobarography of flatfoot.

scholarly journals Radiographic Outcomes after Fixation of Distal Metatarsal Osteotomy for Hallux Valgus Using a Tension Band Construct

2019 ◽  
Vol 4 (4) ◽  
pp. 2473011419S0042
Author(s):  
Alexander Volpi ◽  
Robert Zbeda ◽  
Christopher Katchis ◽  
Lon Weiner ◽  
Stuart Katchis
Keyword(s):  
Hallux Valgus ◽  
Postoperative Period ◽  
Weight Bearing ◽  
Line Tension ◽  
Tension Band ◽  
Metatarsal Osteotomy ◽  
First Metatarsal ◽  
Distal Metatarsal Osteotomy ◽  
The Mean

Category: Bunion Introduction/Purpose: Hallux valgus is a common deformity of the forefoot. There are over 130 procedures described to correct hallux valgus. Classically, the treatment of mild to moderate hallux valgus is with a distal metatarsal osteotomy. A variety of fixation techniques have been described for use with this osteotomy most of which require partial or non-weight bearing until the osteotomy is healed. Tension Band fixation is a well-known principle in orthopedic surgery. The goal of the present study is to radiographically assess the maintenance of distal first metatarsal osteotomy fixation using a novel tension band device (Re+Line tension band bunion plate system, Nextremity Solutions) with immediate post-operative weight-bearing. Methods: The patient database for one surgeon was retrospectively reviewed for patients that underwent hallux valgus correction with the Re+Line tension band device between 2014 and 2017. Postoperative protocol included a soft dressing, firm surgical shoe, and weight-bearing as tolerated with a cane. Patients were excluded if fixation was achieved with something other than a tension band construct. Radiographs were obtained and reviewed retrospectively by 3 authors. Pre and postoperative hallux valgus (HVA) and intermetatarsal angles (IMA) were measured as described previously in the literature, and the changes in correction compared. Maintenance of correction and hardware integrity were assessed at final follow-up after weight bearing as tolerated in a surgical shoe in the postoperative period. Statistical analysis was performed using a Wilcoxon signed-rank test for the changes in HVA and IMA. Results: There was a total of 72 patients and 76 toes that underwent hallux valgus correction with a tension band construct, at a mean follow-up of 4.36 months. 68 of 72 patients were female. The average age was 60.8 years old. The mean preoperative HVA was 27.1 degrees. The mean postoperative HVA was 6.14 degrees, with a mean correction of 20.22 degrees (p<0.001). The mean preoperative IMA was 14.14 degrees. The mean postoperative IMA was 6.10 degrees, with a mean correction of 7.98 degrees (p<0.001). There was loss of reduction found in 6 of 76 toes (7.89%).There were zero cases of hardware failure. All osteotomies healed at final follow-up. Conclusion: This study shows successful radiographic outcome after hallux valgus correction using a tension band construct and allowing immediate full weight-bearing in a surgical shoe in the postoperative period. Significant deformity correction was achieved and maintained and all osteotomies healed. The Re+Line tension band bunion correction system can be safely used as a successful option to fix distal first metatarsal osteotomies, while allowing patients to fully weight bear in a surgical shoe postoperatively and potentially return to activities faster than when using traditional fixation methods. Future studies are needed to assess functional outcomes and patient satisfaction with this novel technique.

scholarly journals Radiological Outcomes of Third Generation Minimally Invasive Chevron Akin Osteotomies (MICA) for Hallux Valgus

2020 ◽  
Vol 5 (4) ◽  
pp. 2473011420S0032
Author(s):  
Thomas L. Lewis ◽  
Robbie Ray; David Gordon
Keyword(s):  
Minimally Invasive ◽  
Hallux Valgus ◽  
Weight Bearing ◽  
Case Series ◽  
Deformity Correction ◽  
Third Generation ◽  
Radiographic Measurements ◽  
Significant Difference ◽  
Patient Reported ◽  
The Mean

Category: Bunion Introduction/Purpose: Minimally invasive surgery for hallux valgus has significantly increased in popularity recently due to smaller incisions, reduced soft tissue trauma, and the ability to achieve large deformity corrections compared to traditional treatments. This study aimed to investigate the radiological outcomes and degree of deformity correction of the intermetatarsal angle (IMA) and the hallux valgus angle (HVA) following third generation (using screw fixation) Minimally Invasive Chevron and Akin Osteotomies (MICA) for hallux valgus. Methods: A single surgeon case series of patients with hallux valgus underwent primary, third generation MICA for hallux valgus. Pre- and post-operative (6 weeks after surgery) radiological assessments of the IMA and HVA were based on weight-bearing dorso-plantar radiographs. Radiographic measurements were conducted by two foot & ankle fellowship trained consultant surgeons (RR, DG). Paired t-tests were used to determine the statistically significant difference between pre- and post-operative measurements. Results: Between January 2017 and December 2019, 401 MICAs were performed in 274 patients. Pre- and post-operative radiograph measurements were collected for 348 feet in 232 patients (219 female; 13 male). The mean age was 54.4 years (range 16.3-84.9, standard deviation (s.d.) 13.2). Mean pre-operative IMA was 15.3° (range 6.5°-27.0°, s.d. 3.4°) and HVA was 33.8° (range 9.3°-63.9°, s.d. 9.7°). Post-operatively, there was a statistically significant improvement in radiological deformity correction; mean IMA was 5.3° (range -1.2°-16.5°, s.d. 2.7°, p<0.001) and mean HVA was 8.8° (range -5.2°-24.0°, s.d. 4.5°, p<0.001). The mean post-operative reduction in IMA and HVA was 10.0° and 25.0° respectively. Conclusion: This is the largest case series demonstrating radiological outcomes following third generation Minimally Invasive Chevron and Akin Osteotomies (MICA) for hallux valgus to date. These data show that this is an effective approach at correcting both mild and severe hallux valgus deformities. Longer term radiological outcome studies are needed to investigate whether there is any change in radiological outcomes. Correlation with patient reported outcomes is planned.

Mechanical behavior of skeletal muscle during intermittent voluntary isometric contractions in humans

1997 ◽  
Vol 83 (5) ◽  
pp. 1557-1565 ◽  
Author(s):  
N. K. Vøllestad ◽  
I. Sejersted ◽  
E. Saugen
Keyword(s):  
Skeletal Muscle ◽  
Mechanical Behavior ◽  
Recovery Period ◽  
Oscillation Amplitude ◽  
Voluntary Contraction ◽  
Knee Extensors ◽  
Isometric Contractions ◽  
Target Force ◽  
The Mean ◽  
Type Of Exercise

Vøllestad, N. K., I. Sejersted, and E. Saugen. Mechanical behavior of skeletal muscle during intermittent voluntary isometric contractions in humans. J. Appl. Physiol. 83(5): 1557–1565, 1997.—Changes in contractile speed and force-fusion properties were examined during repetitive isometric contractions with the knee extensors at three different target force levels. Seven healthy subjects were studied at target force levels of 30, 45, and 60% of their maximal voluntary contraction (MVC) force. Repeated 6-s contractions followed by 4-s rest were continued until exhaustion. Contractile speed was determined for contractions elicited by electrical stimulation at 1–50 Hz given during exercise and a subsequent 27-min recovery period. Contraction time remained unchanged during exercise and recovery, except for an initial rapid shift in the twitch properties. Half relaxation time (RT1/2) decreased gradually by 20–40% during exercise at 30 and 45% of MVC. In the recovery period, RT1/2 values were not fully restored to preexercise levels. During exercise at 60% MVC, the RT1/2 decreased for twitches and increased for the 50-Hz stimulation. In the recovery period after 60% MVC, RT1/2 values declined toward those seen after the 30 and 45% MVC exercise. The force oscillation amplitude in unfused tetani relative to the mean force increased during exercise at 30 and 45% MVC but remained unaltered during the 60% MVC exercise. This altered force-fusion was closely associated with the changes in RT1/2. The faster relaxation may at least partly explain the increased energy cost of contraction reported previously for the same type of exercise.

Radiographic Comparison of the Mechanical Axis Including Calcaneus to the Conventional Mechanical Axis in Medial Unicompartmental Knee Arthroplasty

2019 ◽  
Author(s):  
Yuichi Kuroda ◽  
Koji Takayama ◽  
Kazunari Ishida ◽  
Shinya Hayashi ◽  
Shingo Hashimoto ◽  
...  
Keyword(s):  
Knee Arthroplasty ◽  
Unicompartmental Knee Arthroplasty ◽  
Tibial Component ◽  
Mechanical Axis ◽  
Weight Bearing ◽  
Postoperative Outcome ◽  
Diagnostic Study ◽  
Hindfoot Alignment ◽  
Unicompartmental Knee ◽  
The Mean

AbstractSince a hindfoot alignment is not included in the conventional mechanical axis (hip–ankle [HA] line), a mechanical axis including the calcaneus (hip–calcaneus [HC] line) has recently attracted attention as an alternative weight-bearing line. However, there are few reports on unicompartmental knee arthroplasty (UKA) regarding the HC line. Therefore, this study aimed to compare postoperative alignments after UKA between the HA line and the HC line. Postoperatively, HC radiographs were taken in 88 consecutive patients who underwent medial UKA. The hip–knee–ankle (HKA) and hip–knee–calcaneus (HKC) angles were compared in the same patient. Regarding tibial inclination, the conventional tibial component–ankle (TCA) angle was compared with reference to the HC line (tibial component–calcaneus [TCC] angle). The mean postoperative HKA and HKC angles were 2.8 ± 2.7 and 2.0 ± 2.5 degree, respectively. The mean postoperative TCA and TCC angles were 87.7 ± 2.1 and 88.5 ± 2.1 degree, respectively. There were significant differences between the two groups in both lower limb alignment and tibial component angle. The present study indicated that the HKC and the TCC angles significantly decreased the varus alignment by approximately 1 degree compared with the HKA and TCA angles. Neutral in the HA line corresponds to valgus in reference to the HC line, which may result in overcorrection. Surgeons should consider evaluating the HC line in place of the HA line, which may affect preoperative planning and postoperative outcome during UKA. This is a Level II, diagnostic study.

scholarly journals 2019 IFFAS Award for Excellence Winner: Peri-Prosthetic Cysts and Alignment in Total Ankle Replacement: A 3-D, Weight Bearing Topographical Study

2019 ◽  
Vol 4 (4) ◽  
pp. 2473011419S0004
Author(s):  
Francois Lintz ◽  
Jef Mast ◽  
Nazim Mehdi ◽  
Alessio Bernasconi ◽  
Cesar de Cesar Netto ◽  
...  
Keyword(s):  
Weight Bearing ◽  
Total Ankle Replacement ◽  
Coronal Plane ◽  
Unequal Distribution ◽  
Hindfoot Alignment ◽  
Cyst Volume ◽  
Ankle Replacement ◽  
The Mean ◽  
The Difference

Category: Ankle, Ankle Arthritis Introduction/Purpose: Peri-prosthetic cysts (PPC) in Total Ankle Replacement (TAR) are a common failure cause but the mechanisms of their development remains unclear. One possible explanation could be hindfoot malalignment and subsequent unequal distribution of load inside the joint. However, how residual malalignment influences the evolution of PPC remains unclear. Computed tomography (CT) has demonstrated superiority on conventional radiography in the follow up of PPC. Weight Bearing CT (WBCT), by combining 3D imaging and weight bearing measurements seems a valid tool to investigate this further. The objective for this work was to study the effects of residual hindfoot deformity on the distribution of PPC in the coronal plane. We hypothesized that cysts would be found predominantly medially in varus configuration, and laterally in valgus configuration. Methods: Retrospective comparative study, ethics committee approved. Forty-eight cases of TAR were included, with relevant demographics. Inclusion criteria were cases of primary TAR with available WBCT imaging of their ankle as part of normal follow up. Exclusion criteria were subsequent implant revision or cyst grafting. In each case, the localization and size of PPC’s were documented and their volume calculated by approximation of the closest ellipsoid. Hindfoot alignment was evaluated by the percentage Foot Ankle Offset (FAO) (foot-length normalized 3D ratio between the midline of the foot and the center of the ankle) using a WBCT dedicated semi-automatic software. The mean FAO value with 95%CI for the population was calculated. The difference in medial and lateral cyst volume defined by their position relative to the median axis in the coronal plane was compared in varus and valgus cases by a Mann-Whitney non-parametric test for unpaired samples. Results: Demographic distributions of the series were 32% female, mean age 65 (45-85) years. Mean FAO value was 0.12% (95%CI -1.09 to 1.33). Mean follow up was 43 months (6 to 239). The mean total cyst volume per case was 1190,7 mm3. In varus cases (defined by FAO<-1.09%), the volume of medial cysts was greater than laterally by a mean 197 mm3, whereas in valgus cases (defined by FAO>1.33%), the volume of lateral cysts was greater than medially by a mean 332 mm3. The difference was statistically significant (p<0.05). There was a weak, significant positive correlation (r=0.25, p<0,001) between FAO and total cyst volume and a moderate, significant correlation (r=0,56, p<0,001) between time to follow up and total cyst volume. Conclusion: Our hypothesis was confirmed. Periprosthetic cysts volume in this series of primary TAR was found to be relatively greater medially in postoperative varus configurations and vice-versa laterally in valgus. This confirms a possible correlation between the direction of residual hindfoot malalignment and the coronal localization of PPC in TAR, although this is certainly not the only pathophysiologic factor involved in PPC onset. Weightbearing CT may be helpful in Total Ankle Replacement follow up, in order to early detect PPC development and possibly to identify situations at risk of a more rapid evolution.

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