Intraoperative pedography: a validated method for static intraoperative biomechanical assessment

Robotic-assisted foot and ankle surgery: a review of the present status and the future

The surgical application of robotics has increased significantly since its first application in 1985 for a brain biopsy acquisition. Robotic-assisted surgery has been one of the viable options in various surgical areas, and also in orthopaedic surgery. Robotic-assisted orthopaedic surgery has gained popularity as a mean of improving accuracy, reducing complications and achieving better patient satisfaction. Numerous clinical research studies have demonstrated advantages of robotic-assisted orthopaedic surgery, however, most of that researches were about the total knee arthroplasty, total hip arthroplasty and spine surgery. The application of robotic technology in foot and ankle surgery is in a very nascent stage. Furthermore, there has been little research on intraoperative use of robotics in foot and ankle surgery in literature. A review of previous preclinical studies in foot and ankle robotics and clinical research studies in various fields of robot-assisted orthopaedic surgery shows that its potential application and benefits over conventional techniques, such as total ankle arthroplasty, minimally invasive surgery for foot and ankle trauma or other corrective procedure, and intraoperative biomechanical testing. More studies on practical application of robotic technology to surgical procedure in the field of foot and ankle surgery are needed to confirm its clinical usefulness and cost effectiveness.

Development of Intraoperative Plantar Pressure Measurement System Considering Weight Bearing Axis and Center of Pressure

To prevent postoperative complications in corrective surgery for foot deformities such as hallux valgus and pes planus, it is critical to quantitatively predict the postoperative standing-position plantar pressure distribution during the operation. The authors have previously proposed an intraoperative plantar pressure measurement system (IPPM) that allows for the measurement of a supine patient’s plantar pressure distribution that is equivalent to that in the standing position. This system consists of an IPPM device comprising of a force plate and pressure distribution sensor, an optical three-dimensional position measurement device, a navigation monitor, and a PC. The plantar pressure distribution in the standing position is reproduced by navigating the operator, as he or she presses the IPPM device against the patient’s sole so that the weight-bearing axis (floor reaction force vector) and femoral head center are as close to each other as possible. However, in our previous study, the reproducibility of the standing position plantar pressure distribution was insufficient. Therefore, in the present study, we add a navigational function that can be used to bring the centers of pressure in the standing position and under measurement, as well as to correct the IPPM’s self-weight in the measured force. The improved device was used in an experiment with nine healthy subjects, and the similarity of the plantar pressure distribution in the standing and supine positions was evaluated using normalized cross-correlation, yielding an average of 0.90. Furthermore, in an evaluation experiment with ten orthopedic surgeons, it was observed that using the system reproduced the plantar pressure distribution significantly better than when the system was not used. These results indicate that the present system can predict the plantar pressure distribution in the standing position. We believe that this system can contribute to reducing complications after foot surgery.

Weight-bearing cone-beam computed tomography in the foot and ankle specialty: where we are and where we are going - an update

Cone-beam computed tomography (CBCT) has been applied in dentistry and medicine for nearly two decades. Its application in the foot and ankle specialty has grown exponentially in recent years. Weight-bearing CBCT allows clinicians to obtain weight-bearing images that can be viewed in all three planes and to construct three-dimensional models, similar to those constructed from traditional CT scans, as well as exposing patients to less radiation than do traditional CT scans. This technology has revolutionized diagnoses, improving the understanding of various lesions and surgical planning in the foot and ankle specialty. Ongoing studies of the use of weight-bearing CBCT in foot and ankle surgery are focused on fully automated and semi-automated three-dimensional measurements, as well as bone segmentation, mapping of the distances/orientation of the joints, and the production of customized implants. The aims of this review article are to show the evolution of this emerging tool in the foot and ankle specialty, to update those in related specialties on its use in current clinical practice, and to indicate where the research community is heading.

Development of intraoperative plantar pressure measuring system considering weight bearing axis

PURPOSE

Surgical reconstructions in three dimensions are needed for treatment of foot and ankle deformities. However, surgical results might be influenced by the skill and experience of doctors which complement the limited information for reconstructions in three dimensions. To solve these, studies were carried out to measure plantar pressure distribution during surgery. Though, it was impossible to accurately measure plantar pressure distribution accurately during operation. Therefore, we proposed an intraoperative plantar pressure measurement (IPPM) device that enables proper navigation in the push direction.

METHODS

For this purpose, first, we investigated how the physiological load axis passes through the human body to identify the pushing direction of the pressure sensor of the device toward the patient's foot. In particular, we hypothesized that the physiological load axis passes through the femoral head center and we evaluated this in a measurement experiment with nine healthy subjects. Second, based on these results, we developed the IPPM device that has two force sensors to identify the pushing direction toward the femoral head center and a conductive ink sensor to measure plantar pressure distribution. Finally, we conducted the experiments with nine healthy subjects and two users.

RESULTS

From the first experimental results, the physiological load axis was found to pass through the femoral head center in normal standing posture. From the evaluation experiment, there are no significant differences statistically in plantar pressure distributions between the conditions of using IPPM device and without using it for both a medical student and a surgeon. However, in some cases the plantar pressure distribution can be reproduced similarly to that of the standing posture, and also from the evaluation experiment concerning the relation between CoP position and NCC, the NCC tends to increase when the position of the CoP is closer to that at the standing posture.

CONCLUSION

The IPPM device has possibility to reproduce the plantar pressure distribution during surgery and prevent the recurrence of surgical complications.

Weightbearing CT in normal hindfoot alignment - Presence of a constitutional valgus?

BACKGROUND

The normal hindfoot angle is estimated between 2° and 6° of valgus in the general population. These results are solely based on clinical findings and plain radiographs. The purpose of this study is to assess the hindfoot alignment using weightbear CT.

METHODS

Forty-eight patients, mean age of 39.6±13.2 years, with clinical and radiological absence of hindfoot pathology were included. A weightbear CT was obtained and allowed to measure the anatomical tibia axis (TAx) and the hindfoot alignment (HA). The HA was firstly determined using the inferior point of the calcaneus (HA_IC). A density measurement of this area was subsequently performed to analyze if this point concurred with an increased ossification, indicating a higher load exposure. Secondly the HA was determined by dividing the calcaneus in the long axial view (HALA) and compared to the (HA_IC) to point out any possible differences attributed to the measurement method. Reliability was assessed using an intra class correlation coefficient (ICC).

RESULTS

The mean HA_IC equaled 0.79° of valgus±3.2 (ICC_{HA IC}=0.73) with a mean TAx of 2.7° varus±2.1 (ICCTA=0.76). The HALA equaled 9.1° of valgus±4.8 (ICCHA LA=0.71) and differed significantly by a P<0.001 from the HA_IC, which showed a more neutral alignment. Correlation between both was shown to be good by a Spearman's correlation coefficient of 0.74. The mean density of the inferior calcaneal area equaled 271.3±84.1 and was significantly higher than the regional calcaneal area (P<0.001).

CONCLUSIONS

These results show a more neutral alignment of the hindfoot in this group of non-symptomatic feet as opposed to the generally accepted constitutional valgus. This could have repercussion on hindfoot position during fusion or in quantifying the correction of a malalignment. The inferior calcaneus point in this can be used during pre-operative planning of a hindfoot correction as an anatomical landmark due to its shown influence on load transfer.

Combination of PedCAT Weightbearing CT With Pedography Assessment of the Relationship Between Anatomy-Based Foot Center and Force/Pressure-Based Center of Gravity

BACKGROUND

A customized pedography sensor (Pliance; Novel, Munich, Germany) was inserted into a pedCAT (Curvebeam, Warrington, PA). The aim of this study was to analyze the relative position of the anatomical foot center (FC) and the pedographic center of gravity (COG). The hypothesis was that FC should be a good predictor of mediolateral position of COG but not longitudinal since hindfoot anatomy allows free anteroposterior movement but limited mediolateral movement.

METHODS

In 90 patients (180 feet), a pedCAT scan with simultaneous pedography with full weightbearing in a standing position was performed. The morphology-based definition of the FC was performed with the pedCAT data following the Torque Ankle Lever Arm System (TALAS) algorithm. The force/pressure-based COG was defined with the pedography data using a software-based algorithm. The distance between FC and COG and the direction of a potential shift (distal-proximal, mediolateral) was measured and analyzed. COG motion during data acquisition was recorded and analyzed. Mean age of patients was 53.8 (range, 17-84) years, and 57 (63%) were female.

RESULTS

The distance between FC and COG was 28.7 mm on average (range, 0-60). FC was distal to COG in 175 feet (97%; mean, 27.5 mm; range, -15 to 60) and lateral in 112 feet (62%; mean, 2.0 mm; range, -18 to 20).

CONCLUSIONS

There was a constant and major distal longitudinal shift of COG relative to FC and an inconstant minor mediolateral shift.

CLINICAL RELEVANCE

The data might be taken into consideration for planning and follow-up in foot and ankle surgery.

Matrix-associated stem cell transplantation (MAST) in chondral defects of the 1st metatarsophalangeal joint is safe and effective-2-year-follow-up in 20 patients

The aim of the study was to assess the 2-year-follow-up of matrix-associated stem cell transplantation (MAST) in chondral defects of the 1st metatarsophalangeal joint (MTPJ). In a prospective consecutive non-controlled clinical follow-up study, 20 patients with 25 chondral defect at the 1st MTPJ that were treated with MAST from October 1st, 2011 to March, 30th, 2013 were analysed. The size and location of the chondral defects range of motion (ROM), and the Visual-Analogue-Scale Foot and Ankle (VAS FA) before treatment and at follow-up were registered. Stem cell-rich blood was harvested from the ipsilateral pelvic bone marrow and centrifuged (10min, 1500 RPM). The supernatant was used to impregnate a collagen I/III matrix (Chondro-Guide). The matrix was fixed into the chondral defect with fibrin glue. The age of the patients was 42 years on average (range, 35-62 years). The VAS FA before surgery was 50.5 (range, 18.3-78.4). The defects were located as follows, dorsal metatarsal head, n=12, plantar metatarsal head, n=5, dorsal & plantar, n=8 (two defects, n=5). The defect size was 0.7cm² (range, .5-2.5cm²). ROM was 10.3/0/18.8° (dorsal extension/plantar flexion). All patients completed 2-year-follow-up. VAS FA improved to 91.5 (range, 74.2-100; t-test, p<.01). ROM improved to 34.5/0/25.5 (p=.05). The surgical treatment including MAST led to improved clinical scores and ROM. Even though a control group is missing, we conclude that MAST is a safe and effective method for the treatment of chondral defects of the 1st MTPJ.

In Vivo Plantar Pressures in Adult-Acquired Flatfoot Compared to Control Using an Intraoperative Pedobarographic Device

BACKGROUND

Intraoperative pedobarography has the potential to aid surgical decisions, but no parameters exist to guide its use.

QUESTIONS/PURPOSES

This study compared supine plantar pressures between flatfoot patients and controls using a previously validated intraoperative pedobarographic device and examined associations between supine, walking, and standing plantar pressures.

METHODS

Ten preoperative patients with stage II adult-acquired flatfoot deformity (AAFD) were compared to ten healthy controls. Supine plantar pressures were assessed using the pedobarographic device. Standing and walking plantar pressures were assessed with an EMED-XT sensor array (Novel). Maximum force (MF) and peak pressure (PP) were calculated for nine anatomical foot regions adjusting for age and BMI.

RESULTS

No differences in plantar pressures were found between flatfoot patients and controls in the supine or standing positions. During walking, flatfoot patients had greater MF of the first, second, and third metatarsals (p ≤ 0.018) and greater PP of the first and second metatarsals than controls (p ≤ 0.010). Supine MF and PP were both strongly positively correlated with their respective pressure measurements for both standing and walking in multiple foot regions (p ≤ 0.05, all analyses). Correlations in the first metatarsal region were generally weak and not statistically significant.

CONCLUSION

This device did not show differences in supine plantar pressures of flatfoot patients and healthy subjects, highlighting the limitations of intraoperative devices in guiding flatfoot correction. The differences between flatfoot and controls during walking and the correlations between supine and walking conditions suggest that dynamic plantar pressures are a more useful parameter in guiding flatfoot reconstruction.

Combination of pedCAT® for 3D Imaging in Standing Position With Pedography Shows No Statistical Correlation of Bone Position With Force/Pressure Distribution

pedCAT(®) (CurveBeam, Warrington, PA) is a technology for 3-dimensional (3D) imaging with full weightbearing that has been proved to exactly visualize the 3D bone position. For the present study, a customized pedography sensor (Pliance; Novel, Munich, Germany) was inserted into the pedCAT(®). The aim of our study was to analyze the correlation of the bone position and force/pressure distribution. A prospective consecutive study of 50 patients was performed, starting July 28, 2014. All patients underwent a pedCAT(®) scan and simultaneous pedography with full weightbearing in the standing position. The following parameters were measured on the pedCAT(®) image for the right foot by 3 different investigators 3 times: lateral talo-first metatarsal angle, calcaneal pitch angle, and minimum height of the fifth metatarsal base, second to fifth metatarsal heads, and medial sesamoid. From the pedography data, the following parameters were defined using the standardized software algorithm: midfoot contact area, maximum force of midfoot, maximum force of midfoot lateral, maximum force of entire foot, and maximum pressure of first to fifth metatarsal. The values of the corresponding pedCAT(®) and pedographic parameters were correlated (Pearson). The intra- and interobserver reliability of the pedCAT(®) measurements were sufficient (analysis of variance, p > .8 for each, power >0.8). No sufficient correlation was found between the pedCAT(®) and pedographic parameters (r < 0.05 or r > -0.38).3D bone position did not correlate with the force and pressure distribution under the foot sole during simultaneous pedCAT(®) scanning and pedography. Thus, the bone positions measured with pedCAT(®) do not allow conclusions about the force and pressure distribution. However, the static pedographic parameters also do not allow conclusions about the 3D bone position.one position and force/pressure distribution are important parameters for diagnostics, planning, and follow-up examinations in foot and ankle surgery.

Intraoperative positioning of the hindfoot with the hindfoot alignment guide: a pilot study

BACKGROUND

In a previous study, intraoperative positioning of the hindfoot by visual means resulted in the wrong varus/valgus position by 8 degrees and a relatively large standard deviation of 8 degrees. Thus, new intraoperative means are needed to improve the precision of hindfoot surgery. We therefore sought a hindfoot alignment guide that would be as simple as the alignment guides used in total knee arthroplasty.

METHODS

A novel hindfoot alignment guide (HA guide) has been developed that projects the mechanical axis from the tibia down to the heel. The HA guide enables the positioning of the hindfoot in the desired varus/valgus position and in plantigrade position in the lateral plane. The HA guide was used intraoperatively from May through November 2011 in 11 complex patients with simultaneous correction of the supramalleolar, tibiotalar, and inframalleolar alignment. Pre- and postoperative Saltzman views were taken and the position was measured.

RESULTS

The HA guide significantly improved the intraoperative positioning compared with visual means: The accuracy with the HA guide was 4.5 ± 5.1 degrees (mean ± standard deviation) and without the HA guide 9.4 ± 5.5 degrees (P < .05). In 7 of 11 patients, the preoperative plan was changed because of the HA guide (2 avoided osteotomies, 5 additional osteotomies).

CONCLUSIONS

The HA guide helped to position the hindfoot intraoperatively with greater precision than visual means. The HA guide was especially useful for multilevel corrections in which the need for and the amount of a simultaneous osteotomy had to be evaluated intraoperatively.

LEVEL OF EVIDENCE

Level IV, case series.

Sensitivity of plantar pressure and talonavicular alignment to lateral column lengthening in flatfoot reconstruction

BACKGROUND

Lateral column lengthening (LCL) of the calcaneus is commonly performed as part of correction of the adult acquired flatfoot deformity. Increases in postoperative lateral plantar pressure associated with pain in the lateral aspect of the foot have been reported. The aim of this study was to investigate changes in pressures in the lateral aspect of the forefoot with increments of 6, 8, and 10 mm of LCL in a cadaveric flatfoot model. The hypothesis was that increasing the LCL incrementally by 2 mm will linearly increase the plantar pressures in the lateral aspect of the forefoot.

METHODS

Eight fresh-frozen cadaveric foot specimens were used. A robot compressively loaded the foot to 400 N with a 310-N tensile load applied to the Achilles tendon. A flatfoot model was created by resecting the medial and inferior soft tissues of the midfoot, followed by axial load of 800 N for 100 cycles. Kinematic and plantar pressure data were gathered after the different amounts of LCL (6, 8, and 10 mm) were achieved.

RESULTS

The talonavicular joint demonstrated a median abduction angle of 4.4° in the axial plane and -2.6° in the sagittal plane in the flatfoot condition as compared with the intact condition. The 6, 8, and 10-mm LCLs showed axial correction of talonavicular alignment by -1.4°, -4.9°, and -9.2° beyond that of the intact foot, and sagittal correction of -0.1°, 1.3°, and 2.9°, respectively. LCL of 6, 8, and 10 mm showed consistently increasing lateral forefoot average mean pressure, peak pressure, and contact area.

CONCLUSIONS

LCL in 2-mm increments consistently reduced talonavicular abduction and consistently increased plantar pressure in the lateral aspect of the forefoot.

CLINICAL RELEVANCE

The lateral column should be lengthened judiciously, as a 2-mm difference leads to significant difference not only in angular correction of the talonavicular joint but also with regard to pressure in the lateral aspect of the forefoot.

Arthrorisis with calcaneostop screw in children corrects Talo-1st Metatarsal-Index (TMT-Index)

BACKGROUND

Arthrorisis (other terms: Arthrorhisis or Arthroreisis) with calcaneostop screw is one option for the treatment of flatfoot (Pes abductoplanovalgus) in children. The aim of the study was to analyze the amount of correction (for example Talo-1st Metatarsal-Index (TMT-Index)) and clinical outcome including pedographic assessment.

METHODS

In a prospective consecutive non-controlled clinical follow-up study, all patients that were treated with arthrorisis with calcaneostop screw from September 1st 2006 to August 31st, 2009 were included. One foot was operated at a time, and the contralateral foot was operated 3 months later if indicated. Postoperatively, 15 kg partial weight-bearing was performed for 6 weeks. The screws were removed after 2-year-followup. Assessment was performed before surgery, at two-year-followup, and at 2.5-year-followup. The assessment staging of posterior tibialis insufficiency, radiographs with full weight bearing (TMT-Index), pedography, and Visual-Analogue-Scale Foot and Ankle (VAS FA).

RESULTS

18 patients/31 feet were included in the study (age, 10.6 [8-12], 45% male). No complications were observed. In comparison with the preoperative parameters, the parameters posterior tibialis insufficiency stage, percentage of increased pedographic midfoot contact area and force were decreased, and TMT dorsoplantar/lateral/Index and VAS FA scores were increased at both followups (each p<.05). The parameters did not differ between followups (each p ≥.4).

CONCLUSIONS

All relevant parameters (stage of posterior tibialis insufficiency, TMT dorsoplantar/lateral/Index, pedographic midfoot contact area and force, VAS FA) improved after arthrorisis with calcaneostop screw (before and after screw removal) in pes abductoplanovalgus in children. Since the complication rate is very low, this method allows safe and predictable correction.

Computer aided surgery in foot and ankle: applications and perspectives

PURPOSE

At the beginning of the twenty-first century, the computer has supplemented the possibilities of orthopaedic surgery. This article analyses the feasibility and potential clinical benefit of intraoperative three-dimensional imaging (3D), computer assisted surgery (CAS) and intraoperative pedography (IP) in foot and ankle surgery.

METHODS

The feasibility, accuracy and clinical benefit of 3D, CAS and IP were analysed in ongoing experimental and prospective studies at the institution in which the inventor of IP and principal user of 3D and CAS in foot and ankle surgery operates.

RESULTS

Three dimensional imaging: In approximately one third of the cases, reduction/correction and/or implant position was corrected after intraoperative 3D scan during the same procedure in different prospective, consecutive, non-controlled studies (Level III). CAS: CAS guidance for the correction of deformities of the ankle, hindfoot and midfoot/tarsometatarsal (TMT) joint provided higher accuracy, a faster correction process and better scores at a minimum follow-up of two years in comparison without CAS guidance in a single-centre matched-pair follow-up study (Level II). IP: Additional use of IP as the only difference between two groups with correction and/or arthrodesis at foot and/or ankle led to improved clinical outcome scores at a mean of two years follow-up in a prospective randomised controlled study (Level I).

CONCLUSIONS

Three dimensional imaging provides important information which could not be obtained from two-dimensional C-arm alone. The benefit of CAS is high when improved accuracy may lead to an improved clinical outcome. Intraoperative pedography is useful when intraoperative biomechanical assessment may lead to an immediate improvement of the achieved surgical result.

Lengthening osteotomy of the calcaneus and flexor digitorum longus tendon transfer in flexible flatfoot deformity improves talo-1st metatarsal-Index, clinical outcome and pedographic parameter

Lengthening osteotomy of the calcaneus (LO) and flexor digitorum longus tendon (FDL) transfer to the navicular is one option for the treatment of flexible flatfoot deformity (FD). The aim of the study was to analyse the amount of correction and clinical outcome including pedographic assessment. In a prospective consecutive non-controlled clinical followup study, all patients with FD that were treated with LO and FDL from September 1st 2006 to August 31st, 2009 were included. Assessment was performed before surgery and at 2-year-followup including clinical examination (with staging of posterior tibialis insufficiency) weight bearing radiographs (Talo-1st metatarsal angles (TMT)), pedography (increased midfoot contact area and force) and Visual Analogue Scale Foot and Ankle (VAS FA). 112 feet in 102 patients were analysed (age, 57.6 (13-82), 42% male). In 12 feet (9%) wound healing delay without further surgical measures was registered. All patients achieved full weight bearing during the 7th postoperative week. Until followup, revision surgery was done in 3 patients (fusion calcaneocuboid joint (n=2), correction triple arthrodesis (n=1)). 101 feet (90%) completed 2-year-followup. TMT dorsoplantar/lateral/Index and VAS FA scores were increased, and posterior tibialis insufficiency stage, pedographic midfoot contact area and force percentage were decreased (each p<.05). All relevant parameters (stage of posterior tibialis insufficiency, TMT angles and Index, pedographic midfoot contact area and force percentage, VAS FA) were improved 2 years after LO and FDL transfer to the navicular in FD. The complication rate was low. This method allows safe and predictable correction.

The accuracy of an automasking algorithm in plantar pressure measurements

Masking algorithms provide a way to analyze plantar pressure parameters based on distinct anatomical regions of the foot. No study has addressed their accuracy. The purpose of this study was to determine the accuracy of the Novel® ten-region standard masking algorithm in both dynamic and static measurements in normal feet. Static and dynamic plantar pressure measurements were collected from ten normal subjects (20 ft) with and without 10-mm radiopaque markers placed under the first through fifth metatarsal heads, fifth metatarsal base, and first proximal phalanx. The automask was then applied to subdivide the foot into distinct anatomical areas. Weight-bearing AP radiographs were obtained with and without markers. Plantar pressures and radiographs were overlaid. The percent accuracy of each marker within its appropriate mask region was calculated. The average accuracies of the automasking algorithm regions for dynamic and static measurements, respectively, were 98.8% and 90.4% (1MH), 89.9% and 80.6% (2MH), 98.6% and 81.4% (3MH), 96.8% and 82.3% (4MH), 93.1% and 80.8% (5MH), 97.3% and 92.5% (5MB), and 91.2% and 64.2% (1PPH). Marker presence did not alter foot structure or function as determined by intermetatarsal angles (range, p = 0.361 to p = 0.649) and the center of pressure excursion index (p = 0.727), respectively. The automasking algorithm accurately identifies most foot regions in normal feet, particularly in gait. Such accuracy may be reduced in the setting of foot deformity. Understanding the accuracy of masking algorithms may help guide the interpretation of plantar pressure measurements and ultimately both conservative and operative treatment decisions.

Does alignment in the hindfoot radiograph influence dynamic foot-floor pressures in ankle and tibiotalocalcaneal fusion?

BACKGROUND

The Saltzman-el-Khoury hindfoot alignment view (HAV) is considered the gold standard for assessing the axis from hindfoot to tibia. However, it is unclear whether radiographic alignment influences dynamic load distribution during gait.

QUESTIONS/PURPOSES

We evaluated varus-valgus alignment by the HAV and its influence on dynamic load distribution in ankle and tibiotalocalcaneal (TTC) arthrodesis.

PATIENTS AND METHODS

We clinically assessed 98 patients (ankle, 56; TTC, 42) with SF-36 and American Orthopaedic Foot and Ankle Society (AOFAS) scores, visual hindfoot alignment, HAV angle, and dynamic pedobarography using a five-step method. For comparison, 70 normal feet were evaluated. Minimum followup was 2 years (average, 4.11 years; range, 2-6 years).

RESULTS

The mean HAV angle was -0.8° ± 7.8° for ankle and -1.2° ± 6.9° for TTC arthrodesis. The HAV angle correlated with pedobarographic load distribution (r = 0.35-0.53). Radiographic alignment did not influence SF-36 or AOFAS scores; however, load distribution correlated to qualities of these scores. Visual alignment only predicted the corresponding HAV angle in 48%. To reproduce the dynamic load of healthy subjects, HAV angles of 5° to 10° valgus were needed.

CONCLUSIONS

Visual positioning is inadequate to determine intraoperative positioning and resulted in a varus position with a relatively large SD. The HAV should be used to assess the hindfoot alignment correctly. HAV angles of 5° to 10° valgus are needed to reproduce a physiologic gait pattern.

[Intraoperative pedography]

THE PROBLEM

Intraoperative assessment of the restored or maintained physiological plantar force distribution during foot and ankle corrections is very difficult.

THE SOLUTION

Intraoperative assessment of the restored or maintained physiological plantar force distribution during foot and ankle corrections with intraoperative pedography (IP).

SURGICAL TECHNIQUE

Bilateral pedography with the "Kraftsimulator Intraoperative Pedographie" (KIOP, R-Innovation, Coburg, Germany) and a mat sensor (Pliance, custom-made, Novel, Munich, Germany) in the preparation room under anesthesia. Three measurements each side with a total force corresponding to half of the body weight are performed. Transfer of the patient to the operating room and correction including definitive internal fixation following the planning and findings. Sterile draping of the sensor mat and usage of a sterile KIOP for IP of the operated foot with three measurements, and assessment and comparison with preoperative, contralateral and physiological pedographic findings. When a correction of the force distribution is indicated, modification of the correction and internal fixation and renewed IP.

POSTOPERATIVE MANAGEMENT

IP has no influence on the postoperative management.

RESULTS

IP was validated in an earlier study. In a prospective, randomized, controlled clinical study, the potential clinical benefit of IP in a sufficient number of cases in comparison to cases treated without IP was analyzed. 100 cases were included until April 11, 2008. 52 patients were randomized for the use of IP. Mean interruption of the operative procedure for the IP was 321 +/- 39 s. In 24 of the 52 patients (46%), the correction was modified after IP during the same operation. The changes were done most commonly in midfoot correction arthrodeses (64%), and least commonly in subtalar joint arthrodeses (25%).

Is intraoperative pedography helpful in clinical use--preliminary results of 100 cases from a consecutive, prospective, randomized, controlled clinical study

BACKGROUND

The purpose of this study was to assess the clinical use, and to analyze the potential clinical benefit of intraoperative pedography (IP) in a sufficient number of cases in comparison with cases treated without IP.

METHODS

Patients (age 18 years and older) which sustained an arthrodesis and/or correction of the foot and ankle were included.

RESULTS

One hundred cases were included (ankle correction arthrodesis, n=12; subtalar joint correction arthrodesis, n=14; arthrodesis without correction midfoot, n=15; correction arthrodesis midfoot, n=26; correction forefoot, n=33). Fifty-two patients were randomized for the use of IP. In 24 of the 52 patients (46%), the correction was modified after IP during the same operation.

CONCLUSIONS

In 46% of the cases a modification of the surgical correction was made after IP in the same surgical procedure. Whether IP improve the plantar force distribution of the foot and the mid- or long-term clinical outcome has to be critically analyzed when longer follow-up is completed.

Plantar pressures in patients with and without lateral foot pain after lateral column lengthening

BACKGROUND

Lateral column lengthening, a commonly used adjuvant for the reconstruction of adult flatfoot deformity, can lead to postoperative complaints of lateral plantar pain or discomfort. We hypothesized that patients with such symptoms would have increased lateral plantar pressures when compared with matched controls without these symptoms.

METHODS

Ten subjects who had undergone lateral column lengthening and were experiencing pain or discomfort in the plantar-lateral aspect of the foot were selected. Controls who had undergone lateral column lengthening but who were not experiencing such symptoms were matched for age, sex, accessory reconstructive procedures, and time from surgery. At the time of the present study, the patients had been followed for at least two years after the reconstruction and had had removal of hardware. Radiographs of each foot were assessed before and after surgery. The patients completed the Short Form-36 (SF-36) and Foot and Ankle Outcome Score surveys, and standing plantar pressure measurements were obtained. Average mean pressure, peak pressure, and maximum force were assessed at twelve anatomic regions and the two groups were compared.

RESULTS

There were no significant preoperative differences between the two groups in terms of radiographic parameters. Patients with pain had significantly lower SF-36 Physical Health Summary scores (p < 0.05), SF-36 Physical Function Subscale scores (p < 0.05), and average Foot and Ankle Outcome Scores (p < 0.05). Patients with pain had significantly higher lateral midfoot average mean pressure (p < 0.05), peak pressure (p < 0.05), and maximum force (p < 0.05). No differences were found in the hindfoot or forefoot regions.

CONCLUSIONS

Patients who have undergone lateral column lengthening and who experience lateral plantar pain have increased plantar pressure values in the lateral aspect of the midfoot. The increased pressures in this area cannot be accounted for solely by radiographic or demographic factors.

Leonard J. Goldner Award 2009. Intraoperative pedobarography leads to improved outcome scores: a Level I study

BACKGROUND

The purpose was to compare the clinical outcome scores after additional use of intraoperative pedobarography (IP) in comparison with patients treated without IP.

MATERIALS AND METHODS

Patients with arthrodesis and/or correction of the foot and/or ankle were randomized for use of IP or no IP. American Orthopaedic Foot and Ankle Society (AOFAS) score, Short-Form 36 (SF-36), and Visual Analogue Scale Foot and Ankle (VAS FA) were analyzed.

RESULTS

One hundred patients were included. Fifty-two were randomized for the use of IP, and in 24 of those (46%), the correction was modified after IP during the same operation. At mean followup of 2 years, the average scores were higher in the group with IP than in the group without IP (IP/no IP: AOFAS 89.7/78.2; SF-36 90.3/76.3; VAS FA 90.3/76.3; t-test, all p < 0.05).

CONCLUSION

The use of IP led to improved clinical outcome scores at a mean followup of 2 years.

The development of an intraoperative plantar pressure assessment device

BACKGROUND

The goal of this study was to develop an accurate and reliable supine plantar pressure measurement apparatus that could potentially be used in the operating room to guide operative decision making. It was hypothesized that plantar pressures would be similar in supine and vertical posture trials.

MATERIALS AND METHODS

A supine plantar pressure system was developed using the Pliance 32 sensor array (Novel, Munich, Germany). Accuracy was tested with a standardized manometer and the Trublu calibration system (Novel). Next, bilateral feet of 10 healthy, asymptomatic patients were tested in the apparatus by two separate investigators. Intraclass correlation coefficients (ICC) were calculated to determine intrarater and interrater reliability for parameters of average mean pressure (AMP), peak pressure (PP) and percentage of total force (PF). Finally, plantar pressures were tested in vertical posture and compared to supine parameters.

RESULTS

The sensor was both linear and accurate. The ICC values demonstrated that the sensor was reliable for AMP (0.66 to 0.93), PP (0.75 to 0.94), and PF (0.69 to 0.97). In general, AMP, PP, and PF values were significantly different at most anatomical regions for supine and vertical posture trials (p < 0.0001).

CONCLUSION

This intraoperative pressure measurement system provided an accurate, linear, and reliable method to measure plantar pressure parameters in the supine subject. These measures were similar in magnitude to vertical posture, but were statistically different.

CLINICAL RELEVANCE

This intraoperative plantar pressure system could guide operative reconstruction of foot deformities whose outcome depends on the distribution of pressures across the plantar foot.

Computer Assisted Surgery (CAS) guided arthrodesis of the foot and ankle: an analysis of accuracy in 100 cases

BACKGROUND

Computer Assisted Surgery (CAS) has shown the potential to increase the accuracy of surgical procedures in different fields of orthopedic surgery. The clinical experiences of 100 cases with CAS guided arthrodeses were evaluated.

MATERIALS AND METHODS

Two navigation systems were used (VectorVision/Navivision, Brainlab). Patients with unilateral foot and/or ankle correction arthrodesis from January 1st, 2005 to March 31st, 2008 were included. The correction was planned on the basis of clinical findings, radiographs and computer tomography. Time spent, accuracy, and problems that occurred with CAS guidance were analyzed. The accuracy was assessed by intraoperative three-dimensional imaging with ISO-C 3D or ARCADIS-3D (Siemens). The deviation from the achieved correction in comparison with the planned correction was analyzed.

RESULTS

One hundred patients were included (ankle, n = 19; subtalar, n = 23; ankle and subtalar, n = 12; midfoot/tarsometatarsal (TMT), n = 28, others, n = 18). The average time needed for preparation was 356 seconds (5 minutes, 56 seconds) (range, 4 to 30 minutes), the correction took an average of 28 (range, 12 to 140) seconds. The CAS system encountered malfunctions in 3 procedures (3%). In the remaining cases, all the achieved corrections were within a maximum deviation of 2 degrees/mm when compared to the planned correction (p < 0.05).

CONCLUSION

With CAS guidance for the correction of deformities of the foot and ankle, a surgeon can achieve a high degree of accuracy with a rapid correction. The high accuracy may lead to improved clinical outcomes.

Dynamic and functional gait analysis of severely displaced intra-articular calcaneus fractures treated with a hinged external fixator or internal stabilization

The purpose of this article was to assess functional gait outcome. Fifty-five patients with severely displaced intra-articular calcaneus fractures and soft tissue damage were evaluated prospectively with computerized dynamic pedography and a clinical scoring scale. The treatment protocol assigned 30 patients to open reduction and internal fixation (ORIF) and 25 to closed reduction and stabilization with a biomechanically tested hinged external fixator. Gait parameter was evaluated by measuring plantar pressure distribution, length of a double-step, double-step duration, standing duration, effective foot length, and width of gait. Pedographic measurements were performed with a custom-made gait analysis system (medilogic Gangas, Berlin, Germany). Results were graded by an extended protocol of questionnaires and the American Orthopaedic Foot and Ankle Society (AOFAS) ankle and hindfoot scales. Radiographs were reviewed according to the Sanders classification at the time of follow-up (7.3 years). All measurements were statistically analyzed (t test; Mann-Whitney U test). Aberrations were associated with all calcaneal fractures in both groups. Dynamic gait analysis showed gait asymmetry in all patients. The type of treatment (ORIF or a hinged fixator) of severely displaced calcaneus fractures did not affect gait analysis nor result in significantly different (P > .05) patient outcome scores. The gait analysis system allows a valid dynamic pedographic measurement. The hinged external fixator can be recommended in displaced intra-articular calcaneal fractures with severe soft tissue damage to reduce complications associated with ORIF. ACFAS Level of Clinical Evidence: 2c.

A biomechanical evaluation to optimize the configuration of a hinged external fixator for the primary treatment of severely displaced intraarticular calcaneus fractures with soft tissue damage

The purpose of this investigation was to develop an optimized hinged external fixator for the primary treatment of dislocated, intra-articular calcaneus fractures with associated soft tissue damage. To this end, a calcaneus model was made out of a polyurethane block, and a steel cylinder served as the ankle joint and was connected to a synthetic model of the tibia via a metal clamp. A saw cut served as the fracture in the model. A Steinmann nail and Schanz screw were placed in defined positions in the model and connected medially and laterally with longitudinal support rods. The fixator allowed a total of 20 degrees of plantar- and dorsiflexion, with rotation in the virtual axis of the upper ankle joint. Changes in the model fracture were measured during cyclical strain, and at different screw positions in the model tibia and calcaneus. Miniature force sensors located on the longitudinal support rods, and a plantar tension spring, were used to measure pressure and tension. Reproducible values were determined and, with the optimal configuration, shifting within the osteotomy was minimal. In the experimental configuration, optimal tibial screw placement was 70 mm proximal to the rotation axis of the upper ankle joint, and optimal placement of the Steinmann nail was in the posterior surface of the calcaneus. These findings indicated that the hinged fixator allows 20 degrees of ankle movement without alteration of the rotation axis, and suggest that this type of external fixator can be used in all types of calcaneal fracture regardless of the soft tissue damage. ACFAS Level of Clinical Evidence: 5c.