Computer based systems in foot and ankle surgery at the beginning of the 21st century

The Assessment of Ankle Osteoarthritis with Weight-Bearing Computed Tomography

The standard for diagnostic radiographic imaging in foot and ankle surgery was until 2012 radiographs with full weight-bearing without any useful alternative. Weight-bearing cone-beam computed tomography (WBCT) was introduced 2012 for foot and ankle use as a new technology that allows 3D imaging with full weight-bearing which should be not influenced by projection and/or foot orientation. The assessment of ankle osteoarthritis with WBCT including the description of healthy status, effect of alignment and7or (in)stability is extensively illustrated in this review article.

PedCAT for 3D-imaging in standing position allows for more accurate bone position (angle) measurement than radiographs or CT

BACKGROUND

PedCAT (Curvebeam, Warrington, USA) is a new technology that allows 3D-imaging with full weight bearing which is not influenced by projection and/or foot orientation (as radiographs). The aim of this study was to compare time spent of the image acquisition, and comparison of specific bone position (angle) measurements between three imaging methods (radiographs, CT, pedCAT), and to analyze and compare measurement differences and inter- and intraobserver reliability.

METHODS

In a prospective consecutive controlled study, 30 patients in which standard digital radiographs with full weight bearing in standing position (feet bilateral dorsoplantar and lateral views and Saltzman hindfoot view), CT without weight bearing, and pedCAT scan with full weight bearing in standing position were included, starting July 1, 2013. The following angles were measured for the right foot by three different investigators three times: 1st - 2nd intermetatarsal angle, talo-metatarsal 1-angle (TMT) both dorsoplantar and lateral projection, hindfoot angle, calcaneal pitch. The angles were digitally measured and compared (ANOVA with Post Hoc Scheffe test).

RESULTS

The angles differed between radiographs, CT and pedCAT (ANOVA, all p≤.01). The angles differed between pedCAT and both radiographs and CT (Post Hoc Scheffe test, each p≤.05 except for TMT dorsoplantar and calcaneal pitch angels versus radiographs).

CONCLUSIONS

The angles differed between radiographs, CT and pedCAT, indicating that only pedCAT is able to detect the correct angles. PedCAT includes weight bearing in contrast to CT. PedCAT prevents inaccuracies of projection and foot orientation in contrast to radiographs due to the 3D dataset which is principally independent from projection and foot orientation.

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.

[Navigated retrograde drilling in Osteochondrosis dissecans (OCD) of the talus]

OBJECTIVE

Subchondral decompression and revascularization in Osteochondrosis dissecans (OCD) of the talus with cartilage preservation.

INDICATIONS

Symptomatic talar OCD stage I and II, i.e., cartilage intact or almost intact.

CONTRAINDICATIONS

Talar OCD stage III and IV, i.e., cartilage not intact.

SURGICAL TECHNIQUE

Diagnostic ankle arthroscopy. Insertion of dynamic reference base (DRB) in the talar neck through a stab incision. After 3D image acquisition and planning of the drilling, navigated drilling with a 5 mm drill. Insertion of a 1 mm titanium wire into the canal and 3D image acquisition for evaluation of the canal. Autologous cancellous bone transplantation into the canal. Arthroscopic evaluation.

POSTOPERATIVE MANAGEMENT

For 6 weeks, 15 kg partial weight bearing without immobilization. After 6 weeks full weight bearing.

RESULTS

A total of 52 patients with symptomatic talar OCD stage I and II were included in a clinical follow-up study. Time needed for preparation, including the placement of the DRB, scanning time, and preparation of the trajectories was 7 min 32 s (4-30 min). In 50 cases (96%), the drilling was judged with 3D imaging to be correct. In the remaining 2 cases (4%), the drilling ended in the caudal portion of the lesion. A perforation of the cartilage was not registered arthroscopically. Follow-up after 12 months (range 6-36 months) was possible in 48 patients (92%). Three patients (6%) had been converted to bone cartilage transplantation (OATS) due to recurrent symptoms. These patients were excluded from follow-up. The follow-up scores were Visual Analogue Scale Foot and Ankle (mean 93 points [range 86-100 points]) and the SF 36 (standardized to 100 point maximum, 90 points [range 79-100 points]).

[Computer-assisted surgery-(CAS-)guided correction arthrodesis of the subtalar joint]

OBJECTIVE

Restoration of a stable and plantigrade foot in deformities at the hindfoot and concomitant degenerative changes at the subtalar joint.

INDICATIONS

Deformities at the hindfoot and concomitant degenerative changes at the subtalar joint.

CONTRAINDICATIONS

Active local infection or relevant vascular insufficiency.

SURGICAL TECHNIQUE

Prone position and posterolateral approach to the subtalar joint. Placement of dynamic reference bases in talus and calcaneus through stab incisions. Two-dimensional image acquisition for navigation. Definition of the axes of talus and calcaneus, and of the extent of correction. Exposure of the subtalar joint and removal of remaining cartilage. Computer- assisted surgery-(CAS-)guided correction and transfixation of the corrected position with two 2.5-mm Kirschner wires. Transplantation of autologous cancellous and cortical bone, if necessary. Three-dimensional (3-D) image acquisition for analysis of the accuracy of the correction and planning of the drillings for the screws. CAS-guided drilling and insertion of the screws. 3-D image acquisition for analysis of the accuracy of the correction implant position. Wound closure in layers.

POSTOPERATIVE MANAGEMENT

15 kg partial weight bearing in an orthosis (e.g. Vacuped TM, OPED Inc., Valley, Germany) for 6 weeks, followed by full weight bearing in a stable standard shoe.

RESULTS

From September 1, 2006 to August 31, 2008, 26 correction arthrodeses were performed. The accuracy was assessed by intraoperative 3-D imaging. All achieved angles/translations were within a maximum deviation of 2°/2 mm when compared to the planned correction. Complications that were associated with CAS were not observed. In all 25 cases that completed 2-year follow-up, timely fusion was registered.

[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%).

Arthroscopic-assisted fluoroscopic navigation for retrograde drilling of a talar osteochondral lesion

Level of Evidence: V, Expert Opinion

3D imaging (ARCADIS)-based Computer Assisted Surgery (CAS) guided retrograde drilling in osteochondritis dissecans of the talus

Level of Evidence: V, Expert Opinion

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.

3D imaging (ARCADIS)-based Computer Assisted Surgery (CAS) for nail placement in combined ankle and subtalar fusion

Level of Evidence: V, Expert Opinion

Intraoperative pedography: a validated method for static intraoperative biomechanical assessment

BACKGROUND

A new device was developed to perform intraoperative static pedography. The purpose of this study was to validate the introduced method by a comparison with the standard method for dynamic and static pedography.

METHODS

A device known as Kraftsimulator Intraoperative Pedographie (KIOP) was developed for intraoperative placement of standardized forces to the sole of the foot. Pedographic measurements were done with a custom-made mat that was inserted into the KIOP (Pliance, Novel Inc., St. Paul, MN, USA). Validation was done in two steps: (1) comparison of standard dynamic pedography walking on a platform, standard static pedography in standing on a platform, and pedography with KIOP in supine position in 30 healthy volunteers, and (2) comparison of static pedography in standing position, pedography with KIOP supine awake, and pedography with KIOP supine with 30 patients under anesthesia. Individuals who had operative procedures at the knee or distal to the knee were excluded. The different measurements were compared (one-way ANOVA, t-test; significance level 0.05).

RESULTS

No significant differences were found among all measurements for the hindfoot compared to midfoot-forefoot force distribution. For the medial compared to lateral force distribution and the 10-region-mapping, significant differences were found when comparing all measurements (steps 1 and 2) and when comparing the measurements of step 1 only. No differences were found for these distributions when comparing the measurements of step 2 alone or when comparing the measurements of step 1 and 2 without the platform measurements of step 1 (dynamic walking pedography and static standing pedography). No significant differences in the force distributions were found in step 2 when comparing subjects without anesthesia, with general anesthesia, and with spinal anesthesia.

CONCLUSIONS

The KIOP device allows a valid static intraoperative pedography measurement. No statistically significant force distribution differences were found between standing subjects and anesthetized subjects in the supine position.