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

Computer-assisted surgery and navigation in foot and ankle: state of the art and fields of application

Computer-assisted orthopaedic surgery (CAOS) is a real-time navigation guidance system that supports surgeons intraoperatively.Its use is reported to increase precision and facilitate less-invasive surgery.Advanced intraoperative imaging helps confirm that the initial aim of surgery has been achieved and allows for immediate adjustment when required.The complex anatomy of the foot and ankle, and the associated wide range of challenging procedures should benefit from the use of CAOS; however, reports on the topic are scarce.This article explores the fields of applications of real-time navigation and CAOS in foot and ankle surgery. Cite this article: EFORT Open Rev 2021;6:531-538. DOI: 10.1302/2058-5241.6.200024.

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.

Intraoperative 3-Dimensional Computed Tomography and Navigation in Foot and Ankle Surgery

Computer-assisted orthopedic surgery has developed dramatically during the past 2 decades. This article describes the use of intraoperative 3-dimensional computed tomography and navigation in foot and ankle surgery. Traditional imaging based on serial radiography or C-arm-based fluoroscopy does not provide simultaneous real-time 3-dimensional imaging, and thus leads to suboptimal visualization and guidance. Three-dimensional computed tomography allows for accurate intraoperative visualization of the position of bones and/or navigation implants. Such imaging and navigation helps to further reduce intraoperative complications, leads to improved surgical outcomes, and may become the gold standard in foot and ankle surgery. [Orthopedics.2016; 39(5):e1005-e1010.].

Transfibular ankle arthrodesis using burring, curettage, multiple drilling, and fixation with two retrograde screws through a single lateral incision

PURPOSE

To review the outcome of 23 ankle arthrodeses using burring, curettage, multiple drilling, and fixation with 2 retrograde screws through a single lateral incision.

METHODS

Records of 22 consecutive patients aged 39 to 79 (mean, 62.4) years who underwent 23 ankle arthrodeses for end-stage ankle arthritis were reviewed. Through a single lateral incision, articular cartilage was removed using burring and curettage, and multiple holes were drilled using a Kirschner wire, followed by fixation with 2 retrograde screws. The resected distal fibula was fixed to the distal part of the talus and tibia. The position of the ankle and subtalar joint arthrosis was assessed by 2 orthopaedic specialists. Pre- and post-operative American Orthopaedic Foot and Ankle Society (AOFAS) scores were evaluated.

RESULTS

The mean operating time was 122 minutes. The mean follow-up period was 41 months. The mean postoperative ankle alignment was suboptimal: 2.7º varus, 6.7º plantar flexion, and 2.9º internal rotation. The mean AOFAS score improved from 30 to 71 (p<0.01). The postoperative varus ankle alignment was not associated with the AOFAS score (r= -0.13, p=0.569). Of the 23 cases, one was nonunion and 22 achieved bone union after a mean of 5.4 (range, 2-16) months; 3 of them were delayed union. Despite bone union, 7 patients complained of persistent pain; 4 of them had progressive arthrosis of the adjacent subtalar joints (n=2) or subtalar and talonavicular joints (n=2).

CONCLUSION

Ankle arthrodesis using burring, curettage, multiple drilling, and fixation with 2 retrograde screws achieved a high union rate and acceptable functional score without serious complications.

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.

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.

Four-stage regimen for operative treatment of diabetic foot ulcer with deformity - a results of 300 patients

BACKGROUND

An operative four-stage regimen (stage 1, debridement; stage 2, closure; stage 3, unloading; stage 4, correction) for operative treatment of diabetic foot ulcer with deformity, and first clinical results are introduced.

METHODS AND RESULTS

335 patients entered stage 1 between 01/09/2006 and 31/08/2010. Stage 1: In 189 cases (56%), one debridement resulted in sterile postoperative specimens. Stage 2: 210 cases (63%) sustained secondary closure, 97 (29%) local shifted skin graft, and 20 (6%) functional amputation. Stage 3: 304 (90%) finished stage 3, 14 (4%) presented with recurrent ulcer. Stage 4: In 185 cases (55%), correction arthrodeses were performed successfully.

FOLLOW-UP

300 (90%) completed follow-up at 26months on average (12-48months). Recurrent ulcer was registered in 46 (15%). Overall amputation rate was 14%, the majority at digital or midfoot level. Four cases (1%) required a below-knee amputation.

CONCLUSIONS

The management of diabetic foot ulcer combined with deformity with the introduced regimen showed low major amputation rate and low recurrent ulcer rate compared with the literature.

Navigated treatment of metatarsal V fractures using a new image based guidance system

BACKGROUND

Computer assisted imaging systems are rarely used for fracture treatment and foot surgery. We introduce a new system for image based guidance in traumatology.

METHODS

We included 20 patients with a fracture of the fifth metatarsal. They were randomized on admission into two groups. Ten patients in the metatarsal group were operated conventionally and ten were operated with the assistance of a new image guidance system. This system is based on 2D-fluoro images which are acquired with a conventional c-arm and are transferred to the system workstation. After detecting marked tools, it can be used to display trajectories for K-wire guidance in the c-arm shot.

RESULTS

The average duration of surgery in the image-guided group was 12.7 minutes. In the conventional treated group, it was 17 minutes. The average duration of radiation was 18 seconds in the image-guided group vs. 32.4 seconds in the conventional group. 1.6 trials were necessary to position the K-wire for image-guided procedures in comparison to 2.7 trials in the conventional group.

CONCLUSION

Image-based guidance systems can be used for indications, were hitherto existing navigation systems are limited due to their dependence on fixed reference devices. Image-guided systems can be integrated into existing workflows and can reduce the malpositioning of guidewires.

Clinical outcome and gait analysis of ankle arthrodesis

BACKGROUND

The purpose of our study was to describe and analyze the functional outcomes of mid-term followup patients with ankle arthrodesis.

METHODS

Twenty patients who had an isolated ankle arthrodesis were followed for a mean of 3 years after surgery. We performed physical and functional examination, radiographic examination and CT scan. Each completed standardized, self-reported outcome questionnaires SF-36, AOFAS and Mazur scores. All subjects were evaluated with a kinetic and kinematic gait analysis and a plantar pressure study.

RESULTS

Only one patient used a cane and seven patients required an insole to walk. We observed no relation between the scores obtained. Most of the patients showed good functional results and poor life quality scores. The joints that were significantly more degenerated were the Chopart and the subtalar joints, which were affected in 16 patients in the fused limb. The kinematic parameters showed compensatory motion in the neighboring joints and the kinetic parameters studied were similar in the arthrodesis limb and the control limb. There was no significant difference between the arthrodesis limb and the contralateral limb for plantar pressures.

CONCLUSION

Although ankle arthrodesis will help to relieve pain and to improve overall function, it is considered to be a salvage procedure that causes persistent alterations in gait, with the possible development of symptomatic osteoarthritis in the other joints of the foot. Patients and treating physicians should also expect overall pain and functional limitations to increase over time.

Precision of targeting device for subtalar screw placement

BACKGROUND

When performing subtalar arthrodesis, proper screw placement is fundamental to provide primary stability and to help ensure bone healing. In inexperienced hands this step can be time-consuming and exposes surgeons and patients to radiation. By means of a targeting device these potential drawbacks and dangers could be reduced. It was hypothesized that a specifically designed targeting device would reduce radiation exposure while improving screw placement when compared with the conventional "free-hand'' method.

METHODS

Twenty matched-pairs of cadaveric hindfoot specimens (Thiel fixation) were prepared for the purpose of the study. The specimens were randomly assigned into two groups consisting of 10 specimens each: in Group 1 screw placement was performed with the targeting device and in Group 2 screw placement was performed under fluoroscopic control. Screw placement was radiographically judged to be optimal, suboptimal and poor. An experienced, fellowship-trained foot and ankle surgeon and a resident, who had never done subtalar fusions performed the screw placements. Exposure to radiation was assessed by means of the dose area product given by the fluoroscope.

RESULTS

Optimal screw positioning was achieved in both groups in ten out of 20 specimens (Group 1, n=5; Group 2, n=5). Suboptimal screw placement was found in eight cases (Group 1, n=4; Group 2, n=4). There were two failures which occurred in fusions performed by the resident (Group 1, n=1; Group 2, n=1). Exposure to radiation was significantly reduced in Group 1 when compared with Group 2 (4.1cGy* cm2 versus 8.1cGy* cm2; p=0.012). No lesion of neurovascular structures due to aiming device placement occurred in Group 1.

CONCLUSION

A target-device for screw-placement did not provide a significant technical advantage but did result in less radiation exposure.

Ground Reaction Force Calcaneal Offset: A new measurement of hindfoot alignment

BACKGROUND

The tibio-calcaneal angle (TCA) does not measure individual forefoot contributions to the overall foot balance. Using standard radiographs we calculated the ideal hindfoot alignment based on ground reaction force (GRF), independently from the tibial axis.

METHODS

Thirty-six patients (40ft.) were included. Mean age was 56. Weight bearing radiographs were taken. Calcaneal offsets were measured using tibio-calcaneal angles and GRF algorithms. Measurements were compared using the Bland-Altman method.

FINDINGS

Both methods agreed (p>0.05) but individual discrepancies were found. Mean measured offsets were -11.5mm (SD: 10.2) using TCA and -8mm (SD: 9.3) using GRF. Mean bias between the methods was -0.88mm.

INTERPRETATION

The GRF algorithm successfully measured hindfoot alignment. The absence of a previous gold standard and radiographic variability are a limit. The TCA underestimated calcaneal offset. Discrepancies showed that forefoot position data provided increased accuracy. This could be of particular relevance for surgical planning.

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.

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

OBJECTIVE

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

INDICATIONS

Deformities at the ankle and concomitant degenerative changes at the ankle joint.

CONTRAINDICATIONS

Active local infection or relevant vascular insufficiency.

SURGICAL TECHNIQUE

Supine position and anterior approach to the ankle joint. Placement of dynamic reference bases (DRBs) in tibia and talus. Two-dimensional (2-D) image acquisition for navigation. Definition of axes of tibia and talus, and of the extent of correction. Exposition of the ankle 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. 3-D image acquisition for analysis of the accuracy of the correction and planning of the drillings for the four screws (two parallel from anterolateral, one from posteromedial from the tibia, and one from lateral from the fibula). CAS-guided drilling and insertion of the screws. 3-D image acquisition for analysis of the accuracy of the correction and implant position. Layerwise closure.

POSTOPERATIVE MANAGEMENT

Partial weight bearing with 15 kg in an orthosis for 6 weeks, followed by full weight bearing in a stable standard shoe.

RESULTS

From September 1, 2006 to August 31, 2008, 24 correction ankle arthrodeses were performed. The accuracy was assessed by intraoperative 3-D imaging. All achieved angles/ translations were within a maximum deviation of 2 degrees /2 mm when compared to the planned correction. Complications that were associated with CAS were not observed. In all 20 patients that completed follow-up so far, a timely fusion was registered.

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.