Computer-assisted surgery for subtalar arthrodesis. A study in cadavers

Wire Placement in the Sustentaculum Tali Using a 2D Projection-Based Software Application for Mobile C-Arms: Cadaveric Study

BACKGROUND

Indirect screw fixation of the sustentaculum tali in the lateral-medial direction can be challenging due to the complex calcaneal anatomy. A novel 2-dimensional (2D) projection-based software application detects Kirschner wires (K-wires) and visualizes their intended direction as a colored trajectory. The aim of this prospectively randomized cadaver study was to investigate whether the software would facilitate the indirect K-wire placement in the sustentaculum tali.

METHODS

In 20 cadaver foot specimens, K-wires were placed indirectly in the sustentaculum tali by an experienced and an inexperienced surgeon, with and without using the application. Number of placement attempts, duration of procedure, fluoroscopy time, and number of individual fluoroscopy images were recorded. Each wire's position was analyzed in a 3-dimensional (3D) C-arm scan by an experienced blinded investigator.

RESULTS

Use of the software by the inexperienced surgeon significantly reduced the number of placement attempts from 3.2 to 1.2 ( P = .006). The application also reduced operating time, from 273 s to 199 s ( P = .15), and fluoroscopy time, from 41 s to 29 s ( P = .15). Using the software, the experienced surgeon had a longer operating time (139 s to 183 s; P = .30), longer fluoroscopy time (5.6 s to 9.2 s; P = .17), and more individual fluoroscopy images (11.6 to 14.8; P = .30). Wire position did not show significant differences in both cases.

CONCLUSION

During indirect K-wire placement in the sustentaculum tali, the software appeared to be a useful tool for the inexperienced surgeon. In our chosen study setting, the experienced surgeon did not benefit from the software.

CLINICAL RELEVANCE

Possible indications for the software would be fractures of the proximal femur, sacrum, sacroiliac instabilities, vertebral bodies, scaphoid, Lisfranc joint, talus and calcaneus.

The value of Weight-Bearing CT scan in the evaluation of subtalar distraction bone block arthrodesis: Case report

Subtalar distraction arthrodesis is performed in certain situations where there is loss of subtalar height, reduced talar declination and evidence of anterior tibiotalar impingement. Standard evaluation includes the assessment of the lateral talocalcaneal angle, calcaneal pitch, talocalcaneal height and talar declination angle on a weight bearing lateral radiograph. We present a case of erosive valgus subtalar osteoarthritis with subtalar collapse managed with a subtalar distraction arthrodesis. A weight bearing CT (WB-CT) scan was used in the assessment. The value of WB-CT for this indication is discussed, along with a discussion on surgical technique, complications and future directions.

Distraction subtalar arthrodesis

There is a high potential for disability following calcaneal fracture. This potential exists whether a patient is treated with conservative or operative management. Subfibular impingement and irritation of the peroneal tendon and sural nerve may also be present. Posttraumatic arthritis of the subtalar joint can occur. In patients with symptomatic calcaneal malunion, systematic evaluation is required to determine the source of pain. Nonsurgical treatment may be effective. One surgical treatment option is subtalar distraction arthrodesis. High rates of successful arthrodesis and patient satisfaction have been reported with this surgical option in correctly selected patients.

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.

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.

Intraoperative navigation for minimally invasive resection of periarticular and pelvic tumors

The surgical approach to benign, metastatic, and some low-grade malignant tumors is often difficult due to their typically precarious locations. This article presents a series of cases where intraoperative stealth navigation was used to treat periarticular tumors. The use of paired point imaging with image fusion has made approaching tumors through an accurate and minimally invasive technique a viable option for the treatment of a subset of musculoskeletal tumors.

Overview of subtalar arthrodesis techniques: options, pitfalls and solutions

BACKGROUND

Subtalar arthrodesis (SA) is the preferred treatment for painful isolated subtalar disease. Although results are generally favourable, analysis of current operative techniques will help optimizing this treatment. The aim was to give an overview of SA-techniques and their pitfalls. Possible solutions were identified.

MATERIALS AND METHODS

A literature search was performed for papers that presented SA operative techniques. The general technique was divided into phases: surgical approach, cartilage removal, bone graft selection, hindfoot deformity correction and fixation.

RESULTS

The published series were invariably retrospective reviews of small heterogenous groups of different hindfoot pathologies. The weighted outcome rate for SA was 85% (68-100%) performed in 766 feet and for SA requiring correction of malalignment 65% (36-96%) in 1001 feet. Non-union (weighted percentage 12%), malalignment (18%), and screw removal (17%) were the prevailing late complications.

PITFALLS

The following pitfalls were identified: 1) early complications related to the incisions made in open approaches, 2) insufficient cartilage removal, improper bone graft selection and fixation techniques, all possibly leading to non-union, 3) morbidity caused by bone graft harvesting and secondary screw removal, 4) under- or overcorrection of the hindfoot possibly due to improper intraoperative verification and 5) inadequate assessment of bony fusion.

SOLUTIONS

The review provides solutions to possibly overcome some pitfalls: 1) if applicable use an arthroscopic approach in combination with distraction devices and new burrs, 2) if possible use local bone graft or allografts, 3) use two screws for fixation to prevent rotational micromotion, and 4) improve assessment of operative outcome by application of appropriate assessment of bony fusion and alignment.

CONCLUSION

The review provides practical suggestions to optimize SA-techniques.

MRI-guided navigation surgery with temporary implantable bone markers in limb salvage for sarcoma

BACKGROUND

Technical errors during navigation-assisted bone tumor resection may occur by: (1) incorrect registration of images and corresponding anatomic points of bone sent to the navigation system; and (2) incorrect fusion of two or more images that have been transported to the navigation system.

QUESTIONS/PURPOSES

We investigated new methods of navigation surgery to minimize technical errors during the registration and image fusion processes and specifically asked whether a navigated cannula probe would reduce unnecessary soft tissue dissection, and allow percutaneous registration and implantation of a reference base tracker in the margin of bone to be resected.

METHODS

We performed direct MRI-guided navigation surgery without image fusion on a patient with osteosarcoma using absorbable pins as temporary implanted bone markers that prevent artifacts on MR images.

RESULTS

Direct MRI-guided navigation surgery was possible using bone markers. A navigated cannula probe allowed percutaneous registration and a navigated blade-shaped probe provided a real-time check on the narrow osteotomy gap. The surgical procedure was facilitated by implantation of a reference base tracker on the margin of bone to be resected.

CONCLUSIONS

Our modified technique of MRI-guided navigation surgery for patients with a malignant bone tumor may reduce processing errors by increased accuracy and be helpful for joint preserving surgery.

Minimally invasive, no hardware subtalar arthrodesis with autogenous posterior iliac bone graft

Sixteen patients underwent minimally invasive subtalar arthrodesis through a mini-invasive approach with posterior iliac graft between 2004 and 2006. No hardware was used to transfix the arthrodesis and partial weight bearing was allowed immediately. The primary indication for surgery was the squeal of fracture os calcis in terms of subtalar joint arthritis, loss of heel height, malalignment of the hindfoot, and pain with weight bearing. There were 12 male and 4 female patients with a mean age of 30 (range 17-52). Patients were followed up for a period of 40.8 months (range 36-48 months). The mean interval from injury to fusion was 2 (+0.6) years ranging from 6 months to 6 years post fracture. The average clinical rating scale based on the American Orthopaedic Foot and Ankle Society (AOFAS) improved from 36 preoperatively to 78 at the latest follow-up (P < 0.05). Union rate was 94%. Radiographic evaluation revealed a mean increase in calcaneal inclination of 6.25 + 8.3 degrees (P < 0.07) and a mean increase in the lateral talocalcaneal angle of 7.42 + 10.2 degrees (P < 0.08). Complications were graft nonunion in 1 patient and transient tendoachilles tendinitis in another. This technique can be used to decrease the morbidity associated with the late complications of os calcis fractures by aligning the hindfoot, restoring the heel height and correcting calcaneal and talar inclination. It offers the advantage of early weight bearing while avoiding hardware complications.