Michael Kammal

Accuracy Analysis of a Novel Electromagnetic Navigation Procedure Versus a Standard Fluoroscopic Method for Retrograde Drilling of Osteochondritis Dissecans Lesions of the Knee

Background: Retrograde drilling for osteochondritis dissecans (OCD) remains a challenging operation. Purpose: A novel radiation-free electromagnetic navigation system (ENS)–based method was developed and its feasibility and accuracy for retrograde drilling procedures evaluated and compared with the standard freehand fluoroscopic method in an experimental setting. Study Design: Controlled laboratory study. Methods: A controlled laboratory study with 16 standard freehand fluoroscopically and 16 electromagnetically guided retrograde drilling procedures was performed on 8 cadaveric human knees. Four artificial cartilage lesions (2 on each condyle) were set per knee. Drilling accuracy was determined by final distance from the tip of the drill bit to the tip of the probe hook (D1) and distance between the tip of the drill and the marked lesion on the cartilage surface (D2). Intraoperative fluoroscopy exposure times were documented, as were directional readjustments or complete restarts. All procedures were timed using a stopwatch. Results: Successful retrograde drilling was accomplished in all 16 cases using the novel ENS-based method and in 11 cases using the standard fluoroscopic technique. The overall mean time for the fluoroscopy-guided procedures was 10 minutes 55 seconds ± 3 minutes 19 seconds and for the ENS method was 5 minutes 34 seconds ± 38 seconds, providing a mean time benefit of 5 minutes 35 seconds (P < .001). Mean D1 was 3.8 ± 1.6 mm for the standard and 2.3 ± 0.6 mm using the ENS technique (P = .021), and mean D2 was 2.5 ± 1.3 mm for the standard and 0.9 ± 0.7 mm for the ENS-based method (P < .001). Conclusion: Compared with the standard fluoroscopic technique, the novel ENS-based method used in this study showed superior accuracy, required less time, and utilized no radiation. Clinical Relevance: The novel method improves a standard operating procedure in terms of accuracy, operation time for the retrograde drilling procedure, and radiation exposure.

Evaluation of cartilage specific matrix synthesis of human articular chondrocytes after extended propagation on microcarriers by image analysis.

BACKGROUND Cell-based technologies for the repair of cartilage defects usually rely on the expansion of low numbers of chondrocytes isolated from biopsies of healthy cartilage. Proliferating chondrocytes are known to undergo dedifferentiation characterized by downregulation of collagen type II and proteoglycan production, and by upregulation of collagen type I synthesis. Re-expression of cartilage specific matrix components by expanded chondrocytes is therefore critical for successful cartilage repair. METHODS Human articular chondrocytes were expanded on microcarriers Cytodex 3. The growth area was increased by adding empty microcarriers. Added microcarriers were colonized by bead-to-bead transfer of the cells. The chondrocytes were harvested from the microcarriers and characterized by their ability to synthesize collagen type II when cultivated in alginate beads using chondrogenic growth factors. A semi-automatic image analysis technique was developed to determine the fractions of collagen type II and type I positive cells. RESULTS The expansion of human articular chondrocytes on microcarriers yielded high cell numbers and propagation rates compared to chondrocytes expanded in flask culture for one passage. The proportion of collagen type II positive cells compared to collagen type I synthesizing cells was increased compared to chondrocytes expanded using conventional methods. The matrix synthesis upon treatment with chondrogenic factors IGF-I and BMP-7 was enhanced whereas TGF-ss had an inhibitory effect on microcarrier expanded chondrocytes. CONCLUSIONS Expanding human articular chondrocytes on microcarriers omitting subcultivation steps leads to superior ratios of collagen type II to type I forming cells compared to the expansion in conventional monolayer culture.

Retrograde Drilling of Talar Osteochondritis Dissecans Lesions: A Feasibility and Accuracy Analysis of a Novel Electromagnetic Navigation Method Versus a Standard Fluoroscopic Method

PURPOSE A novel method using an electromagnetic navigation system (ENS) was developed, and its feasibility and accuracy for retrograde drilling procedures were evaluated and compared with the standard freehand fluoroscopic method in an experimental setting. METHODS A controlled laboratory study of 16 standard freehand fluoroscopically guided and 16 electromagnetically navigated retrograde drilling procedures was performed on 4 cadaveric human ankle joints. Four artificial cartilage lesions were consecutively set, 2 on the medial and 2 on the lateral talar dome. Drilling accuracy was measured in terms of the distance from the final position of the drill bit to the tip of the probe hook and the distance between the tip of the drill bit and the center of the cartilage lesion on the articular cartilage surface. Intraoperative fluoroscopy exposure times were documented, as were readjustments of drilling directions or complete restarts. All procedures were timed with a stopwatch. RESULTS Successful retrograde drilling was accomplished in 12 cases with the standard fluoroscopy-guided technique and in all 16 ENS-guided procedures. The overall mean time for the fluoroscopy-guided procedures was 660.00 ± 239.87 seconds and the overall mean time for the ENS method was 308.06 ± 54.03 seconds, providing a mean time benefit of 420.13 seconds. The mean distance from the final position of the drill bit to the tip of the probe hook was 3.25 ± 1.29 mm for the standard method and 2.19 ± 0.54 mm for the ENS method, and the mean distance between the tip of the drill bit and the center of the cartilage lesion on the articular cartilage surface was 2.50 ± 0.97 mm for the standard method and 0.88 ± 0.81 mm for the ENS method. CONCLUSIONS Compared with the standard fluoroscopic technique, the ENS method used in this study showed higher accuracy and a shorter procedure time and required no X-ray radiation. CLINICAL RELEVANCE The novel method considerably improves on the standard operating procedure in terms of safety, operation time, and radiation exposure.

A novel electromagnetic navigation tool for acetabular surgery

BACKGROUND Acetabular fracture surgery is demanding and screw placement along narrow bony corridors remains challenging. It necessitates x-ray radiation for fluoroscopically assisted screw insertion. The purpose of this cadaver study was to evaluate the feasibility, accuracy and operation time of a novel electromagnetic navigation system for screw insertion along predefined acetabular corridors. METHODS A controlled laboratory study with a total of 24 electromagnetically navigated screw insertions was performed on 8 cadaveric acetabula. 3 peri-acetabular bony corridors (QSS, Quadrilateral Surface Screw; IAS, Infra-Acetabular Screw; PCS, Posterior Column Screw) were defined and screws were placed in a defined order without fluoroscopy. Operation time was documented. Postoperative CT scans were performed to analyse accuracy of screw placement. RESULTS Mean cadaver age was 70.4 ± 11.7. Successful screw placement was accomplished in 22 out of 24 (91.7%) cases. The overall mean time for all 3 acetabular screws was 576.6 ± 75.9s. All 3 complications occurred during the placement of the IAS due to an impassable narrow bony corridor. QSS mean length was 50 ± 5mm, IAS mean length was 85 ± 10mm and PCS mean length was 120 ± 5mm. CONCLUSION In this cadaver study the novel electromagnetic navigation system was feasible to allow accurate screw placement without fluoroscopy in defined narrow peri-acetabular bony corridors.

Primary aorto-enteric fistula as a rare cause of massive gastrointestinal haemorrhage

The incidence of primary aorto-enteric fistula (PAEF) is low with only few case reports and case series published. Depending on the location of the PAEF, the perforation leads to upper or lower gastrointestinal haemorrhages. We conducted a MEDLINE search according to the PRISMA statement. Articles with publication dates from 2000 to 2016 were included and present an own case report. We considered all case reports and series reporting on PAEF and identified 85 individual patients from 32 case reports and five case series. The majority of PAEF is associated with atherosclerotic or aneurysmatic findings of the aorta and in particular with inflammatory aortic diseases. Most commonly, the duodenum (64 %) was mentioned as location of the perforation. Other cases involved the jejunum (< 10 %) and the colon (5 %). Almost all patients were diagnosed either with gastrointestinal haemorrhage, abdominal or back pain, or anaemia due to bleeding. The immediate and correct diagnosis of this entity remains difficult. Therefore, treatment is delayed leading to an extraordinary high mortality of almost 100 % in untreated cases. Duplex ultrasound and contrast-enhanced CT angiography have high diagnostic sensitivity and specificity to rule out acute abdominal aortic pathologies. New endovascular approaches can help to lower mortality.

Expansion of Human Articular Chondrocytes on Microcarriers Enhances the Production of Cartilage Specific Matrix Components

Cell based technologies for the repair of cartilage defects usually rely on the expansion of low numbers of chondrocytes isolated from biopsies of healthy cartilage. Proliferating chondrocytes are known to undergo dedifferentiation which is characterised by down-regulation of collagen type II and proteoglycan production, and by up-regulation of collagen type I synthesis. Re-expression of cartilage specific matrix components by expanded chondrocytes is therefore critical for successful cartilage repair. In this study, it is shown that the quality of matrix synthesis by expanded chondrocytes is highly dependent on the method of expansion. Expanding human articular chondrocytes (HAC) on microcarriers without subcultivation steps leads to higher matrix synthesis rates and to superior ratios of collagen type II to type I forming cells than the expansion in conventional monolayer culture.