Complications after cryosurgery with new miniature cryoprobes in long hollow bones: An animal trial

BACKGROUND: In vitro studies show that new miniature cryoprobes are suitable for cryoablation of bone tissue. The aim of this animal trial on 24 sheep was to examine the perioperative complications, particularly the danger of embolism, of cryoablation when using miniature cryoprobes. METHODS: Cryoablations with 2 freeze-thaw cycles each were carried out in the epiphysis of the right tibia and the metaphysis of the left femur. Pulmonary artery pressure (PAP) and central venous pressure (CVP) were measured. Throughout the intra- and perioperative phase, heart rate and oxygen saturation by pulse oxymetry, blood gas and electrolytes were monitored regularly. Postoperative complications were examined up to 24 weeks postoperativ. RESULTS: As result, no significant increase of PAP, CVP or heart rate were observed. Blood gases were unremarkable, with pO(2 )and pCO(2 )remaining constant throughout the operation. Regarding pH, standard bicarbonate and base excess, only a non-significant shift towards a slight acidosis was seen. There was a mean hemoglobin decrease of 0.5 g/dl. One animal showed postoperative wound infection and wound edge necrosis. No major peri- and postoperative complications associated with cryosurgery of bone were observed, especially regarding clinically relevant pulmonary embolism. CONCLUSION: Surgery with new types of miniature cryoprobes appears to be a safe alternative to or a complement to conventional resection of abnormal bone tissue

Deformation stimulates bone – feasibility of an innovative surgical approach for in-vivo measurements of bone deformation

Introduction: Bone deformation stimulates bone and is crucial for astronauts during space flight. Knowledge on bone deformation during activities could help improve astronaut training and osteoporosis treatment. A new method for in vivo bone deformation measurements was developed by the authors, offering technical advantages over previous approaches. Using motion capturing, it computes deformation from the relative displacement between reflective markers attached to the bone via screws. This technique is less invasive than strain gauges attached to the bone surface. However, feasibility of the approach had been almost unanimously rejected by colleagues and experts in the up-run for this study. Their main concerns were pain and infection. Materials and Methods: Aim of the study was to evaluate feasibility regarding surgical technique, pain, risk of infection, bleeding and wound healing in five healthy subjects between 26 and 50 years of age (mean 37.2 years +/- 7.8). Three titanium screws were inserted 3 mm into the cortical bone of the tibia in local anesthesia fig. 1). Screws were in place for 6 to 8 hours, during which a variety of exercises were performed including running, jumping, stairs and squats. A pain questionnaire was used to assess pain levels during experiments. The visual analog scale ranging from 0 to 10 and open questions were employed. Bone scans were taken to locate and evaluate screw holes. Opening of the medulla would aggravate outcomes in case of infection. Results: Feasibility was good and screws remained in place throughout experiments. The average pain level throughout the experiment day was 0. Screw implantation and explantation can be done in local anesthesia, and a large number of exercises can be performed with only a minimum of pain medication. PQCT-images showed the bone medulla was not opened in any case. In the first subject, bleeding caused interruptions. This problem was controlled through size-reduction of skin incisions, application of ‘steri strips’ and extensive cauterization. Wound healing was without complications in all subjects. Discussion: The new optical method is feasible from a surgical point of view with astoundingly low levels of pain and discomfort. The threat of infection was minimized. Bleeding was efficiently reduced and wound healing was without complications. The new method is feasible from a surgical point of view and opens a variety of options for new clinical and scientific applications

In vivo measurements of human bone deformation using optical segment tracking: surgical approach and validation in a three-point bending test

The purpose of the study was to validate optical segment tracking, a new method for in vivo human tibia deformation measurements and to assess bending in a three-point bending test. The approach relies upon optical motion capturing of reflecting marker clusters affixed to the bone via screws inserted three millimeters into the corticalis in local anesthesia. The method was tested in five healthy subjects. Screws were left in place for six to eight hours and a variety of exercises performed. A pain questionnaire was used to assess pain levels. PQCT-images were taken to locate screw holes in the bone. A three-point bending test was performed and repeatability evaluated. The new method shows good feasibility though this was previously considered impossible by many experts. Local anesthesia works for screw implantation and explantation. Results show linearity with an average of 0.25 degrees per 10 kg of weight applied with good repeatability (average variation coefficient 8%). Optical segment tracking is feasible for human in vivo bone deformation measurements. There is a variety of possible clinical and experimental applications including stability testing of osteosyntheses and joints, monitoring of bone healing, evaluation of exercises in physiotherapy, and assessment of bone deformation patterns in bone disease

Reply to the letter to the editor by Liu and Li

We thank the colleagues Liu and Li for their interest in our work and for their commenting letter. As to the first comment, the location of the bone screws has, of course, been a concern when planning the study. To apply the technique, it was necessary to choose locations with a cortical thickness of at least 4 mm. This was always the case in the locations we chose for screw implantation. However, 4 mm will not always be present in the locations the colleagues Liu and Li suggested. In future studies, screw positioning may be optimized, and one might consider using a surgical navigation system for exact screw positioning

Assessment of Lumbar Intervertebral Disc Glycosaminoglycan Content by Gadolinium-Enhanced MRI before and after 21-Days of Head-Down-Tilt Bedrest

During spaceflight, it has been shown that intervertebral discs (IVDs) increase in height, causing elongation of the spine up to several centimeters. Astronauts frequently report dull lower back pain that is most likely of discogenic origin and may result from IVD expansion. It is unknown whether disc volume solely increases by water influx, or if the content of glycosaminoglycans also changes in microgravity. Aim of this pilot study was to investigate effects of the spaceflight analog of bedrest on the glycosaminoglycan content of human lumbar IVDs. Five healthy, non-smoking, male human subjects of European descent were immobilized in 6° head-down-tilt bedrest for 21 days. Subjects remained in bed 24 h a day with at least one shoulder on the mattress. Magnetic Resonance Imaging (MRI) scans were taken according to the delayed gadolinium-enhanced magnetic resonance imaging (dGEMRIC) protocol before and after bedrest. The outcome measures were T1 and DT1. Scans were performed before and after administration of the contrast agent Gd-DOTA, and differences between T1-values of both scans (DT1) were computed. DT1 is the longitudinal relaxation time in the tissue and inversely related to the glycosaminoglycan-content. For data analysis, IVDs L1/2 to L4/5 were semi-automatically segmented. Zones were defined and analyzed separately. Results show a highly significant decrease in DT1 (p<0.001) after bedrest in all IVDs, and in all areas of the IVDs. The DT1-decrease was most prominent in the nucleus pulposus and in L4/5, and was expressed slightly more in the posterior than anterior IVD. Unexpected negative DT1-values were found in Pfirrmann-grade 2-discs after bedrest. Significantly lower T1 before contrast agent application was found after bedrest compared to before bedrest. According to the dGEMRIC-literature, the decrease in DT1 may be interpreted as an increase in glycosaminoglycans in healthy IVDs during bedrest. This interpretation seems contradictory to previous findings in IVD unloading

Muscular forces affect the glycosaminoglycan content of joint cartilage

BACKGROUND AND PURPOSE: Unloading alters the thickness of joint cartilage. It is unknown, however, to what extent unloading leads to a loss of glycosaminoglycans (GAGs) in the cartilage tissue. We hypothesized that muscle forces, in addition to axial loading, are necessary to maintain the joint cartilage GAG content of the knee and the upper and lower ankle. PATIENTS AND METHODS: The HEPHAISTOS orthosis was worn unilaterally by 11 men (mean age 31 (23-50) years old) for 56 days. The orthosis reduces activation and force production of the calf muscles while it permits full gravitational loading of the lower leg. MRI measurements of the knee and ankle were taken before the intervention, during the intervention (on day 49), and 14 days after the end of the intervention. Cartilage segmentation was conducted semiautomatically for the knee joint (4 segments) and for the upper (tibio-talar) and lower (subtalar) ankle joints (2 segments each). Linear mixed-effects (LME) models were used for statistical analysis. RESULTS: 8 volunteers completed the MRI experiment. In the lower ankle joint, differences in ΔT1 were found between the end of the intervention and 14 days after (p = 0.004), indicating a decrease in GAG content after reloading. There were no statistically significant differences in ΔT1 values in the knee and upper ankle joints. INTERPRETATION: Our findings suggest that in addition to gravitational load, muscular forces affect cartilage composition depending on the local distribution of forces in the joints affected by muscle contractio

Bending and torsion predominate the in vivo human tibia deformation regimes during locomotive activities and its relationship to muscular contractions

Introduction Bone deformation plays a decisive role in bone adaptation to the environment. Insufficient mechanical loading on bone under weightlessness may contribute to bone loss in astronauts. However, our understanding of the in vivo human bone deformation is limited due to technical difficulties. The contribution of muscular contractions on the bone loading is currently under debate. Taking the human tibia as a subject, the tibia deformation regimes and its relationship with muscular activities during different locomotor activities were investigated in the present study. Methods Tibia deformation was recorded in five subjects utilizing a novel optical approach established in our lab. Briefly, two marker clusters with three non-collinear retro-reflective markers on each cluster were affixed into the proximal and distal anterior-medial aspect of tibia cortex by bone screws. The markers trajectories were captured at 300 Hz with an optical system during different activities. Tibia deformations regimes, namely bending and torsion angles, were computed from the relative movement of the proximal cluster with respect to the distal cluster. Results The proximal tibia primarily bends to the posterior aspect (bending angle: 0.15° - 1.30°), medial aspect (bending angle: 0.38° - 0.90°) and twisted to the external aspect (torsion angle: 0.67° - 1.66°) during walking at between 2.5 and 6.1 km/h. Peak posterior bending and peak torsion occurred during the first (22%) and second half (76%) stance phase, respectively. Peak to peak (p2p) antero-posterior (AP) bending angles increased linearly with speed during walking and running, but p2p torsion angles remained constant. The largest p2p bending angle was observed during maximum single leg hopping, with p2p AP bending angle of 5.05 ± 0.33°. The p2p torsion angle was larger with forefoot than rear foot stair ascent and running. The tibia deformation regimes were characterized by torsion (1.35° ± 0.07°) rather than bending (0.52° ± 0.07°) during maximum isometric plantar flexion. Discussion and Conclusions Bending and torsion predominated the tibia deformation regimes during the investigated activities. Unexpected large torsion deformation, at least partially contributed by muscle contractions, might be another candidate to drive the long bone adaption. These findings therefore are relevant to the development of countermeasures, e.g. muscles training protocol, against bone loss in space

Computed tomography measurements of the lumbar spinous processes and interspinous space

Purpose This study examines the anatomic proportions of the interspinous space and the spinous processes, considering the optimal placement of an interspinous spacer. Methods Between January 2008 and December 2009, 565 patients undergoing computed tomography (CT) scans of the abdomen for various reasons were collected retrospectively for the study. Using the CT scan data, spinous processes of the lumbar spine L1-5 and the interspinous spaces T12-L5 were measured. Results The average measured interspinous space was 9.1 +/- 2.5 mm. This space became significantly (p<0.001) smaller from anterior to posterior. Average cortical thickness of all lumbar spinous processes was 2.5 +/- 0.5 mm. Cortical thickness decreased significantly (p<0.001) from anterior to posterior. The cortex of the spinous processes from L2 (2.67 +/- 0.45 mm) and L3 (2.66 +/- 0.94 mm) was significantly thicker (p<0.001) than that of the others. The spinous process of L5 had the thinnest (p<0.001) cortex (2.10 +/- 0.41 mm), as well as the smallest (p<0.001) volume (3.0 +/- 1.0 ml) and the shortest (p<0.001) height (16.6 +/- 3.6 mm). Conclusions The spinous processes of L2 and L3 are the largest and sturdiest, and that of L5 is the weakest. The L4/5 segment features the smallest interspinous space with the thinnest cortex of all lumbar spinous processes. Because the interspinous space narrows posteriorly and the cortex is thicker anteriorly, it seems that the best anatomic position for a stand alone interspinous spacers is anterior

In vivo application of an optical segment tracking approach for bone loading regimes recording in humans: A reliability study

This paper demonstrates an optical segment tracking (OST) approach for assessing the in vivo bone loading regimes in humans. The relative movement between retro-reflective marker clusters affixed to the tibia cortex by bone screws was tracked and expressed as tibia loading regimes in terms of segment deformation. Stable in vivo fixation of bone screws was tested by assessing the resonance frequency of the screw-marker structure and the relative marker position changes after hopping and jumping. Tibia deformation was recorded during squatting exercises to demonstrate the reliability of the OST approach. Results indicated that the resonance frequencies remain unchanged prior to and after all exercises. The changes of Cardan angle between marker clusters induced by the exercises were rather minor, maximally 0.06°. The reproducibility of the deformation angles during squatting remained small (0.04°/m–0.65°/m). Most importantly, all surgical and testing procedures were well tolerated. The OST method promises to bring more insights of the mechanical loading acting on bone than in the past

T2-relaxation time increases in lumbar intervertebral disks after 21d head-down tilt bed-rest

Objectives: Spaceflight back pain and intervertebral disc (IVD) herniations cause problems in astronauts. Purpose of this study was to assess changes in T2-relaxation-time through MRI measurements before and after head-down tilt bed-rest, a spaceflight analog. Methods: 8 men participated in the bed-rest study. Subjects remained in 6° head down tilt bed-rest in two campaigns of 21 days, and received a nutritional intervention (potassium bicarbonate 90 mmol/d) in a cross-over design. MRI measurements were performed 2 days before bed-rest, as well as one and five days after getting up. Image Segmentation and data analysis were conducted for the IVDs Th12/L1 to L5/S1. Results: 7 subjects, average age of 27.6 (SD 3.3) years, completed the study. Results showed a significant increase in T2-time in all IVDs (p < 0.001), more pronounced in the nucleus pulposus than in the annulus fibrosus (p<0.001). Oral potassium bicarbonate did not show an effect p=0.443). Pfirrmanngrade correlated with the T2-time (p<0.001). Conclusions: 6° head-down tilt bed-rest leads to a T2-time increase in lumbar IVDs. Oral potassium bicarbonate supplementation does not have an effect on IVD T2-time