Variations in medial and lateral slope and medial proximal tibial angle.

PURPOSE: The primary objective of this study was to quantify the variations of the medial posterior tibial slope (MPTS) and the lateral posterior tibial slope (LPTS), as well as of the medial proximal tibial angle (MPTA), and to determine the fraction of patients for which standard techniques including different alignment techniques would result in alteration of the patient's individual posterior tibial slope (PTS) and MPTA. Furthermore, it was of interest if a positive correlation between PTS and MPTA or between medial and lateral slope exists. METHODS: A retrospective study was performed on CT-scans of 234 consecutively selected European patients undergoing individual total knee replacement. All measurements were done on three-dimensional CAD models, which were generated on the basis of individual CT-scans, including the hip, knee, and ankle center. Measurements included the medial and lateral PTS and the MPTA. PTS was measured as the angle between the patient's articular surface and a plane perpendicular to the mechanical axis of the tibia in the sagittal plane. MPTA was defined as the angle between the tibial mechanical axis and the proximal articular surface of the tibia in the coronal plane. RESULTS: Analysis revealed a wide variation of the MPTS, LPTS, and MPTA among the patients. MPTS and LPTS varied significantly both interindividually and intraindividually. The range of PTS was up to 20° for MPTS (from - 4.3° to 16.8°) and for LPTS (from - 2.9 to 17.2°). The mean intraindividual difference between MPTS and LPTS in the same knee was 2.6° (SD 2.0) with a maximum of 9.5°. MPTA ranged from 79.8 to 92.1° with a mean of 86.6° (SD ± 2.4). Statistical analysis revealed a weak positive correlation between MPTA and MPTS. CONCLUSION: The study demonstrates a huge interindividual variability in PTS and MPTA as well as significant intraindividual differences in MPTS and LPTS. Therefore, the question arises, whether the use of standard techniques, including fixed PTSs and MPTAs, is sufficient to address every single patient's individual anatomy. LEVEL OF EVIDENCE: III.

What Is the Possible Impact of High Variability of Distal Femoral Geometry on TKA? A CT Data Analysis of 24,042 Knees.

BACKGROUND: Previous studies analyzing femoral components of TKAs have demonstrated the limited ability of these components to accommodate size variations seen in the patient population, particularly width and femoral offset. QUESTIONS/PURPOSES: The purpose of this study was to use a large data set of knee CT scans (1) to determine the variations in the distal and posterior femoral geometries and to determine whether there is a correlation between distal condylar offset and posterior femoral offset as a potential parameter for symmetry/asymmetry; and (2) to evaluate what proportion of knees would have a substantial mismatch between the implant's size or shape and the patient's anatomy if a femoral component of a modern standard TKA of symmetric (sTKA) or asymmetric (asTKA) designs were to be used. METHODS: A retrospective study was performed on 24,042 data sets that were generated during the design phase for a customized TKA implant. This data set was drawn from European and US-American patients. Measurements recorded for the femur included the overall AP and mediolateral (ML) widths, widths of the lateral condyle and the medial condyle, the distal condylar offset (DCO) between the lateral and medial condyles in the superoinferior direction, and the posterior femoral offset (PFO) as the difference between the medial and lateral posterior condylar offset (PCO) measured in the AP direction. A consecutively collected subset of 2367 data sets was further evaluated to determine the difference between the individual AP and ML dimensions of the femur with that of modern TKA designs using two commercially available implants from different vendors. RESULTS: We observed a high degree of variability in AP and ML widths as well as in DCO and PFO. Also, we found no correlation between DCO and PCO of the knees studied. Instances of a patient having a small DCO and higher PCO were commonly seen. Analysis of the DFOs revealed that overall, 62% (14,906 of 24,042) of knees exhibited DCO > 1 mm and 83% (19,955 of 24,042) of femurs exhibited a > 2-mm difference between the lateral and medial PCO. Concerning AP and ML measurements, 23% (544 of 2367) and 25% (592 of 2367) would have a mismatch between the patient's bony anatomy and the dimensions of the femoral component of ± 3 mm if they would have undergone a modern standard sTKA or asTKA design, respectively. CONCLUSIONS: Analysis of a large number of CT scans of the knee showed that a high degree of variability exists in AP and ML widths as well as in DCO and PFO. CLINICAL RELEVANCE: These findings suggest that it is possible that a greater degree of customization could result in surgeons performing fewer soft tissue releases and medial resections than now are being done to fit a fixed-geometry implant into a highly variable patient population. However, as an imaging study, it cannot support one approach to TKA over another; comparative studies that assess patient-reported outcomes and survivorship will be needed to help surgeons decide among sTKA, asTKA, and customized TKA.

Off-loading strategies in diabetic foot syndrome-evaluation of different devices.

INTRODUCTION: Diabetic foot syndrome is one of the most dreaded complications in diabetes mellitus. The purpose of this study was to assess the value of different offloading devices compared to walking in barefoot condition and in normal shoes both in healthy subjects and in patients with diabetes and neuropathy. METHODS: Twenty patients with diabetes and polyneuropathy and ten healthy probands were included. Pedobarographic examination was performed in barefoot condition, with sneakers, postoperative shoes, Aircast® Diabetic Pneumatic Walker™ and VACO®diaped. In the diabetic group, a total contact cast was additionally tested. RESULTS: The most effective reduction of force was achieved by TCC (75%) and VACOdiaped (64.3%) with the VACO®diaped resulting in the most homogeneous distribution of forces all over the foot. DISCUSSION/CONCLUSION: A customized device like the TCC is still the most proven offloading device. However, a removable cast walker being based on vacuum pads and a cushioning sole, provides better results concerning force distribution.

Postural stability after patient-specific interpositional knee spacer or total knee arthroplasty: a comparative study.

PURPOSE: Total knee arthroplasty provides excellent results concerning functional demands, patient satisfaction and range of motion. Short-term results after implantation of patient-specific knee spacers also show encouraging results. We hypothesised that patient-specific interpositional devices provide better proprioception and postural stability by preserving the whole bone stock and both cruciate ligaments. METHODS: In this study we compared functional results, proprioception and postural stability 16 months after 20 consecutive patient-specific interpositional device implantations of the knee (group A) and 20 consecutive total knee arthroplasties (group B). Patients were evaluated using the Knee Society Score (KSS) and the Western Ontario and McMaster Universities Arthritis Index (WOMAC). Postural stability was analysed during single leg stance on a force platform (Biodex). RESULTS: There were no significant differences between both groups concerning functional results 16 months after the procedure. Concerning postural stability, significant differences were found between both groups. Comparing the operated-on and non-operated-on sides in single leg stance, the operated-on leg gained the same stability as the non-operated-on side in both groups. CONCLUSIONS: The successful treatment of knee osteoarthritis can restore postural stability to the level of the unaffected side-independent from the implanted devices and with preservation of soft tissue and bone stock. Superior postural stability in joint-preserving patient-specific interpositional knee devices compared with total knee arthroplasty had to be attributed to the different age of both groups.

Retrospective comparative study shows no significant difference in postural stability between cruciate-retaining (CR) and cruciate-substituting (PS) total knee implant systems.

PURPOSE: Modified postural stability after retaining the posterior cruciate ligament (PCL) in total knee arthroplasty is still discussed controversially. The objective of this study was to evaluate whether a PCL-retaining implant design should be preferred over a PCL-substituting implant design regarding postural stability in one-leg stance and clinical outcome. METHODS: Forty patients underwent total knee arthroplasty, 20 of them with a cruciate-retaining (CR) and 20 of them with a cruciate-substituting (PS) implant system. Postural stability was analysed 6 months postoperatively in one-leg stance using the Biodex Balance System. In addition, the Western Ontario and McMaster Universities Arthritis Index (WOMAC) and Knee Society Score were completed. RESULTS: This study shows that there is no significant difference in postural stability between CR and PS) implant systems with PS implants showing better results in WOMAC score. CONCLUSIONS: In case it is necessary to use a PS implant, no negative influence on postural stability is to be expected compared to a CR implant.

Speckle Suppression by Decoherence in Fluctuation Electron Microscopy.

We compare experimental fluctuation electron microscopy (FEM) speckle data with electron diffraction simulations for thin amorphous carbon and silicon samples. We find that the experimental speckle intensity variance is generally more than an order of magnitude lower than kinematical scattering theory predicts for spatially coherent illumination. We hypothesize that decoherence, which randomizes the phase relationship between scattered waves, is responsible for the anomaly. Specifically, displacement decoherence can contribute strongly to speckle suppression, particularly at higher beam energies. Displacement decoherence arises when the local structure is rearranged significantly by interactions with the beam during the exposure. Such motions cause diffraction speckle to twinkle, some of it at observable time scales. We also find that the continuous random network model of amorphous silicon can explain the experimental variance data if displacement decoherence and multiple scattering is included in the modeling. This may resolve the longstanding discrepancy between X-ray and electron diffraction studies of radial distribution functions, and conclusions reached from previous FEM studies. Decoherence likely affects all quantitative electron imaging and diffraction studies. It likely contributes to the so-called Stobbs factor, where high-resolution atomic-column image intensities are anomalously lower than predicted by a similar factor to that observed here.

Gait analysis after tibialis anterior tendon rupture repair using Z-plasty.

Other than limited reports regarding surgical outcomes, little information is available regarding whether Z-plasty of the tibialis anterior results in normal gait kinematics. We included 5 patients with spontaneous ruptures in the present retrospective study. The mean interval between rupture and operative treatment was 2.6 ± 2.6 months (standard deviation). The mean age of the patients was 63 (range 40 to 80) years. All patients were treated operatively with Z-plasty. Gait analysis was used to study the outcome, comparing the operated and nonoperated limbs. The patients were tested after a mean follow-up of 22 (range 12 to 33) months. No repeat ruptures were noted. Plantarflexion was significantly diminished during the preswing phase and initial swing phase in the operated limbs compared with the uninjured limbs. Plantarflexion was significantly increased during the terminal swing phase on the operated side. Knee flexion was nearly symmetrical. No significant differences regarding the temporospatial parameters were noted. We recommend Z-plasty for ruptures of the tibialis anterior tendon as a safe and effective procedure. However, this technique does not fully restore a physiologic gait pattern.

Arterial anatomy of the hallucal sesamoids.

The aim of this study was to analyze the arterial supply of the sesamoid bones of the hallux. Twenty-two feet from adult cadavers were injected with epoxide resin or an acrylic polymer in methyl methacrylate (Acrifix) and subsequently processed by two slice plastination methods and the enzyme maceration technique. Afterwards, the arterial supply of the sesamoid bones was studied. The first plantar metatarsal artery provided a medial branch to the medial sesamoid bone. The main branch of the first plantar metatarsal artery continued its course distally along the lateral side of the lateral sesamoid and supplied it. The supplying arteries penetrated the sesamoid bones on the proximal, plantar, and distal sides. The analysis and cataloging of the microvascular anatomy of the sesamoids revealed the first plantar metatarsal artery as the main arterial source to the medial and lateral sesamoid bones. In addition, the first plantar metatarsal artery ran along the lateral plantar side of the lateral sesamoid bone, suggesting that this artery is at increased risk during soft-tissue procedures such as hallux valgus surgery.

Leg axis correction with ConforMIS iForma (interpositional device) in unicompartmental arthritis of the knee.

Degeneration of the meniscus and the articular cartilage in unicompartmental osteoarthritis of the knee results in progressive deformity of the leg axis. It is the aim of this study to evaluate if a leg axis correction can be achieved by implanting a customised metallic interpositional device for the knee (ConforMIS iForma). Before and after implanting a ConforMIS iForma knee implant, a radiological analysis of the leg axis deviation in the frontal plane was performed prospectively in 27 patients by evaluating anteroposterior single-leg stance radiographs. We achieved a sufficient leg axis correction with an average correction of 3.8 degrees and an averaged small under-adjustment of 0.9 degrees by inserting the ConforMIS iForma interpositional knee implant. Apart from the primary treatment objective of articular surface restitution the ConforMIS iForma knee implant can be reliably used to correct axis deformity occurring with unicompartmental osteoarthritis of the knee.

Predominance of synovial sensory nerve fibers in arthrofibrosis following total knee arthroplasty compared to osteoarthritis of the knee.

BACKGROUND: So far, there exists no golden standard for the treatment of arthrofibrosis (AF) following total knee arthroplasty (TKA). Although pain is a hallmark of AF, nociceptive nerve fibers have never been investigated in affected joint tissue. METHODS: A total of 24 patients with osteoarthritis (OA) of the knee (n = 12) and post-TKA AF of the knee (n = 12) were included. Along evaluation of typical clinical signs and symptoms by using the Knee Society Clinical Rating System (KSS), the Knee Injury and Osteoarthritis Outcome Score (KOOS), and the Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC index), the innervation of joint tissue was studied by semiquantitative immunofluorescence of nerve fibers. RESULTS: Patients with AF compared to OA had a lower KSS and lower KOOS. In all compartments (anterior, medial, and lateral recesses), the density of synovial sympathetic nerve fibers was significantly higher in OA compared to AF, which was also true for the density of sensory nerve fibers in the medial and lateral recesses. In synovial tissue of the anterior recess of patients with AF compared to OA, the density of nociceptive sensory nerve fibers was significantly higher relative to sympathetic nerve fibers. This was similarly observed in the neighboring infrapatellar fat pad of the knee. CONCLUSIONS: Similar as in many painful musculoskeletal diseases, this study indicates that patients with arthrofibrosis of the knee after TKA demonstrate a preponderance of profibrotic sensory nerve fibers over antifibrotic sympathetic nerve fibers. This could serve as a starting point for AF therapy with specific antifibrotic pain medication or regional anesthetic techniques.

Evaluation of implant position and knee alignment after patient-specific unicompartmental knee arthroplasty.

Implant positioning and knee alignment are two primary goals of successful unicompartmental knee arthroplasty. This prospective study outlines the radiographic results following 32 patient-specific unicompartmental medial resurfacing knee arthroplasties. By means of standardized pre- and postoperative radiographs of the knee in strictly AP and lateral view, AP weight bearing long leg images as well as preoperative CT-based planning drawings an analysis of implant positioning and leg axis correction was performed.The mean preoperative coronal femoro-tibial angle was corrected from 7° to 1° (p<0.001). The preoperative medial proximal tibial angle of 87° was corrected to 89° (p<0.001). The preoperative tibial slope of 5° could be maintained. The extent of the dorsal femoral cut was equivalent to the desired value of 5mm given by the CT-based planning guide. The mean accuracy of the tibial component fit was 0mm in antero-posterior and +1mm in medio-lateral projection. Patient-specific fixed bearing unicompartmental knee arthroplasty can restore leg axis reliably, obtain a medial proximal tibial angle of 90°, avoid an implant mal-positioning and ensure maximal tibial coverage.

Marked loss of sympathetic nerve fibers in chronic Charcot foot of diabetic origin compared to ankle joint osteoarthritis.

The pathogenesis of Charcot foot is based on three disputed factors: (1) loss of neurotrophic influence, (2) microtraumatic lesions, and (3) neurovascular disturbances. These etiological causes were uncovered by clinicophysiological tests. However, no results of quantitative nerve density studies of sympathetic and sensory substance P-positive (SP+) nerve fibers are available. We studied the density of sympathetic and SP+ nerve fibers in three distinct areas of the tarsus. Fifteen patients with ankle osteoarthritis (OA) and 15 patients with diabetic Charcot foot were included. Patients with OA did not differ from those with Charcot foot in SP+ sensory nerve fiber density. However, at all three areas, the density of sympathetic nerve fibers was significantly lower in patients with Charcot foot compared to OA (p = 0.006). In addition, we found that the sympathetic nerve repellent factor semaphorin 3C was highly expressed in inflamed tissue in Charcot patients. In Charcot foot of diabetic origin a severe loss of sympathetic nerve fibers was observed. These findings in chronically inflamed Charcot foot lend support to the neurovascular theory in the late chronic phase, which probably depends on the inflammatory upregulation of nerve repellent factors.

Preponderance of sensory versus sympathetic nerve fibers and increased cellularity in the infrapatellar fat pad in anterior knee pain patients after primary arthroplasty.

Sensory nerve fibers transmit pain perception and secrete pro-inflammatory substance P (SP). Sympathetic nerve fibers secrete anti-inflammatory norepinephrine and endogenous opioids, which inhibit pain perception in a bidirectional crosstalk with sensory fibers. In patients with anterior knee pain after primary arthroplasty of the knee (AKP), this study investigated in parallel the innervation of the infrapatellar fat pad by sensory and sympathetic nerve fibers. A total of 32 patients with osteoarthritis (OA) of the knee (n = 10), AKP after primary knee joint replacement (n = 7), and OA of the hip (n = 15) were included. Sensory nerve fibers were semiquantitatively detected by immunohistochemistry against SP, and sympathetic nerve fibers were stained with an antibody against tyrosine hydroxylase. Cellular density of the tissue was investigated by counting cell nuclei. The density of sympathetic nerve fibers in the fat tissue was similar in knee OA as compared to AKP. In the fat tissue, density of sensory substance P-positive nerve fibers was higher in AKP than in knee OA, which was not observed in the fibrosis capsule of the fat pad. The preponderance of sensory over sympathetic nerve fibers was accompanied by an increased cellular density in fat tissue in patients with AKP compared to knee OA. A positive correlation existed between cellularity and sensory nerve fiber density in fat tissue. This study revealed a preponderance of sensory over sympathetic innervation in the infrapatellar fat pad in AKP after primary arthroplasty of the knee, which possibly leads to aggravation and continuation of AKP and local inflammation.