Fast acclimation of freezing resistance suggests no influence of winter minimum temperature on the range limit of European beech

Low temperature extremes drive species distribution at a global scale. Here, we assessed the acclimation potential of freezing resistance in European beech ( Fagus sylvatica L.) during winter. We specifically asked (i) how do beech populations growing in contrasting climates differ in their maximum freezing resistance, (ii) do differences result from genetic differentiation or phenotypic plasticity to preceding temperatures and (iii) is beech at risk of freezing damage in winter across its distribution range. We investigated the genetic and environmental components of freezing resistance in buds of adult beech trees from three different populations along a natural large temperature gradient in north-western Switzerland, including the site holding the cold temperature record in Switzerland. Freezing resistance of leaf primordia in buds varied significantly among populations, with LT 50 values (lethal temperature for 50% of samples) ranging from −25 to −40 °C, correlating with midwinter temperatures of the site of origin. Cambial meristems and the pith of shoots showed high freezing resistance in all three populations, with only a trend to lower freezing resistance at the warmer site. After hardening samples at −6 °C for 5 days, freezing resistance of leaf primordia increased in all provenances by up to 4.5 K. After additional hardening at −15 °C for 3 days, all leaf primordia were freezing resistant to −40 °C. We demonstrate that freezing resistance of F. sylvatica has a high ability to acclimate to temperature changes in winter, whereas the genetic differentiation of freezing resistance among populations seems negligible over this small geographic scale but large climatic gradient. In contrast to the assumption made in most of the species distribution models, we suggest that absolute minimum temperature in winter is unlikely to shape the cold range limit of beech. We conclude that the rapid acclimation of freezing resistance to winter temperatures allows beech to track changing climatic conditions, especially during unusually warm winters interrupted by very cold weather

Overview of Methods to Quantify Invasiveness of Surgical Approaches in Orthopedic Surgery-A Scoping Review

BACKGROUND: There is a trend toward minimally invasive and more automated procedures in orthopedic surgery. An important aspect in the further development of these techniques is the quantitative assessment of the surgical approach. The aim of this scoping review is to deliver a structured overview on the currently used methods for quantitative analysis of a surgical approaches' invasiveness in orthopedic procedures. The compiled metrics presented in the herein study can serve as the basis for digitization of surgery and advanced computational methods that focus on optimizing surgical procedures. METHODS: We performed a blinded literature search in November 2020. In-vivo and ex-vivo studies that quantitatively assess the invasiveness of the surgical approach were included with a special focus on radiological methods. We excluded studies using exclusively one or multiple of the following parameters: risk of reoperation, risk of dislocation, risk of infection, risk of patient-reported nerve injury, rate of thromboembolic event, function, length of stay, blood loss, pain, operation time. RESULTS: The final selection included 51 articles. In the included papers, approaches to 8 different anatomical structures were investigated, the majority of which examined procedures of the hip (57%) and the spine (29%). The different modalities to measure the invasiveness were categorized into three major groups "biological" (23 papers), "radiological" (25), "measured in-situ" (14) and their use "in-vivo" or "ex-vivo" was analyzed. Additionally, we explain the basic principles of each modality and match it to the anatomical structures it has been used on. DISCUSSION: An ideal metric used to quantify the invasiveness of a surgical approach should be accurate, cost-effective, non-invasive, comprehensive and integratable into the clinical workflow. We find that the radiological methods best meet such criteria. However, radiological metrics can be more prone to confounders such as coexisting pathologies than in-situ measurements but are non-invasive and possible to perform in-vivo. Additionally, radiological metrics require substantial expertise and are not cost-effective. Owed to their high accuracy and low invasiveness, radiological methods are, in our opinion, the best suited for computational applications optimizing surgical procedures. The key to quantify a surgical approach's invasiveness lies in the integration of multiple metrics

Gluteus maximus tendon transfer as a salvage option for painful chronic hip abductor insufficiency: clinical and MRI results with a minimum follow-up of 24 months

INTRODUCTION: Chronic hip abductor insufficiency is a rare debilitating condition. In cases refractory to conservative treatment and not amenable to direct repair an augmentation becomes necessary. The preferred salvage method at our institution is augmentation with the anterior third of the gluteus maximus tendon. The aim of this study is to describe the results of 8 patients, treated for painful chronic hip abductor insufficiency with gluteus maximus muscle transfer, after a minimal follow-up of 24 months including a full clinical and MRI evaluation of the hip abductors pre- and postoperatively. METHODS: We retrospectively reviewed a consecutive series of 8 patients who were surgically managed for painful chronic hip abductor insufficiency. All patients had a Trendelenburg sign, impaired muscle strength (M ⩽ 3) as well as a complete avulsion of the hip abductors with marked fatty degeneration (⩾3). Pain levels, muscle strength, functional scores as well as a postoperative MRI was obtained after a minimal follow-up of 24 months. RESULTS: The mean age of the patients was 69 years, mean follow-up was 35 (26-54) months. Pain was significantly reduced postoperatively to VAS 2.5 from VAS 5 (p = 0.046). Trendelenburg sign remained positive in all patients and hip abductor strength did not improve significantly from 2.4 to 3.1 (p = 0.19). Complete healing of the transferred tendon was confirmed by MRI in all patients at last follow-up. CONCLUSIONS: In the setting of painful chronic hip abductor insufficiency refractory to conservative treatment with advanced muscle degeneration without the possibility of a direct reconstruction the gluteus maximus tendon transfer significantly decreased pain. The effect on hip abductor strength and patient-reported functional outcome scores is limited. Despite the modest results it remains our preferred salvage treatment option for lack of better alternatives. Larger studies are necessary to confirm these findings

Subtrochanteric osteotomy in the management of femoral maltorsion results in anteroposterior malcorrection of the greater trochanter: computed simulations of 3D surface models of 100 cadavers

Aim: The purpose of this study was to investigate the greater trochanter's (GT) behaviour in simulated subtrochanteric osteotomy. Materials and methods: Measurement of functional and anatomical femoral torsion, and position of the GT and lesser trochanter was performed using 3-dimensional (3D) surface models of 100 cadaveric femora. Femoral torsion between 2° and 22° was defined as normal, femora with 22° of femoral torsion were assigned to the low- and high-torsion group. Subtrochanteric osteotomy was simulated to normalise torsional deformities to 12°. Results: With subtrochanteric osteotomy, functional torsion was simultaneously corrected while adjusting anatomical torsion (R2 = 0.866, p < 0.001). Compared to the normal-torsion group, an anteroposterior (AP) overcorrection of ±0.5 centimetres (range 0.02-1.1 cm) of the GT resulted in the high- and low-torsion group, respectively (p < 0.001): Mean AP GT distance to a standardised coronal plane was 2.1 ± 0.3 cm (range 12-30 cm) in the normal-torsion group compared to 1.61 ± 0.1 cm (range 1.4-1.71 cm) and 2.6 ± 0.6 cm (range 1.8-3.6 cm) for the corrected high and low-torsion groups, respectively. The extent of the GT shift in AP direction correlated strongly with the extent to which anatomical femoral torsion was corrected (R2 = 0.946; p < 0.001). Conclusions: Subtrochanteric osteotomy for femoral maltorsion reliably adjusts anatomical and functional torsion, but also results in a ±1 cm AP shift of the GT per 10° of torsional correction. However, this effect of the procedure is most likely not clinically relevant in relation to hip abductor performance. Keywords: Femoral anteversion; maltorsion; subtrochanteric osteotomy; torsional correctio

Hip arthroscopy versus total hip arthroplasty-A study on patients with obesity above 40 years of age

Patients older than 40 years with a body-mass-index (BMI) >30 kg/m$^{2}$ , a femoroacetabular-impingement (FAI) and little cartilage damage are a challenge for hip surgeons. Hip-arthroscopy (HAS) or conservative therapy until a total hip arthroplasty (THA) is needed are possible treatments. Our research purpose was to compare the clinical results and complication/reoperation rate after HAS and THA in patients with obesity over 40 years. This retrospective study includes a consecutive series of patients with obesity (BMI >30 kg/m$^{2}$ ) who underwent HAS (19 hips) and THA (37 hips) over 40 years of age between 2007 and 2013 at our institution with a minimum of 12-months follow-up. Outcome measures were WOMAC (Western Ontario und McMaster Universities Arthritis Index), subjective-hip-value (SHV), residual complaints and the reoperation rate. Patient data and scores were collected pre-operative, 12 months post-operatively and at the last follow-up. Both groups showed a comparable age (mean 48 years). Regarding SHV-Scores the THA-group shows continuous significant improvements. Reaching 87% (range 50%-100%), the HAS-group showed in case of the SHV no significant change after 1 year and an improvement from preoperative to the last follow-up reaching 72% (range 30%-100%) at the last follow-up. Residual groin pain was significant higher in the HAS-group. Two deep infections (5.4%) requiring reoperations were reported in the THA-group. The conversion rate to THA after a mean time of 60 months was 26% (5 of 19). Patients with obesity over 40 years demonstrated inferior SHV, more often residual pain and revision surgery after HAS, when compared to THA at short-term, with conversions rate of one fourth. However, THA in this patient group showed high infection rate of 5%. This information is relevant for counselling above-mentioned patients

Revision rate of THA in patients younger than 40 years depends on primary diagnosis - a retrospective analysis with a minimum follow-up of 10 years

BACKGROUND Treating osteoarthritis in elderly patients with THA is very successful. However, surgeons hesitate to recommend THA in younger patients. The spectrum of etiologies for end stage hip disease in the younger population is diverse and therefore different courses may be assumed. Our objective was to evaluate THA revision rate within a minimum follow-up period of 10 years in young patients and to analyze the difference between different primary diagnoses. METHODS We included 144 consecutive hips in 127 patients younger than 40 years, who received a primary THA from 01/1996 to 12/2007. Operative reports, clinical and radiographic documentation were reviewed to determine primary diagnosis, prior hip surgery, component specifications and revision surgery. 111 hips in 97 patients were available for outcome analysis with a minimum follow-up of 10 years. RESULTS The mean age was 33 years (range 15-40 years) at the time of the index THA, 68 patients were female and 59 were male. Ten years revision rate on the prosthetic components was 13%. The most common primary diagnosis was DDH. DDH was associated with a risk of 17% for requiring a reoperation on the prosthetic components because of mechanical fatigue and therefore, significantly higher than for any other primary diagnosis (p = 0.005). CONCLUSION THA in young patients is associated with a high revision rate of 13% in 10 years. 17% of patients with DDH required revision surgery for mechanical fatigue within 10 years, which was significantly higher than for any other primary diagnosis (1.2%, OR 16.8)

Combining the advantages of 3-D and 2-D templating of total hip arthroplasty using a new tin-filtered ultra-low-dose CT of the hip with comparable radiation dose to conventional radiographs

BACKGROUND Inaccurately scaled radiographs for total hip arthroplasty (THA) templating are a source of error not recognizable to the surgeon and may lead to inaccurate reconstruction and thus revision surgery or litigation. Planning based on computed tomography (CT) scans is more accurate but associated with higher radiation exposure. The aim of this study was (1) to retrospectively assess the scaling deviation of pelvic radiographs; (2) to prospectively assess the feasibility and the radiation dose of THA templating on radiograph-like images reconstructed from a tin-filtered ultra-low-dose CT dataset. METHODS 120 consecutive patients were retrospectively analyzed to assess the magnification error of our current THA templates. 27 consecutive patients were prospectively enrolled and a radiographic work-up in the supine position including a new tin-filtered ultra-low-dose CT scan protocol was obtained. THA was templated on both images. Radiation dose was calculated. RESULTS Scaling deviations between preoperative radiographs and CT of ≥ 5% were seen in 25% of the 120 retrospectively analyzed patients. Between the two templates trochanter tip distance differed significantly (Δ2.4 mm, 0-7 mm, p = 0.035)), predicted femoral shaft size/cup size was the same in 45%/41%. The radiation dose of the CT (0.58 mSv, range 0.53-0.64) was remarkably low. CONCLUSION Scaling deviations of pelvic radiographs for templating THA may lead to planning errors of ≥ 3 mm in 25% and ≥ 6 mm in 2% of the patients. 2-D templating on radiograph-like images based on tin-filtered ultra-low-dose CT eliminates this source of error without increased radiation dose. LEVEL OF EVIDENCE Retrospective and prospective comparative study, Level III

Accuracy of pelvic measurements on virtual radiographic projections based on computed tomography scans compared to conventional radiographs pre- and postoperatively

BACKGROUND The anteroposterior (ap) radiograph of the pelvis is decisive in the diagnosis of different pathologies of the hip joint. Technical advantages have reduced the radiation dose of pelvic CT to levels comparable to radiographs. The purpose of this study was to validate if standard radiographic parameters (lateral center edge angle, medial center edge angle, acetabular index, acetabular arc, extrusion index, crossover sign and posterior wall sign) can accurately be determined on radiograph-like projections reconstructed from the CT dataset pre- and postoperatively. METHODS A consecutive series of patient with symptomatic dysplasia of the hip and a full radiologic workup (radiographs and CT scan pre- and postoperatively) who underwent periacetabular osteotomy were included. Standard radiographic parameters were compared between radiographs and radiograph-like projections by two authors pre- and postoperatively. RESULTS A total of 16 hips (32 radiographs/32 radiograph-like projections) were included in the study. No significant difference was found between the radiographs and radiograph-like images for all parameter for both examiners. ICC between radiograph and radiograph-like projections for all investigated parameters showed good to excellent reliability (0.78-0.99) pre- and postoperatively. CONCLUSION Radiograph-like projections show comparable results to radiographs with regard to the important investigated parameters (lateral center edge angle, medial center edge angle, acetabular index, acetabular arc, extrusion index, crossover sign and posterior wall sign). Thus, ultra-low-dose CT scans may reduce the need for conventional radiographs in pre- and postoperative analyses of 3-dimensional hip pathologies in the future, as the advantages increasingly outweigh the disadvantages

Augmented reality-guided pelvic osteotomy of Ganz: feasibility in cadavers

INTRODUCTION The periacetabular osteotomy is a technically demanding procedure with the goal to improve the osseous containment of the femoral head. The options for controlled execution of the osteotomies and verification of the acetabular reorientation are limited. With the assistance of augmented reality, new possibilities are emerging to guide this intervention. However, the scientific knowledge regarding AR navigation for PAO is sparse. METHODS In this cadaveric study, we wanted to find out, if the execution of this complex procedure is feasible with AR guidance, quantify the accuracy of the execution of the three-dimensional plan, and find out what has to be done to proceed to real surgery. Therefore, an AR guidance for the PAO was developed and applied on 14 human hip cadavers. The guidance included performance of the four osteotomies and reorientation of the acetabular fragment. The osteotomy starting points, the orientation of the osteotomy planes, as well as the reorientation of the acetabular fragment were compared to the 3D planning. RESULTS The mean 3D distance between planned and performed starting points was between 9 and 17 mm. The mean angle between planned and performed osteotomies was between 6° and 7°. The mean reorientation error between the planned and performed rotation of the acetabular fragment was between 2° and 11°. CONCLUSION The planned correction can be achieved with promising accuracy and without serious errors. Further steps for a translation from the cadaver to the patient have been identified and must be addressed in future work

Total hip arthroplasty through the direct anterior approach for sequelae of Legg-Calvé-Perthes disease

INTRODUCTION Due to multiplanar deformities of the hip, total hip arthroplasty (THA) for sequelae of Legg-Calvé-Perthes disease (LCPD) is often technically demanding. This study aimed to compare the clinical and radiographic outcomes of patients with sequelae of LCPD undergoing THA through the direct anterior approach (DAA) and non-anterior approaches to the hip. METHODS All patients with sequelae of LCPD who underwent primary THA between 2004 and 2018 (minimum follow-up: 2 years) were evaluated and separated into two groups: THA through the DAA (Group AA), or THA through non-anterior approaches to the hip (Group non-AA). Furthermore, a consecutive control group of patients undergoing unilateral THA through the DAA for primary hip osteoarthritis (Group CC) was retrospectively reviewed for comparison. RESULTS Group AA comprises 14 hips, group non-AA 17 hips and group CC 30 hips. Mean follow-up was 8.6 (± 5.2; 2-15), 9.0 (± 4.6; 3-17) and 8.1 (± 2.2; 5-12) years, respectively. At latest follow-up, Harris Hip Score was 90 (± 20; 26-100), 84 (± 15; 57-100), and 95 (± 9; 63-100) points, respectively. Overall, 6 patients treated for LCPD (each 3 patient in the AA and non-AA group) developed postoperative sciatic nerve palsy, of which only one was permanent. Complication-related revision rate at the latest follow-up was 15% in the AA-group and 25% in the non-AA group, respectively. CONCLUSION THA through the DAA might be a credible option for the treatment of sequelae of LCPD with comparable complication rates and functional outcomes to non-anterior approaches