Higher femoral anteversion restoration accuracy after total hip arthroplasty with a proximally fixed anatomic stem than with a generic straight double-tapered stem.

BACKGROUND: Femoral antetorsion in uncemented hip replacement hardly can be modified and the restoration of the anatomic anteversion might be difficult with standard stems. We compared femoral anteversion restoration of a generic straight stem with a proximally fixed anatomic stem that included a dual sagittal curvature and a proximal torsion. It was hypothesised that the restoration of the anteversion was more accurate with the anatomic stem. PATIENTS AND METHODS: In this comparative study data were collected prospectively of 80 consecutive patients with total hip arthroplasty for primary osteoarthritis. In the first 40 patients (Group I) a cementless proximally fixed anatomic stem with 15° antetorsion of the shaft and a dual sagittal curvature was used. Its design was based on a database of 3D CT images of 600 hips. For comparison a cementless generic straight double-tapered stem was implanted in the next 40 patients (Group II). All operations were performed by one experienced surgeon. All patients had a preoperative 3D planning. A low-dose CT scan was performed at 3 months postoperatively to determine the postoperative stem anteversion. RESULTS: The demographics were similar in both groups. In group I the mean postoperative femoral anteversion was similar to the preoperative one (22.1° ± 10.2° vs. 20.4° ± 9°; p = 0.2). In Group II, the mean postoperative femoral anteversion was lower (12.9° ± 10.8°, vs. 18.3° ± 12°; p = 0.02). CONCLUSIONS: Uncemented standard femoral stems tend to reduce femoral anteversion. The used anatomic stem restored femoral anteversion better. The clinical impact of this finding has to be proven.

Does the bone mineral density measured on a preoperative CT scan before total hip arthroplasty reflect the bone's mechanical properties?

INTRODUCTION: No method exists to quantify the bone quality and factors that will ensure osteointegration of total hip arthroplasty (THA) implants. A preoperative CT scan can be used to evaluate the bone mineral density (BMD) when planning a THA procedure. The aim of this study was to validate BMD measurement as a marker of bone quality based on a preoperative CT scan. HYPOTHESIS: BMD reflects the bone's mechanical properties for the purposes of preoperative THA planning. METHODS: Patients who underwent primary THA for hip osteoarthritis or dysplasia with cementless implants and 3D preoperative plan were enrolled prospectively. The cortical BMD was calculated on CT scans used in the preoperative planning process. During the surgical procedure, the femoral head and neck were collected. These bone samples were subsequently scanned with a calibrated micro-CT scanner. The BMD was derived from the micro-CT scan and used as input for a finite element model to determine the bone's mechanical properties. Correlations between BMD, apparent moduli of elasticity and porosity were calculated. RESULTS: The values of cortical BMD measured on the micro-CT and CT scan were significantly correlated (cc=0.52). The mean angular cortical BMD measured with the micro-CT scan was 1472.33mg/cm3 (SD: 357.53mg/cm3, 980.64-2830.6mg/cm3). There was no significant correlation between cortical BMD and the various apparent moduli of elasticity, except for Eyy and Gzy. Cortical BMD and porosity were inversely correlated with a Spearman coefficient of -0.41 (CI95: [-0.71; -0.02], p=0.03). There was also an inverse correlation between the apparent moduli of elasticity (independent of their orientation) and porosity (p<0.01). DISCUSSION: BMD provides information about porosity, which is a major factor when evaluating the bone's mechanical properties before THA. LEVEL OF EVIDENCE: IV.

Surgical epicondylar axis is not orthogonal to the femoral mechanical knee axis in valgus knees with primary osteoarthritis: Three-dimensional analysis according to knee coronal alignment in 112 patients.

BACKGROUND: During total knee arthroplasty (TKA), most surgeons align the femoral component along the surgical epicondylar axis (SEA) considering it as orthogonal to the femoral mechanical axis. However, it is still unclear how SEA coronal alignment varies according to the native coronal knee alignment. The main goal of this study was to analyze the SEA orientation according to the native coronal knee morphotype. METHODS: A total of 112 patients underwent a three-dimensional (3D) -planning-based TKA. The SEA was then determined by locating the epicondyles on 3D models. The 3D femoral and tibial mechanical axes were marked and the femoral (FMA) and tibial (TMA) mechanical angles were measured. The native HKA angle was measured as FMA + TMA. The SEA orientation angles were measured in the coronal (SEA-α) and axial (SEA-ß) plane. SEA orientation was compared between the valgus, neutral, and varus knees. RESULTS: The mean SEA-α angle was 90.2 ± 3° and the mean axial SEA-ß angle was 92.2 ± 1.3°. The SEA-α angle was significantly higher in the valgus group compared with the neutral group (92.3 ± 2.9°, 90 ± 2.9°, P = 0.0009) whereas there was no significant difference in the SEA-α angle between the varus and the neutral group (89.7 ± 2.3°, 90 ± 2.9°, P = 0.32). CONCLUSIONS: In contrast to the neutral and varus knees, the SEA was not orthogonal to the femoral mechanical axis in patients undergoing TKA for primary osteoarthritis. Our results suggest adapting the coronal alignment of the femoral component during TKA, while maintaining an average 2° valgus in valgus knees. By contrast, with varus and neutral knees, our data support the use of a mechanical alignment.

A higher reliability with a computed tomography scan-based three dimensional technique than with a two dimensional measurement for lower limb discrepancy in total hip arthroplasty planning.

PURPOSE: The goal was to compare the reliability of a novel 3D method with the standard 2D technique for lower limb discrepancy (LLD) measurement during pre-operative THA planning. METHODS: This prospective study included 100 consecutive patients who underwent THA using 3D planning based on a low-dose CT scan. The LLD was subdivided into three parameters: the intra-articular LLD (IA-LLD), the segmental extra-articular LLD (EA-LLD), and the total LLD (T-LLD). The LLD was assessed with a standard 2D technique on CT scanograms and also with a 3D method. A pelvic reference line (PBL) was determined as the 3D line joining the deepest part of the two great sciatic notches. The IA length was measured from the lesser trochanters (MLT) to the PBL. The EA length was measured from the MLT to the ankle center, and the total length was measured from the ankle center to the PBL. The intra- and inter-observer reliability of the measurements was assessed with the intra-class correlation coefficient (ICC). RESULTS: The intra-observer ICC was higher with the 3D technique for IA-LLD (0.96-0.97 vs. 0.79-0.84), EA-LLD (0.96 vs. 0.78-0.92), and T-LLD (0.99 vs. 0.90-0.97). Inter-observer ICC was also higher with the 3D technique for IA-LLD (0.90-0.94 vs. 0.70-0.84) and EA-LLD (0.93-0.96 vs. 0.80-0.82), but not for T-LLD (0.91-0.94 vs. 0.91-0.94). CONCLUSION: The presented 3D method has a higher reliability than 2D assessment of LLD during pre-operative THA planning. This article presents the first discussion of measuring LLD from 3D models. As 3D reconstruction becomes both more feasible and less-invasive, this study has interest to the orthopaedic surgeon.

Pre-operative bone mineral density is a predictive factor for excellent early patient-reported outcome measures in cementless total hip arthroplasty using a proximally fixed anatomic stem. A prospective study at two year minimum follow-up.

PURPOSE: The goal of the study was to analyze the impact of the pre-operative bone mineral density on the patients' reported outcomes at two year minimum follow-up of cementless THA using a proximally fixed anatomic stem. METHODS: A prospective study included all patients who underwent a cementless THA using a specific proximally fixed anatomic stem and a 3D preoperative CT scan-based planning. The bone mineral density (BMD) of the metaphyseal cancellous bone was computed in a volume (of 1 mm thick and of 1 cm2 surface) at the level of the calcar 10 mm above the top of the lesser trochanter. Patients were assessed at two year follow-up using self-administered auto-questionnaires corresponding to the modified Harris (mHHS), the Oxford (OHS), and the Forgotten Hip (FHS) scores. A multiple linear regression statistical analysis was performed to assess the link between the mHHS, the age, body mass index (BMI), BMD, gender, and ASA grade. RESULTS: Fifty patients were included (29 men, 21 women), with an average age of 62 ± 12 years and an average BMI of 27 ± 5 kg/m2. At two year follow-up, on multivariate analysis, excellent mHHS (≥ 90%) was significantly associated with only two parameters: a BMI ≤ 25 kg /m2 with an odd ratio OR = 10 (CI95% [2.1-48.3], p = 0.004) and a BMD ≥ 72 mg/cm3 with an odd ratio OR = 4.87 (CI95% [1.2-18.6], p = 0.02). CONCLUSION: The short-term PROMs after cementless THA are impacted by pre-operative cancellous bone density. However, the BMI remains the most influential parameter on the clinical outcomes.

Modification of regional bone mineral density due to femoral rasping in cementless proximally fixed total hip arthroplasty.

BACKGROUND: Three-dimensional planning (3DP) in total hip arthroplasty using computed tomography (CT) to analyze bone mineral density (BMD) at the stem-femur interface has a high reported accuracy and excellent mid-term results in the literature. However, 3DP does not take into account the effect of femoral rasping on BMD distribution within the rasped cavity. Characterizing the impact of femoral rasping on BMD may help avoid mechanical failures, but this data is not accurately investigated. Therefore, we set out a cadaveric study to identify if: (1) Femoral rasping modified regional BMD in areas considered critical for bone anchorage of cementless metaphyseally fixed anatomic stems. (2) In areas of bone-implant contact with an initial high BMD, does femoral rasping increase BMD? HYPOTHESIS: Femoral rasping increases BMD in some zones considered critical for bone anchorage of cementless metaphyseally fixed anatomic stems within the rasped femoral cavity. METHODS: Four cadaveric femurs were selected to undergo a rasping procedure similar to surgical techniques used for metaphyseally fixed anatomic stems. Images of femurs before and after rasping were obtained with a micro-CT scanner (pixel size 35µm). BMD values before and after rasping were compared in a trabecular bone ring of 3mm thickness around the cavity created by the rasps, in a region extending 3cm above and 2cm below the middle of the lesser trochanter. RESULTS: Average BMD increased significantly after rasping in 3 of the 4 femurs (13% (0.27 to 0.30) (p=0.004)), 12% (0.32 to 0.36 (p=0.034)) and 15% (0.4 to 0.46 (p=0.001)), while there was no significant variation in the last femur (0.32 to 0.32 (p>0.05)). Increases in regional BMD were significantly higher in the lateral and medial areas, as well as in the most distal femoral regions. There were significantly lower variations of BMD in regions with initially higher BMD. DISCUSSION: Current opinion considers trabecular bone debris from femoral rasping to have an impact on final stem position and outcome. Our study has demonstrated an overall positive effect of femoral rasping on BMD in the rasped cavity. Understanding this in the context of 3DP may help avoid mechanical failures such as, suboptimal implant fit, fill, and stability as well as femoral fractures during stem implantation. LEVEL OF EVIDENCE: IV, Prospective in vitro study.

Same-stage total knee arthroplasty and osteotomy for osteoarthritis with extra-articular deformity. Part II: Femoral osteotomy, prospective study of 6 cases.

BACKGROUND: Same-stage (1S) total knee arthroplasty (TKA) and femoral osteotomy (FO) may deserve consideration in patients with both knee osteoarthritis and severe extra-articular knee deformity (EKD). The objective of this study was to assess clinical and radiological outcomes and morbidity (complications and revisions) in 6 patients managed with S1-TKA-FO. HYPOTHESIS: 1S-TKA-FO produces satisfactory outcomes and is not associated with higher morbidity rates compared to two-stage TKA-TO or TKA with intra-articular EKD correction, while also significantly shortening total treatment duration. MATERIAL AND METHODS: A prospective study was performed in 6 patients managed with 1S-TKA-FO between 1999 and 2011; mean age was 64 years (range, 59-72 years) and mean body mass index was 29.5 (range, 26-35). The EKD was consistently greater than 10°. The cause was post-traumatic mal-union in 4 patients, constitutional EKD in 1 patient, and FO in 1 patient. In each patient, the clinical International Knee Society (IKS) score and the hip-knee-ankle angle (HKA), femoral mechanical angle (FMA) and tibial mechanical angle (TMA), were recorded prospectively before and after surgery. RESULTS: A long uncemented extension stem was used in all 6 patients and a posterior-stabilised implant in 5 patients. No hinged implants were used. In 4 patients, internal fixation of the FO was performed. Mean follow-up was 10 years (range, 4-15 years). From baseline to last follow-up, the mean IKS score increased from 46 to 161 and mean flexion from 95° (range, 70-110°) to 107° (range, 90-120°). The HKA measured radiographically was between 178° and 182° in all 6 patients. The complications consisted of deep vein thrombosis in 1 patient and knee stiffness requiring manipulation under general anaesthesia in 1 patient. No patient experienced mal-union or required revision surgery. DISCUSSION: Apart from a case-series study of 11 patients, very few data are available on 1S-TKA-FO. In our small population, no major complications were recorded. The encouraging long-term outcomes warrant a recommendation to perform 1S-TKA-FO in patients with knee osteoarthritis and an intra-femoral deformity greater than 10°. LEVEL OF EVIDENCE: IV, prospective observational cohort study.

Same-stage total knee arthroplasty and osteotomy for osteoarthritis with extra-articular deformity. Part I: Tibial osteotomy, prospective study of 26 cases.

BACKGROUND: In patients with advanced knee osteoarthritis and extra-articular knee deformity (EKD), ligament balance may be difficult to achieve during total knee arthroplasty (TKA). Treatment options include two-stage surgery with the first stage involving correction of the EKD and same-stage TKA and tibial osteotomy (1S-TKA-TO). The objective of this study was to assess outcomes in 26 patients managed with 1S-TKA-TO. HYPOTHESIS: 1S-TKA-TO produces satisfactory clinical and anatomical outcomes and is not associated with higher morbidity rates compared to TKA alone or two-stage TKA-TO. MATERIAL AND METHODS: A prospective study was conducted in 25 patients (26 knees) managed with 1S-TKA-TO between 1995 and 2014. There were 16 males and 9 females with a mean age of 64 years (range, 29-80 years) and a mean body mass index of 29.6 (range, 24-49). The EKD was constitutional in 14 knees, post-traumatic in 5 knees, and induced by TO in 7 knees. None of the patients received a hinged knee implant. In each patient, the clinical International Knee Society (IKS score) was assessed and the hip-knee-ankle angle (HKA), tibial mechanical angle (TMA), and femoral mechanical angle (FMA) were measured on radiographs before surgery and at last follow-up. RESULTS: The mean IKS score increased significantly, from 70 before surgery to 170 at the end of the mean 9-year follow-up. Mean flexion range increased from 98° to 107°. The clinical and anatomical outcomes were satisfactory in 25 patients. In the remaining patient, who had a history of multiple surgeries for Blount disease and a body mass index of 49, a severe complication consisting in massive skin necrosis followed by infection occurred; this was the only patient who required revision surgery with implant removal. DISCUSSION: These findings are consistent with the satisfactory outcomes observed in earlier studies, most of which included small numbers of patients. The alternatives to 1S-TKA-TO are under evaluation. The best indication for 1S-TKA-TO may be knee osteoarthritis with a greater than 10° intra-osseous deformity. LEVEL OF EVIDENCE: IV, prospective observational cohort study.

Comparison of custom cutting guides based on three-dimensional computerized CT-scan planning and a conventional ancillary system based on two-dimensional planning in total knee arthroplasty: a randomized controlled trial.

PURPOSE: Incorrect positioning of components during total knee arthroplasty (TKA) increases the risk of pain, instability, and early revision. The purpose of this study was to compare 3D planning-assisted and a conventional system for TKA positioning. We hypothesized that the use of three-dimensional CT-scan planning and custom cutting guides would increase the accuracy of component positioning. METHODS: A randomized, controlled, prospective study of two groups was performed. In one group, patient-specific custom cutting guides (PSCG) were used for component positioning based on 3D CT-scan planning. In the control group, TKA was performed with a conventional ancillary system. The components' positioning angles were measured on 3D reconstructions. The main evaluation criterion was the percentage of outliers outside of a target zone of ± 3° for the coronal positioning of the femoral component. RESULTS: Eighty patients were included. The percentage of outliers for the femoral component was significantly lower in the 3D-guided group (1 patient) compared to the control group (7 patients p = 0.02). The coronal femoral angle was restored with greater accuracy in the 3D-assisted group (- 0.1° ± 1.4°) compared to the control group (1.6° ± 2.5°). Surgery was significantly shorter in the 3D group. The clinical outcomes were better in the 3D group at the two year follow-up with fewer failures and a lower standard deviation in IKS scores. CONCLUSION: The use of a 3D planning and custom guides can improve TKA component positioning by increasing the accuracy of implants alignment and reducing the percentage of outliers. The same benefit was not demonstrated for the global knee alignment and the clinical scores with no indisputable clinical advantage for the PSCG.

Translation, cross-cultural adaption and validation of the French version of the Forgotten Joint Score in total hip arthroplasty.

INTRODUCTION: The ability to "forget" a joint implant in everyday life is considered to be the ultimate objective in arthroplasty. Recently, a scoring system, the Forgotten Joint Score (FJS-12), was published based on a self-administered questionnaire comprising 12 questions assessing how far patients had been able to forget their hip or knee prosthesis. The main objective of the present study was to translate, adapt and assess a French-language version of the FJS-12 in total hip arthroplasty (THA) patients. PATIENTS AND METHODS: The questionnaire was translated by 2 orthopedic surgeons and a medical physician, all bilingual, then back-translated into English by two native English-speaking translators unacquainted with the original. A concertation meeting adopted a beta-version of this Score de Hanche Oubliée (SHO-12), which was then tested on 15 randomly selected THA patients and adapted according to their comments. The final version was validated following the international COSMIN methodology. Data collection was prospective, included all patients operated on by a single surgeon using a single technique. Reference questionnaires comprised Oxford Hip Score (OHS-12) and modified Harris Hip Score (HHS). The 3 assessments were conducted with a minimum 1 year's follow-up. The SHO-12 was administered twice, with a 1-week interval. Statistical tests assessed construct validity (Pearson correlation test), internal coherence (Cronbach alpha), reliability (intraclass correlation coefficient) and feasibility (percentage missing values, administration time and ceiling and floor effects). RESULTS: Translation/back-translation encountered no particular linguistic problems. Fifty-eight patients (63 THAs) responded to all questionnaires: 22 female, 36 male; mean age, 62.7±15.2 years. Mean follow-up was 1.6±0.4 years. SHO-12 correlated strongly with OHS-12 and HHS. Internal coherence was good (alpha=0.96) and reproducibility excellent. No floor or ceiling effects were found. CONCLUSION: SHO-12, the French-language version of the FJS-12 in THA, is a valid, reproducible self-administered questionnaire, comparable to the English-language version. LEVEL OF EVIDENCE: I, Testing of previously developed diagnostic criteria on consecutive patients - Diagnostic study.

Clinical outcomes following arthroscopic treatment of femoro-acetabular impingement using a minimal traction approach and an initial capsulotomy. Minimum two year follow-up.

PURPOSE: Although the arthroscopic management of femoroacetabular impingement (FAI) is increasing, severe complications have been reported due to traction. We developed an arthroscopic technique based on an initial capsulotomy and a minimal traction approach. The main purpose of this study was to analyze the clinical outcomes of FAI treatment using this technique after at least two years of follow-up. METHODS: Forty-seven consecutive patients underwent surgery for FAI. There were two initial portals: a proximal anterolateral portal and a distal anterior instrumental portal. An anterior working space was created and a T-shaped incision was made in the anterior capsule to relieve joint distraction. Short traction (less than 20 mn) made it possible to approach the central compartment. Acetabuloplasty was performed in the presence of pincer impingement. Traction was then released. A head-neck femoral osteochondroplasty was performed in case of bump impingement. All patients underwent a mean 3.3 ± one years of follow-up based on two self-administered questionnaires: the Harris hip score and the QOL Oxford score. None of the patients were lost to follow-up. RESULTS: There were three complications: two ossifications and one case of injury to the femoral cutaneous nerve with good clinical outcomes at the final follow-up. Five patients (10%) underwent surgical revision after a mean 1.4 years of follow-up: three total hip arthroplasties, one peri-acetabular osteotomy, and one repeat arthroscopic hip debridement. The Harris score increased significantly from 60 ± 10 to 86 ± 15 (p < 0.0001) and the Oxford score improved from 34 ± 15 to 50 ± 11. Only 25% of patients had a "forgotten hip" at the final follow-up. CONCLUSION: Our clinical results were comparable to previously reported outcomes with other surgical techniques for the management of FAI. However, it should also be noted that despite these good clinical outcomes, the percentage of patients with a "forgotten hip" is low, and patients should be informed of this.

Modal analysis for the assessment of cementless hip stem primary stability in preoperative THA planning.

This numerical vibration finite element (FE) study introduces resonance three-dimensional planning (RP3D) to assess preoperatively the primary stability of a cementless stem for total hip arthroplasty. Based on a patient's CT-scan and a numerical model of a stem, RP3D aims at providing mechanical criteria indicative of the achievable primary stability. We investigate variations of the modal response of the stem to changes of area and apparent stiffness of the bone-implant interface. The model is computationally cheap as it does not include a mesh of the bone. The apparent stiffness of the bone is modeled by springs attached to the nodes of the stem's mesh. We investigate an extended range of stiffness values while, in future works, patient's specific Hounsfield values could be used to define stiffness. We report modal frequencies, shapes, and a ratio of elastic potential energies (rEPE) that quantifies the proximal motion that should be minimum for a stable stem. The modal response exhibits a clear transition between loose and tight contact as area and stiffness of the interface increase. rEPE thresholds that could potentially discriminate preoperatively between stable and unstable stems are given for a Symbios SPS® size C stem.

Three-dimensional analysis of the proximal anterior femoral flare and torsion. Anatomic bases for metaphyseally fixed short stems design.

PURPOSE: The use of femoral stems with a short metaphyseal fixation may lead to fractures or subsidence. Such failures may be related to a mismatch between the torsions or the sagittal flares of the stem and the femur. The goal of our study was to perform a 3D analysis of the proximal metaphyseal femur anatomy with a special focus on the anterior proximal flare and torsion. Such data may help to detect the outlier patients for whom a short metaphyseal fixation should be avoided. METHODS: A prospective study included 80 consecutive patients who underwent a primary cementless THA with a 3D CT-scan based pre-operative planning. A femoral frame was determined in order to analyse the proximal metaphyseal torsion and flares of the femur. RESULTS: The mean metaphyseal torsion was 21.6° ± 7° at 5 mm above the lesser trochanter (LT) and 34.7° ± 8.8 at 15 mm under LT generating a differential torsion of 13° around the LT. The mean flare index was 4.3 ± 0.9 medially, 3.7 ± 0.8 laterally, 2 ± 0.6 anteriorly and 3.1 ± 0.6 posteriorly. The anterior flare was the only flare significantly correlated to the bone density, to the age and to the femoral off-set: the higher the anterior flare index, the younger the patient, the higher the bone density and the higher the femoral offset. The anterior flare was not significantly correlated to the femoral anteversion, the metaphyseal torsion and the coronal neck-shaft angle. CONCLUSION: The proximal femoral metaphysis presents a highly variable anterior flare and torsion that may explain a mismatch between the femur and the femoral stem, consequently generating a risk of subsidence or fracture when using shortly fixed stems. LEVEL OF EVIDENCE: Level IV.

Three-dimensional planning-guided total hip arthroplasty through a minimally invasive direct anterior approach. Clinical outcomes at five years' follow-up.

PURPOSE: The direct anterior approach is an attractive option for total hip arthroplasty (THA) in order to achieve a quicker rehabilitation. However, this surgical technique presents a longer learning curve and a higher complications rate compared with the standard approach. We investigated whether three-dimensional (3D) planning anticipated the surgical difficulties and helped to achieve a low complications rate with respect to intra-operative complications, dislocation risk and lower limb discrepancy (LLD). METHODS: One hundred and fifty-four consecutive patients underwent a primary cementless THA using a direct anterior approach. A 3D planning was performed in order to anticipate the difficulties that may be encountered regarding femur perforation or fracture, dislocation and LLD. All patients were assessed at a mean five years' follow-up. RESULTS: No false route and no fracture occurred at the time of surgery. All the surgical difficulties were anticipated. A motorised reaming procedure of the femur was required in six patients because of a very dense bone or a narrow femur. A retroverted neck was used in 7 % of patients because of a torsional abnormality and enabled an increase in stability. The real implant sizes were the same as the ones planned in 97 % for the cup, 96 % for the stem and 100 % for the neck. At five years' follow-up, no dislocation occurred, no patient complained about LLD and excellent clinical outcomes were achieved. CONCLUSIONS: This study demonstrates that 3D pre-operative planning-guided THA through a minimally invasive direct anterior approach is a safe and accurate procedure. LEVEL OF EVIDENCE: Level IV.

Comparison of anatomic vs. straight femoral stem design in total hip replacement - femoral canal fill in vivo.

INTRODUCTION: The femoral canal fill between an anatomic and a straight prosthesis design in cementless total hip arthroplasty (THA) was compared. We hypothesised that the anatomic SPS stem has higher proximal fill and lesser distal fill than the straight stem. MATERIAL AND METHODS: The femoral canal fill was measured on 3 months routine postoperative x-rays at 5 levels of the stem in 50 consecutive patients, aged 35-83 years, who underwent 56 THA procedures by a single surgeon in this hospital. 22 patients received a straight design Ceramconcept Global stem, 34 patients received an anatomic design Symbios SPS stem. Both anteroposterior (AP) and lateral x-rays were combined to suggest a 3-D measurement. RESULTS: On the AP x-rays, the canal fill was significantly higher using the anatomic design stem at the proximal measurement levels, and was significantly higher at the distal levels using the straight stem. With the AP and lateral x-rays combined, the canal fill at the proximal levels was also significantly higher in the anatomic groups, nonsignificantly lower at the central level and significantly lower at the distal levels. DISCUSSION: In THA surgery, achieving high fill at the metaphysis of the femur and less fill at the diaphysis has been suggested to result in satisfactory outcome and high stability of the prosthesis. This study demonstrated that, compared to straight stem design, an anatomically designed stem has a significantly higher metaphyseal femoral canal fill.

Comparison of Three-Dimensional Planning-Assisted and Conventional Acetabular Cup Positioning in Total Hip Arthroplasty: A Randomized Controlled Trial.

BACKGROUND: Malpositioning of the acetabular cup during total hip arthroplasty increases the risk of dislocation, edge-loading, squeaking, early wear, and loosening. We hypothesized that the use of three-dimensional (3-D) visualization tools to identify the planned cup position relative to the acetabular edge intraoperatively would increase the accuracy of cup orientation. The purpose of this study was to compare 3-D planning-assisted implantation and freehand insertion of the acetabular cup. METHODS: This was a prospective randomized controlled study of two groups of twenty-eight patients each. In the first group, cup positioning was guided by 3-D views of the cup within the acetabulum obtained during 3-D preoperative planning. In the control group, the cup was placed freehand. All of the patients were operated on by the same surgeon, through a minimally invasive direct anterior approach with the patient in the supine position. Cup anteversion and abduction angles were measured on 3-D computed tomography (CT) reconstructions. The main evaluation criterion was the percentage of outliers according to the Lewinnek safe zone. RESULTS: Operative time did not differ between the two groups. The cup anteversion was more accurate in the 3-D planning group (mean difference from the planned angle [and standard deviation], -2.7° ± 5.4°) compared with the freehand-placement group (6.6° ± 9.5°). According to the Lewinnek safe zone, overall, the percentage of outliers was lower in the 3-D planning group (21%; six patients) than in the control group (46%; thirteen patients). According to the Callanan safe zone, the percentage of outliers was also lower in the 3-D planning group (25% versus 64%). Although cup abduction was also restored with greater accuracy in the 3-D planning group, on the basis of the Lewinnek safe zone, the percentage of abduction outliers was comparable between groups, with fewer high-abduction values, but more low-abduction values, in the 3-D planning group. CONCLUSIONS: Preoperative 3-D planning increased the accuracy of anteversion restoration and reduced the percentage of outliers without increasing the operative time. In this study, the same advantage could not be demonstrated for abduction. LEVEL OF EVIDENCE: Therapeutic Level I. See Instructions for Authors for a complete description of levels of evidence.

Low Dose Computed Tomography for 3D Planning of Total Hip Arthroplasty: Evaluation of Radiation Exposure and Image Quality.

OBJECTIVE: The aim of the study was to compare radiation exposure and image quality between dedicated computed tomography (CT) protocols for preoperative total hip arthroplasty (THA) planning. METHODS: Three protocols with automated tube current modulation using 64-slice (n = 177) and 128-slice CT scanners without (n = 129) and with automated tube voltage preselection (n = 84) were compared. RESULTS: All 390 CTs were of sufficient quality for THA planning. Mean DLP was 235.0 mGy*cm (effective dose 2.8 mSv). Lowest radiation exposure (2.5 mSv) was seen with automated voltage preselection and the algorithm's selection was 100 kV (90.5% of patients) and 120 kV. Lowest image noise was seen in the highest dose group (3.1 mSv, 128-slice CT fixed tube voltage). A significant difference in cortical bone radiodensity was seen between 100 kV and 120 kV (P < 0.0001). CONCLUSIONS: Preoperative pelvic CT for THA planning is possible with very low radiation dose and reliable quality. Automated voltage preselection further decreases the effective dose by 18.2%.

Endplate denervation correlates with Nogo-A muscle expression in amyotrophic lateral sclerosis patients.

OBJECTIVE: Data from mouse models of amyotrophic lateral sclerosis (ALS) suggest early morphological changes in neuromuscular junctions (NMJs), with loss of nerve-muscle contact. Overexpression of the neurite outgrowth inhibitor Nogo-A in muscle may play a role in this loss of endplate innervation. METHODS: We used confocal and electron microscopy to study the structure of the NMJs in muscle samples collected from nine ALS patients (five early-stage patients and four long-term survivors). We correlated the morphological results with clinical and electrophysiological data, and with Nogo-A muscle expression level. RESULTS: Surface electromyography assessment of neuromuscular transmission was abnormal in 3/9 ALS patients. The postsynaptic apparatus was morphologically altered for almost all NMJs (n = 430) analyzed using confocal microscopy. 19.7% of the NMJs were completely denervated (fragmented synaptic gutters and absence of nerve terminal profile). The terminal axonal arborization was usually sparsely branched and 56.8% of innervated NMJs showed a typical reinnervation pattern. Terminal Schwann cell (TSC) morphology was altered with extensive cytoplasmic processes. A marked intrusion of TSCs in the synaptic cleft was seen in some cases, strikingly reducing the synaptic surface available for neuromuscular transmission. Finally, high-level expression of Nogo-A in muscle was significantly associated with higher extent of NMJ denervation and negative functional outcome. INTERPRETATION: Our results support the hypothesis that morphological alterations of NMJs are present from early-stage disease and may significantly contribute to functional motor impairment in ALS patients. Muscle expression of Nogo-A is associated with NMJ denervation and thus constitutes a therapeutic target to slow disease progression.

Evaluation of spinal cord compression and hyperintense intramedullary lesions on T2-weighted sequences in patients with cervical spondylotic myelopathy using flexion-extension MRI protocol.

BACKGROUND CONTEXT: Acquired cervical stenosis is caused by the combination of disc protrusion, facet joint degeneration, hypertrophy of the ligamentum flavum, and osteophyte formation. Although these mechanical factors seem to play an important role in the pathogenesis of myelopathy, the role of dynamic factors has been suggested by many authors. Based on these results, dynamic magnetic resonance imaging (MRI) was proposed to improve diagnostic techniques in patients with cervical myelopathy. PURPOSE: The purpose of the study was to evaluate the importance of dynamic MRI in the assessment of cervical canal stenosis and to determine the percentage of levels in which cord impingement was only visible in the extension MRI and the percentage of cases in which hyperintense intramedullary lesions (HILs) were identified only on the flexion MRI. STUDY DESIGN: This is a retrospective case series study. PATIENT SAMPLE: Patients with spondylotic myelopathy who had dynamic cervical MRI at our department from October 2005 to February 2007 were included. MATERIALS AND METHODS: Fifty-one consecutive patients with spondylotic myelopathy had MRI in the neutral, flexion, and extension positions of the cervical spine. OUTCOME MEASURES: The following entities were evaluated: canal stenosis (the evaluation of the stenosis was based on the Muhle classification) and the presence or absence of HILs. RESULTS: Two hundred fifty-five levels were evaluated in the three positions. At each level, the stages in extension were higher than the stages in neutral and flexion positions (p<.05). From C3 to C6, around 22.5% of Stage 3 levels in the extension were Stage 1 in the neutral position. In flexion, HILs are better identified than in neutral and extension positions (p<.05). In 10% of the patients, HILs were identified only in the flexion T2-weighted sequence. CONCLUSIONS: Extension MRI helps to identify significant cervical canal stenosis that is partially or completely absent on neutral and flexion MRI and to determine the exact number of levels to decompress surgically. Flexion MRI permits better visualization of HILs on T2-weighted sequences.

Charcot spine and Parkinson's disease.

Charcot spine is rare condition whose association with Parkinson's disease (PD) has not been reported yet. The authors reported the cases of two patients with PD who developed Charcot spine. Both patients presented with a history of back pain and bilateral radicular leg pain. They had complete clinical and radiological assessment. Lumbar spine was involved in both patients. Clinical features and response to treatment were described. In the first case, circumferential fusion and stabilization were performed on the dislocated vertebral levels. A solid and stable fusion of the spine was obtained with satisfactory clinical outcome. Surgical treatment has been recommended to the other patient. In both cases, no other neurological etiology was found to account for Charcot spine. In conclusion, Charcot spine is associated with several neurological affections but has not previously been reported in association with Parkinson's disease.