Cadaveric Hips Research Articles

Effect of acetabular labral tears, repair and resection on hip cartilage strain: A 7 T MR study

Background Tears of the acetabular labrum are frequently present in patients with groin pain. While it is clear that the labrum contributes to the surface area articulating with the femoral head, it is not clear whether labral repair yields different load distribution in the hip compared to labral resection. Purpose Determine whether labral repair reduces cartilage strain more effectively than labral resection. Methods Six human cadaveric hips (mean age 37 years) were loaded in a simulated single-leg stance within the bore of a 7 T MR scanner. After cartilage had reached a steady-state thickness distribution, a scan of the cartilage was acquired with a voxel size of 0.1×0.1×0.3 mm. This method was repeated for each of six specimens when the labrum was intact, after a surgically simulated labral tear, after an arthroscopic labral repair and after labral resection. Cartilage thickness and strain in an anterosuperior region of interest were measured from the MR scans. A paired t-test was used to compare mean and maximum cartilage strain when the labrum was intact vs. torn, torn vs. repaired and repaired vs. resected. Three-dimensional patterns of cartilage strain distribution were qualitatively compared for the different labral conditions. Results For the number of specimens tested we found no change in mean and maximum cartilage strain, and little obvious change in the pattern of cartilage strain distribution after a simulated labral tear. Labral repair caused a 2% decrease in mean cartilage strain compared to a torn labrum ( p=0.014). Labral resection caused a 4% and 6% increase in mean and maximum cartilage strain, respectively, compared to labral repair ( p=0.02), and the cartilage strain distribution was elevated throughout the region of interest. Conclusion Based on our ex vivo findings of increased cartilage strain after labral resection when compared to labral repair, we have demonstrated the associated consequences to the mechanical environment of the cartilage following surgical treatment of the labrum.

Evaluation of formal methods in hip joint center assessment: An in vitro analysis

Background The hip joint center is a fundamental landmark in the identification of lower limb mechanical axis; errors in its location lead to substantial inaccuracies both in joint reconstruction and in gait analysis. Actually in Computer Aided Surgery functional non-invasive procedures have been tested in identifying this landmark, but an anatomical validation is scarcely discussed. Methods A navigation system was used to acquire data on eight cadaveric hips. Pivoting functional maneuver and hip joint anatomy were analyzed. Two functional methods – both with and without using the pelvic tracker – were evaluated: specifically a sphere fit method and a transformation techniques. The positions of the estimated centers with respect to the anatomical center of the femoral head, the influence of this deviation on the kinematic assessment and on the identification of femoral mechanical axis were analyzed. Findings We found that the implemented transformation technique was the most reliable estimation of hip joint center, introducing a – Mean (SD) – difference of 1.6 (2.7) mm from the anatomical center with the pelvic tracker, whereas sphere fit method without it demonstrated the lowest accuracy with 25.2 (18.9) mm of deviation. Otherwise both the methods reported similar accuracy (<3 mm of deviation). Interpretation The functional estimations resulted in the best case to be in an average of less than 2 mm from the anatomical center, which corresponds to angular deviations of the femoral mechanical axis smaller than 1.7 (1.3)° and negligible errors in kinematic assessment of angular displacements.

Degenerative Changes in the Ligamentum Teres of the Hip

Review and classify the pathologic abnormalities of the ligamentum teres in degenerative hip joints. Eleven cadaveric hip joints were examined with magnetic resonance arthrography and were then sectioned. The appearance of the ligamentum teres and its attachment seen by inspection of the anatomical sections was correlated with findings seen at magnetic resonance imaging. Histologic evaluation was done. Magnetic resonance arthrographic and histologic findings showed a spectrum of ligamentum teres degeneration. The thickest ligamentum teres revealed mucoid and fibromatous degeneration with microscopic tear. Ligamentum teres with intermediate thickness revealed fatty replacement with and without fibromatous degeneration, fibromatous degeneration with and without mucoid degeneration, and eosinophilic change. The thinnest ligamentum teres was near-complete disruption of the ligament. The ligamentum teres revealed degenerative changes that were similar histologically to degenerative changes in tendons. Magnetic resonance arthrography provided a sensitive technique for demonstration of the ligamentum teres and various patterns of degeneration.

Femoral Neck Cut Level Affects Positioning of Modular Short-Stem Implant

A trend in total hip arthroplasty surgery has been to design more bone-preserving procedures, especially for younger patients. This study investigated the final implant positioning of a short metaphyseal femoral neck type of implant to determine whether leg length, caput collum diaphysis (CCD) angle, and offset could be re-created with different levels of femoral neck resection. Ten cadaveric hips in 6 whole-body specimens were used, with 3 fiducial markers to allow registration of computer navigation points to computed tomography scan data. Three femoral neck resection levels were investigated: 0 mm, +5 mm (the recommended level of resection), and +10 mm from the base of the femoral neck. Results showed that the CCD angle was significantly higher with 0-mm neck cut and the offset was lower, whereas the highest neck cut had longer leg-length results. Surgeons who use a short metaphyseal stem need to realize the importance of a proper femoral neck cut to restore anatomic parameters as well as the possible benefit of computer-assisted surgery to restore these anatomic parameters during surgery.

The Ischial Spine Sign: Does Pelvic Tilt and Rotation Matter?

Although the ischial spine sign (ISS) has been advocated to detect acetabular retroversion, it is unknown whether the sign is valid on anteroposterior (AP) pelvic radiographs with tilted or rotated pelves. We therefore evaluated reliability of the ISS as a tool for diagnosing acetabular retroversion in the presence of considerable pelvic tilt and/or malrotation. We obtained radiographs of 20 cadaver pelves in 19 different malorientations resulting in 380 pelvis images (760 hips) for evaluation. In addition, 129 clinical radiographs of patients' hips that had varying pelvis orientations were reviewed. We found an overall sensitivity of 81% (90%), specificity of 70% (71%), positive predictive value of 77% (80.7%), and negative predictive value of 75% (85%) in the cadaver (patient) hips. Our data suggest the ISS is a valid tool for diagnosing acetabular retroversion on plain radiographs taken using a standardized technique regardless of the degree of pelvic tilt and rotation.

Changes in the Acetabular Fossa of the Hip: MR Arthrographic Findings Correlated With Anatomic and Histologic Analysis Using Cadaveric Specimens

The objective of our study was to determine the morphologic and histologic pattern of tissue changes in the acetabular fossa and evaluate its association with osteoarthritis of the hip joint. Eleven cadaveric hip joints derived from elderly persons were examined using MR arthrography. All 11 joints were then sectioned. The pattern of acetabular fossa changes determined during inspection of the anatomic and histologic sections in all cadaveric specimens was correlated with MR arthrographic findings. We classified acetabular fossa changes into three stages. Imaging findings of osteoarthritis were reviewed to assess for an association between acetabular cartilage changes and acetabular fossa changes. MR arthrographic findings of changes in the acetabular fossae included low signal intensity related to multiple thin or thick fibrous strands in the acetabular fat and a decrease in the amount of peripheral fatty tissue. Histologic findings revealed fat necrosis, fibrous strands, a decrease in the amount of fat, fibrocartilaginous metaplasia of fat, and chondroid metaplasia at the bony surface of the acetabular fossa. There was a statistically significant correlation between the advanced stage (stage IV) of acetabular cartilage degeneration and the advanced stage (stage 3) of acetabular fossa change (p < 0.001). In a small number of specimens, MR arthrographic findings and histologic analyses showed fibrofatty tissue changes and chondroid metaplasia in the acetabular fossae of cadavers derived from an elderly population. The advanced stage of acetabular fossa change was correlated statistically with the advanced stage of acetabular cartilage degeneration.

Effects of hip joint position and intra-capsular volume on hip joint intra-capsular pressure: a human cadaveric model

BackgroundIncrease in hip intra-capsular pressure has been implicated in various hip pathologies, such as avascular necrosis complicating undisplaced femoral neck fracture. Our study aimed at documenting the relationship between intra-capsular volume and pressure in various hip positions.MethodsFifty-two cadaveric hips were studied. An electronic pressure-monitoring catheter recorded the intra-capsular hip pressure after each instillation of 2 ml of normal saline and in six hip positions.ResultsIn neutral hip position, the control position for investigation, intra-capsular pressure remained unchanged when its content was below 10 ml. Thereafter, it increased exponentially. When the intra-capsular volume was 12 ml, full abduction produced a 2.1-fold increase (p = 0.028) of the intra-capsular hip joint pressure; full external rotation and full internal rotation increased the pressure by at least 4-fold (p < 0.001). Conversely, there was a 19% (p = 0.046) and 81% (p = 0.021) decrease in intra-capsular hip joint pressure with flexion of the hip joint to 90-degree and 45-degree, respectively.ConclusionIntra-capsular pressure increases with its volume, but with a wide variation with different positions. It would be appropriate to recommend that hips with haemarthrosis or effusion should be positioned in 45-degree flexion.

Greater trochanter displacements after Charnley’s trochanterotomy, during passive hip movements: a real-time 3D cadaveric approach

Non-unions of greater trochanter (GT) fractures or osteotomies are the source of frequent complications. Two muscles are involved in the genesis of such non-unions, the gluteus medius and the gluteus minimus. Literature says that, during hip flexion, their terminal insertions on the faces of the GT generate an anterior translation of the GT responsible for contact loosening and healing defect. The main goal of this paper was to assess this hypothesis into the 3D space and to quantify the 3D displacements (three translations and three rotations) of the GT after trochanterotomy during passive motions of the hip joint (flexion, abduction-adduction, internal and external rotation). Therefore, we used 13 fresh cadaveric hips, on which we registered the GT displacements thanks to a 3D infrared localizer. An ultra low weight dynamic reference based has been developed to track the motion of the GT without any interference. The results have shown rotatory displacements of the GT around the three axes. This produces a posterior and lateral opening of the osteotomy site associated with a posterior rotatory shear of the GT. Above 45 degrees of hip flexion these three rotations combine together to exert shear on the osteotomy site which is harmful to the osteosynthesis material and the consolidation potential and may explain implant loosening.

Measuring leg length and offset with an imageless navigation system during total hip arthroplasty: is it really accurate?

A novel imageless measurement algorithm to assess leg length (LL) and offset (OS) changes during total hip arthroplasty (THA) has been established, the purpose of this study was to describe the process and establish whether or not it is accurate. THA was performed on 17 cadaver hip specimens. LL and OS changes were determined intra-operatively, using an imageless navigation system. Pre- and postoperatively, all specimens had a computed tomography scan (CT) and the LL and OS changes were analysed by two blinded investigators. With mean differences of less than 1 mm (LL, 0.74; SD, 2.4 mm; OS, 0.89; SD, 1.8 mm) supported by substantial significant correlations [r = 0.83 (LL) and r = 0.92 (OS)] imageless navigation values demonstrated a high accuracy when compared to CT measurements. Intra-operative LL and OS measures are reliable and accurate when using an imageless calculation algorithm which stores the position of the femoral reference frame in relation to the pelvic coordinate system before and after reconstruction.

The proximal hip joint capsule and the zona orbicularis contribute to hip joint stability in distraction

The structure and function of the proximal hip joint capsule and the zona orbicularis are poorly understood. We hypothesized that the zona orbicularis is an important contributor to hip stability in distraction. In seven cadaveric hip specimens from seven male donors we distracted the femur from the acetabulum in a direction parallel to the femoral shaft with the hip in the neutral position. Eight sequential conditions were assessed: (1) intact specimen (muscle and skin removed), (2) capsule vented, (3) incised iliofemoral ligament, (4) circumferentially incised capsule, (5) partially resected capsule (distal to the zona orbicularis), (6) completely resected capsule, (7) radially incised labrum, and (8) completely resected labrum. The reduction of the distraction load was greatest between the partially resected capsule phase and completely resected capsule phase at 1, 3, and 5 mm joint distraction (p = 0.018). The proximal to middle part of the capsule, which includes the zona orbicularis, appears grossly and biomechanically to act as a locking ring wrapping around the neck of the femur and is a key structure for hip stability in distraction.

Deformation and recovery of cartilage in the intact hip under physiological loads using 7 T MRI

Accurate measurement of cartilage deformation in loaded cadaver hip joints could be a valuable tool to answer clinically relevant research questions. MRI is a promising tool, but its use requires an understanding of cartilage deformation and recovery properties in the intact hip. Our objective was to answer the following questions: (1) How long does it take for hip cartilage to reach a deformed steady-state thickness distribution under simulated physiological load, and how much does the cartilage deform? (2) How long does it take for hip cartilage to return to the original cartilage thickness distribution once the load is removed? Methods Five human hip specimens were axially loaded to 1980 N in a 7 T MR scanner and scanned every 15 min throughout loading. One specimen was scanned every hour throughout recovery from load. One repeatability specimen was loaded and scanned every day for 4 days. Hip cartilage was segmented as a single unit and thickness was measured radially. Results The hip cartilage reached a steady-state thickness distribution after 225 min of load, and 16.5 h of recovery. Mean strain after 225 min of load was 30.9%. The repeatability specimen showed an average day-to-day change in mean cartilage thickness of 0.10 mm over 4 days of data collection. The amount of deformation (0.96 mm) was far greater than the image resolution (0.11 mm) and error due to repeatability (0.10 mm). Conclusion Using an ex vivo model, this method has potential for assessing changes in hip cartilage strain due to injury or surgical intervention.

How Accurately Can the Acetabular Rim Be Trimmed in Hip Arthroscopy for Pincer-Type Femoral Acetabular Impingement: A Cadaveric Investigation

The purpose of this study was to evaluate the precision of central hip arthroscopy in the assessment and treatment of pincer-type femoroacetabular impingement (FAI) avoiding the posterolateral portal, with its close proximity to the main arterial blood supply of the femoral head, the medial circumflex femoral artery. Seven human cadaveric hips underwent arthroscopic trimming of the acetabular labrum and rim along a preoperatively defined 105 degrees arc of resection for treatment of a presumed pincer-type lesion. After the arthroscopic procedure, all specimens were dissected and measured for evaluation of the location, quantity, and quality of the area undergoing resection. The difference between the actual and planned arc of resection was 18.7 degrees +/- 4.7 degrees (range, 2 degrees to 34 degrees). This was mainly because of a lack of accuracy in the presumed posterior starting point (PSP), with a mean deviation of 19 degrees +/- 3.4 degrees (range, 10 degrees to 36 degrees). Correlation analysis showed that variance in the arc of resection was mainly dependent on the PSP (r = 0.739, P = .058). Central hip arthroscopy is a feasible option in treating anterosuperior pincer-type FAI by use of the anterior and anterolateral portals only. This cadaveric study showed that there is a significant risk of underestimating the actual arc of resection compared with the planned arc of resection for posterosuperior pincer-type lesions because of the modest accuracy in determining the PSP of the resection. Accurate preoperative planning and arthroscopic identification of anatomic landmarks at the acetabular side are crucial for the definition of the appropriate starting and ending points in the treatment of pincer-type FAI. Whereas anterosuperior pincer-type lesions can be addressed very precisely with our technique, the actual resection of posterosuperior lesions averaged 19 degrees less than the planned resection, which may have clinical implications.

Die Weber'schen Versuche zur hüftstabilisierenden Wirkung des atmosphärischen Druckes – ein historischer und experimenteller Rückblick

The stabilising effect of atmospheric pressure on the hip joint was first described by the brothers Eduard and Wilhelm Weber in 1836. Later in 1837, they conducted an experiment in which they examined a weight-bearing cadaveric hip joint in an evacuable container and could repeatedly demonstrate dislocation of the femur head due to the significant reduction of surrounding pressure and its repositioning by normalisation of the pressure. In our study we aimed to honour the contribution of the Weber brothers, to reflect on the historical argument about the hip stabilising effect of atmospheric pressure they initiated, to repeat the famous experiment they did in 1837 using advanced sensors and radiological equipment and to demonstrate the consequences of the effect on total hip arthroplasty. A weight-bearing human cadaveric hip joint was placed in a radiolucent evacuable container, in which the pressure was reduced with a vacuum pump and normalised by opening a valve. Pressure and dislocation distance were measured continuously by sensors. The state of the hip joint was documented both by X-ray as well as by permanent fluoroscopy with video recording. Conforming to the experiments published in 1837 we demonstrated dislocation of the hip joint as a result of a significant reduction of pressure. Normalisation of the pressure caused joint reduction. The ability of the cadaveric hip to bear weight depended to a great extent on its quality. Reduction of the pressure harmed the cadaveric hip and reduced the number of possible experiments. The stabilising effect of atmospheric pressure on the hip joint is a fact, which was proved in 1836/37 by the Weber brothers, who conducted convincing experiments with human cadaveric hip joints. Nevertheless, the investigation into this relationship continues until today. We repeated and reproduced their experiment published in 1837 which irrefutably proved the stabilising effect of atmospheric pressure on the hip joint. The surgical application is of the utmost importance in the field of hip arthroplasty. Careful handling and reconstruction of the capsula, the use of size-adapted large hip balls as well as the intra-articular drainage provide the basis for maintaining the optimal mechanical environment and avoiding postoperative dislocation. Due to the variation in quality and anatomic characteristics of cadaveric hip specimens, we decided to use standardised model joints for further experiments.

Evaluation of stretching position by measurement of strain on the ilio-femoral ligaments: An in vitro simulation using trans-lumbar cadaver specimens

The ilio-femoral ligament is known to cause flexion contracture of the hip joint. Stretching positioning is intended to elongate the ilio-femoral ligaments, however, no quantitative analysis to measure the effect of stretching positions on the ligament has yet been performed. Strains on the superior and inferior ilio-femoral ligaments in 8 fresh/frozen trans-lumbar cadaveric hip joints were measured using a displacement sensor, and the range of movement of the hip joints was recorded using a 3Space Magnetic Sensor. Reference length ( L 0) for each ligament was determined to measure strain on the ligaments. Hip positions at 10° adduction with maximal external rotation, 20° adduction with maximal external rotation, and maximal external rotation showed larger strain for the superior ilio-femoral ligament than the value obtained from L 0, and hip positions at 20° external rotation with maximal extension and maximal extension had larger strain for the inferior ilio-femoral ligament than the value obtained from L 0 ( p < 0.05). Superior and inferior ilio-femoral ligaments exhibited positive strain values with specific stretching positions. Selective stretching for the ilio-femoral ligaments may contribute to achieve lengthening of the ligaments to treat flexion contracture of the hip joint.

Validation of Finite Element Predictions of Cartilage Contact Pressure in the Human Hip Joint

Methods to predict contact stresses in the hip can provide an improved understanding of load distribution in the normal and pathologic joint. The objectives of this study were to develop and validate a three-dimensional finite element (FE) model for predicting cartilage contact stresses in the human hip using subject-specific geometry from computed tomography image data, and to assess the sensitivity of model predictions to boundary conditions, cartilage geometry, and cartilage material properties. Loads based on in vivo data were applied to a cadaveric hip joint to simulate walking, descending stairs, and stair-climbing. Contact pressures and areas were measured using pressure sensitive film. CT image data were segmented and discretized into FE meshes of bone and cartilage. FE boundary and loading conditions mimicked the experimental testing. Fair to good qualitative correspondence was obtained between FE predictions and experimental measurements for simulated walking and descending stairs, while excellent agreement was obtained for stair-climbing. Experimental peak pressures, average pressures, and contact areas were 10.0 MPa (limit of film detection), 4.4-5.0 MPa, and 321.9-425.1 mm(2), respectively, while FE-predicted peak pressures, average pressures, and contact areas were 10.8-12.7 MPa, 5.1-6.2 MPa, and 304.2-366.1 mm(2), respectively. Misalignment errors, determined as the difference in root mean squared error before and after alignment of FE results, were less than 10%. Magnitude errors, determined as the residual error following alignment, were approximately 30% but decreased to 10-15% when the regions of highest pressure were compared. Alterations to the cartilage shear modulus, bulk modulus, or thickness resulted in +/-25% change in peak pressures, while changes in average pressures and contact areas were minor (+/-10%). When the pelvis and proximal femur were represented as rigid, there were large changes, but the effect depended on the particular loading scenario. Overall, the subject-specific FE predictions compared favorably with pressure film measurements and were in good agreement with published experimental data. The validated modeling framework provides a foundation for development of patient-specific FE models to investigate the mechanics of normal and pathological hips.

Comparison of MR-arthrography and CT-arthrography in hyaline cartilage-thickness measurement in radiographically normal cadaver hips with anatomy as gold standard

To compare magnetic resonance (MR)-arthrography and multidetector-spiral-computed-tomography (MDSCT)-arthrography in cartilage-thickness measurement, in hips without cartilage loss, with coronal anatomic slices as gold standard. Institutional review board permission to study cadavers of individuals who willed their bodies to science was obtained. Two independent observers measured femoral and acetabular cartilage thicknesses of 12 radiographically normal hips (six women, five men; age range, 52-98 years; mean age, 76.5 years), on MDSCT-arthrographic and MR-arthrographic reformations, and on coronal anatomic slices, excluding regions of cartilage loss. Inter- and intraobserver reproducibilities were determined. Analysis of variance (ANOVA) was used to test differences between MR-arthrographic and MDSCT-arthrographic measurement errors compared to anatomy. By MR-arthrography, cartilage was not measurable at approximately 50% of points on sagittal and transverse sections, compared to 0-6% of the points by MDSCT-arthrography. In the coronal plane, the difference between MDSCT-arthrographic and MR-arthrographic measurement errors was not significant (P=0.93). In the coronal plane, MR-arthrography and MDSCT-arthrography were similarly accurate for measuring hip cartilage thickness.

The Safe Zone for Hip Arthroscopy: A Cadaveric Assessment of Central, Peripheral, and Lateral Compartment Portal Placement

This study evaluated 11 arthroscopic portals (4 central, 4 peripheral, and 3 peritrochanteric) with regard to their proximity to neurovascular structures and the extra-articular path taken before entering their intended compartments. We established 11 standard portals in 10 cadaveric hips, under arthroscopic and fluoroscopic visualization, using 3/16-inch Steinmann pins. Each hip was dissected, and the relation of the pins to the pertinent anatomy was recorded to the nearest 1 mm. Only 2 of the 11 portals, the anterior and midanterior portals, came within 2 cm of a neurovascular structure before entering their respective compartments. The anterior portal placed the lateral femoral cutaneous nerve at risk, lying at a mean of 15.4 mm (range, 1 to 28 mm) away. The midanterior portal lies a mean of 19.2 mm (range, 5 to 42 mm) from the ascending branch of the lateral circumflex femoral artery. In addition, a small terminal branch of this artery courses a mean of 14.7 mm (range, 2 to 33 mm) and 10.1 mm (range, 1 to 23 mm) from the anterior portal and midanterior portal, respectively. This study showed that 11 arthroscopic portals can be safely inserted into the central, peripheral, and peritrochanteric compartments of the hip. The midanterior and anterior portals pass in close proximity to a small terminal branch of the ascending lateral circumflex femoral artery. The greatest risk still comes from the proximity of the anterior portal to the lateral femoral cutaneous nerve. However, a slightly more lateral location seems to provide substantial benefits. This study investigated 11 arthroscopic hip portals inserted in a standardized fashion. This knowledge should help surgeons place the necessary portals both safely and accurately.

Validation of a computer navigation system and a CT method for determination of the orientation of implanted acetabular cup in total hip arthroplasty: A cadaver study

Background Successful hip reconstruction to restore the normal hip biomechanics requires precise placement of implants. Computer assisted navigation in total hip arthroplasty has been proposed to have the potential to help achieve a high accuracy in implant placement. The goal of the study was to evaluate the accuracy of an imageless computer navigation system on cadavers and to validate a non-invasive computed tomography method for post-operative determination of acetabular cup orientation. Methods Total hip arthroplasty was performed on seven cadaver hips with the aid of an imageless computer navigation system. The achieved cup orientation were recorded using three methods, (1) intra-operatively using the imageless computer navigation system, (2) post-operatively with direct bone digitization and (3) with a computed tomography based three dimensional model interpreted by three raters. Measurement from the direct bone digitization was taken as the gold standard to evaluate the other two methods. The intra-rater and inter-rater consistency of the computer tomography-model method were assessed by Cronbach’s alpha determination. Findings Compared with the cup orientation obtained from the direct bone digitization, the average difference for anteversion and abduction were 3.3 (3.5)° ( P = 0.045) and 0.6 (3.7)°, respectively, for navigation reading. The average differences for computer tomography-model for three raters were 0.5 (2.1)°, 0.8 (1.5)° and 3.2 (3.3)° ( P = 0.043) for anteversion and 0.4 (1.6)°, 0.3 (1.6)° and 2.1 (2.7)° for abduction. The intra-rater consistency ranged from 0.626 for a novice rater to over 0.97 for experience raters. The inter-rater consistency (including novice and experienced raters) was over 0.90. Interpretation While the values for cup orientation determined with imageless computer navigation were comparable to those from direct bone and implant digitization, the measurement for anteversion obtained was not as accurate as that for abduction. The proposed computer tomography-model method has an excellent intra-rater consistency for experienced raters, as well as an excellent overall inter-rater consistency. The study confirms that a non-invasive computed tomography based model analysis can be used in clinical practice as a valid method for post-operatively evaluating the orientation of the acetabular component.

Radiographic analysis of femoroacetabular impingement with Hip2norm—reliable and validated

The purpose of this study was to validate the accuracy, consistency, and reproducibility/reliability of a new method for correction of pelvic tilt and rotation of radiographic hip parameters for pincer type of femoroacetabular impingement on an anteroposterior pelvic radiograph. Thirty cadaver hips and 100 randomized, blinded AP pelvic radiographs were used for investigation. To detect the software accuracy, the calculated femoral head coverage and classic hip parameters determined with our software were compared to reference measurements based on CT scans or conventional radiographs in a neutral orientation as gold standard. To investigate software consistency, differences among the different parameters for each cadaver pelvis were calculated when reckoned back from a random to the neutral orientation. Intra- and interobserver comparisons were used to analyze the reliability and reproducibility of all parameters. All but two parameters showed a good-to-very good accuracy with the reference measurements. No relevant systematic errors were detected in the Bland-Altman analysis. Software consistency was good-to-very good for all parameters. A good-to-very good reliability and reproducibility was found for a substantial number of the evaluated radiographic acetabular parameters. The software appears to be an accurate, consistent, reliable, and reproducible method for analysis of acetabular pathomorphologies.

Injury to the Lateral Femoral Cutaneous Nerve During Minimally Invasive Hip Surgery: A Cadaver Study

A smaller skin incision as part of minimally invasive surgery (MIS) for total hip arthroplasty (THA) is thought to reduce local tissue trauma. Preservation of cutaneous nerves may reduce postoperative pain and improve rehabilitation. The standard lateral approach (SLA) and two MIS approaches (anterolateral [ALA] and posterior [PA]) were compared to determine which incision preserved cutaneous nerves. Fifteen cadaveric hip specimens were dissected to establish the course of branches of the lateral femoral cutaneous nerve. The number of branches divided by each of the three incisions was recorded. The MIS incisions resulted in significantly less nerve division compared with the SLA. The mean difference between the SLA and the ALA was 4.4 (P < 0.0001), and between the SLA and the PA was 1.4 (P = 0.0005). The ALA divided significantly fewer nerves compared with the PA (mean difference = 3; P = 0.0001). There is little evidence of the benefit of one MIS approach over another in the literature. The ALA preserved significantly more cutaneous nerves in this study. These results need corroboration with clinical outcomes to determine their significance.