Aim: The aim of this study was to determine if a correlation exists between the impingement test and the arthroscopic findings at the acetabular rim in non-dysplastic hips. Secondarily, we also wanted to establish if there was a correlation between the pain experienced on the impingement test and the pathology identified. Patients and Methods: Sixty-two consecutive patients who were due to have an arthroscopy of the hip in our unit were prospectively recruited into the study. All the dysplastic hips were excluded from the study. One observer was involved in examining all the patients and another one in performing all the arthroscopies. The impingement test was considered positive if at 90 degrees of flexion, adduction and internal rotation, the patient complained of discomfort or pain. If the patient experienced pain this was described as a strongly positive test and if there was discomfort experienced it was considered as a weakly positive test. The test was performed on the morning of the arthroscopy and all the intra-articular findings recorded at arthroscopy. A tear of the acetabular labrum and chondral damage in the antero-superior margin of the acetabulum were considered as positive pathology at the acetabular rim. Results : There were 40 males and 22 females in the study group. The impingement test was positive in 57 patients, strongly positive in 42 and weakly positive in 15. The arthroscopy revealed positive pathology in terms of an acetabular labrum tear and/or chondral damage at the acetabular rim in 55 patients. A negative test was recorded in 5 patients but there was positive rim pathology in two of these 5 patients. Conclusion: The impingement test correlates positively with the pathology at the acetabular rim; the sensitivity of the test for diagnosing acetabular rim pathology is 96.4 % and the specificity is only 60 % in non-dysplastic hips. However, we did not identify any correlation between the level of pain and the pathology observed

Radiodense structures resembling ossicles at the acetabular rim have received multiple names including “Os acetabuli, Os supertilii, Os marginale superius acetabuli, and Os coxae quartum”. Various theories regarding their origin have been postulated. These structures commonly are observed in dysplastic hips and hips suffering from femoro-acetabular impingement and represent fractures of the acetabular rim. In our series we observed acetabular rim fragments in 4.9% of the dysplastic hips and in 6.4% of the hips with femoro-acetabular impingement. Two different pathomechanics are responsible for the occurrence of these rim fragments. In dysplasia the short acetabular roof reduces the amount of available loading surface which leads to an overload on the lateral margin of the acetabulum, propagating the development of a fatigue fracture. However, as in all hips additional cysts were visible, it must be postulated, that cysts have to be present additionally and act as stress risers through which the rim bone eventually will fail. In hips with femoro-acetabular impingement the mode of failure is different. The relative anterior overcover in retroverted hips is subjected to stress during flexion of the hip, which is further increased by the frequent presence of an non-spheric extension of the femoral head as seen in cam impingement. The nonspheric femoral head-neck junction is jammed into the rim area. By repetitive traumatization the anterior rim eventually will fracture. The clinical importance of acetabular rim fractures in the dysplastic hip is readily understood even by an unexperienced observer. However, it has to be considered as a sign that the hip has decompensated and it usually goes with significant articular cartilage damage. Because the radiographic appearance of the hip with femoro-acetabular impingement seems normal at first sight, the mechanism leading to anterior rim fracture may be overlooked. However, recognition and adequate treatment is important to prevent further degeneration of the hip

Purpose of the study: The anterior rim of the arthroplasty cup can overhang the bone in certain situations: oversized cup, insufficient anteversion, insufficient ace-tabular reaming, cylindrospherical reaming overriding the acetabular opening. The straight or concave shape of the anterior wall of the acetabulum also affects prosthetic overhang. The purpose of this anatomic study was to use a navigation system to quantify, in vitro, the height of the iliopubic psoas notch. Material and methods: Sixty-eight acetabuli from 34 cadaver pelvi free of osteoarthritis (13 male and 21 female) were analyzed using the Stryker™ hip navigation system. Morphological data were collected for mathematical processing which defined the diameter and the center of the articular surface. Results: Considerable intra- and inter-individual differences in the shape of the acetabular rim were noted and quantified, particularly concerning the psoas notch. When the lateral view of the acetabular rim is projected onto a plane it produces a succession of three summits and three valleys explaining the difficulty encountered in obtaining a precise mean plane for the acetabular opening. Discussion: More or less pronounced protrusion of the cup could explain potentially painful anterior impingement of the psoas, especially for certain types of acetabular morphology

The acetabular rim syndrome is a pathological entity which we illustrate by reference to 29 cases. The syndrome is a precursor of osteoarthritis of the hip secondary to acetabular dysplasia. The symptoms are pain and impaired function. All our cases were treated by operation which consisted in most instances of re-orientation of the acetabulum by peri-acetabular osteotomy and arthrotomy of the hip. In all cases, the limbus was found to be detached from the bony rim of the acetabulum. In several instances there was a separated bone fragment, or 'os acetabuli' as well. In acetabular dysplasia, the acetabular rim is subject to abnormal stress which may cause the limbus to rupture, and a fragment of bone to separate from the adjacent bone margin. Dysplastic acetabuli may be classified into two radiological types. In type I there is an incongruent shallow acetabulum. In type II the acetabulum is congruent but the coverage of the femoral head is deficient

Introduction. Ectopic ossification (EO) at the acetabular rim has been suggested to be associated with pincer impingement and to lead to ossification of the labrum. However, this has never been substantiated with histological, radiographic and MRI findings in large cohorts of patients. We hypothesized that it is more a bone apposition of the acetabular rim and that it occurs more frequently in coxa profunda (CP) hips. Materials and Methods. In the first part, a cohort of 20 hips with this suspected ectopic rim ossification (EO) pattern were identified. The radiographic features that could be associated with this ossification pattern were described and evaluated by a histologic examination of intra-operative samples taken from the rim trimming. In the second part, we assessed the prevalence of this ectopic ossification process in a cohort of 203 patients treated for FAI. Results. Histologic examination revealed that new acetabular bone formation was either overgrowing the non-ossified labrum or moving it away from the native rim. Radiologically, this was associated with an “indentation sign” and/or a “double line sign”. There were no specimens that had shown any evidence of labral ossification. EO was found in 26 hips (18%) of the second cohort. Twenty of 26 hips (77%) with EO had CP morphology and 29% of CP hips had EO signs. In contrast, only 6 non-profunda hips (8%) were associated with EO. There was a high correlation between XR and MRI findings as >80% of XR findings were confirmed on MRI. Sixty-nine hips had CP morphology. The double line sign (N = 13), the indentation sign (N = 12) and a prominent lateral rim (N = 11) were found. Hips with an EO pattern were found in patients that were significantly older than those without EO (p = 0.01). The acetabular characteristics of the EO groups were not significantly different from the CP hips without EO. The femoral characteristics were significantly different between groups with lower neck shaft angles (128° vs 134°;p = 0,0002) and shorter femoral necks lengths (62mm vs 65mm; p = 0,04)) in the EO group. The mean Tonnis classification was not significantly different (p = 0,18). In addition, the mean acetabular cartilage degeneration status was not different between both groups (p = 0,9). Rim trimming down to the native acetabular bone was done in all cases either by arthroscopy (N = 40) or open surgical dislocation (N = 17). Discussion. Ectopic ossification of the acetabular rim predominantly occurs in CP and is associated with specific anatomic features of the proximal femur. This type of impingement seems to be different and less aggressive than other described impingement processes. The double line sign and indentation sign are highly indicative for this EO process and are indicative for a longstanding impingement problem. Trimming of the acetabular rim should be conducted

Purpose. The effects of Acetabular Rim Osteophytes (ARO) in Total Hip Arthroplasty (THA), has not been quantified. During THA their presence and location is variable, and the effect on post-operative Range of Motion (ROM) is unknown. The purpose of this study was to evaluate the ROM of a modern hip implant in five cadaver models utilizing computerized virtual surgery, and to analyze the effect of AROs given their location on the acetabulum, and position of the prosthesis during motion. Method. CT scans of five cadaveric pelvises and femurs were used to create 3-D Models. Surgery, using virtual Stryker components was then performed to restore the natural anatomic offset and leg length. ROM to impingement was evaluated for each model in eight vectors: flexion/extension, internal/external rotation, abduction/adduction, and 90 degrees of flexion with internal/external rotation. An Osteophyte Impingement Model was then created by elevating the natural acetabular rim by 10 millimeters circumferentially in each virtual cadaver pelvis. Using the same THA components, ROM was then evaluated in this pelvic model and compared to the cadaveric models. Results. ROM in the Osteophyte Impingement Model yielded a statistically significant decrease in five of the eight vectors tested, when compared to the Cadaveric Model: Flexion, Extension, External Rotation, Flexion to 90 degrees with Internal Rotation, and Flexion to 90 degrees with External Rotation. Only 3 of these 5 vectors were within normal human physiological ROM: Flexion, External Rotation, and Flexion to 90 degrees with Internal Rotation. The osteophyte model yielded a decrease in absolute ROM in the following: Flexion to 101 vs 113 degrees (p= 0.03), External Rotation to 30.4 vs 49.5 degrees (p= 0.01), and Flexion to 90 degrees with Internal Rotation 16.7 vs 31.6 degrees (p=0.01). When mapped on the acetabulum of right-sided hip, with the 12 o'clock position as the superior pole of the acetabulum, impingement on the osteophyte was noted at the following locations: with Flexion, and Flexion to 90 degrees with Internal Rotation, impinged was noted between 1 and 2 o'clock on the acetabulum. In External Rotation impinged occurred between 7 and 8 o'clock on the acetabulum. Conclusion. This study showed that a 10 millimeter osteophyte can potentially decrease range of motion and lead to impingement in THA in certain planes of motions: Flexion, External Rotation and Flexion to 90 degrees with Internal Rotation. The location of this impingement is between the 1 and 2 o'clock in Flexion, and Flexion to 90 degrees with Internal Rotation. In External Rotation, the impingement will occur between the 7 and 8 o'clock. The above applies to a right-sided acetabulum, the left side will demonstrate the mirror image of this impingement: Between the 10 to 11 o'clock, and 4 to 5 o'clock positions respectively. Osteophytes 10 millimeters or more in height at these positions should be carefully evaluated intra-operatively and removed safely if possible

Aims

Hip arthroscopy has gained prominence as a primary surgical intervention for symptomatic femoroacetabular impingement (FAI). This study aimed to identify radiological features, and their combinations, that predict the outcome of hip arthroscopy for FAI.

Introduction

Retrieval investigations have shown that cracking or rim failure of polyethylene hip liners may occur at the superior aspect of the liner, in the area that engages the locking ring of the shell¹. Failure could occur due to acetabular liner/stem impingement and/or improper cup position. Other contributing factors may include high body mass index, patient activity and design characteristics such as polyethylene material properties, thin liner rim geometry and cup rim design. Currently no standard multi-axis simulator methodology exists for high angle rim fatigue testing, although tests have been developed using static uniaxial load frames². The purpose of this study was to develop a technique to create a clinically relevant rim crack/fracture event on a 4-axis hip simulator, and to understand the contribution of component design and loading and motion parameters.

INTRODUCTION

Within total hip replacement, articulation of the femoral head near the rim of the acetabular liner creates undesirable conditions leading to a propensity for dislocation[1], increased contact stresses[2], increased load and torque imparted on the acetabular component[3], and increased wear[4]. Propensity for rim loading is affected by prosthesis placement, as well as the kinematics and loading of the patient. The present study investigates these effects.

High tensile stress has been considered as a contributing factor to the rim fracture of polyethylene acetabular cup liner. We performed the 3 D Finite Element Analysis (FEA) to compare the stress patterns at the polyethylene liner rim as a function of polyethylene thicknesses and whether or not rim was supported by the titanium acetabular shell extension. Two 3.1 mm thick generic 52 mm titanium alloy acetabular shells with and without 2 mm high rim support extension were modelled. Six corresponding Ultra High Molecular Weight Polyethylene (UHMWPE) liners with inner bearing diameters ranging from 22 mm to 44 mm and same outer diameters, were fixed in the shells. A 2 450 N load was applied through the corresponding CoCr femoral heads to the rims of liners while the acetabular shells were fixed on the outer spherical surface. The FEA was performed in half body of the assembly. The maximum principal stresses at the rim regions of UHMWPE liners were recorded.

The results showed that in all rim supported conditions, the maximum principal stress were in compressive patterns, a preferred pattern to reduce the potential polyethylene liner fracture. In rim unsupported conditions, the stresses was in tensile on the internal bearing surface when polyethylene liner thickness was bellow 5 mm, or was bellow 9 mm if the average maximum principal stress cross the rim was considered.

We conclude that the metal rim support changes the stress pattern in the rim region of UHMWPE liner to compressive for all liner thicknesses. The stress pattern turns to tensile, or there will be a higher potential for rim fracture, if UHMWPE liner is unsupported and the polyethylene rim thickness is less than 9 mm.

Although components used this study did not include the locking details which add higher stress concentrations, the trend of stress patterns should follow the results found in this study.

Previous studies suggested the lack of capture wall of acetabular Ultra High Molecular Weight Polyethylene (UHMWPE) liner can significantly increase the risk of hip joint dislocation. To date, the dislocation studies have been focused on the femoral neck impingement models. The purpose of this study was to identify a new Dislocating Force (DF) generated by rim directed joint force alone and investigate the factors to affect the magnitudes of the DF. The 3 D Finite Element Analysis (FEA) models were constructed by (30) 10 mm thick UHMWPE liners with six inner bearing diameters ranging from 22 mm to 44 mm and five capture wall heights in each bearing size from 0 mm to 2 mm. A load of 2 446 N was applied through the corresponding CoCr femoral head to the rim of the liner. The DF was recorded as a function of capture wall height and head diameter. The results were verified by the physical tests of two 28 mm head bearing liners with 0 and 1.5 mm capture wall heights respectively.

The results showed that the highest DF was 1 269N in 0 mm capture wall and 22 mm head. The lowest DF was 171 N in 2 mm capture wall and 44 mm head. The DF decreased as the capture wall and head size increased. When capture wall increased from 0 mm to 1 mm, the DF was reduced more than 50%. Two experimental data points were consistent with the trend of DF curve found in the FEA.

We concluded that the new intrinsic dislocating force DF can be induced by the rim directed joint loading force alone and can reach as high as 51% of the femoral loading force. A capture wall height above 1mm can effectively reduce DF to less than 25% of the joint force. In addition, the larger head diameter also resulted in less DF generation.

Cam-type femoroacetabular impingement is caused by bone excess on the femoral neck abutting the acetabular rim. This can cause cartilage and labral damage due to increased contact pressure as the cam moves into the acetabulum. However, the damage mechanism and the influence of individual mechanical factors (such as sliding distance) are poorly understood. The aim of this study was to identify the cam sliding distance during impingement for different activities in the hip joint. Motion data for 12 different motion activities from 18 subjects, were applied to a hip shape model (selected as most likely to cause damage, anteriorly positioned with a maximum alpha angle of 80°). The model comprised of a pointwise representation of the acetabular rim and points on the femoral head and neck where the shape deviated from a sphere (software:Matlab). The movement of each femoral point was tracked in 3D while an activity motion was applied, and impingement recorded when overlap between a cam point and the acetabular rim occurred. Sliding distance was recorded during impingement for each relevant femoral point. Angular sliding distances varied for different activities. The highest mean (±SD) sliding distance was for leg-crossing (42.62±17.96mm) and lowest the trailing hip in golf swing (2.17±1.11mm). The high standard deviation in the leg crossing sliding distances, indicates subjects may perform this activity in a different manner. This study quantified sliding distance during cam impingement for different activities. This is an important parameter for determining how much the hip moves during activities that may cause damage and will provide information for future experimental studies

Aims. Research on hip biomechanics has analyzed femoroacetabular contact pressures and forces in distinct hip conditions, with different procedures, and used diverse loading and testing conditions. The aim of this scoping review was to identify and summarize the available evidence in the literature for hip contact pressures and force in cadaver and in vivo studies, and how joint loading, labral status, and femoral and acetabular morphology can affect these biomechanical parameters. Methods. We used the PRISMA extension for scoping reviews for this literature search in three databases. After screening, 16 studies were included for the final analysis. Results. The studies assessed different hip conditions like labrum status, the biomechanical effect of the cam, femoral version, acetabular coverage, and the effect of rim trimming. The testing and loading conditions were also quite diverse, and this disparity limits direct comparisons between the different researches. With normal anatomy the mean contact pressures ranged from 1.54 to 4.4 MPa, and the average peak contact pressures ranged from 2 to 9.3 MPa. Labral tear or resection showed an increase in contact pressures that diminished after repair or reconstruction of the labrum. Complete cam resection also decreased the contact pressure, and acetabular rim resection of 6 mm increased the contact pressure at the acetabular base. Conclusion. To date there is no standardized methodology to access hip contact biomechanics in hip arthroscopy, or with the preservation of the periarticular soft-tissues. A tendency towards improved biomechanics (lower contact pressures) was seen with labral repair and reconstruction techniques as well as with cam correction. Cite this article: Bone Joint Res 2023;12(12):712–721

Femoroacetabular impingement (FAI) deformities are a potential precursor to hip osteoarthritis and an important contributor to non-arthritic hip pain. Some hips with FAI deformities develop symptoms of pain in the hip and groin that are primarily position related. The reason for pain generation in these hips is unclear. Understanding potential impingement mechanisms in FAI hips will help us understand pain generation. Impingement between the femoral head-neck contour and acetabular rim has been proposed as a pathomechanism in FAI hips. This proposed pathomechanism has not been quantified with direct measurements in physiological postures. Research question: Is femoroacetabular clearance different in symptomatic FAI hips compared to asymptomatic FAI and control hips in sitting flexion, adduction, and internal rotation (FADIR) and squatting postures?. We recruited 33 participants: 9 with symptomatic FAI, 13 with asymptomatic FAI, and 11 controls from the Investigation of Mobility, Physical Activity, and Knowledge Translation in Hip Pain (IMAKT-HIP) cohort. We scanned each participant's study hip in sitting FADIR and squatting postures using an upright open MRI scanner (MROpen, Paramed, Genoa, Italy). We quantified femoroacetabular clearance in sitting FADIR and squatting using beta angle measurements which have been shown to be a reliable surrogate for acetabular rim pressures. We chose sitting FADIR and squatting because they represent, respectively, passive and active maneuvers that involve high flexion combined with internal/external rotation and adduction/abduction, which are thought to provoke impingement. In the squatting posture, the symptomatic FAI group had a significantly smaller minimum beta angle (−4.6º±15.2º) than the asymptomatic FAI (12.5º ±13.2º) (P= 0.018) and control groups (19.8º ±8.6º) (P=0.001). In the sitting FADIR posture, both symptomatic and asymptomatic FAI groups had significantly smaller beta angles (−9.3º ±14º [P=0.010] and −3.9º ±9.7º [P=0.028], respectively) than the control group (5.7º ±5.7º). Our results show loss of clearance between the femoral head-neck contour and acetabular rim (negative beta angle) occurred in symptomatic FAI hips in sitting FADIR and squatting. We did not observe loss of clearance in the asymptomatic FAI group for squatting, while we did observe loss of clearance for this group in sitting FADIR. These differences may be due to accommodation mechanisms in the active, squatting posture that are not present in the passive, sitting FADIR posture. Our results support the hypothesis that impingement between the femoral head-neck contour and acetabular rim is a pathomechanism in FAI hips leading to pain generation

Femoroacetabular impingement (FAI) results from a morphological deformity of the hip and is associated with osteoarthritis (OA). Increased bone mineral density (BMD) is observed in the antero-superior acetabulum rim where impingement occurs. It is hypothesized that the repeated abnormal contact leads to damage of the cartilage layer, but could also cause a bone remodelling response according to Wolff's Law. Thus the goal of this study was to assess the relationship between bone metabolic activity measured by PET and BMD measured in CT scans. Five participants with asymptomatic cam deformity, three patients with uni-lateral symptomatic cam FAI and three healthy controls were scanned in a 3T PET-MRI scanner following injection with [18F]NaF. Bone remodelling activity was quantified with Standard Uptake Values (SUVs). SUVmax was analyzed in the antero-superior acetabular rim, femoral head and head-neck junction. In these same regions, BMD was calculated from CT scans using the calibration phantom included in the scan. The relationship between SUVmax and BMD from corresponding regions was assessed using the coefficient of determination (R. 2. ) from linear regression. High bone activity was seen in the cam deformity and acetabular rim. SUVmax was negatively correlated with BMD in the antero-superior region of the acetabulum (R. 2. =0.30, p=0.08). SUVmax was positively correlated with BMD in the antero-superior head-neck junction of the femur (R. 2. =0.359, p=0.067). Correlations were weak in other regions. Elevated bone turnover was seen in patients with a cam deformity but the relationship to BMD was moderate. This study demonstrates a pathomechanism of hip degeneration associated with FAI deformities, consistent with Wolff's law and the proposed mechanical cause of hip degeneration in FAI. [18F]-NaF PET SUV may be a biomarker of degeneration, especially in early stages of degeneration, when joint preservation surgery is likely to be the most successful

Aims. Cam and pincer morphologies are potential precursors to hip osteoarthritis and important contributors to non-arthritic hip pain. However, only some hips with these pathomorphologies develop symptoms and joint degeneration, and it is not clear why. Anterior impingement between the femoral head-neck contour and acetabular rim in positions of hip flexion combined with rotation is a proposed pathomechanism in these hips, but this has not been studied in active postures. Our aim was to assess the anterior impingement pathomechanism in both active and passive postures with high hip flexion that are thought to provoke impingement. Methods. We recruited nine participants with cam and/or pincer morphologies and with pain, 13 participants with cam and/or pincer morphologies and without pain, and 11 controls from a population-based cohort. We scanned hips in active squatting and passive sitting flexion, adduction, and internal rotation using open MRI and quantified anterior femoroacetabular clearance using the β angle. Results. In squatting, we found significantly decreased anterior femoroacetabular clearance in painful hips with cam and/or pincer morphologies (mean -11.3° (SD 19.2°)) compared to pain-free hips with cam and/or pincer morphologies (mean 8.5° (SD 14.6°); p = 0.022) and controls (mean 18.6° (SD 8.5°); p < 0.001). In sitting flexion, adduction, and internal rotation, we found significantly decreased anterior clearance in both painful (mean -15.2° (SD 15.3°); p = 0.002) and painfree hips (mean -4.7° (SD 13°); p = 0.010) with cam and/pincer morphologies compared to the controls (mean 7.1° (SD 5.9°)). Conclusion. Our results support the anterior femoroacetabular impingement pathomechanism in hips with cam and/or pincer morphologies and highlight the effect of posture on this pathomechanism. Cite this article: Bone Jt Open 2021;2(11):988–996

Aims. The effect of pelvic tilt (PT) and sagittal balance in hips with pincer-type femoroacetabular impingement (FAI) with acetabular retroversion (AR) is controversial. It is unclear if patients with AR have a rotational abnormality of the iliac wing. Therefore, we asked: are parameters for sagittal balance, and is rotation of the iliac wing, different in patients with AR compared to a control group?; and is there a correlation between iliac rotation and acetabular version?. Methods. A retrospective, review board-approved, controlled study was performed including 120 hips in 86 consecutive patients with symptomatic FAI or hip dysplasia. Pelvic CT scans were reviewed to calculate parameters for sagittal balance (pelvic incidence (PI), PT, and sacral slope), anterior pelvic plane angle, pelvic inclination, and external rotation of the iliac wing and were compared to a control group (48 hips). The 120 hips were allocated to the following groups: AR (41 hips), hip dysplasia (47 hips) and cam FAI with normal acetabular morphology (32 hips). Subgroups of total AR (15 hips) and high acetabular anteversion (20 hips) were analyzed. Statistical analysis was performed using analysis of variance with Bonferroni correction. Results. PI and PT were significantly decreased comparing AR (PI 42° (SD 10°), PT 4° (SD 5°)) with dysplastic hips (PI 55° (SD 12°), PT 10° (SD 6°)) and with the control group (PI 51° (SD 9°) and PT 13° (SD 7°)) (p < 0.001). External rotation of the iliac wing was significantly increased comparing AR (29° (SD 4°)) with dysplastic hips (20°(SD 5°)) and with the control group (25° (SD 5°)) (p < 0.001). Correlation between external rotation of the iliac wing and acetabular version was significant and strong (r = 0.81; p < 0.001). Correlation between PT and acetabular version was significant and moderate (r = 0.58; p < 0.001). Conclusion. These findings could contribute to a better understanding of hip pain in a sitting position and extra-articular subspine FAI of patients with AR. These patients have increased iliac external rotation, a rotational abnormality of the iliac wing. This has implications for surgical therapy with hip arthroscopy and acetabular rim trimming or anteverting periacetabular osteotomy (PAO). Cite this article: Bone Jt Open 2021;2(10):813–824

Introduction. Malalignment of cup in total hip replacement (THR) increases rates of dislocation, impingement, acetabular migration, pelvic osteolysis, leg length discrepancy and polyethylene wear. Many surgeons orientate the cup in the same anteversion and inclination as the inherent anatomy of the acetabulum. The transverse acetabular ligament (TAL) and acetabular rim can be used as a reference. No study has yet defined the exact orientation of the TAL. The aim of this study was to describe the orientation of acetabular margin and compare it with TAL orientation. Materials and Methods. Sixty eight hips with osteoarthritis undergoing THR with computer navigation were investigated. Anterior pelvic plane was registered using anterior superior iliac spines and pubic symphysis. Orientation of the natural acetabulum as defined by the acetabular rim with any osteophytes excised was measured. Since TAL is a rectangular band like structure, three recordings were done for each corresponding to the outer middle and inner margin of the band. All the readings were given by software as radiological anteversion and inclination. Results. All patients were Caucasian, 30 males and 38 females with mean age 67.4 years (SD 9.6) and BMI 30 (SD 5). Inclination was 54.7(SD7.9), 53(SD6.9), 47.5(SD6.8), 42.1(6.7) and anteversion 5.7(SD8.7), 5.4(SD9.9), 9.7(SD9.6), 13.5(SD9.4) for acetabular rim, outer, middle and inner borders of the TAL respectively. For inclination TAL outer border was not significantly different to acetabular rim (mean difference 1.7°, 95%CIs −0.2° to 3.6°, p=0.082) but the middle (mean difference 7.3°, 95%CIs 5.6° to 8.9°) and inner (mean difference 12.6°, 95%CIs 11.0° to 14.2°) borders were (both p<0.001). For anteversion TAL outer border was not significantly different to acetabular rim (mean difference 0.2°, 95%CIs −1.3° to 1.8°, p=0.758) but the middle and inner borders were (mean difference −4.0° 95%CIs −5.5° to −2.5° and −7.9°, 95%CIs −9.6° to −6.1° respectively, both p<0.001). Anteversion for males was significantly lower than females with a mean difference of 4 for the rim and 5.7, 4.8 and 5.1 for the TAL outer, middle and inner margins respectively. Overall 57,53,40&26 of 68 patients had a combined inclination and anteversion of the native acetabulum that fell outside the “safe zone” of Lewinnek with acetabular rim, outer, middle and inner margins of TAL respectively. Compared to Lewinnek safe zones for inclination TAL inner margin performed best with 14.7% outliers and acetabular rim performed worst with 72% outliers. For anteversion TAL inner margin performed best with 25% outliers while outer margin of TAL performed worst with 39.7% outliers. Conclusion. Orientation of the acetabulum differs a lot between individuals. The TAL middle and inner margins differ in orientation as compared to acetabular rim and TAL outer border. TAL inner border provides the best bet for placing the cup in Lewinnek's safe zone. When using the natural acetabular orientation or TAL as a guide, it should not be assumed this will orientate the cup in Lewinnek safe zone although the validity of safe zones itself is questionable. Variation between patients must be taken into account and the difference between males and females, particularly in terms of anteversion, should be considered

To quantify the acetabular coverage of the femoral head, Lequesne's vertical-center-anterior edge (VCA) angle is used on the false profile view. Lateral coverage is determined by Wiberg's lateral-center-edge (LCE) angle on an ap pelvic view. The delimitation of the weightbearing area is defined by the end of the subchondral sclerosis line for both views. To our knowledge the exact anatomic location of the points used for measurement on the acetabular rim are not known. Six hips from three cadaver pelvises (3 male and 3 female) were investigated. The anterior and lateral points of interested were identified radiographically using fluoroscopy and marked with 1mm ceramic bullets. Standard false profile views and ap pelvic views in neutral inclination and rotation were taken to check the correct location of the ceramic bullets. A CT of each pelvis was made to locate the ceramic bullets and to define the exact anatomic location of the measurement points on the o'clock position. 6 o‘clock was defined as the midpoint between anteroinferior and the posteroinferior rim edges. Values were normalized for a right hip. The mean clockface location for the VCA was 1:33 (range, 1:15 to 1:40) and for the LCE 0:38 (range, 0:20 to 0:50). The LCEA is slightly anterior to the 12 o'clock position and remains useful to quantify the lateral coverage. Surprisingly, the point used for measuring the VCA is only about 30° (1h) anterior of the point used for measuring the LCEA. Its value for determining anterior cover has to be questioned. The discrepancy to other studies in the literature is because this study identifies and measures the end of the weight bearing zone, and not the border of the bony acetabulum

Mixed Reality has the potential to improve accuracy and reduce required dissection for the performance of peri-acetabular osteotomy. The current work assesses initial proof of concept of MR guidance for PAO. A PAO planning module, based on preoperative computed tomography (CT) imaging, allows for the planning of PAO cut planes and repositioning of the acetabular fragment. 3D files (holograms) of the cut planes and native and planned acetabulum positions are exported with the associated spatial information. The files are then displayed on mixed reality head mounted device (HoloLens2, Microsoft) following intraoperative registration using an FDA-cleared mixed reality application designed primary for hip arthroplasty (HipInsight). PAO was performed on both sides of a bone model (Pacific Research). The osteotomies and acetabular reposition were performed in accordance with the displayed holograms. Post-op CT imaging was performed for analysis. Cutting plane-accuracy was evaluated using a best-fit plane and 2D angles (°) between the planned and achieved supra (SA)- and retroacetabular (RA) osteotomy and retroacetabular and ischial osteotomies (IO) were measured. To evaluate the accuracy of acetabular reorientation, we digitized the acetabular rim and calculated the acetabular opening plane. Absolute errors of planned and achieved operative inclination and anteversion (°) of the acetabular fragment, as well as 3D lateral-center-edge (LCE) angles were calculated. The mean absolute difference between the planned and performed osteotomy angles was 3 ± 3°. The mean absolute error between planned and achieved operative anteversion and inclination was 1 ± 0° and 0 ± 0° respectively. Mean absolute error between planned and achieved 3D LCE angle was 0.5 ± 0.7°. Mixed-reality guidance for the performance of pelvic osteotomies and acetabular fragment reorientation was feasible and highly accurate. This solution may improve the current standard of care by enabling reliable and precise reproduction of the desired acetabular realignment

We examined the relationship between the size of the femoral cam in femoroacetabular impingement (FAI) and acetabular pathomorphology to establish if pincer impingement exists in patients with a femoral cam. CT scans of 37 symptomatic impinging hips with a femoral cam were analysed in a three-dimensional study and were compared with 34 normal hips. The inclination and version of the acetabulum as well as the acetabular rim angle and the bony acetabular coverage were calculated. These measurements were correlated with the size and shape of the femoral cams. While the size of the femoral cam varied characteristically, the acetabular morphology of the two groups was similar in terms of version (normal mean 23° (. sd. 7°); cam mean 22° (. sd.  9°)), inclination (normal mean 57° (. sd. 5°); cam mean 56° (. sd. 5°)), acetabular coverage (normal mean 41% (. sd. 5%); cam mean 42% (. sd. 4%)) and the mean acetabular rim angle (normal mean 82° (. sd. 5°); cam mean 83° (. sd. 4°)). We found no correlation between acetabular morphology and the severity of cam lesion and no evidence of either global or focal over-coverage to support the diagnosis of ‘mixed’ FAI. The femoral cam may provoke edge loading but removal of any acetabular bearing surface when treating cam FAI might induce accelerated wear. Cite this article: Bone Joint J 2013;95-B:314–19

INTRODUCTION. Mal-positioning of the acetabular component in total hip replacement (THR) could lead to edge loading, accelerated component wear, impingement and dislocation [1,2]. In order to achieve a successful position for the acetabular component, the assessment of the acetabular orientation with reference to different coordinate systems is important [3]. The aims of the present study were to establish a pelvic coordinate system and a global body coordinate system, and to assess the acetabular orientations of natural hips with reference to the two coordinate systems. METHODS. Three-dimensional (3D) computed tomographic (CT) images of 56 subjects (28 males and 28 females) lying supine were obtained from a public image archive (Cancer Image Archive, website: . www.cancerimagingarchive.net. ). 3D solid models of pelvis and spine were generated from the CT images. Two coordinate systems, pelvic and global body coordinate systems, were established. The pelvic coordinate system was established based on four bony landmarks on the pelvis: the bilateral anterior superior iliac spines (RASIS and LASIS) and the bilateral pubic tubercles (RPT and LPT). The global body coordinate system was generated based on the bony landmarks on the spine: the geometric centers of five lumbar vertebrae bodies and the most dorsal points of five corresponding spinous processes, as well as the anterior sacral promontory (Fig 1a and 1b). The acetabular rim plane was obtained by fitting a set of point along the acetabular rim to a plane using least squares method. The acetabular orientation was defined as the three coordinate components (x-, y- and z- components) of the unit normal vector of the acetabular rim plane in the two coordinate systems (Fig. 1c). RESULTS. Statistically significant differences of y- and z- components of the unit normal vector of the acetabular rim plane were calculated in the two coordinate systems (p<0.05). However, no significant difference of x- components was found (p=0.22) (Fig. 2). The differences of y- and z- components of the unit normal vector between the two coordinate system measurements were positive for most subjects. In addition, the differences and their standard deviations were larger for females compared to those for males (Fig. 3). DISCUSSION. Significantly different acetabular orientations were measured in the two coordinate systems, with larger variations in the global body coordinate system. The statistical analysis indicates that the different orientations measured in the two coordinate systems are primarily attributed to the pelvic tilt in the sagittal plane. The results also indicates that there was a trend of forward inclination of pelvis for most subjects considered in the present study and that the females generally have larger forward inclination and greater variation of pelvic tilt compared to males. SIGNIFICANCE. The study suggested that the consideration of pelvic tilt in THR placement is necessarily required in order to achieve a successful positioning of THR component with respect to the biomechanical axis of the body

Arthroscopic management of femoroacetabular impingement (FAI) has become the mainstay of treatment. However, chondral lesions are frequently encountered and have become a determinant of less favourable outcomes following arthroscopic intervention. The aim of this systematic review and meta-analysis was to assess the outcomes of hip arthroscopy (HA) in patients with FAI and concomitant chondral lesions classified as per Outerbridge. A systematic search was performed using the PRISMA guidelines on four databases including MEDLINE, EMBASE, Cochrane Library and Web of Science. Studies which included HA as the primary intervention for management of FAI and classified chondral lesions according to the Outerbridge classification were included. Patients treated with open procedures, for osteonecrosis, Legg-Calve-Perthes disease, and previous ipsilateral hip fractures were excluded. From a total of 863 articles, twenty-four were included for final analysis. Demographic data, PROMs, and radiological outcomes and rates of conversion to total hip arthroplasty (THA) were collected. Risk of bias was assessed using ROBINS-I. Improved post-operative PROMs included mHHS (mean difference:-2.42; 95%CI:-2.99 to −1.85; p<0.001), NAHS (mean difference:-1.73; 95%CI: −2.23 to −1.23; p<0.001), VAS (mean difference: 2.03; 95%CI: 0.93-3.13; p<0.001). Pooled rate of revision surgery was 10% (95%CI: 7%-14%). Most of this included conversion to THA, with a 7% pooled rate (95%CI: 4%-11%). Patients had worse PROMs if they underwent HA with labral debridement (p=0.015), had Outerbridge 3 and 4 lesions (p=0.012), concomitant lesions of the femoral head and acetabulum lesions (p=0.029). Reconstructive cartilage techniques were superior to microfracture (p=0.042). Even in concomitant lesions of the femoral head and acetabulum, employing either microfracture or cartilage repair/reconstruction provided a benefit in PROMs (p=0.027). Acceptable post-operative outcomes following HA with labral repair/reconstruction and cartilage repair in patients with FAI and concomitant moderate-to-severe chondral lesions, can be achieved. Patients suffering from Outerbridge 3 and 4 lesions, concomitant acetabular rim and femoral head chondral lesions that underwent HA with labral debridement, had worse PROMs. Reconstructive cartilage techniques were superior to microfracture. Even in concomitant acetabular and femoral head chondral lesions, employing either microfracture or cartilage repair/reconstruction was deemed to provide a benefit in PROMs

Introduction: There have been several recent studies outlining the role of femoroacetabular impingement (FAI) as a cause of early osteoarthritis in the non-dysplastic hip. The lesions can either be on the femoral side “cam” or acetabular “pincer”. The aim of surgical treatment of FAI is to improve the femoral head neck offset thereby improving joint clearance and preventing abutment of the femoral neck against the acetabulum. The classic treatment for FAI pioneered by Ganz involves dislocation of the femoral head through a trochanteric flip osteotomy. The procedure is extensive, technically difficult and not without complications. Hip arthroscopic debridement of FAI lesions offers similar results to open procedures allowing for full inspection of the joint and the treatment of any chondral lesion but with a quicker recovery time. It nonetheless has a very long learning curve and even in the most experienced hands the treatment of impingement lesions is complicated and technically challenging. The purpose of this cadaveric study was to assess the degree of exposure obtained using two different limited anterior approaches to the hip which would allow effective surgical treatment of cam and pincer FAI. Methods: We investigated two mini anterior approaches to the hip joint based on the Heuter and direct anterior approach to compare the parts of the acetabulum and femoral head exposed for the treatment of FAI in a total of 20 hips in 10 (5 male, 5 female) cadaveric specimens. Neurovascular structures were recorded in relation to the two approaches. The area of femoral head and acetabular rim exposed via each approach was documented and quantified. Results: We found that the two approaches were easy and reproducible. Both allowed exposure to the anterolateral aspect of the femoral head. The mean length of acetabular rim accessible via the Heuter approach was 1.9cm (1.1–2.4) and 2.2cm (1.2–3) using the direct anterior approach The area of acetabular rim accessible varied according to the approach (p< 0.001). We also found that the position of the anterior inferior iliac spine in relation to the acetabular rim also affected the area of acetabular rim exposed (p< 0.001). The most proximal nerve branch to sartorious was found 7.3cm (6.5–8.7cm) distal to the anterior inferior iliac spine. The most proximal nerve branch to rectus femoris was located 8.6cm (7–10) distal to the anterior inferior iliac spine and was consistently found to be distal to the nerve to sartorious. Discussion: Treating impingement of the hip through a direct open approach is not a novel idea. A recent report of failed arthroscopic labral debridement, describes treatment of the underlying bony impingement in some cases by a combination of hip arthroscopy followed by anterior arthrotomy. In summary cam and pincer impingement of the hip can be treated by either the direct anterior or Heuter approach. The choice of approach would be dictated after careful consideration as to which portion of the anterior acetabular rim required surgery, with more lateral acetabular lesions being favoured by the Heuter approach and more medial impingement sites by the anterior approach we have described

Introduction and Objective. To estimate the prevalence of acetabular ossifications in the adult population with asymptomatic, morphologically normal hips at CT and to determine whether the presence of labral ossifications is associated with patient-related (sex, age, BMI), or hip-related parameters (joint space width, and cam- and pincer-type femoroacetabular impingement morphotype). Materials and Methods. We prospectively included all patients undergoing thoracoabdominal CT over a 3-month period. After exclusion of patients with a clinical history of hip pathology and/or with signs of osteoarthritis on CT, we included a total of 150 hips from 75 patients. We analyzed the presence and the size of labral ossifications around the acetabular rim. The relationships between the size of labral ossifications and patient- and hip-related parameters were tested using multiple regression analysis. Results. The prevalence of labral ossifications in this population of asymptomatic, non-OA hips was 96% (95%CI=[80.1; 100.0]). The presence of labral ossifications and their size were correlated between right and left hips (Spearman coefficient=0.64 (95%CI=[0.46; 0.79]), p<0.05)). The size of labral ossifications was significantly associated with age (p<0.0001) but not with BMI (p=0.35), gender (p=0.05), joint space width (p≥0.53 for all locations) or any of the qualitative or quantitative parameters associated with femoroacetabular morphotype (all p≥0.34). Conclusions. Labral ossifications are extremely common in asymptomatic, non-osteoarthritic hips. Their size is not correlated with any patient-, or hip-related parameters except for the age. These findings suggest that the diagnosis of osteoarthritis or femoroacetabular impingement morphotype should not be made based on the sole presence of acetabular labral ossifications

Introduction. Optimal orientation of the acetabular cup is vital issue not only for primary but revision total hip arthroplasty (THA). Especially in revision THA, malorientation of the cup is likely to occur because anatomical landmark around acetabular rim often disappeared by the osteolytic bony destruction or the process of cup removal. As a consequence, higher dislocation rate and accelerated wear of bearing surface compared with primary THA, which affect the outcome of revision THA, are concerned. On the other hand, computer aided navigation system has been developed in recent years because of substantial errors of manual technique in cup placement even with experienced surgeon. The purpose of this study was to evaluate the accuracy of the cup orientation in revision cementless THA using CT based navigation system. Materials and Methods. Thirteen patients who underwent revision cementless THA with CT based navigation system (Stryker Japan) were employed for this study. The average age at surgery was 64 years (range, 45–78 years, 3 men and 11 women). Primary surgery was cementless THA in 4 and BHA in 9 hips. Disorder which led to revision THA was loosening of the cup, massive retroacetabular osteolysis, and severe proximal migration of bipolar outer head. In most cases, acetabular rim was not conserved. After removal of the cup or outer head, we revised acetabular components with cementless hemispherical TriAD cups (Stryker Japan) using direct lateral approach in lateral decubitus position. For all the patients, post-operative CT scans were performed and the cup inclination and anteversion angle were measured using 3D image-processing software (Stryker, Japan). The difference between the intra-operative target angle and the angle measured from the post-operative CT image were calculated. Results. The average cup orientation measured by postoperative CT was 39.6±3.8° (range, 34–46°) in inclination and 20.5±5.0° (range, 17–29°) in anteversion. The accuracy (calculated as a mean of the absolute difference between intra-operative target angle and post-operative CT angle) of inclination and anteversion angle were 2.0 ± 1.8° (range, 0–5°) and 2.3±2.2° (range, 0–5°), respectively. The accuracy was within 5° in all cases and there was no postoperative dislocation. Discussion. Our study showed that CT based navigation system provided accurate orientation of the acetabular component even in revision cementless THA as well as in primary THA. Although the basic process of the navigation system in revision THA is same as primary THA, several pitfalls exist. Metal artifact from preexisting hardware such as screws, cup, and head-neck of the stem makes it difficult to do preoperative planning, intraoperative point matching, and surface registration. We have to pay maximum attention to avoid including metal artifact especially around acetabular rim when editing surface of the pelvis at preoperative planning, and also avoid pointing the area around acetabular rim when doing surface registration intraoperatively

Cam femoroacetabular impingement (FAI) is currently treated by resecting the femoral cam lesion. Some surgeons advocate additional anterosuperior acetabular rim resection. However, the exact acetabular contribution to cam-FAI has yet to be described. Using 3D-CT analysis, we set out to quantify the acetabular rim shape and orientation in this condition, and to determine the roles of these factors in cam-FAI. The acetabula of twenty consecutive cam hips (defined by α-angle of Notzli greater than 55° on plain radiographs) undergoing image based navigated surgery. These were compared with twenty normal hips (defined as disease free sockets with a normal femoral head-neck junction) obtained from a CT colonoscopy database. Using 3D reconstruction software, the pelvis was aligned to the anterior pelvic plane (APP). Starting at the most anterior rim point, successive markers were placed along the rim. A best-fit acetabular rim plane (ARP) was derived, and the subtended angle (SA) between each rim marker and a normal vector from the acetabular centre was calculated. Values above 90° indicated a peak, with less than 90° representing a trough. Inclination and version were measured from the APP. Our results showed that the rim profile of both cam-type and normal acetabular is an asymmetric succession of three peaks and three troughs. However, the cam-type acetabulum is significantly shallower overall than normal (Mean SA: 84±5° versus 87±4°, p< 0.0001). In particular, at anatomical points in the impingement zone between 12 and 3 o’clock, the subtended angle of cam hips were never higher than normal, and, in fact, at certain points were lower (iliac eminence: 90±5° vs. 93±4° p=0.0094, iliopubic trough: 79±5° vs. 83±4° p=0.0169, pubic eminence 83±7° vs. 84±4° p=0.4445). The orientation of cam and normal hips were almost identical (Inclination: 53±4°vs. 51±3° p=0.2609 and Anteversion: 23±7° vs. 24±6° p=0.3917). We concluded that cam-type acetabula are significantly shallower than normal. The subtended angles at all points around the hip were lower, and in particular, in the impingement zone between 12 and 3 o’clock not one cam had a subtended angle over 90°. We have therefore been unable to support the hypothesis of mixed-type FAI in cam-type hips. Bony rim resection in cam hips therefore runs the risk of rendering the acetabulum more morphologically abnormal and even functionally dysplastic. We do not recommend acetabular rim resection in patients with pure cam-type impingement, and await the longer-term results of this practice with apprehension

Cam-type femoroacetabular impingement (cam-FAI) can be treated with femoral neck osteochondroplasty to increase the clearance between the femoral head/neck and the acetabular rim. Because femur-acetabulum contact is very difficult to assess directly in patients, it is not clear if this surgery achieves its objective of reducing femur-acetabulum contact, and it is not clear how much of the femoral head/neck region should be resected to allow clearance in all activities. Our research question was: “Does femoral neck osteochondroplasty increase femur-acetabulum clearance in an extreme hip posture in patients with cam FAI?”. We recruited 8 consecutive patients scheduled to undergo arthroscopic femoral neck osteochondroplasty to treat cam-type FAI. We assessed clearance between the acetabulum and the femoral neck before surgery and at 6 months post-op using an upright open MRI scanner that allowed the hip to be scanned in flexed postures. We scanned each subject in a supine hip flexion (90 degree), adduction and internal rotation (FADIR) posture. We measured the beta angle, which describes clearance between the acetabular rim and the femoral head/neck deformity. Osteochondroplasty increased clearance from a mean beta angle of −9.4 degrees (SD 19.3) to 4.4 degrees (SD 16.2°) (p<0.05). This finding suggests that femoral neck osteochondroplasty increases femur-acetabulum clearance substantially for a posture widely accepted to provoke symptoms in patients with cam-FAI

Lesions of the acetabular rim have been implicated as a cause of hip pain in various pathologic conditions and are considered to predispose the hip to development of accelerated degenerative disease. In developmental dysplasia of the hip (DDH) and anterior femoroacetabular impingement (FAI), intrinsically normal intraarticular soft tissue structures are exposed to joint loading forces that physically exceed their tolerance level posing these pathomorphologies as precursors of osteoarthritis. In DDH, the deficient acetabular coverage of the femoral head has been related to osteoarthrosis, while the orientation of the femoral head is considered to play a less important role. The resulting instability and anterolateral migration tendency of the femoral head leads to chronic shear stresses at the acetabular margin. In FAI, repetitive peak contact pressures occur when the femoral head-neck junction abuts against the acetabular rim during joint flexion. Predisposing morphologies are femoral abnormalities such as an insufficient femoral head-neck offset seen in head tilt or pistol grip deformities, slipped capital femoral epiphysis, or malunited femoral neck fractures with the orientation and shape of the acetabulum contributing to this pathology. In classical DDH and FAI, diagnosis is primarily based on clinical signs and symptoms and conventional radiography. However, in cases of clinical and radiographic borderline disease establishment of the correct diagnosis is sometimes difficult. This presentation reports how the MRarthrographic appearance of acetabular rim pathologies can be used to differentiate both conditions. In DDH and FAI, labral pathologies localize identically with a predilection to the anterosuperior quadrant of the acetabulum. Labral tears are found in 64% in both groups. The volume of the labrum is increased in 86% DDH hips but in none of the FAI hips. Ganglion formation in the periacetabular area is seen in 71% DDH and 21% FAI hips. These findings provide evidence that the anterosuperior acetabular rim represents the initial fatiguing site of the hip under both DDH and FAI. The capability of MR-arthrography to depict differences in labral pathologies suggests this method as a helpful diagnostic tool to define the most appropriate treatment strategy specifically in borderline cases

Major bone loss involving the acetabulum can be seen during revision THA due to component loosening, migration or osteolysis and can also occur as a sequela of infected THA. Uncemented porous ingrowth components can be used for reconstruction of the vast majority of revision cases, where smaller segmental or cavitary defects are typically present. But when stable structural support on host bone is lacking, highly porous metal acetabular augments have been described as an alternative to large structural allograft. The fundamental concept behind these acetabular augments is the provision of critical additional fixation, structural support and increased contact area against host bone over the weeks following surgery while the desired ingrowth into porous implant surfaces is occurring. Three separate patterns of augment placement have been utilised in our practice since the development of these implants a decade ago: Type 1 - augment screwed onto the superolateral acetabular rim in a “flying buttress” configuration for treatment of a segmental rim defect, Type 2 – augment placed superiorly against host and then fixed to the acetabular component adjacent to the cup to fill a mainly elliptical cavitary defect, and Type 3 – augment(s) placed medial to the cup to fill a protrusio type cavitary or combined cavitary segmental defect of the superomedial or medial wall, and allow peripheral cup placement against the still intact acetabular rim. In all cases the acetabular component and augment interface is fixed together with cement, with care to prevent any cement extrusion between any implant and the bone. When possible, we now prefer to place the acetabular component first and fix it provisionally with 2 or more screws, and then place the augments second as this is technically quicker and easier. This order of insertion is only possible in type 1 and a few select type 2 cases. Type 3 cases always require placement of one or more augments first, before cup insertion. Supplemental cancellous bone graft is used routinely, but the need for structural bone is avoided. From 2000 through 2007, porous tantalum acetabular augments were used very selectively in 85 revision THA procedures out of total of the 1,789 revision hip cases performed at our institution. All cases had associated massive acetabular deficiency precluding stable mechanical support for a cup alone. Fifty-eight hips had complete radiographic and clinical follow at minimum 5 years. The majority of patients had either Paprosky type 3A defects (28/58, 48%) or 3B defects (22/58, 38%). Ten out of 58 had pre-operative pelvic discontinuities. Three separate patterns of augment placement were utilised: Type 1 - augment screwed onto the superolateral acetabular rim (21%), Type 2 – augment fixed to the acetabular component adjacent to the cup to fill a mainly elliptical cavitary defect (34%), and Type 3 – augment(s) placed medial to the cup to fill a protrusio type cavitary or combined cavitary segmental defect of the superomedial medial wall (45%). At 5 years, 2/58 (3%) were revised for aseptic loosening and another 6/58 demonstrated incomplete radiolucencies between the acetabular shell and zone 3. One of the revised cups and 5 of 6 of the cups with radiolucencies had an associated pelvic discontinuity. Highly porous metal acetabular augments are an infrequently needed, but extremely valuable, versatile and reliable adjunctive fixation method for use with uncemented acetabular components during complex revision THA associated with major bone deficiency. Smaller patients are more likely to require this approach as reaming away defects to allow insertion of a jumbo cup is more difficult with a smaller AP dimension to the acetabular columns and less local bone for implant support. Intermediate term durability and apparent radiographic incorporation has been very good despite the complex reconstructions originally required. This technique can allow the avoidance of structural bone grafting for even the most massive of bone defect problems, but additional followup is needed to see how durable these encouraging results are over the longer term

Introduction. In recent years, there has been a significant advancement in our understanding of femoro-acetabular impingement and associated labral and chondral pathology. Surgeons worldwide have demonstrated the successful treatment of these lesions via arthroscopic and open techniques. The aim of this study is to validate a simple and reproducible classification system for acetabular chondral lesions. Methods. In our classification system, the acetabulum is first divided into 6 zones as described by Ilizalithurri VM et al [Arthroscopy 24(5) 534-539]. The cartilage is then graded as 0 to 4 as follows: Grade 0 – normal articular cartilage lesions; Grade 1 softening or wave sign; Grade 2 - cleavage lesion; Grade 3 - delamination and Grade 4 –exposed bone. The site of the lesion is further typed as A, B or C based on whether the lesion is 1/3 distance from acetabular rim to cotyloid fossa, 1/3 to 2/3 distance from acetabular rim to cotyloid fossa and > 2/3 distance from acetabular rim to cotyloid fossa. For validating the classification system, six surgeons reviewed 14 hip arthroscopy video clips. All surgeons were provided with written explanation of our classification system. Each surgeon then individually graded the cartilage lesion. A single observer then compared results for observer variability using kappa statistics. Results. We observed a high inter-observer reliability of the classification system with a kappa coefficient of 0.89 (range 0.78 to 0.91) and high intra-observer reliability with a kappa coefficient of 0.91 (range 0.89 to 0.96). In conclusion we have developed a simple reproducible classification system for acetabular cartilage lesions seen at hip arthroscopy

Introduction:. The transverse acetabular ligament (TAL) antomy is not a well explored aspect of the hip joint with limited morphological description in the reviewed literature. It is often used as an anatomical landmark for orientation of the acetabular component in total hip arthroplasty (THA). There is debate as to whether it represents an appropriate guide to cup placement in THA. Present descriptions in orthopaedic literature conside it as a single plane structure to which the surgeon can align the cup. The aim of the current study was to investigate the morphology of the TAL and it was hypothesised that the current description of it being a plane would prove insufficient. Materials and methods:. Seven dry bone hemi-pelves were reconstructed using a microscribe and rhinoceros 4.0 3D software to visualise attachment sites. Three hips from two female donors were dissected to expose the acetabulum and the TAL. This structure was removed and a footprint taken of its perimeter and attachment sites for measurement of ligament length, breadth and area of attachment from digital photographs. Finally, 3D models of the dissected acetabuli with an outline of the TAL and attachment sites were created as before. Results:. The TAL extended beyond the acetabular notch, around the circumference of the acetabular rim. Two attachment sites were identified in each specimen, found at two sites in the superior half of the acetabular rim; one anterior and one posterior. In one specimen, an additional attachment site was identified on the posterior horn. TAL length in each specimen as measured from 2D digital photographs were 132 mm, 117 mm and 179 mm, with attachment areas of 215 mm. 2. , 150 mm. 2. and 350 mm. 2. , respectively. There was marked variation in ligament breadth both between and within individual specimens, ranging from 2.6 to 5.3mm in the smallest specimen and 3.2 to 6.3mm in the largest specimen. The whole structure as one does not conform to be a plane of orientation. Discussion:. Contrary to previous literature assumption, the TAL extended far beyond the acetabular notch. Likewise, its attachment sites were found further round the acetabular rim than previously described. The unexpected breadth may explain the disagreement between studies looking at the structure as an anatomical plane. Further biomechanical research may determine which part – if any – of the ligament, should the acetabular component be orientated to. The details will be presented in the paper

Background. Femoro-acetabular impingement (FAI) is increasingly recognised as a cause of mechanical hip symptoms in sportspersons. In femoro-acetabular impingement abnormal contact occurs between the proximal femur and the acetabular rim during terminal motion of the hip as a result of abnormal morphologic features involving the proximal femur (CAM) or the acetabulum (Pincer) or both (Mixed) leading to lesions of acetabular labrum and the adjacent acetabular cartilage. It is likely that it is a cause of early hip degeneration. Ganz developed a therapeutic procedure involving trochanteric flip osteotomy and dislocation of the hip, and have reported good results. We have developed an arthroscopic technique to reshape the proximal femur and remove prominent antero-superior acetabular rim thereby relieving impingement. Methods. Twelve patients presented with mechanical hip symptoms and had demonstrable cam-type (eight patients) or mixed (four patients) FAI on radially-reconstructed MR arthrography, were treated by arthroscopic femoral osteochondroplasty and acetabular rim resection if indicated. All patients were competing at the highest level in their respective sport (football, rugby and athletics). All patients were followed up and post-operative Non-Arthritic Hip Scores (NAHS, maximum possible score 100) compared with pre-operative NAHS. Results. There were no complications. All patients were asked to be partially weight-bearing with crutches for four weeks and most returned to training within six weeks. All of them returned to competitive sports by 14 weeks. Symptoms improved in all patients, with mean NAHS improving from 72 pre-operatively to 97 at 3 months. Conclusion. Arthroscopic reshaping to relieve FAI is feasible, safe and reliable. However it is technically difficult and time-consuming. The results are comparable to open dislocation and debridement, but avoid the prolonged disability and the complications associated with trochanteric flip osteotomy. This is important in elite athletes as they can return to training and competitive sports much quicker with less morbidity

Introduction: In recent years, there has been a significant advancement in our understanding of femoro-acetabular impingement and associated labral and chondral pathology. Surgeons worldwide have demonstrated the successful treatment of these lesions via arthroscopic and open techniques. The aim of this study is to validate a simple and reproducible classification system for acetabular chondral lesions. Methods: In our classification system, the acetabulum is first divided into 6 zones as described by Ilizalithurri VM et al [Arthroscopy 24(5) 534–539]. The cartilage is then graded as 0 to 4 as follows: Grade 0 – normal articular cartilage lesions; Grade 1 softening or wave sign; Grade 2 – cleavage lesion; Grade 3 – delamination and Grade 4 -exposed bone. The site of the lesion is further typed as A, B or C based on whether the lesion is 1/3 distance from acetabular rim to cotyloid fossa, 1/3 to 2/3 distance from acetabular rim to cotyloid fossa and > 2/3 distance from acetabular rim to cotyloid fossa. For validating the classification system, six surgeons reviewed 14 hip arthroscopy video clips. All surgeons were provided with written explanation of our classification system. Each surgeon then individually graded the cartilage lesion. A single observer then compared results for observer variability using kappa statistics. Results: We observed a high inter-observer reliability of the classification system with a kappa coefficient of 0.89 (range 0.78 to 0.91) and high intra-observer reliability with a kappa coefficient of 0.91 (range 0.89 to 0.96). Discussion: In conclusion we have developed a simple reproducible classification system for acetabular cartilage lesions

Abstract. Background. Optimal acetabular component position in Total Hip Arthroplasty is vital for avoiding complications such as dislocation, impingement, abductor muscle strength and range of motion. Transverse acetabular ligament (TAL) and posterior labrum have been shown to be a reliable landmark to guide optimum acetabular cup position. There have been reports of iliopsoas impingement caused by both cemented and uncemented acetabular components. Acetabular component mal-positioning and oversizing of acetabular component are associated with iliopsoas impingement. The Psoas fossa (PF) is not a well-regarded landmark to help with Acetabular Component positioning. Our aim was to assess the relationship of the TAL and PF in relation to Acetabular Component positioning. Methods. A total of 12 cadavers were implanted with the an uncemented acetabular component, their position was initially aligned to TAL. Following optimal seating of the acetabular component the distance of the rim of the shell from the PF was noted. The Acetabular component was then repositioned inside the PF to prevent exposure of the rim of the Acetabular component. This study was performed at Smith & Nephew wet lab in Watford. Results. Out of the twelve acetabular components that were implanted parallel to the TAL, all had the acetabular rim very close or outside to the psoas notch with a potential to cause iliopsoas impingement. Alteration of the acetabular component position was necessary in all cadavers to inside the PF to prevent iliopsoas impingement. It was evident that the edge of PF was not aligned with TAL. Conclusion. Optimal acetabular component position is vital to the longevity and outcome following THA. TAL provides a landmark to guide acetabular component position. We feel the PF is a better landmark to allow appropriate positioning of the acetabular component inside bone without exposure of the component rim and thus preventing iliopsoas impingement at the psoas notch. Declaration of Interest. (b) declare that there is no conflict of interest that could be perceived as prejudicing the impartiality of the research reported:I declare that there is no conflict of interest that could be perceived as prejudicing the impartiality of the research project

Introduction. Geometric variations of the hip joint can give rise to repeated abnormal contact between the femur and acetabular rim, resulting in cartilage and labrum damage. Population-based geometric parameterisation can facilitate the flexible and automated in silico generation of a range of clinically relevant hip geometries, allowing the position and size of cams to be defined precisely in three dimensions. This is advantageous compared to alpha angles, which are unreliable for stratifying populations by cam type. Alpha angles provide an indication of cam size in a single two-dimensional view, and high alpha angles have been observed in asymptomatic individuals. Parametric geometries can be developed into finite element models to assess the potential effects of morphological variations in bone on soft tissue strains. The aim of this study was to demonstrate the capabilities of our parameterisation research tool by assessing impingement severity resulting from a range of parametrically varied femoral and acetabular geometries. Methods. Custom made MATLAB (MathWorks) and Python codes. [1]. were used to generate bone surfaces, which were developed into finite element models in Abaqus (SIMULIA). Parametric femoral surfaces were defined by a spherical proximal head and ellipse sections through the neck/cam region. This method produced surfaces that were well fitted to bone geometry segmented from CT scans of cam patients and capable of producing trends in results similar to those found using segmented models. A simplified spherical geometry, including the labrum and acetabular cartilage, represented the acetabulum. Femoral parameters were adjusted to define relevant variations in cam size and position. Two radii (small and large cams) and two positions (anterior and superior cams) were defined resulting in four models. Alpha angles of these parametric femurs were measured in an anterior-posterior view and a cross-table lateral view using ImageJ (NIH). A further model was developed using a femur with a medium cam size and position, and the level of acetabular coverage and labrum length were varied. Bones were modelled as rigid bodies and soft tissues were modelled as transversely isotropic linearly elastic materials. With the acetabulum fully constrained in all cases, the femurs were constrained in translation and rotated to simulate flexion followed by internal rotation to cause impingement against the labrum. Results and Discussion. Models generated using the parametric approach showed that potential for tissue damage, indicated through local strain, was not predicted by measured alpha angle, but resulted from cam extent and position as defined by the ellipses. When variations were made to the acetabular rim, an increase in bone coverage had the greatest effect on impingement severity, indicated by strain in the cartilage labral-junction. An increase in labral length increased labral displacement, but had less effect on cartilage-labral strain. Patient specific models currently require full image segmentation, but there is potential to further develop these parametric methods to assess likely impingement severity based on a series of measures of the neck and acetabulum when three-dimensional imaging of patients is available

Background: Femoro-acetabular impingement (FAI) is increasingly recognised as a cause of mechanical hip symptoms in sportspersons. In femoro-acetabular impingement abnormal contact occurs between the proximal femur and the acetabular rim during terminal motion of the hip as a result of abnormal morphologic features involving the proximal femur (CAM) or the acetabulum (Pincer) or both (Mixed) leading to lesions of acetabular labrum and the adjacent acetabular cartilage. It is likely that it is a cause of early hip degeneration. Ganz developed a therapeutic procedure involving trochanteric flip osteotomy and dislocation of the hip, and have reported good results. We have developed an arthroscopic technique to reshape the proximal femur and remove prominent antero-superior acetabular rim thereby relieving impingement. Methods: Twelve patients presented with mechanical hip symptoms and had demonstrable cam-type (eight patients) or mixed (four patients) FAI on radially-reconstructed MR arthrography, were treated by arthroscopic femoral osteochondroplasty and acetabular rim resection if indicated. All patients were competing at the highest level in their respective sport (football, rugby and athletics). All patients were followed up and post-operative Non-Arthritic Hip Scores (NAHS, maximum possible score 100) compared with pre-operative NAHS. Results: There were no complications. All patients were asked to be partially weight-bearing with crutches for four weeks and most returned to training within six weeks. All of them returned to competitive sports by 14 weeks. Symptoms improved in all patients, with mean NAHS improving from 72 preoperatively to 97 at 3 months. Conclusion: Arthroscopic reshaping to relieve FAI is feasible, safe and reliable. However it is technically difficult and time-consuming. The results are comparable to open dislocation and debridement, but avoid the prolonged disability and the complications associated with trochanteric flip osteotomy. This is important in elite athletes as they can return to training and competitive sports much quicker with less morbidity

The present study investigates the repeatability of two new methods of measuring acetabular wear with differing levels of automation. Experimental evaluation showed that the more automated method was more repeatable. Both methods segmented the femoral head and acetabular rim with ellipses. The displacement of the ellipse centres was measured and the difference at year 1 and 5 taken as a measure of wear. Measurements were obtained twice for each case. The less automated of the two methods involved the annotation of 9 points on the femoral head and 18 on the acetabular rim to which two least squares ellipse fits[. 1. ] were performed. The second and more automated method was active ellipses[. 2. ][. 3. ]. This method uses iterative robust ellipse fitting and a model of appearance learned from a training set to cause two ellipses to converge on the contours of the femoral head and acetabular rim from a single starting point. Fifty cases with radiographs taken at year 1 and year 5 were measured by both methods. The radiographs contained CPTs with 28mm heads and were digitized at 150 dpi. Fifty postoperative radiographs containing 22.225mm Zimmer CPT heads trained the more automated method. None of the radiographs had metal backed cups or highly eccentric rims. The repeatability coefficient (2 standard deviations) of the active ellipses was 0.23mm and that of the best annotator was 0.40mm while the worst was 2.69mm due to an outlying measurement. Limits of agreement were calculated between the two methods as −0.61mm to 0.91mm and show the active ellipses could replace annotation. Given that the active ellipses are nearly twice as repeatable this is desirable. The range of difference in measurements for the active ellipses is less than that of the annotator

The acetabular labrum is a soft-tissue structure which lines the acetabular rim of the hip joint. Its role in hip joint biomechanics and joint health has been of particular interest over the past decade. In normal hip joint biomechanics, the labrum is crucial in retaining a layer of pressurised intra-articular fluid for joint lubrication and load support/distribution. Its seal around the femoral head is further regarded as a contributing to hip stability through its suction effect. The labrum itself is also important in increasing contact area thereby reducing contact stress. Given the labrum’s role in normal hip joint biomechanics, surgical techniques for managing labral damage are continuously evolving as our understanding of its anatomy and function continue to progress. The current paper aims to review the anatomy and biomechanical function of the labrum and how they are affected by differing surgical techniques. Take home message: The acetabular labrum plays a critical role in hip function and maintaining and restoring its function during surgical intervention remain an essential goal. Cite this article: Bone Joint J 2016;98-B:730–5

Pincer femoroacetabular impingement (FAI) is cited as being the result of a socket that is either too deep or retroverted, or both. Using 3D-CT analysis, we set out to quantify the acetabular rim shape and orientation to determine the roles of these two factors in FAI. Twenty pincer acetabulae were selected from patients undergoing image based navigated surgery, where the lateral centre edge angle was greater than 40° on plain radiographs. The normal group of disease free sockets were obtained from a CT colonography database. Using 3D reconstruction of their CT scans, a novel method of mapping the acetabular rim profile was created. The pelvis was aligned to the anterior pelvic plane. Starting at the most anterior rim point, successive markers were placed along the rim. A best fit plane (ARP) through the acetabulum was derived, and the subtended angle (SA) between each rim marker and a normal vector from the acetabular centre was calculated. Values above 90° indicated a peak, with less than 90° representing a trough. Inclination and version were measured from a horizontal plane and the ARP, in the coronal and axial view respectively. The results showed that asymmetric acetabular rim profiles in normal and pincer hips were very similar. However, pincer hips are significantly deeper overall (Mean SA 96±5° vs. 87±4° p< 0.00001) and at each anatomical point of the three eminences (pubic [SA: Normal 84±4° vs. Pincer 94±7° p< 0.00001], iliac [SA: 93±4° vs. 100±6° p=0.00021] and ischial [SA: 92±3° vs. 102±8° p=0.00005]) and two troughs (ilio-pubic [SA: Normal 83±4° vs. Pincer 94±8° p=0.00001] and ilio-ischial [SA: 92±3° vs. 102±8° p=0.00002]). The orientation of normal and pincer were almost identical (Inclination: 51±3° vs. 51±6° p=0.54 and Version: 24±6° vs. 25°±7° p=0.67). We conclude that the rim shape of pincer hips follows the same contour as normal hips. In agreement with current radiographic diagnosis, pincer-type hips are characterised by a deeper acetabulum. This ‘overcoverage’ of the femoral head confirms the biomechanical model of pincer-type impingement. Both inclination and version in these two groups were almost identical, with no truly retroverted acetabulum seen. Pincer impingement resulting from ‘acetabular retroversion’ is a concept currently based upon radiographic signs that we have been unable to confirm in this small 3D study using the subtended angle as the key descriptor of acetabular morphology

Hip impingement is a diagnosis that has been increasingly recognized among young patients with hip pain. Two different types of impingement have been described. Over coverage impingement, or a “pincer” effect, occurs between the anterior wall or labrum of the acetabulum and the femoral head. This is typically due to a decrease in anteversion of the acetabulum or over-coverage of the femoral head (coxa profunda or protrusio). A so-called cam-effect impingement occurs when the femoral head-neck junction has an abnormally large radius resulting in insufficient offset. Widening of the femoral neck reduces its concavity, creating an impingement over the acetabular rim. Thus, the anterolateral junction is forced under the acetabular rim, resulting in labral injury and deterioration of the cartilage. Options for treatment of impingement include non-operative management, arthroscopic débridement, trimming of the anterior aspect of the acetabular rim after surgical dislocation of the hip, periacetabular osteotomy when impingement is secondary to an acetabular torsion abnormality, and surgical resection of a femoral neck bump and/or part of the anterolateral aspect of the neck when the primary anatomic abnormality is secondary to insufficient head-neck offset. Resection of a portion of the anterolateral aspect of the femoral head-neck junction improves the femoral head-neck ratio, increasing the range of motion before impingement occurs. Recently, surgical dislocation has been used for achieving full access to the femoral head and the acetabulum. Surgical dislocation and resection osteochondroplasty were performed in 22 hips from January 2001 to Decem-ber 2004 because of anterior impingement resulting from an idiopathic nonspherical femoral head, mild slipped capital femoral epiphysis, or poor offset at the head-neck junction. Osteonecrosis was not observed in the hips treated with this method. Pain and function markedly improved after the index operation. Two patients required hardware removal. Treatment goals in young patients with hip impingement should be pain relief and, prevention of further damage to the cartilage and subsequent osteoarthritis. Surgeons using this technique need to know the amount of bone that can be removed safely before catastrophic weakening of the femoral neck occurs

Standard evaluation and diagnosis of pincer-type femoroacetabular impingment (FAI) relies on anteroposterior (AP) radiographs, clinical evaluation, and/or magnetic resonance imaging (MRI). However, the current evaluation techniques do not offer a method for accurately defining the amount of acetabular rim overcoverage in pincer-type FAI. Several studies have remarked on the particular problems with radiographic evaluation, including beam divergence, difficulty with defining the acetabular rim, and pelvic tilt. Some studies have proposed methods to mitigate these issues; however, radiographic analysis still relies on projected and distorted images, making it difficult to acquire an accurate quantitative estimate of the amount of crossover. We propose a technique that utilises computed tomography (CT) data to accurately quantify the amount of acetabular crossover while accounting for known diagnostic problems, specifically pelvic tilt. This work describes a novel method that utilises CT data of a patient's afflicted hip joint region to assess the amount of acetabular overcoverage due to pincer deformity. The amount of overcoverage was assessed using a spline curve defined through the segmentation of the acetabular rim from CT data. To mitigate pelvic tilt, the user selected points to define both the pubic symphysis and the promontory in a lateral digitally reconstructed radiograph. The algorithm corrected the pelvic tilt by adjusting to a defined neutral position (in our case, a 60°), and the user adjusted for slight rotation differences ensuring there was a vertical line connecting the symphysis and the sacrococcygeal joint. After successfully repositioning the pelvis, the algorithm computed the amount of acetabular overcoverage. The algorithm identified the superolateral point of the acetabulum and the most inferior points of the anterior and posterior rim. A line, the mid-acetabular axis, was constructed between the superolateral point and the midpoint of the most inferior points on the anterior and posterior rims; the mid-acetabular axis was extended anterior and posterior to create a plane. Crossover occurred when the anterior rim of the acetabulum intersected this plane. If an intersection occurred, the algorithm measured the length of the mid-acetabular axis, and the length and width of the section representing overcoverage. These points were then projected onto anteroposterior DRRs and again measured to generate a basis of comparison. We tested our method on four cadaveric specimens to analyze the relationship between radiographic assessment and our technique. We simulated varying degrees of impingement in the cadavers by increasing the amount of pelvic tilt and defining that as the neutral position for a given trial. Moreover, we assessed interobserver variability in repositioning the pelvis as to the effect this would have on the final measurement of crossover length and width. The software achieved consistent, quantitative measurements of the amount of acetabular overcoverage due to pincer deformity. When compared with conventional radiographic measurements for crossover, there was a significant different between the two modalities. Specifically, both the ratios of crossover length to acetabular length and crossover width to crossover length were less using the CT-based approach (p < 0.001). Moreover, there were no significant differences between observers using our approach. The proposed technique can form the basis for a new way to diagnosis and measure acetabular overcoverage resulting in pincer impingement. This computational method can help clinicians to accurately correct for tilt and rotation, and subsequently provide consistent, quantitative measurement of acetabular overcoverage

Introduction. The Exeter RimFit™ flanged cemented cup features ultra-highly cross-linked polyethylene and was introduced onto the market in the UK in 2010. We aimed to examine the rates of radiolucent lines observed when the Rimfit™ cup was implanted using a ‘rimcutter’ technique with the cup sitting on a prepared acetabular rim, and a ‘trimmed flange’ technique were the flange is cut so that it sits inside the prepared acetabular rim. Patients/Materials & Methods. The radiographs of 150 (75 ‘rimcutter’, 75 ‘trimmed flange’) Rimfit™ hip replacements were critically evaluated to assess for radiolucency at the cement bone interface. This group was then compared to a historic pre-Rimfit™ cohort of 76 patients. Results. Rimfit™ Cups inserted using the rimcutter technique exhibited significantly higher rates of radiolucency than cups inserted using the trimmed flange technique at 1 year post surgery (1 Delee and Charnley zone: rimcutter=73/77 (95%) versus trimmed flange=14/75 (19%); 2 zones: 43/75 (57%) versus 0/75 (0%); all 3 zones: 13/75 (17%) versus 0/75 (0%):(p<0.01)). There were significantly more radiolucencies for the ‘rimcutter’/Rimfit™ group when compared to a historic group of non-‘rimcutter’/non-Rimfit™ cups implanted by the same surgeon (p<0.01). Discussion. 95% of Rimfit™ cups inserted using the rimcutter technique exhibited radiolucent lines at 12 months. This may be due to increased flange stiffness related to the ultra-highly cross-linked polyethylene and the closer seal due to the narrow circumferential ridge created by the rimcutter. Insertion of the cup may lead to lower initial cement penetration which further deteriorates with weight bearing due to the flange offloading the socket. This may be exacerbated by hydraulic pumping of fluid trapped under the flange at the time of implantation that further degrades the cement bone interface. Conclusion. On the basis of these results we have stopped using the Rimfit™ cup in combination with the rimcutter device and technique

Major bone loss involving the acetabulum can be seen during revision THA due to component loosening, migration or osteolysis and can also occur as a sequela of infected THA. Uncemented porous ingrowth components can be used for reconstruction of the vast majority of revision cases, where smaller segmental or cavitary defects are typically present. But when stable structural support on host bone is lacking, highly porous metal acetabular augments have been described as an alternative to large structural allograft, avoiding the potential for later graft resorption and the resulting loss of mechanical support that can follow. The fundamental concept behind these acetabular augments is the provision of critical additional fixation, structural support and increased contact area against host bone over the weeks following surgery while the desired ingrowth into porous implant surfaces is occurring. Three separate patterns of augment placement have been utilised in our practice since the development of these implants a decade ago: Type 1 – augment screwed onto the superolateral acetabular rim in a “flying buttress” configuration for treatment of a segmental rim defect, Type 2 – augment placed superiorly against host and then fixed (with cement) to the acetabular component adjacent to the cup to fill a mainly elliptical cavitary defect, and Type 3 – augment(s) placed medial to the cup to fill a protrusio type cavitary or combined cavitary segmental defect of the superomedial or medial wall, and allow peripheral cup placement against the still intact acetabular rim. In all cases the acetabular component and augment interface is fixed together with cement, with care to prevent any cement extrusion between any implant and the bone. When possible, we now prefer to place the acetabular component first and fix it provisionally with 2 or more screws, and then place the augments second as this is technically quicker and easier. This order of insertion is only possible though in type 1 and a few select type 2 cases. Type 3 cases always require placement of one or more augments first, before cup insertion. Supplemental cancellous bone graft is used routinely, but the need for structural bone is avoided. Highly porous metal acetabular augments are an infrequently needed, but extremely valuable, versatile and reliable adjunctive fixation method for use with uncemented acetabular components during complex revision THA associated with major bone deficiency. Smaller (often female) patients are more likely to require this approach as reaming away defects to allow insertion of a jumbo cup is more difficult in small patients with a smaller AP dimension to the acetabular columns and less local bone for implant support. Intermediate term durability and apparent radiographic incorporation has been very good despite the complex reconstructions originally required. This technique can allow the avoidance of structural bone grafting for even the most massive of bone defect problems, but additional followup is needed to see how durable these encouraging results are over the longer term

To assess the current literature on suture anchor placement for the purpose of identifying factors that lead to suture anchor perforation and techniques that reduce the likelihood of complications. Three databases (PubMed, Ovid MEDLINE, EMBASE) were searched, and two reviewers independently screened the resulting literature. Methodological quality of all included papers was assessed using Methodological Index for Non-Randomized Studies criteria and the Cochrane Risk of Bias Assessment tool. Results are presented in a narrative summary fashion using descriptive statistics. Fourteen studies were included in this review. Four case series (491 patients, 56.6% female, mean age 33.9 years), nine controlled cadaveric/laboratory studies (111 cadaveric hips and 12 sawbones, 42.2% female, mean age 60.0 years), and one randomized controlled trial (37 hips, 55.6% female, mean age 34.2 years) were included. Anterior cortical perforation by suture anchors led to pain and impingement of pelvic neurovascular structures. The anterior acetabular positions (three to four o'clock) had the thinnest bone, smallest rim angles, and highest incidence of articular perforation. Drilling angles from 10° to 20° measured off the coronal plane were acceptable. The mid-anterior (MA) and distal anterolateral (DALA) portals were used successfully, with some studies reporting difficulty placing anchors at anterior locations via the DALA portal. Small-diameter (< 1 .8-mm) suture anchors had a lower in vivo incidence of articular perforation with similar stability and pull-out strength in biomechanical studies. Suture anchors at anterior acetabular rim positions (3–4 o'clock) should be inserted with caution. Large-diameter (>2.3-mm) suture anchors increase the likelihood of articular perforation without increasing labral stability. Inserting small-diameter (< 1 .8-mm) all-suture suture anchors (ASAs) from 10° to 20° using curved suture anchor drill guides, may increase safe insertion angles from all cutaneous portals. Direct arthroscopic visualization, use of fluoroscopy, distal-proximal insertion, and the use of nitinol wire can help prevent articular violation

Major bone loss involving the acetabulum can be seen during revision THA due to component loosening, migration or osteolysis and can also occur as a sequela of infected THA. Uncemented porous ingrowth components can be used for reconstruction of the vast majority of revision cases, where smaller segmental or cavitary defects are typically present. But when stable structural support on host bone is lacking, highly porous metal acetabular augments have been described as an alternative to large structural allograft, avoiding the potential for later graft resorption and the resulting loss of mechanical support that can follow. The fundamental concept behind these acetabular augments is the provision of critical additional fixation, structural support and increased contact area against host bone over the weeks following surgery while the desired ingrowth into porous implant surfaces is occurring. Technique: Three separate patterns of augment placement have been utilised in our practice since the development of these implants: Type 1 - augment screwed onto the superolateral acetabular rim in a “flying buttress” configuration for treatment of a segmental rim defect, Type 2 – augment placed superiorly against host and then fixed (with cement) to the acetabular component adjacent to the cup to fill a mainly elliptical cavitary defect, and Type 3 – augment(s) placed medial to the cup to fill a protrusio type cavitary or combined cavitary segmental defect of the superomedial or medial wall, and allow peripheral cup placement against the still intact acetabular rim. In all cases the acetabular component and augment interface is fixed together with cement, with care to prevent any cement extrusion between any implant and the bone. When possible, we now prefer to place the acetabular component first and fix it provisionally with 2 or more screws, and then place the augments second as this is technically quicker and easier. This order of insertion is only possible though in type 1 and a few select type 2 cases. Type 3 cases always require placement of one or more augments first, before cup insertion. Supplemental cancellous bone graft is used routinely. Results: From 2000 through 2007, porous tantalum acetabular augments were used very selectively in 85 revision THA procedures out of total of 1,789 revision hip cases performed at our institution in that time frame. All cases had associated massive acetabular deficiency precluding stable mechanical support for a cup alone. Fifty-eight hips had complete radiographic as well as clinical follow at minimum 5 years. The majority of patients had either Paprosky type 3A defects (28/58, 48%) or 3B defects (22/58, 38%). Ten out of 58 had pre-operative pelvic discontinuities. At 5 years, 2/58 (3%) were revised for aseptic loosening and another 6/58 demonstrated incomplete radiolucencies between the acetabular shell and zone 3. One of the revised cups and 5 of 6 of the cups with radiolucencies had an associated pelvic discontinuity. Summary: Highly porous metal acetabular augments are an infrequently needed, but extremely valuable, versatile and reliable adjunctive fixation method for use with uncemented acetabular components during complex revision THA associated with major bone deficiency. Intermediate term durability and apparent radiographic incorporation has been very good despite the complex reconstructions originally required. This technique can allow the avoidance of structural bone grafting for even the most massive of bone defect problems, but additional followup is needed to see how durable these encouraging results are over the longer term

The β-angle is a radiological tool for measuring the distance between the pathological head-neck junction and the acetabular rim with the hip in 90° of flexion in patients with femoroacetabular impingement. Initially it was measured using an open-chamber MRI. We have developed a technique to measure this angle on plain radiographs. Correlation analysis was undertaken to determine the relationship between the range of movement and the β-angle in 50 patients with femoroacetabular impingement and 50 asymptomatic control subjects. Inter- and intra-observer reliability of the β-angle was also evaluated. Patients with femoroacetabular impingement had a significantly smaller (p < 0.001) mean β-angle (15.6°, 95% confidence interval (CI) 13.3 to 17.7) compared with the asymptomatic group (38.7°, 95% CI 36.5 to 41.0). Correlation between internal rotation and the β-angle was high in the impingement group and moderate in the asymptomatic group. The β-angle had excellent inter- and intra-observer reliability in both groups. Our findings suggest that the measurement of the β-angle on plain radiography may represent a valid, reproducible and cost-effective alternative to open MRI in the assessment of the pathological bony anatomy in patients with cam, pincer and mixed femoroacetabular impingement

Recently, femoroacetabular impingement has been recognised as a cause of early osteoarthritis. There are two mechanisms of impingement: 1) cam impingement caused by a non-spherical head and 2) pincer impingement caused by excessive acetabular cover. We hypothesised that both mechanisms result in different patterns of articular damage. Of 302 analysed hips only 26 had an isolated cam and 16 an isolated pincer impingement. Cam impingement caused damage to the anterosuperior acetabular cartilage with separation between the labrum and cartilage. During flexion, the cartilage was sheared off the bone by the non-spherical femoral head while the labrum remained untouched. In pincer impingement, the cartilage damage was located circumferentially and included only a narrow strip. During movement the labrum is crushed between the acetabular rim and the femoral neck causing degeneration and ossification. Both cam and pincer impingement lead to osteoarthritis of the hip. Labral damage indicates ongoing impingement and rarely occurs alone

HXLPE acetabular liners were introduced to reduce wear-related complications in THA. However, post-irradiation thermal free radical stabilization can compromise mechanical properties, leave oxidation-prone residual free radicals, or both. Reports of mechanical failure of HXLPE acetabular liner rims raise concerns about thermal free radical stabilization and in vivo oxidization on implant properties. The purpose of this study is to explore the differences in the mechanical, physical and chemical properties of HXLPE acetabular liner rims after extended time in vivo between liners manufactured with different thermal free radical stabilization techniques. Remelted, single annealed and sequentially annealed retrieved HXLPE acetabular liners with in vivo times greater than 4.5 years were obtained from our implant retrieval laboratory. All retrieved liners underwent an identical sanitation and storage protocol. For mechanical testing, a total of 55 explants and 13 control liners were tested. Explant in vivo time ranged from 4.6 – 14 years and ex vivo time ranged from 0 – 11.6 years. Rim mechanical properties were tested by microindentation hardness testing using a Micromet II Vickers microhardness tester following ASTM standards. A subset of 16 explants with ex vivo time under one year along with five control liners were assessed for oxidation by FTIR, crystallinity by Raman spectroscopy, and evidence of microcracking by SEM. No significant difference in in vivo or ex vivo was found between thermal stabilization groups in either set of explants studied. In the mechanically tested explants, there was no significant correlation between in vivo time and Vickers hardness in any thermal stabilization group. A significant correlation was found between ex vivo time and hardness in remelted liners (r=.520, p = .011), but not in either annealed cohort. ANCOVA with ex vivo time as a covariate found a significant difference in hardness between the thermal free radical stabilization groups (p 0.1) was found in retrieved remelted (25%), single annealed (100%) and sequentially annealed (75%) liner rims. Crystallinity was increased in the subsurface region relative to control liners for both annealed, but not remelted, liner rims. Hardness was increased in oxidized rims for both annealed cohorts but not in the remelted cohort. Microcracking was only found along the surface of one unoxidized remelted liner rim. Mechanical properties were reduced at baseline and worsened after in vivo time for remelted HXLPE liner rims. Rim oxidation was detected in all groups. Oxidation was associated with increased crystallinity and hardness in annealed cohorts, but not remelted liners. Increased crystallinity and oxidation do not appear to be directly causing the worsened mechanical behavior of remelted HXLPE liner rims after extended in vivo time

Optimal alignment of the acetabular cup component is crucial for good outcome of total hip arthroplasty [THA]. Increased accuracy of implant positioning may improve clinical outcome. To achieve this, patient specific instrumentation was developed. A patient-specific guide manufactured by 3D printing was designed to aid in positioning of the cup component with a pre-operatively defined anteversion and inclination angle. The guide fits perfectly on the acetabular rim. An alignment K-wire in a pre-operatively planned orientation is used as visual reference during cup implantation. Accuracy of the device was tested on 6 cadaveric specimens. During the experiment, cadavers were positioned for a THA procedure using a posterolateral approach. A normal-sized incision was made and approach used as in the conventional surgical procedure. The PSI was subsequently fitted onto the acetabular rim and secured into its unique position due to its patient specific design. The metallic pin was placed in a drill hole of the PSI. Post-operative CT image data of each acetabulum with the placed pin were transferred to Mimics and the 3D model was registered to the pre-operative one. The anteversion and inclination of the placed pin was calculated and compared to the pre-operatively planned orientation. The absolute difference in degrees was evaluated. A secondary test was carried out to assess the error during impaction while observing the alignment K-wire as a visual reference. In a laboratory setting, error during impaction with a visual reference of the K-wire was measured. Deviation from planning showed to be on average 1.04° for anteversion and 2.19° for inclination. By visually aligning the impactor with this alignment K-wire, the surgeon may achieve cup placement as pre-operatively planned. The effect of the visual alignment itself was also evaluated in a separate test-rig showing minimal deviations in the same range. The alignment validation test resulted in an average deviation of 1.2° for inclination and 1.4° for anteversion between the metallic alignment K-wire used as visual reference and the metallic K-wire impacted by the test subjects. The inter-user variability was 0.9° and 0.8° for anteversion and inclination respectively. The intra-user variability was 1.6° and 1.0° for anteversion and inclination respectively. Tests per test subject were conducted in a consecutive manner. We investigated the accuracy of two factors affecting accuracy in the cup insertion with PSI, i.e. accuracies of the errors of bony fitting and cup impaction. Since the accuracy of the major contributing factors to the overall accuracy of PSI for cup insertion with linear visual reference of a metallic K-wire was within the acceptable range of 2 to 3 degrees, we state that the PSI we have designed assists to achieve the preoperatively planned orientation of the cup and as such leads to the reduction of outliers in cup orientation. This acetabular cup orientation guide can transfer the pre-operative plan to the operating room

Femoroacetabular impingement recently was recognized as cause for osteoarthritis of the hip. There are two mechanism of impingement: (1) cam impingement caused by a non-spherical head, and (2) pincer impingement due to acetabular overcover. We hypothesized that both mechanism result in different articular damage patterns. Of 302 analyzed hips only 26 had an isolated cam and 16 an isolated pincer impingement. Cam impingement caused anterosuperior acetabular cartilage damage with a separation between labrum and cartilage. During flexion the cartilage is sheared off the bone by the non-spherical part of the femoral head. In pincer impingement the cartilage damage was located circumferentially, invovolving only a narrow strip along the acetabular rim. During motion the labrum is crushed between the acetabular rim and the femoral neck causing degeneration and ossification of the labrum. Cam and pincer impingement are two basic mechanism that lead to osteoarthrosis of the hip. The articular damage pattern differs substantially. Isolated cam or pincer impingement is rare, in most hips a combination is present. Labral damage indicates ongoing impingement and rarely occurs alone

Introduction. Femoroacetabular impingement (FAI) causes anterior hip pain, labral tears and damage to the articular cartilage leading to early osteoarthritis of the hip. Surgical hip dislocation and osteoplasty of the femoral neck and acetabular rim is a technique pioneered by the Bernese group for the treatment of FAI. We present and discuss our results of this technique. Methods. Functional outcome was measured in hips with over 12 month follow-up using the Oxford hip and McCarthy non-arthritic hip scores pre- and post-operatively. Results. From March 2003 to December 2005, 79 hips underwent surgical hip dislocation for treatment of FAI. Ten were skeletally immature and excluded. In 16 hips, grade 4 osteoarthritis was present in greater than 10 × 10mm regions after reshaping of the abnormal anatomy. In these cases, hip resurfacing was performed. Of the 53 hips preserved (average age 37(17-65)), 35 had the labrum detached, debrided and reattached using bone anchors, 32 underwent recession of the acetabular rim at the site of impingement, 21 had chondral ‘carpet’ flaps debrided, 5 had removal of medial osteophytes, 7 had labral and/or bony cysts excised and grafted and 1 underwent an osteochondral graft. In 5 hips osteoarthritis progressed requiring hip resurfacing at an average of 8 months. Oxford Hip Score improved from an average 32 (range 13-59) to 23 (12-45) and McCarthy hip score from 50 (19-76) to 63 (28-79) in the preserved hips at an average 20 months following surgery (range 12-38 months). Conclusion. The early results of surgical hip dislocation are encouraging. The open procedure has distinct advantages compared to arthroscopy enabling a wider range of lesions to be treated. Careful patient selection is important in order to exclude patients with hip osteoarthritis. Long-term follow-up is required to see if this technique prevents the natural progression to osteoarthritis

Introduction. Highly crosslinked, ultra-high molecular weight polyethylene (HXLPE) acetabular liners inherently have a risk of fatigue failure associated with femoral neck impingement. One of the potential reasons for liner failure was reported as crosslinking formulations of polyethylene, increasing the brittleness and structural rigidity. In addition, the acetabular component designs greatly affect the mechanical loading scenario, such as the offset (lateralized) liners with protruded rim above the metal shells, which commonly induce a weak resistance to rim impingement. The purpose of the present study was to compare the influence of the liner offset length on the impingement resistance in the annealed (first generation) and vitamin E-blended (second-generation) HXLPE liners with a commercial design. Materials and Methods. The materials tested were the 95-kGy irradiated annealed GUR1020, and the 300-kGy irradiated vitamin E-blended GUR1050 HXLPE offset liners, which were referred to as “20_95” and “50E_300”, respectively. These liners had 2, 3, 4-mm rim offset, 2.45-mm rim thickness, and 36-mm internal diameter. Their rims were protruded above the metal rim at 2, 3, 4mm. Rim impingement testing was performed using an electrodynamic axial-torsional machine. The cyclic impingement load of 25–250N was applied on the rims through the necks of the femoral stems at 1Hz. The rotational torque was simultaneously generated by swinging the stem necks on the rims at 1Hz and its rotational angle was set at the range of 0–10˚. The percent crystallinity was analyzed on the as-received (intact) and impinged HXLPE acetabular rims by confocal Raman microspectroscopy. Results. The number of cycles to failure was dependent on the offset length (2, 3, 4-mm) in 20_95 and 50E_300 liners. Our results showed that the shorter the rim offset, the shorter the number of cycles to failure. In both HXLPEs, accumulation of impingement damages significantly decreased crystallinity in their near-surfaces, indicating the occurrence of crystallographic breakdown. In each offset length tested, the fracture always occurred much earlier in 50E_300 than 20_95. However, the magnitudes of the microstructural changes at the time of failure were much less in 50E_300 than 20_95. Conclusions. Although it is known that vitamin E blend into HXLPE can improve the fatigue resistance of HXLPE, the impingement resistance of 50E_300 was lower than vitamin-E free 20_95, indicating a larger negative contribution of high-dose radiation (300kGy) over a positive contribution of the vitamin E blend in 50E_300. Our results implied that the reduction of the protruded rim length in the offset liners may increase the neck-rim contact stresses at the time of impingement, causing a decrease in the fatigue durability. Therefore, if HXLPE offset liner is used, surgeons should take special care in maximizing the volume of the protruded lip section

Introduction: Femoroacetabular impingement (FAI) causes anterior hip pain, labral tears and damage to the articular cartilage leading to early osteoarthritis of the hip. Surgical hip dislocation and osteoplasty of the femoral neck and acetabular rim is a technique pioneered by the Bernese group for the treatment of FAI. We present and discuss our results of this technique. Methods: Functional outcome was measured using the Oxford hip and McCarthy non-arthritic hip scores pre and post-operatively. Results: Since January 2003, 36 hips in 34 patients (average age of 43 years (14–65)) underwent surgical hip dislocation for treatment of FAI. In 9 hips, grade 4 osteoarthritis was present in greater than 10 x 10mm regions after reshaping of the abnormal anatomy. In these cases, hip resurfacing was performed. Of the 27 hips preserved, 14 had chondral ‘carpet’ flaps debrided, 17 underwent recession of the acetabular rim at the site of impingement, 6 had removal of medial osteophytes, 6 had labral and/or bony cysts excised and grafted and 1 underwent an osteochondral graft. Oxford Hip Score improved from an average 36 (range 17–59) to 23 (12–45) and McCarthy hip score from 43 (9–74) to 62 (36–72) in the preserved hips at an average 15 months following surgery (range 6–33 months). Discussion: The early results of surgical hip dislocation are encouraging. Careful patient selection is important in order to exclude patients with hip osteoarthritis. Long-term follow-up is required to see if this technique prevents the natural progression to osteoarthritis

Summary. The cartilage layer from cam-type femoroacetabular impingement deformities had lower stiffness and increased permeability compared to normal cartilage. This is consistent with osteoarthritis and supports the hypothesis of abnormal contact stresses. Introduction. Femoroacetabular impingement (FAI) has recently been associated with osteoarthritic (OA) degeneration of the hip and may be responsible for up to 90% of adult idiopathic OA cases. FAI results from deformities in the hip joint which may lead to abnormal contact stresses and degeneration. The more common cam-type deformity consists of a convex anterior femoral head-neck junction which impinges the anterosuperior acetabular rim during flexion and internal rotation of the hip. Increased subchondral bone density has been reported in this region which may be a bone remodelling response to increased contact stress. The abnormal contact is expected to cause degeneration of the cartilage layer. The goal of this study was to assess the mechanical properties of cartilage retrieved from the cam deformity and to compare this with normal articular cartilage from the femoral head. It is hypothesised that the cartilage will have a lower elastic modulus and higher permeability than normal cartilage. Patients & Methods. Osteochondral biopsies were retrieved from nine patients undergoing surgical correction of a symptomatic cam deformity as well as 10 fresh cadaveric specimens (10 hips, 6 donors). An indentation stress relaxation test was performed on each specimen to 10% of the estimated cartilage thickness. A needle penetration test was performed to accurately measure the thickness. The equilibrium modulus was calculated per Hayes et al. A specimen-specific axisymmetric finite element model was used in a non-linear optimization to obtain the fibril-reinforced poroelastic properties of the cartilage that best fit the experimental data. The material properties were non-fibrillar modulus (E. s. ), Poisson's ratio (ν. s. ) and permeability (k) and strain-independent and –dependent moduli (E. 0. , E. ε. )[4]. Results. The equilibrium modulus was 0.14 MPa and 0.63 from surgical and cadaver specimens, respectively (p=0.002). Compared to cadaver specimens, E. s. in surgical specimens was 73% lower (p=0.01), ν. s. was 43% lower (p=0.01) and k was an order of magnitude higher (p=0.02). Fibril moduli were not significantly different (p>0.35). Discussion/Conclusions. This study showed decreased elastic modulus and increased permeability in cartilage from cam deformities compared to cadaver controls. These differences are consistent with changes expected in osteoarthritic cartilage degeneration. Fibril moduli were 14% to 57% lower in surgical specimens consistent with fibrillation, however results were not significant due to high variability. Altered cellular activity and proteoglycan depletion has been reported in cartilage of cam deformities, which are similar to changes expected in osteoarthritis. The altered mechanical and biochemical properties of this cartilage therefore support the hypothesis that osteoarthritis is secondary to cam FAI deformities and is a result of abnormal contact stresses between the deformity and acetabular rim

There have been considerable recent advances in the understanding and management of femoroacetabular impingement and associated labral and chondral pathology. We have developed a classification system for acetabular chondral lesions. In our system, we use the six acetabular zones previously described by Ilizaliturri et al. The cartilage is then graded on a scale of 0 to 4 as follows: grade 0, normal articular cartilage lesions; grade 1, softening or wave sign; grade 2, cleavage lesion; grade 3, delamination; and grade 4, exposed bone. The site of the lesion is further classed as A, B or C based on whether the lesion is less than one-third of the distance from the acetabular rim to the cotyloid fossa, one-third to two-thirds of the same distance and greater than two-thirds of the distance, respectively. In order to validate the classification system, six surgeons graded ten video recordings of hip arthroscopy. Our findings showed a high intra-observer reliability of the classification system with an intraclass correlation coefficient of 0.81 and a high interobserver reliability with an intraclass correlation coefficient of 0.88. We have developed a simple reproducible classification system for lesions of the acetabular cartilage, which it is hoped will allow standardised documentation to be made of damage to the articular cartilage, particularly that associated with femoroacetabular impingement

Sixty-nine hips in 62 patients were treated by the Pavlik harness for congenital dislocation. Ultrasonography showed three degrees of residual head displacement when the harness was first applied. In type A, the femoral head showed contact with the inner posterior wall of the acetabulum. In type B, it contacted the posterior margin of the socket, with its centre at or anterior to the acetabular rim. In type C, the femoral head was displaced outside the socket, with its centre posterior to the acetabular rim. All 51 hips with type A displacement remained reduced. Of nine hips of type B, five were reduced, but the other four were not. None of the nine hips with type C dislocation became reduced with continued use of the harness. The Pavlik harness is indicated for type A and some type B dislocations, but the latter need daily ultrasound monitoring, with a change in method of treatment if type C displacement appears or if the hip is not reduced within one or two weeks. Treatment by Pavlik harness is not indicated in hips with type C dislocations

Purpose: The purpose of this study was to examine the arthroscopy findings in the hips of patient with persistent pain after surgical hip dislocation for femoroacetabular impingement syndrome. Type of study: Retrospective, consecutive series of patients. Patients and Methods: Sixteen consecutive patients (6 male/10 female; average age 33,5 years 19–60y) with persistent pain after surgical hip dislocation for the treatment of femoroacetabular impingement were included. At the index surgery, all patients had an osteo-chondroplasty of the head neck junction and a resection of the acetabular rim with reattachment of the labrum in 9 cases. All patients had a preoperative arthro-MRI and were treated with arthroscopy of the hip. Results: At arthroscopy all reattached labra were stable. In the cases without preservation of the labrum, the joint capsule was attached level with the acetabular rim and had important synovitis. All patients had adhesions between the neck of the femur and joint capsule or between labrum and capsule. In 3 patients the arthroscopic procedure was technically limited by massive thickening of the capsule. Overall 75% (12 of 16) patients showed less pain or were pain free. MDA improved from preoperatively 13 to 16 points at last follow up. Conclusions: Persistent pain after surgical dislocation of the hip could result from intraarticular adhesions that can be shown in the MRI. Hip arthroscopy after previous surgery can be demanding due to scarring. If the adhesions can be released good results can be achieved. Hip arthroscopy is a save therapeutical tool to treat patients with intraarticulary adhesions after surgical dislocation of the hip for femoroacetabular impingement

Interest on acetabular version arose from unstable developmental dysplastic hips. Initial studies and clinical observations described the dysplastic hip as being excessively anteverted. The advent of computed tomography allowed further detailed analysis of the acetabulum in the axial plane, yet these studies failed to determine conclusively whether or not the dysplastic acetabulum is abnormally anteverted. Much controversy evolved from different methods of measuring and from the fact that a more anteriorly located acetabular deficiency results in excessive anteversion while a more posteriorly located deficiency in retroversion. It remains inconclusive to what extent acetabular dysplasia is due to a mal-orientation of an otherwise normal configured acetabulum or to a deficient acetabulum which is otherwise normally orientated. Furthermore, the acetabular opening spirals gradually from mild anteversion proximally to increasing anteversion distal to it and therefore render its measurement dependent from pelvic inclination and from the level of the transverse CT scan slice. On an orthograde pelvic X-ray, both, pelvic inclination and rotation can be controlled. Therefore, acetabular version is best estimated from the relationship of the anterior and posterior acetabular rim to each other on an orthograde pelvic X-ray. The main hip pathologies, acetabular rim overload and anterior femoro-acetabular impingement, both occur in the superior part of the acetabulum, the acetabular dome, and that’s where version is best measured. We called this version of the acetabular dome. Interest on retroversion of the acetabular dome arose from analysis of complications such as persistent posterior subluxation after acetabular reorienting procedures. They resulted in the hypothesis that the site of acetabular deficiency may vary and be more posteriorly located in some cases resulting in a rather retroverted than anteverted acetabular dome. In fact, retroversion of the acetabular dome was found to be a characteristic feature of specific hip disorders. A review of ten patients with posttraumatic premature closure of the triradiate cartilage before age 5 showed beside a bowed hemipelvis with lateralized and caudalized acetabulum a mean retroversion of the acetabular dome of 27°. A review of 14 patients suffering from proximal femoral focal deficiency with a functional hip joint revealed a mean retroversion of the acetabular dome of 24°. Typically this was accompanied by femoral retrotorsion and coxa vara. Finally, bladder exstrophy, when treated without pelvic osteotomy, typically end up with externally rotated or retroverted acetabula (Sponseller, 1995) Even in DDH, retroversion of the acetabular dome has been shown to be a significant variation as 40 of 232 such acetabula showed to have a retroverted dome (Li, 2003). Furthermore retroversion typically can result from pelvic osteotomy in childhood as 26 from 97 subjects, who underwent either Salter or Le Coeur osteotomy in childhood ended up with retroverted acetabular domes after closure of the pelvic bone growth plates. In the context of neuromuscular or genetic disorders, dysplastic hips also may have retroverted acetabular domes and may additionally be influenced from fixed spine deformities. Finally, retroverted acetabular domes may be found in otherwise non dysplastic hips. The relevance of acetabular retroversion is both technical and clinical: First, it calls for a more individual approach to acetabular dysplasia because presence of retroversion will affect the manner in which corrective osteotomy will be done. Salter-like reorientation maneuvers will result in worsening the pre-existing posterior deficiency or acetabular rim overload and risk continued posterior subluxation or dislocation of a previously reduced hip (Lee, 1991). Second, anterior overcorrection of a primarily retroverted acetabula may necessitate a further intervention to remove bone from the anterior aspect of the acetabulum or anterior part of the femoral head-neck junction due to limited hip flexion (Crockarell 1999, Myers 1999). Third, evidence that the long-term effect of retroversion of the acetabular dome is harmful is increasing: An association between decreased acetabular anteversion and osteoarthritis was found as soon as 1991 (Menke, 1991) and the prevalence of retroversion among patients with idiopathic hip osteoarthritis has been found to be 20% versus 5% among the general population (Giori, 2003). Furthermore, decreased acetabular and femoral anteversion was found to be a major cause of altered rotation, hip pain and osteoarthritis (Tönnis, 1999). A positive impingement test was the key clinical finding (Reynolds,1999). This anterior impingement of the femoral head-neck junction against the border of the prominent anterior acetabular wall which over a long period of time may lead to fatiguing and destruction of the acetabular labrum and the adjacent cartilage is thought to initiate groin pain and early osteoarthritis. Finally, even for total hip replacement, severe retroversion of the acetabular dome will make surgery more difficult

A well-fixed uncemented acetabular component is most commonly removed for chronic infection, malposition with recurrent dislocation, and osteolysis. However, other cups may have to be removed for a broken locking mechanism, a bad “track record”, and for metal-on-metal articulation problems. Modern uncemented acetabular components are hemispheres which have 3-dimensional ingrowth patterns. Coatings include titanium or cobalt-chromium alloy beads, mesh, and now the so-called “enhanced coatings”, such as tantalum trabecular metal, various highly porous titanium metals, and 3-D printed metal coatings. These usually pose a problem for safe removal without fracture of the pelvis or creation of notable bone deficiency. Preoperative planning is essential for safe and efficient removal of these well-fixed components. Strongly consider getting the operative report, component “stickers”, and contacting the implant manufacturer for information. There should a preoperative check list of the equipment and trial implants needed, including various screwdrivers, trial liners, and a chisel system. The first step in component removal is excellent 360-degree exposure of the acetabular rim, and this can be accomplished by several approaches. Then, the acetabular polyethylene liner is removed; a liner that is cemented into a porous shell can be “reamed out” using a specific device. Following this, any central or peripheral screws are removed; broken or stripped screw heads add an additional challenge. A trial acetabular liner is placed, and an acetabular curved chisel system is used. There are two manufacturers of this type of system. Both require the known outer acetabular diameter and the inner diameter of the trial liner. With the curved chisel system and patience, well-fixed components can be safely removed, and the size of the next acetabular component to be implanted is usually 4mm larger than the one removed. There are special inserts for removal of monobloc metal shells. Remember that removal of these well-fixed components is more difficult in patients compared to models, and is just the first step of a successful acetabular revision

Introduction: Femoro-acetabular impingement (FAI) causes anterior hip pain, labral tears and damage to the articular cartilage leading to early osteoarthritis of the hip. Surgical hip dislocation and osteoplasty of the femoral neck and acetabular rim is a technique pioneered by the Bernese group for the treatment of FAI. We present and discuss our results of this technique. Methods: functional outcome was measured using the oxford hip and McCarthy non-arthritic hip scores pre and post-operatively. Results: Since January 2003, 36 hips in 34 patients (average age of 43 years (14–65)) underwent surgical hip dislocation for treatment of FAI. In 9 hips, grade 4 osteoarthritis was present in greater than 10 x 10mm regions after reshaping of the abnormal anatomy. In these cases, hip resurfacing was performed. Of the 27 hips preserved, 14 had chondral ‘carpet’ flaps debrided, 17 underwent recession of the acetabular rim at the site of impingement, 6 had removal of medial osteophytes, 6 had labral and/or bony cysts excised and grafted and 1 underwent an osteochondral graft. In 3 hips (12%) osteoarthritis progressed requiring hip resurfacing within the first year. Oxford Hip Score improved from an average 36 (range 17–59) to 23 (12–45) and McCarthy hip score from 43 (9–74) to 62 (36–72) in the preserved hips at an average 15 months following surgery (range 6–33 months). Discussion: The early results of surgical hip dislocation are encouraging. The open procedure has distinct advantages compared to arthroscopy enabling a wider range of lesions to be treated. Careful patient selection is important in order to exclude patients with hip osteoarthritis. Long-term follow-up is required to see if this technique prevents the natural progression to osteoarthritis

Late presentation of DDH continues to remain a major problem particularly in the developing countries. Femoro-Acetabular Zones (FAZ) system is created to find a relation between acetabular maturity and severity of dislocation, in one hand, and the success of closed reduction, on the other hand. We hypnosis that the lower the acetabular index and the closer the femoral head to the acetabulum, the more likely the success of treatment. Thus, a retrospective study was performed on late diagnosed DDH hips that underwent closed treatment at a particular hospital in the Middle East. FAZ are drawn on the AP view of the pelvic x-ray and is based on a perpendicular from the acetabular index at the lateral margin of the superior acetabular rim then another perpendicular to Perkin's line is drawn. This gives three zones, graded I-III. The center of femoral metaphysis is identified denoting the position of the femoral head in relation to the zone classification. FAZ system was applied on 65 pelvic radiographs; mean patient age was 24 months (range: 12 to 36 months) with a minimum follow up of 3 years. Overall, 37 of 65 hips (57%) achieved a satisfactory outcome (Severin I&II), while 22 hips (33%) were found to be unsatisfactory (Severin III). 6 hips (10%) needed an open reduction (p-value 0.001). FAZ could perfectly predict the successful cases. FAZ system is a simple and novel classification and if employed, could reasonably predict the outcome of non-surgical treatment of DDH after walking age

Background. Cementless acetabular cups rely on press-fit fixation for initial stability; an essential pre-requisite to implant longevity. Impaction is used to seat an oversized implant in a pre-prepared bone cavity, generating bone strain, and ‘grip’ on the implant. In certain cases (such as during revision) initial fixation is more difficult to obtain due to poorer bone quality. This increases the chance of loosening and instability. No current study evaluates how a surgeon's impaction technique (mallet mass, mallet velocity and number of strikes) may be used to maximise cup fixation and seating. Questions/purposes. (1) How does impaction technique affect a) bone strain & fixation and b) seating in different density bones? (2) Can an impaction technique be recommended to minimize risk of implant loosening while ensuring seating of the acetabular cup?. Methods. A custom drop tower was used to simulate surgical strikes, seating acetabular cups into a synthetic bone model (Fig. 1). Strike velocity (representing surgeon strike level) and drop mass (representing mallet mass) were varied through representative low, medium and high levels. Polar gap between the implant and bone was measured using optical tracking markers. Strain gauges were used to measure acetabular rim strain. Following seating, cup pushout force was measured in a materials testing machine. Both measurements were used to quantify the level of fixation of the implant for two conditions: For the first, the cup was optimally seated (moving no more than 0.1mm on the previous strike, representing ideal conditions); For the second the cup was impacted 10 times (excessively impacted). Repeats (N = 5) were conducted in low and high density bone; a total of 180 tests. Results. For ideally impacted cups, increasing mallet mass and velocity improved fixation and reduced polar gap. However a phenomenon of bone strain deterioration was identified if an excessive number of strikes were used to seat a cup, resulting in loss of implant fixation. This effect was most severe in low density bone (Fig. 2). For high strike velocity and mallet mass, each excessive strike halved the measured bone strain (78 ± 7 με/strike). This reduced fixation strength from 630 ± 65 N (optimally seated) to just 49 ± 6 N at 10 strikes (Fig. 3). Discussion. These results identify a possible mechanism of loss of implant stability with excessive acetabular impaction. A high mallet mass with low strike velocity resulted in satisfactory fixation (442 ± 38 N) and polar gap (1 ± 0.1 mm) whilst minimizing the fixation deterioration due to excessive mallet strikes. Extreme caution must be exercised to avoid excessive impaction high velocity strikes in low density bone for any mallet mass. Conclusion & Clinical relevance. As it may be difficult for a surgeon to accurately infer when an implant is optimally seated, this study informs surgeons of the effects of different impaction techniques, particularly in lower density bones. For any figures or tables, please contact the authors directly

Introduction: The operation method selected for acetabular revisions depends on the type of deþciency; Type 1: contained cavitary; the acetabular rim is preserved and thus supportive. Type 2: non-contained deþciencies; the acetabular rim and the peripheral zones are non- supportive defects. In non-contained, rim non-supportive defects acetabular reinforcement rings are used as a rule. Material and methods: Between July 1988 and December 1997 465 acetabular revisions with 229 Reinforcement Rings and 236 Press- Fit Cups (4 bilaterally) were performed. A 7.5 (5.0–10.8) year clinical and radiological follow-up of the Press-Fit Cup inserted in 130 women and 102 men was effected. Mean age at revisions surgery was 70 in women and 73 in men. 39 patients (17%) died without needing a re-revision, and 17 (7%) could only be interviewed by phone. One patient was lost to follow-up. Of the remaining 175 patients (75%) with 179 hips (76%) were available for complete evaluation. Results: The clinical results (according to Merle dñAubignŽ) was excellent and good in 82% 143 pts), moderate in 17% (30 pts) and poor in 1% (2 pts). 22 (9%) reinterventions were noted during the observation period: 12 for dislocations, 5 for aseptic stem loosening, 1 for septic loosening, 2 for secondary periprosthetic fractures and 2 for removal of heterotopic ossiþcations. Conclusions: No Press-Fit Cup had to be re-revised for aseptic loosening. Reconstruction for contained, rim supportive defects with the Press-Fit Cup provides excellent results, comparable to those of primary arthroplasties

Acetabular rim damge due to rim impingement is frequently found on retrievals and may be associated with increased wear and contact stresses, instability, and implant loosening of total hip replacement devices. Large X3 bearings (> 36mm) from Stryker have increased implant range of motion and improved polyethylene material (sequentially crosslinked and annealed). A hip simulator wear study was performed with and without femoral neck to acetabular rim impingement to determine the wear performance of these new bearings under aggressive impingement conditions. Two sizes of these new components were tested (36mm with 3.9mm thickness and 40mm with 3.8mm thickness) with two standard sized controls (28mm with 7.9mm thickness in X3 and conventional polyethylene. The 36mm component was chosen to be the largest component utilizing the same shell as the standard 28mm size components while the 40mm component was chosen to be the thinnest bearing currently offered. Impingement significantly increased wear for all bearings (p< 0.05) but no cracking or failures of the rim occurred. Wear rates for all X3 bearings were statistically indifferent under each testing condition despite bearing size and thickness. Average wear rates for X3 bearings were 0.3mm3/million cycles (mc) under standard conditions and 3.5mm3/mc under impingement conditions. Average wear rates for conventional bearings were 19.5mm3/mc under standard conditions and 48.3mm3/mc under impingement conditions. Overall the X3 bearings exhibited a 93% reduction in wear under impingement conditions and 99% reduction in wear under standard conditions. Increased bearing range of motion reduces the chance of impingement. This study shows the simulated outcome even if these larger bearings were to impinge. We conclude that these larger X3 bearings exhibits the same wear performance as standard X3 bearings and significantly superior wear performance compared to conventional polyethylene bearings under standard and impingement conditions

Resurfacing arthroplasty of the hip is a relatively new procedure. This paper reports the technical and clinical problems one surgeon encountered in the first 50 consecutive resurfacing arthroplasties of the hip. The mean age of the 14 women and 32 men at the time of surgery was 44.8 years (20 to 65). Four patients underwent bilateral arthroplasty. Technical problems included failure of the acetabular component to seat fully in six hips and failure of the femoral component to seat fully in four. There was varus malalignment of the femoral component in three cases, retention of the alignment pin in one, and retention of a cable fragment in one. Surgical complications included one case of intra-operative femoral neck fracture, one transection of the psoas tendon during capsulotomy, and a femoral nerve palsy, which recovered after six months. Postoperative problems included superficial wound inflammation in five hips and one dislocation. There were radiological signs of impingement of the femoral neck on the acetabular rim in four cases and clinical symptoms of impingement in one. An undisplaced fracture of the femoral neck that occurred eight weeks after surgery was successfully managed conservatively by keeping the limb non-weight-bearing. Despite these problems, only one patient retains any noteworthy symptoms, apparently due to impingement of the femoral neck on the acetabular rim. Modest malalignment or seating failure appears to be of minimal clinical consequence. Patients typically mobilise rapidly and are able to return to a high level of physical activity. It is possible to avoid most technical problems by taking specific precautions

The use of rim mesh to augment acetabular defects at the time of revision hip surgery is a valuable technique. Where acetabular containment is compromised by segmental rim defects, it can be achieved by using a flexible wire mesh fixed to the wall of the ilium by multiple screws. Morsilised bone graft is then impacted onto the acetabular bed and wire mesh thus creating a new hemi-spherical acetabular bed for cementation of a new socket. Standard AP and lateral radiographs are acceptable methods for assessing conventional socket revisions. However if a rim mesh has been used the mesh itself will obscure the socket and both columns of the acetabulum making interpretation difficult. We have modified the Judet views classically used in acetabular fracture surgery to allow better imaging of the socket. The views taken are dependant upon rim mesh position at surgery. Technique: Positioning for posterior acetabular rim mesh. From the supine position the patient is rotated 45° so that the side under examination is raised. Radiolucent pads are used to support the pelvis and leg. The hips and knees should not be flexed. Positioning for anterior acetabular rim mesh. From the supine position the patient is rotated 45° so the non affected side is raised. Using radiolucent pads the pelvis is supported. The femur should not be flexed and externally rotated as they would be for an oblique hip. The film is centred approximately 2cm below the ASIS of the hip being examined. These views of the hip allow complete imaging of the socket and the reconstructive construct. Radiographic evaluation of the bone graft and bone cement-graft interface can be reliably made. We would recommend these views for the radiographic follow up of socket revisions involving the rim mesh technique

Introduction. HXLPE acetabular liners were introduced to reduce wear-related complications in THA. However, post-irradiation thermal free radical stabilization can compromise mechanical properties, leave oxidation-prone residual free radicals, or both. Reports of mechanical failure of HXLPE acetabular liner rims raise concerns about thermal free radical stabilization and in vivo oxidization on implant properties. The purpose of this study is to explore the differences in the mechanical, physical and chemical properties of HXLPE acetabular liner rims after extended time in vivo between liners manufactured with different thermal free radical stabilization techniques. Material and Methods. Remelted, single annealed and sequentially annealed retrieved HXLPE acetabular liners with in vivo times greater than 4.5 years were obtained from our implant retrieval laboratory. All retrieved liners underwent an identical sanitation and storage protocol. For mechanical testing, a total of 55 explants and 13 control liners were tested. Explant in vivo time ranged from 4.6 – 14.0 years and ex vivo time ranged from 0 – 11.6 years. Rim mechanical properties were tested by microindentation hardness testing using a Micromet II Vickers microhardness tester following ASTM standards. A subset of 16 explants with ex vivo time under one year along with five control liners were assessed for oxidation by FTIR, crystallinity by Raman spectroscopy, and evidence of microcracking by SEM. Results. No significant difference in in vivo or ex vivo time was found between thermal stabilization groups in either set of explants studied. In the mechanically tested explants, there was no significant correlation between in vivo time and Vickers hardness in any thermal stabilization group. A significant correlation was found between ex vivo time and hardness in remelted liners (r=.520, p=.011), but not in either annealed cohort. ANCOVA with ex vivo time as a covariate found a significant difference in hardness between the thermal free radical stabilization groups (p<.0005, η. 2. = 0.322). Post hoc analysis revealed hardness was significantly lower in the retrieved remelted group compared to both the single annealed (p=.001) and sequentially annealed (p<.0005) cohorts. Hardness was significantly higher in the retrieved remelted liners compared to controls (p=.007), with no different in either annealed cohort. Detectable subsurface oxidation (OI > 0.1) was found in retrieved remelted (25%), single annealed (100%) and sequentially annealed (75%) liner rims. Crystallinity was increased in the subsurface region relative to control liners for both annealed, but not remelted, liner rims. Hardness was increased in oxidized rims for both annealed cohorts but not in the remelted cohort. Microcracking was only found along the surface of one unoxidized remelted liner rim. Conclusion. Mechanical properties were reduced at baseline and worsened after in vivo time for remelted HXLPE liner rims. Rim oxidation was detected in all groups. Oxidation was associated with increased crystallinity and hardness in annealed cohorts, but not remelted liners. Increased crystallinity and oxidation do not appear to be directly causing the worsened mechanical behavior of remelted HXLPE liner rims after extended in vivo time. For any figures or tables, please contact authors directly

1. One hundred patients with dislocation of the hip joint have been reviewed, many having been re-examined at intervals ranging from two to five years after injury. 2. There were forty-six simple dislocations, forty-three dislocations with fracture of the acetabular rim, seven dislocations with fracture of the acetabular floor, and five dislocations with fracture of the femoral head. 3. Complete recovery, as judged by clinical and radiographic examination, was observed in 76 per cent. of simple dislocations, 63 per cent. of dislocations with fracture of the acetabular rim, and 40 per cent. of dislocations with fracture of the femoral head; in no case of dislocation with fracture of the acetabular floor was recovery complete. 4. Only in one case did myositis ossificans develop, and that was the only case treated by "massage and movements" throughout the first ten weeks after injury. 5. Avascular necrosis of the femoral head was recognised in a smaller proportion of patients than had been expected, but since the follow-up review extended only to four years after injury the results, in this respect, are unreliable. The incidence of this complication after injury to the hip joint cannot be assessed unless the follow-up period is at least five to ten years. 6. Early traumatic arthritis developed in 26 per cent. of patients—in 15 per cent. of simple dislocations, 25 per cent. of dislocations with fracture of the acetabular margin, 60 per cent. of dislocations with fracture of the femoral head, and 100 per cent. of dislocations with fracture of the acetabular floor. 7. When central or posterior dislocations are accompanied by fracture of the acetabular floor, early arthrodesis is the treatment of choice. 8. Displacement of marginal acetabular fragments is usually corrected by manipulative reduction or by traction. 9. Sciatic paralysis in dislocation of the hip joint is nearly always due to damage of the nerve by a displaced acetabular fragment. In such cases, if the fragment is not replaced accurately by manipulation or traction, operative reduction is urgently indicated

Total hip replacement procedures are among the most frequent surgical interventions in all industrialized countries. Although it is a routine operationliterature reports that important parameters regarding for example cup orientation and leg length discrepancy often turn out to be not satisfying after surgery. This paper presents a novel concept to improve the reproducibility and accuracy for implantation of cup and stem prosthesis at exactly the desired locations. Existing computer- based commercial products either offer software solutions for just pre-operative planning, or imageless navigation systems that are only used during surgery in the operating theatre. The innovation of our approach is based on an integrated computer-assisted solution that combines pre-operative planning and intra-operative navigation to support THR procedures. The software for pre-operative planning can process both, 3D CT images and standard 2D x-ray images. A custom-built navigation system using optical 3D localizing technology has been developed to transfer planning results to the OR. The main objective of our approach is to implant the artificial joint in a way to restore the natural anatomy of the joint before surgery as close as possible, or with exactly planned modifications. In particular, cup inclination, cumulative anteversion of cup and stem, CCD angle and lateral offset, centre of rotation, leg length discrepancy, and joint range of motion are considered. It is not necessary to determine numerical values for all of these parameters because our approach uses a unique procedure to record the natural anatomical situation by combining pre-operative planning and intra-operative navigation, and subsequently supports implantation of the prosthesis components by surgical navigation in order to restore this situation. In case planar 2D x-ray images are used for pre-operative planning accurate scaling of these images is a prerequisite for exact determination of relevant parameters. The patient-specific scaling factor depends on the distance of the hip joint rotation centre from the x-ray detector or film. We have designed a low-cost localization system to be mounted close to the x-ray apparatus. It localizes the 3D position of the rotation centre by small motions of the leg and eliminates uncertainties of conventional methods that are caused by improper positioning of a calibration body. Easy and robust setup and application have been key objectives for the development of our custom-built navigation system. Acquisition of intraoperative parameters for example includes the determination of the acetabular centre axis by localizing selected landmarks at the acetabular rim. Intra-operative parameters are combined with pre-operative parameters without needing sophisticated matching procedures with the pre-operative images. A preliminary surgical workflow that will be detailed in the conference presentation has been designed for evaluation of the concept using sawbones models. Based on the promising results of our laboratory tests we have started to prepare first clinical experiments in close cooperation with surgeons

Introduction. HXLPE acetabular liners were introduced to reduce wear-related complications in THA. However, post-irradiation thermal free radical stabilization can compromise mechanical properties, leave oxidation-prone residual free radicals, or both. Reports of mechanical failure of HXLPE acetabular liner rims raise concerns about thermal free radical stabilization and in vivo oxidization on implant properties. The purpose of this study is to explore the differences in the mechanical, physical and chemical properties of HXLPE acetabular liner rims after extended time in vivo between liners manufactured with different thermal free radical stabilization techniques. Material and methods. Remelted, single annealed and sequentially annealed retrieved HXLPE acetabular liners with in vivo times greater than 4.5 years were obtained from our implant retrieval laboratory. All retrieved liners underwent an identical sanitation and storage protocol. For mechanical testing, a total of 55 explants and 13 control liners were tested. Explant in vivo time ranged from 4.6 – 14.0 years and ex vivo time ranged from 0 – 11.6 years. Rim mechanical properties were tested by microindentation hardness testing using a Micromet II Vickers microhardness tester following ASTM standards. A subset of 16 explants with ex vivo time under one year along with five control liners were assessed for oxidation by FTIR, crystallinity by Raman spectroscopy, and evidence of microcracking by SEM. Results. No significant difference in in vivo or ex vivo was found between thermal stabilization groups in either set of explants studied. In the mechanically tested explants, there was no significant correlation between in vivo time and Vickers hardness in any thermal stabilization group. A significant correlation was found between ex vivo time and hardness in remelted liners (Δ=.520, p=.011), but not in either annealed cohort. ANCOVA with ex vivo time as a covariate found a significant difference in hardness between the thermal free radical stabilization groups (p<.0005, η. 2. = 0.322). Post hoc analysis revealed hardness was significantly lower in the retrieved remelted group compared to both the single annealed (p=.001) and sequentially annealed (p<.0005) cohorts. Hardness was significantly higher in the retrieved remelted liners compared to controls (p=.007), with no different in either annealed cohort (figure 1). Detectable subsurface oxidation (OI > 0.1) was found in retrieved remelted (25%), single annealed (100%) and sequentially annealed (75%) liner rims (figure 2). Crystallinity was increased in the subsurface region relative to control liners for both annealed, but not remelted, liner rims. Hardness was increased in oxidized rims for both annealed cohorts but not in the remelted cohort. Microcracking was only found along the surface of one unoxidized remelted liner rim. Conclusion. Mechanical properties were reduced at baseline and worsened after in vivo time for remelted HXLPE liner rims. Rim oxidation was detected in all groups. Oxidation was associated with increased crystallinity and hardness in annealed cohorts, but not remelted liners. Increased crystallinity and oxidation do not appear to be directly causing the worsened mechanical behavior of remelted HXLPE liner rims after extended in vivo time. For any tables or figures, please contact the authors directly

Three-dimensional surface models of the normal hemipelvis derived from volumetric CT data on 42 patients were used to determine the radius, depth and orientation of the native acetabulum. A sphere fitted to the lunate surface and a plane matched to the acetabular rim were used to calculate the radius, depth and anatomical orientation of the acetabulum. For the 22 females the mean acetabular abduction, anteversion, radius and normalised depth were 57.1° (50.7° to 66.8°), 24.1° (14.0° to 33.3°), 25 mm (21.7 to 30.3) and 0.79 mm (0.56 to 1.04), respectively. The same parameters for the 20 males were 55.5° (47.7° to 65.9°), 19.3° (8.5° to 32.3°), 26.7 mm (24.5 to 28.7) and 0.85 mm (0.65 to 0.99), respectively. The orientation of the native acetabulum did not match the safe zone for acetabular component placement described by Lewinnek. During total hip replacement surgeons should be aware that the average abduction angle of the native acetabulum exceeds that of the safe zone angle. If the concept of the safe zone angle is followed, abduction of the acetabular component should be less than the abduction of the native acetabulum by approximately 10°

The term of hip dysplasia means an abnormality of shape, size or spatial configuration of the acetabulum. It also concerns the femoral head, with mutual relationships, proportions and alignment between the femoral head and the acetabulum the most crucial factors. The reason of any symptoms in hip dysplasia is the dysplastic acetabulum and its disproportion in relation to the femoral head. Dysplasia of the acetabulum appearing at puberty has been attributed to secondary “absorption” of bony acetabulum. The presence of fatigue fractures at a later age has been considered as resulting from trauma. However, the fragments of the acetabular rim should be ascribed to overloading of the rim in dysplastic hips, causing fracture and separation of its segment. They are sometimes associated with cysts in the acetabular roof. Limbus tears with or without an associated bony fragment are known to occur after traumatic dislocation of the hip but also without any history of injury. There is no explanation of their cause or their relation to acetabular dysplasia. Limbus tears have been diagnosed by arthroscopy, arthrography and CT scans. Clinical signs. No hip dysplasia in adults is really symptom-free. A casual examination applied between the painful episodes may appear so normal, that the articular origin of the pain may be doubted. In most cases pain is elicited by passive movement of the thigh into full flexion, adduction and internal rotation. This combination of movements brings the proximal and anterior parts of the femoral neck into the contact with the rim of the acetabulum, exactly at the point where the labrum is likely to be damaged. Preop imaging. An anteroposterior radiograph, or “faux profil” view of Lequesne de Seze may demonstrate a congruent but short acetabular roof (Type II) or an incongruent hip with a shallow acetabulum and a more vertical than normal acetabular roof (Type I). Type I hip is potentially or really unstable. The femoral head has migrated laterally or anteriorly or in both directions, distorting the spherical shape of actebular inlet into an oval. A simple 3-dimensional classification is recommended by myself using conventional X-ray and CT scan on equatorial level. The CE angle and sectors angle acc. Anda are used to describe the anterior, lateral and posterior coverage. To check the possibilities of reduction, the anteroposterior radiograph is made in max. abduction of the hip. To simulate the correction movement of the acetabular part we use our own “Super pelvis” software. Intra-op control. For intraoperative correction control we use a C-arm, which also controls step by step all stages of the periacetabular osteotomy. To check the final correction the X-ray of both hips is absolutely obligatory. What we should check is: the displacement of the acetabular fragment (to avoid lateralization, if necessary to make medialisation) and the positions of the anterior and posterior acetabular rim. If this is impossible with the normal a-p X-ray, the C-arm is used for achieving the “faux profil”. The computer assisted orthopaedic surgery system appears the most accurate intra-op control

Most patients presenting with loss of hip motion secondary to FAI have a combination of cam and pincer morphology. In this study, we present a composite index for predicting joint ROM based on anatomic parameters derived from both the femur and acetabulaum using a single reformatted CT slice. Computer models of the hip joint were reconstructed from CT scans of 31 patients with mixed-type FAI (Average alpha angle: 73.6±11.1°, average LCE: 38.9±7.2°). The internal rotation of the hip at impingement was measured at 90° flexion using custom software. With the joint in neutral, a single slice perpendicular to the acetabular rim was taken at the 2 o'clock position. A set of 11 femoral and acetabular parameters measured from this slice were correlated with hip ROM using stepwise logistic regression. Three anatomic parameters provided significant discrimination of cases impinging at <15 and >15 degrees IR: femoral anteversion (28%, p=0.026), the arc of anterior femoral head sphericity (10%, p=0.040), and the LCE in the 2 o'clock plane (10%, p=0.048). This led to the following definition of the Impingement Index: 0.16*(fem version) +0.11*(ant arc)−0.17*(LCE) which correctly classified 82% of cases investigated. None of the traditional parameters (e.g. alpha angle) were significantly correlated with ROM. Our study has identified alternative morphologic parameters that could act as strong predictors of FAI in preoperative assessments. Using this information, each patient's individual risk of impingement may be estimated, regardless of the relative contributions of deformities of the femur and the acetabulum

The success of total hip replacement (THR) is closely linked to the positioning of the acetabular component. Malalignment increases rates of dislocation, impingement, acetabular migration, pelvic osteolysis, leg length discrepancy and polyethylene wear. Many surgeons orientate the cup in the same anteversion and inclination as the inherent anatomy of the acetabulum. The transverse acetabular ligament and acetabular rim can be used as a reference points for orientating the cup this way. Low rates of dislocation have been reported using this technique. Detailed understanding of the anatomy and orientation of the acetabulum in arthritic hips is therefore very important. The aim of this study was to describe the anteversion and inclination of the inherent acetabulum in arthritic hips and to identify the number that fall out with the ‘safe zone’ of acetabular position described by Lewinnek et al. (anteversion 15°±10°; inclination 40°±10°). A series of 65 hips, all with symptomatic osteoarthritis undergoing THR were investigated. Patients with developmental dysplastia of hip (DDH) were excluded. All patients had a navigated THR as part of their normal clinical treatment. A posterior approach to the hip was used. A commercially available non image based computer navigation system (Orthopilot BBraun Aesculap, Tuttlingen, Germany) was used. Rigid bodies (using active trackers) were attached to pelvis and femur. Anterior pelvic plane was registered using the two anterior superior iliac spines and pubic symphysis. The femoral head dislocated and removed and the labrum and soft tissue were excised to clear floor and rim of the acetabulum. Inner size of the empty acetabulum was sized with cup trials and appropriately size trial fixed with a computer tracker was then aligned in the orientation of the natural acetabulum as defined by the acetabular rim ignoring any osteophytes. The inclination and anteversion were calculated by the software. Surgery then proceeded with guidance of the computer navigation system. The computer software defines the anatomical values of orientation, to allow comparison with radiographs these were converted to radiological values as described by Murray et al. The acetabular inclination in all hips was also measured on pre-operative anteroposterior pelvic radiographs. This was done using digital radiographs analysed with the PACS system (Kodak, Carestream PACS Client, version 10.0). Acetabular inclination was measured using as the angle between a line passing through the superior and inferior rim of the acetabulum and a line parallel to the pelvis as identified by the tear drops, using the method described by Atkinson et al. All patients were Caucasian and had primary osteoarthritis. There were 29 males and 36 females. The average age was 68 years (SD 8). Mean anteversion was 9.3° (SD 10.3°). Anteversion for males was significantly lower than females with a mean difference of −5.5° (95%CI −10.5°,−0.5°) p = 0.033 but there was no significant difference in the number falling outside the “safe zone”. Mean inclination was 50.4° (SD 7.4°). There was no significant difference between males and females with respect to inclination angle or the number that fell outside the “safe zone”. Overall 69% of patients had a combined inclination and anteversion of the native acetabulum that fell outside the “safe zone” of Lewinnek. Mean acetabular inclination falls out with the ‘safe zone’. This trend has been seen in a recent study of arthritic hips using CT scans which found that the average angle of inclination in both males and females was greater than the upper limit of the safe zone. This study using CT also demonstrated a statistically significant 5.5° difference between males and females in terms of anteversion. This is the same as the figure we have found in our work. Inherent acetabular orientation in arthritic hips falls out with the safe zone defined by Lewinnek in 69% of cases. When using the natural acetabular orientation as a guide for positioning implants it should therefore not be assumed this will fall with in the safe zone although the validity of safe zones itself is questionable. Variation between patients must be taken into account and the difference between males and females, particularly in terms of anteversion, should also be considered

Aims

Femoroacetabular impingement (FAI) patients report exacerbation of hip pain in deep flexion. However, the exact impingement location in deep flexion is unknown. The aim was to investigate impingement-free maximal flexion, impingement location, and if cam deformity causes hip impingement in flexion in FAI patients.

Aims

Hip arthroscopy (HA) has become the treatment of choice for femoroacetabular impingement (FAI). However, less favourable outcomes following arthroscopic surgery are expected in patients with severe chondral lesions. The aim of this study was to assess the outcomes of HA in patients with FAI and associated chondral lesions, classified according to the Outerbridge system.

Total hip replacement in Germany has been performed in 227293 cases in 2015 and tendency is increasing. Although it is a standard intervention, freehand positioning of cup protheses has frequently poor accuracy. Image-based and image-free navigation systems improve the accuracy but most of them provide target positions as alphanumeric values on large-size screens beneath the patient site. In this case the surgeon always has to move his head frequently to change his eye-focus between incision and display to capture the target values. Already published studies using e.g. IPod-based displays or LED ring displays, show the chance for improvement by alternative approaches. Therefore, we propose a novel solution for an instrument-mounted small display in order to visualise intuitive instructions for instrument guidance directly in the viewing area of the surgeon. For this purpose a solution consisting of a MicroView OLED display with integrated Arduino microcontroller, equipped with a Bluetooth interface as well as a battery has been developed. We have used an optical tracking system and our custom-designed navigation software to track surgical instruments equipped with reference bodies to acquire the input for the mini-display. The first implementation of the display is adapted to total hip replacement and focuses on assistance while reaming the acetabulum. In this case the reamer has to be centred to the middle point of the acetabular rim circle and its rotation axis must be aligned to the acetabular centre axis by Hakki. By means of these references the actual deviations between instrument and target pose are calculated and indicated. The display contains a cross-hair indicator for current position, two bubble level bars for angular deviation and a square in square indicator for depth control. All display parts are furnished with an adaptive variable scale. Highest possible resolution is 0.5 degrees angular, 1 millimeter for position and depth resolution is set to 2 mm. Compared to existing approaches for instrument-mounted displays, the small display of our solution offers high flexibility to adjust the mounting position such that it is best visible for the surgeon while not constraining instrument handling. Despite the small size, the proposed visualisation symbols provide all information for instrument positioning in an intuitive way

Aims

Avascular femoral head necrosis in the context of gymnastics is a rare but serious complication, appearing similar to Perthes’ disease but occurring later during adolescence. Based on 3D CT animations, we propose repetitive impact between the main supplying vessels on the posterolateral femoral neck and the posterior acetabular wall in hyperextension and external rotation as a possible cause of direct vascular damage, and subsequent femoral head necrosis in three adolescent female gymnasts we are reporting on.

Down syndrome (DS), is a genetic disorder caused by a third copy of the 21st chromosome (Trisomy 21), featuring typical facial characteristics, growth delays and varying degrees of intellectual disability. Some degree of immune deficiency is variably present. Multiple orthopaedic conditions are associated, including stunted growth (90%), ligamentous laxity (90%), low muscle tone (80%), hand and foot deformities (60%), hip instability (30%), and spinal abnormalities including atlanto-axial instability (20%) and scoliosis. Hip disease severity varies and follows a variable time course. Rarely a child presents with DDH, but during the first 2 years the hips are characteristically stable but hypermobile with well-formed acetabulae. Spontaneous subluxation or dislocation after 2 presents with painless clicking, limping or giving way. Acute dislocation is associated with moderate pain, increased limp and reduced activity following minor trauma. Hips are reducible under anesthesia, but recurrence is common. Eventually concentric reduction becomes rarer and radiographic dysplasia develops. Pathology includes: a thin, weak fibrous capsule, moderate to severe femoral neck anteversion and a posterior superior acetabular rim deficiency. A number of femoral and acetabular osteotomies have been reported to treat the dysplasia, with acetabular redirection appearing to be most successful. However, surgery can be associated with a relatively high infection rate (20%). Additionally, symptomatic femoral head avascular necrosis can occur as a result of slipped capital femoral epiphysis. Untreated dysplasia patients can walk with a limp and little pain into the early twenties even with fixed dislocation. Pain and decreasing hip function is commonly seen as the patient enters adult life. Occasionally the hip instability begins after skeletal maturity. Total hip arthroplasty (THA) is the standard treatment when sufficient symptoms have developed. The clinical outcomes of 42 THAs in patients with Down syndrome were all successfully treated with standard components. The use of constrained liners to treat intra-operative instability occurred in eight hips and survival rates were noted between 81% and 100% at a mean follow-up of 105 months (6 – 292 months). A more recent study of 241 patients with Down syndrome and a matched 723-patient cohort from the Nationwide Inpatient Sample compared the incidence of peri-operative medical and surgical complications in those who underwent THA. Compared to matched controls, Down syndrome patients had an increased risk of complications: peri-operative (OR, 4.33; P<.001), medical (UTI & Pneumonia OR, 4.59; P<.001) and surgical (bleeding OR, 3.51; P<.001), Mean LOS was 26% longer (P<.001). While these patients can be challenging to treat, excellent surgical technique and selective use of acetabular constraint can reliably provide patients with excellent pain-relief and improved function. Pre-operative education of all clinical decision makers should also reinforce the increased risk of medical and surgical complications (wound hemorrhage), and lengths of stay compared to the general population

Introduction. Aseptic acetabular component failure rates have been reported to be similar or even slightly higher than femoral component failure. Obtaining proper initial stability by press fitting the cementless acetabular cup into an undersized cavity is crucial to allow for secondary osseous integration. However, finding the insertion endpoint that corresponds to an optimal initial stability is challenging. This in vitro study presents an alternative method that allows tracking the insertion progress of acetabular implants in a non-destructive, real-time manner. Materials and Methods. A simplified acetabular bone model was used for a series of insertion experiments. The bone model consisted of polyurethane solid foam blocks (Sawbones #1522-04 and #1522-05) into which a hemispherical cavity and cylindrical wall, representing the acetabular rim, were machined using a computer numerically controlled (CNC) milling machine (Haas Automation Inc., Oxnard, CA, USA). Fig. 1 depicts the bone model and setup used. A total of 10 insertions were carried out, 5 on a low density block, 5 on a high density block. The acetabular cups were press fitted into the bone models by succeeding hammer hits. The acceleration of the implant-insertor combination was measured using 2 shock accelerometers mounted on the insertor during the insertion process (PCB 350C03, PCB Depew, NY, USA). The force applied to the implant-insertor combination was also measured. 15 hammer hits were applied per insertion experiment. Two features were extracted from the acceleration time signal; total signal energy (E) and signal length (LS). Two features and one correlation measure were extracted from the acceleration frequency spectra; the relative signal power in the low frequency band (PL, from 500–2500Hz) and the signal power in the high frequency band (P Hf, from 4000–4800 Hz). The changes in the low frequency spectra (P Lf, from 500–2500 Hz) between two steps were tracked by calculating the Frequency Response Assurance Criterion (FRAC). Force features similar to the ones proposed by Mathieu et al., 2013 were obtained from the force time data. The convergence behavior of the features was tracked as insertion progressed. Results. Differences were noted visually between the acceleration data recorded at the beginning of insertion and towards the end, both in the time domain (fig. 2A) as well as in the frequency domain (fig. 2B). These differences were also captured by the proposed features. Fig. 3 shows a typical representation of how the time (A), frequency (B) and force (C) features evolved during insertion. Based on a simple convergence criterion, the insertion endpoint could be determined. Conclusions. The convergence behavior, and the insertion endpoint thus identified, of the force-based and acceleration based features correlated well. The different features capture the changes in damping and stiffness of the implant-bone system that are occurring as the insertion progresses and combining them improves the robustness of the endpoint detection method. For any figures or tables, please contact the authors directly

There are a number of progressive conditions that afflict the hip and result in degenerative arthritis. Along the path of progression of the disease and prior to the development of arthritis, some of these conditions may be treatable by joint preservation procedures. Periacetabular osteotomy for developmental dysplasia of the hip (DDH), femoroacetabular osteoplasty for femoroacetabular impingement (FAI), and a variety of surgical procedures for management of early osteonecrosis of the femoral head are some examples of joint preservation of the hip. DDH is characterised by abnormal development of the acetabulum and the proximal femur that leads to suboptimal contact of the articular surfaces and the resultant increase in joint reaction forces. FAI is a condition characterised by an abnormal contact between the femoral neck and the acetabular rim. FAI is believed to exist when a triad of signs (abnormal alpha angle, labral tear, and chondral lesion) can be identified. The question that remains is whether joint preservation procedures are able to avert the need for arthroplasty or just an intervention along the natural path of progression of the hip disease. There is an interesting study that followed 628 infants born in a Navajo reservation, including 8 infants with severe dysplasia, for 35 years. None of the children with DDH had surgical treatment and all had developed severe arthritis in the interim. The latter study and a few other natural history studies have shown that the lack of administration of surgical treatment to patients with symptomatic DDH results in accelerated arthritis. The situation is not so clear with FAI. Some believe that FAI is a pre-arthritic condition and surgical treatment is only effective in addressing the symptoms and does not delay or defer an arthroplasty. While others believe that restoration of the normal mechanical environment to the hip of FAI patients, by removing the abnormal contact and repair of the labrum, is likely to change the natural history of the disease and at minimum delay the need for an arthroplasty. There is a need for natural history studies or case series to settle the latter controversy

Aims

The aim of this study was to compare the biomechanical models of two frequently used techniques for reconstructing severe acetabular defects with pelvic discontinuity in revision total hip arthroplasty (THA) – the Trabecular Metal Acetabular Revision System (TMARS) and custom triflange acetabular components (CTACs) – using virtual modelling.

Aims

Although there are various pelvic osteotomies for acetabular dysplasia of the hip, shelf operations offer effective and minimally invasive osteotomy. Our study aimed to assess outcomes following modified Spitzy shelf acetabuloplasty.

Revision hip approaches can be divided into posterior, anterior, transgluteal, and transtrochanteric. The approach chosen is dictated by what needs to be exposed and the approaches with which the surgeon is comfortable. The posterior approach remains posterior to the gluteus medius and protects the hip abductors. The disadvantage of a posterior approach is post-operative dislocation. The direct anterior approach is currently enjoying popularity as a primary technique. Surgeons experienced in the primary technique are applying it to revision surgery. The anterior approaches also protect the hip abductors. The disadvantage is poor access to the posterior acetabular column and mobilization of the femur to gain access to the femoral diaphysis. Transgluteal approaches split the gluteus medius typically keeping the anterior portion of the medius intact with the vastus lateralis. Proximal exposure is limited by the superior gluteal nerve, which is 4 cm above the tip of the trochanter. The disadvantage of the transgluteal approach is difficult access to the posterior acetabular column and occasional abductor weakness. The advantage of both the anterior and transgluteal approaches is a lower dislocation rate. All three approaches are acceptable for revisions that only require acetabular rim and proximal femoral exposure. More extensive exposure requires modifications to these approaches or the use of a transtrochanteric approach. Transtrochanteric approaches are defined by the length of the osteotomy (conventional or extended) and if the vastus lateralis remains attached to the trochanteric fragment (slide). Distally extended osteotomies improve access to the femur. Osteotomies without a distal attachment to the lateralis can be retracted proximally thus improving exposure of the ilium

Aims

The aims of this study were to determine the success of a reconstruction algorithm used in major acetabular bone loss, and to further define the indications for custom-made implants in major acetabular bone loss.

Aims

The aim of this study is to evaluate whether acetabular retroversion (AR) represents a structural anatomical abnormality of the pelvis or is a functional phenomenon of pelvic positioning in the sagittal plane, and to what extent the changes that result from patient-specific functional position affect the extent of AR.

Aims

Periacetabular osteotomy (PAO) is widely recognized as a demanding surgical procedure for acetabular reorientation. Reports about the learning curve have primarily focused on complication rates during the initial learning phase. Therefore, our aim was to assess the PAO learning curve from an analytical perspective by determining the number of PAOs required for the duration of surgery to plateau and the accuracy to improve.

Aims

Custom triflange acetabular components (CTACs) play an important role in reconstructive orthopaedic surgery, particularly in revision total hip arthroplasty (rTHA) and pelvic tumour resection procedures. Accurate CTAC positioning is essential to successful surgical outcomes. While prior studies have explored CTAC positioning in rTHA, research focusing on tumour cases and implant flange positioning precision remains limited. Additionally, the impact of intraoperative navigation on positioning accuracy warrants further investigation. This study assesses CTAC positioning accuracy in tumour resection and rTHA cases, focusing on the differences between preoperative planning and postoperative implant positions.

Aims

The purpose of this study was to evaluate the mid-term outcomes of autologous matrix-induced chondrogenesis (AMIC) for the treatment of larger cartilage lesions and deformity correction in hips suffering from symptomatic femoroacetabular impingement (FAI).

Aims

Hip dysplasia (HD) leads to premature osteoarthritis. Timely detection and correction of HD has been shown to improve pain, functional status, and hip longevity. Several time-consuming radiological measurements are currently used to confirm HD. An artificial intelligence (AI) software named HIPPO automatically locates anatomical landmarks on anteroposterior pelvis radiographs and performs the needed measurements. The primary aim of this study was to assess the reliability of this tool as compared to multi-reader evaluation in clinically proven cases of adult HD. The secondary aims were to assess the time savings achieved and evaluate inter-reader assessment.

Introduction. Acetabular retroversion is an accepted cause of Pincer-type femoroacetabular impingement. There is increasing evidence that acetabular retroversion is rather a rotational abnormality of the pelvis than an overgrowth of the acetabular wall or even a dysplasia of the posterior wall. Initially, patients with a retroverted acetabulum were treated with an open rim trimming through a surgical hip dislocation (SHD) based on the early understanding of the pathomorphology. Theoretically, the reduction of the anterior wall can decrease the already small joint contact area in retroverted hips to a critical size. Based on the most recent literature, anteverting periacetabular osteotomy (PAO) seems to be the more appropriate surgical treatment. With this technique, the anterior impingement conflict can be treated efficiently without compromising the joint contact area. However, it is unknown whether this theoretical advantage in turn results in better mid term results of treatment. Objectives. We asked if anteverting PAO results in better clinical and radiographical mid term results compared to rim trimming through a surgical hip dislocation. Methods. We performed a retrospective comparative study based on 257 hips (221 patients) with symptomatic femoroacetabular impingement due to acetabular retroversion. Acetabular retroversion was defined by a cross-over sign, a posterior wall sign, and a positive ischial spine sign. We then formed two matched groups consisting of 73 hips undergoing open acetabular rim trimming and 54 hips with an anteverting periacetabular osteotomy. Patients with incomplete radiographic documentation, previous surgery, and hip dysplasia (LCE < 20°) were excluded. Some patients were excluded due to a matching process (Fig. 1). Patients were generally followed clinically and radiographically after two, five and ten years. A Kaplan-Meier survivorship analysis was performed using the following endpoints: a low clinical score, radiographic progression of osteoarthritis, and/or the conversion to total hip arthroplasty. The Log Rank Score was used to compare the two survivorship curves. Results. Patients undergoing anteverting PAO for acetabular retroversion had a significantly increased survivorship (82%, 95% confidence interval, 72–91%) at seven years in comparison to open surgical rim trimming (63%, 95%CI, 49–76%, p<0.0001). The two survivorship curves are comparable for the first four years with a substantial drop for the rim trimming group after year five (Fig. 2). Conclusion. This study proofs for the first time that the theoretical advantages of anteverting periacetabular osteotomy in hips with symptomatic acetabular retroversion results in an increased survivorship at mid term follow-up in comparison to open rim trimming. For any figures or tables, please contact authors directly (see Info & Metrics tab above).

Introduction. Hips following in-situ pinning for slipped capital femoral epiphysis (SCFE) have an altered morphology of the proximal femur with cam type deformity. This deformity can result in femoroacetabular impingement and early joint degeneration. The modified Dunn procedure allows to reorientate the slipped epiphysis to restore hip morphology and function. Objectives. To evaluate (1) hip pain and function, (2) 10-year survival rate and (3) subsequent surgeries and complications in hips undergoing modified Dunn procedure for SCFE. Methods. Between April 1998 and December 2005 we performed the modified Dunn procedure for 43 patients (43 hips) with SCFE. Twenty-five hips (58) presented with an acute or acute on chronic slip. The mean slip angle was 43° (range, 15° – 80°). A majority of 53% of procedures were performed in male patients and the mean age at operation was 13 years (10 – 19 years). We could followup all except one hip (followup of 5.5 year) for a minimum of 10 years (mean followup 13 [10 – 18 years]). We used the anterior impingement test to assess pain and the Merle d'Aubigné- ostel score to assess function. Survivorship calculation was performed using the method of Kaplan and Meier and any of the following factors as a definition of failure: radiographic evidence of worsening osteoarthritis (OA), or a Merle d'Aubigné-Postel score less than 15. Results. (1) The prevalence of a positive anterior impingement test decreased from 100% to 16% (p<0.001). The mean Merle d'Aubigné-Postel score improved from 13 (7 – 14) to 17 (14 – 18) at most recent followup (p<0.001). (2) Four hips (9%) showed progression of OA and three hips (7%) had a Merle d'Aubigné-Postel score of less than 15 at most recent followup. This resulted in a 93% survival rate at 10-year followup. (3) No hip developed avascular necrosis. Five hips (12%) had complications with reosteosynthesis due to screw breakage or nonunion. Another nine hips (21%) had subsequent surgeries including acetabular rim trimming / offset creation in 5 hips and screw removal in 4 hips. Conclusion. The modified Dunn procedure is a safe method to correct the morphology of the proximal femur in hips with SCFE. Ninety-free percent of the hips showed no progression of OA and a good clinical result at the 10-year followup. Twelve percent required revision surgery for complications all including screw breakage with nonunion of the greater trochanter

Introduction. Optimal alignment of the acetabulum cup component is crucial for good outcome of Total Hip Arthroplasty (THA). A patient-specific instrumentation (PSI) for cup alignment manufactured by 3D printing might improve cup alignment in conventional THAs with patient's lateral decubitus position. In this study, we developed PSI for cup alignment which transferred preoperatively planned cup alignment to the operation room as a linear visual reference(Figure 1), then investigated its accuracy in terms of fitting of PSI on the bony surface and angle deviation between pre- and post-operative cup alignments. Methods. 3-Dimensional bone models created from CT images of both sides of 6 cadaveric specimens were used in the current study. In the first experiment (first 3 specimens and six hips), we designed PSI to fit on the acetabular rim, and we inserted a Kirschner wire (K-wire) through PSI after PSI's fitting. In the second experiment (remaining 3 specimens and six hips), after the same steps like the first experiment were done, we reamed and finally impacted plastic cups with the visual reference of the K-wire. Using postoperative CT images taken after both experiments, we measured deviation of the K-wire placement for the first experiment, and measured deviation of the cup placement from planned cup alignment. Results. The angle deviation of the K-wire alignment on the basis of radiographic inclination and anteversion angles was on average 2.2°±2.5° and 1.0°±1.3° respectively in the first experiment. The angle deviation of the cup alignment with the same definition was on average 2.88°±1.63° and 4.15°±2.56°. For one cadaveric specimen data for the first experiment were missing. Conclusion. We conclude that the accuracy of acetabular cup placement can be improved by the use of patient-specific cup orientation guides

Impaction bone grafting for the reconstitution of bone stock in revision hip surgery has been used for nearly 30 years. Between 1995 and 2001 we used this technique in acetabular reconstruction, in combination with a cemented component, in 304 hips in 292 patients revised for aseptic loosening. The only additional supports used were stainless steel meshes placed against the medial wall or laterally around the acetabular rim to contain the graft. All Paprosky grades of defect were included. Clinical and radiographic outcomes were collected in surviving patients at a minimum of ten years after the index operation. Mean follow-up was 12.4 years (. sd. 1.5) (10.0 to 16.0). Kaplan–Meier survival with revision for aseptic loosening as the endpoint was 85.9% (95% CI 81.0 to 90.8) at 13.5 years. Clinical scores for pain relief remained satisfactory, and there was no difference in clinical scores between cups that appeared stable and those that appeared radiologically loose. . Cite this article: Bone Joint J 2014;96-B:188–94

Aims

This study uses prospective registry data to compare early patient outcomes following arthroscopic repair or debridement of the acetabular labrum.

Acetabular protrusio is defined radiographically as migration of the femoral head medial to Kohler's line (a line from the lateral border of the obturator foramen to the medial border of the sciatic notch). Protrusio can develop in association with metabolic bone diseases such as osteogenesis imperfecta, Marfan's Syndrome, and Paget's disease, inflammatory arthritis or osteoarthritis, tumors, or result from prior trauma. Acetabular protrusio can cause limited hip motion due to impingement of the femoral neck against the acetabular rim. When protrusio develops in association with osteoarthritis, coxa vara is often also present. Surgical treatment of acetabular protrusio during total hip arthroplasty should lateralise the center of the hip to its anatomic position. This typically can be achieved with use of a larger, slightly oversized, rim fit cementless acetabular component and medial morselised femoral head bone autograft. In cases with more severe deformity, a reconstruction cage may be required. Alternatively a medialised acetabular shell can be used with a lateralised liner. If coxa vara is also present, standard femoral component position (approximately 1cm above the lesser trochanter) can result in an increase in leg length. Careful pre-operative templating should be performed and may require more distal placement of the femoral component to avoid overlengthening the limb

Revision hip approaches can be divided into posterior, anterior, transgluteal, and transtrochanteric. The approach chosen is dictated by what needs to be exposed and the approaches with which the surgeon is comfortable. The posterior approach remains posterior to the gluteus medius and protects the hip abductors. The disadvantage of a posterior approach is post-operative dislocation. The direct anterior approach is currently enjoying popularity as a primary technique. Surgeons experienced in the primary technique are applying it to revision surgery. The anterior approaches also protect the hip abductors. The disadvantage is poor access to the posterior acetabular column and mobilisation of the femur to gain access to the femoral diaphysis. Transgluteal approaches split the gluteus medius typically keeping the anterior portion of the medius intact with the vastus lateralis. Proximal exposure is limited by the superior gluteal nerve, which is 4cm above the tip of the trochanter. The disadvantage of the transgluteal approach is difficult access to the posterior acetabular column and occasional abductor weakness. The advantage of both the anterior and transgluteal approaches is a lower dislocation rate. All three approaches are acceptable for revisions that only require acetabular rim and proximal femoral exposure. More extensive exposure requires modifications to these approaches or the use of a transtrochanteric approach. Transtrochanteric approaches are defined by the length of the osteotomy (conventional or extended) and if the vastus lateralis remains attached to the trochanteric fragment (slide). Distally extended osteotomies improve access to the femur. Osteotomies without a distal attachment to the lateralis can be retracted proximally thus improving exposure of the ileum

Aims

The use of a porous metal shell supported by two augments with the ‘footing’ technique is one solution to manage Paprosky IIIB acetabular defects in revision total hip arthroplasty. The aim of this study was to assess the medium-term implant survival and radiological and clinical outcomes of this technique.

Complete reduction of a dislocated hip may be blocked by a partial separation of the acetabular rim. The diagnosis is radiological and is easily missed. Treatment is by open operation and resection of the partly detached fibrocartilaginous rim