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

In Japan, osteoarthritis (OA) of the hip secondary to acetabular dysplasia is very common, and there are few data concerning the pathogeneses and incidence of femoroacetabular impingement (FAI). We have attempted to clarify the radiological prevalence of painful FAI in a cohort of Japanese patients and to investigate the radiological findings. We identified 176 symptomatic patients (202 hips) with Tönnis grade 0 or 1 osteoarthritis, whom we prospectively studied between August 2011 and July 2012. There were 61 men (65 hips) and 115 women (137 hips) with a mean age of 51.8 years (11 to 83). Radiological analyses included the α-angle, centre–edge angle, cross-over sign, pistol grip deformity and femoral head neck ratio. Of the 202 hips, 79 (39.1%) had acetabular dysplasia, while 80 hips (39.6%) had no known aetiology. We found evidence of FAI in 60 hips (29.7%). Radiological FAI findings associated with cam deformity were the most common. There was a significant relationship between the pistol grip deformity and both the α-angle (p < 0.001) and femoral head–neck ratio (p = 0.024). Radiological evidence of symptomatic FAI was not uncommon in these Japanese patients.

Cite this article: Bone Joint J 2013;96-B:172–6.

Abstract. Objective. A higher prevalence of cam morphology has been reported in the athletic population but the development of the cam morphology is not fully understood. The purpose of this systematic review is to establish the timing of development of the cam morphology in athletes, the proximal femoral morphologies associated with its development, and other associated factors. Methods. Embase, MEDLINE and the Cochrane Library were searched for articles related to development of the cam morphology, and PRISMA guidelines were followed. Data was pooled using random effects meta-analysis. Study quality was assessed using the Downs and Black criteria and evidence quality using the GRADE framework. Results. This search identified 16 articles involving 2,028 participants. In males, alpha angle was higher in athletes with closed physes than open physes (SMD 0.71; 95% CI 0.23, 1.19). Prevalence of cam morphology was associated with age during adolescence when measured per hip (β 0.055; 95% CI 0.020, 0.091) and per individual (β 0.049; 95% CI 0.034, 0.064). Lateral extension of the epiphysis was associated with an increased alpha angle (r 0.68; 95% CI 0.63, 0.73). A dose-response relationship was frequently reported between sporting frequency and cam morphology. There was a paucity of data regarding the development of cam morphology in females. Conclusions. Very low and low quality evidence suggests that in the majority of adolescent male athletes’ osseous cam morphology developed during skeletal immaturity, and that prevalence increases with age. Very low quality evidence suggests that osseous cam morphology development was related to lateral extension of the proximal femoral epiphysis

Objectives. The spinopelvic relationship (including pelvic incidence) has been shown to influence pelvic orientation, but its potential association with femoroacetabular impingement has not been thoroughly explored. The purpose of this study was to prove the hypothesis that decreasing pelvic incidence is associated with increased risk of cam morphology. Methods. Two matching cohorts were created from a collection of cadaveric specimens with known pelvic incidences: 50 subjects with the highest pelvic incidence (all subjects > 60°) and 50 subjects with the lowest pelvic incidence (all subjects < 35°). Femoral version, acetabular version, and alpha angles were directly measured from each specimen bilaterally. Cam morphology was defined as alpha angle > 55°. Differences between the two cohorts were analysed with a Student’s t-test and the difference in incidence of cam morphology was assessed using a chi-squared test. The significance level for all tests was set at p < 0.05. Results. Cam morphology was identified in 47/100 (47%) femurs in the cohort with pelvic incidence < 35° and in only 25/100 (25%) femurs in the cohort with pelvic incidence > 60° (p = 0.002). The mean alpha angle was also greater in the cohort with pelvic incidence < 35° (mean 53.7°, . sd. 10.7° versus mean 49.7°, . sd. 10.6°; p = 0.008). Conclusions. Decreased pelvic incidence is associated with development of cam morphology. We propose a novel theory wherein subjects with decreased pelvic incidence compensate during gait (to maintain optimal sagittal balance) through anterior pelvic tilt, creating artificial anterior acetabular overcoverage and recurrent impingement that increases risk for cam morphology. Cite this article: W. Z. Morris, C. A. Fowers, R. T. Yuh, J. J. Gebhart, M. J. Salata, R. W. Liu. Decreasing pelvic incidence is associated with greater risk of cam morphology. Bone Joint Res 2016;5:387–392. DOI: 10.1302/2046-3758.59.BJR-2016-0028.R1

Introduction. Acetabular and spino-pelvic (SP) morphological parameters are important determinants of hip joint dynamics. This study aims to determine whether acetabular and SP morphological differences exist between hips with and without cam morphology and between symptomatic and asymptomatic hips with cam morphology. Patients/Materials & Methods. A prospective cohort of 67 patients/hips was studied. Hips were either asymptomatic with no cam (Controls, n=18), symptomatic with cam (n=26) or asymptomatic with cam (n=23). CT-based quantitative assessments of femoral, acetabular, pelvic and spino-pelvic parameters were performed. Measurements were compared between controls and those with a cam deformity, as well as between the 3 groups. Morphological parameters that were independent predictors of a symptomatic Cam were determined using a regression analysis. Results. Hips with cam deformity had slightly smaller subtended angles superior-anteriorly (87° Vs 84°, p=0.04) and greater pelvic incidence (53° Vs 48°, p=0.003) compared to controls. Symptomatic Cams had greater acetabular version (p<0.01), greater subtended angles superiorly and superior-posteriorly (p=0.01), higher pelvic incidence (p=0.02), greater alpha angles and lower femoral neck-shaft angles compared to asymptomatic cams (p<0.01) and controls (p<0.01). The four predictors of symptomatic cam included antero-superior alpha angle, femoral neck-shaft angle, acetabular depth and pelvic incidence. Discussion. Symptomatic hips had a greater amount of supero-posterior coverage; which would be the contact area between a radial cam and the acetabulum, when the hip is flexed to 90°. Furthermore, individuals with symptomatic cam morphology had greater PI. Acetabular- and SP parameters should be part of the radiological assessment of femoro-acetabular impingement. Conclusion. Because of the association between a high PI and an increased risk of hip OA (also shown to be increased with c-FAI), the relationship between the PI and FAI should be taken into consideration in prospective longitudinal studies looking at factors influencing the formation of cam morphology as well as those at risk of developing symptoms and degenerative changes

Background. Cam morphology develops during adolescence and predisposes individuals to future hip pain and osteoarthritis. An improved understanding of cam development is required to determine whether the process is modifiable. Hypothesis/Purpose. The aim of this study was to characterise the risk factors, timing, and pathogenesis of cam formation. Study Design. Longitudinal prospective observational cohort study. Methods. Longitudinal observational cohort study over three years of individuals from football club academies and an age-matched control population, aged 9–18 years at baseline. Assessments include questionnaires, clinical examination, and MRI of both hips. Alpha angle and epiphyseal extension were measured on radial images. Results. Cohort comprised male academy footballers (121 at baseline and 78 at follow-up) and male and female controls (107 at baseline and 71 at follow-up). Mean change in cartilage alpha angle was 12.4° (SD 8.4) for footballers, 7.3° (SD 6.0) for male controls and 4.0° (SD 4.1) for female controls. A positive correlation was found between Physical Activity Questionnaire Score and change in cartilage alpha angle (coefficient 0.787, p=<0.001). The greatest change in cartilage alpha angle occurred in individuals aged 11–12 years at baseline, with no significant change after 14 years of age. A positive correlation between mean cartilage alpha angle and lateral epiphyseal extension was observed (r. 2. = 0.294, p=0.029). Conclusions. Males undertaking intense sporting activity during adolescence at greatest risk of developing cam morphology, but there is no significant change in hip morphology after 14 years of age. The findings are consistent with physiological adaptation and epiphyseal extension in response to hip loading during skeletal immaturity

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

Introduction:. Cam type femoroacetabular impingement (FAI) may lead to osteoarthritis (OA)[1]. In 2D studies, an alpha angle greater than 55° was considered abnormal however limitations of 2D alpha angle measurement have led to the development of 3D methods [2–4]. Failure to completely address the bony impingement lesions during surgery has been the most common reason for unsuccessful hip arthroscopy surgery [5]. Robotic technology has facilitated more accurate surgery in comparison to the conventional means. In this study we aim to assess the potential application of robotic technology in dealing with this technically challenging procedure of cam sculpting surgery. Methods:. CT scans of three patients' hips with severe cam deformity (A, B and C models) were obtained and used to construct 3D dry bone models. A 3D surgical plan was made in custom written software. Each 3D plan was imported into the Acrobot Sculptor robot and bone resection was carried out. In total, 42 femoral models were sculpted (14/subset), thirty of which were performed by a single operator and the remaining 12 femurs were resected by two other operators. CT of the pre/post resected specimens was segmented and a 3D alpha angle and head neck ratios were measured [3–4] and compared using Mann-Whitney U test. Coefficient of variation (CV) was used to determine the degree of variation between the mean and maximum observed alpha angles for inter and intra observer repeatability. Results:. The maximal alpha angle in cam A, B and C (90.8°, 91.3° and 87.1°). There was significant reduction (p < 0.001) in maximum alpha angles post-operatively within all three models when compared to original model (Figure 1). The HNRs for cam A, B and C prior to surgery were found to be 3.2, 3.4 and 3.1 respectively that were reduced to a mean of 3.0 ± 0.1, 3.1 ± 0.1 and 3.1 ± 0.0, following resection surgery. The results of the intra and inter-observer repeatability study found good reproducibility (CV<10%) of the maximum and mean alpha angles between the 12 resected femurs. Discussion:. In this study we evaluated the use of robotic system to perform cam correction surgery by evaluating the 3D morphology of head/neck prior to and post surgery. With existing surgical options there is a potential for under or over-resection of the cam lesion, which runs the risk of the need for further surgery or rarely neck fracture and dislocation. Based on the calculated alpha angles and HNRs we have proved that we have successfully performed the surgery by avoiding under and over resection respectively. Amore accurate bony resection performed here may minimize the complications due to over and under resection and hence will decrease the burden on the health service

The Bisurface knee prosthesis (BP) has a posterior stabilising cam (ball-and-socket joint) in the mid-posterior region of the femorotibial joint in an attempt to improve the range of movement. Based on an in vitro weight-bearing study contact areas of the Insall/Burstein 2 (IB2) and the BP knee were compared using pressure-sensitive films. The stability afforded by the cam was evaluated by means of dislocation distances in the vertical and horizontal planes. Significant adverse anterior translation in mid-flexion was not observed with the BP knee since the cam was effective above 60° of flexion. At flexion of 60° or more, the total contact areas were larger, as the cam represented a weight-bearing surface. The dislocation distances for the BP knee compared favourably with those for the IB2 knee. We conclude that the cam of the BP knee allows good movement, stability and wear

We reviewed the clinical outcome of arthroscopic femoral osteochondroplasty for cam femoroacetabular impingement performed between August 2005 and March 2009 in a series of 40 patients over 60 years of age. The group comprised 26 men and 14 women with a mean age of 65 years (60 to 82). The mean follow-up was 30 months (12 to 54). The mean modified Harris hip score improved by 19.2 points (95% confidence interval 13.6 to 24.9; p < 0.001) while the mean non-arthritic hip score improved by 15.0 points (95% confidence interval 10.9 to 19.1, p < 0.001). Seven patients underwent total hip replacement after a mean interval of 12 months (6 to 24 months) at a mean age of 63 years (60 to 70). The overall level of satisfaction was high with most patients indicating that they would undergo similar surgery in the future to the contralateral hip, if indicated. No serious complications occurred. Arthroscopic femoral osteochondroplasty performed in selected patients over 60 years of age, who have hip pain and mechanical symptoms resulting from cam femoroacetabular impingement, is beneficial with a minimal risk of complications at a mean follow-up of 30 months

Purpose. To determine the differences of biomechanical properties in three conditions including 1) native cam deformity 2) cam deformity with incomplete resection and 3) cam deformity with complete resection. Methods. A cadaveric study was performed using 8 frozen, hemi-pelvises with cam-type deformity (alpha angle >55°) measured on CT scan and an intact labrum. Intraarticular pressure maps were produced for each specimen under the following conditions: 1) native cam deformity, 2) cam deformity with incomplete resection and 3) cam deformity with complete resection. A 5.5-mm burr was used to resect the lateral portion of the cam deformity to a depth of 3–4 mm. The specimen was placed in a custom designed jig in the MTS electromechanical test system to create pressure and area map measurements. In each condition, three biomechanical parameters were obtained including contact pressure, contact area and peak force within a region-of-interest (ROI). Repeated measurements were performed for three times in each condition and the average value of each parameter was used for statistical analysis. ANOVA was used to compare biomechanical parameters between three conditions. Results. Repeated measures ANOVA analysis demonstrated that the pressures averages of hips with complete resection of cam lesions were significantly lower when compared to averages of hips with incomplete femoral cam lesion and intact cam deformity (2.48. +. 0.56 kg/cm. 3. vs 2.32. +. 0.50 kg/cm. 3. vs 2.02. +. 0.54 kg/cm. 3. , respectively; p-value=0.01). Percentage reduction of contact pressure in the complete resection and incomplete resection groups compared to the native CAM deformity groups were 18.49% and 1.58% respectively. There was no statistically significant difference in contact pressures between the incomplete resection and unoperated groups. Contact area and peak force showed no statistically significant differences across three conditions. Conclusion. There are lower intraarticular hip contract pressures in complete resection of the cam lesions when compared to an incomplete resection and intact hip without resection. These observations underscore the importance of ensuring complete resection of femoral cam lesions in patients undergoing hip arthroscopy for femoroacetabular impingement syndrome. For any tables or figures, please contact the authors directly

Introduction: Previously, in vivo kinematic studies have determined the in vivo kinematics of the femur relative to the metal base-plate. These kinematic studies have reported posterior femoral rollback in posterior stabilized (PS) TKA designs, but the actual time of cam/post engagement was not determined. The objective of this present study was to determine, under in vivo conditions, the time of cam/post engagement and the kinematics of the femur relative to the polyethylene insert. Methods: Femorotibial contact positions for twenty subjects having a PS TKA, implanted by two single surgeons, were analyzed using video fluoroscopy. Ten subjects were implanted with a PS TKA that is designed for early cam/post engagement (PSE) and ten subjects with a PS TKA designed for later cam/post engagement (PSL). Each subject, while under fluoroscopic surveillance, performed a weight-bearing deep knee bend to maximum flexion. Video images were downloaded to a workstation computer and analyzed at ten-degree increments of knee flexion. Femorotibial contact paths for the medial and lateral condyles, axial rotation and condylar lift-off were then determined using a computer automated model-fitting technique. Results: Subjects implanted with the PSE TKA experienced, on average, the cam engaging the post at 48° (10 to 80°). Subjects having the PSL TKA experienced more consistent results and did experience engagement in deep flexion (Average 75°). Subjects having the PSE TKA experienced, on average, −5.5 mm (1.5 to −9.3) of posterior femoral rollback (PFR), while subjects having the PSL TKA experienced only −2.6 mm (8.5 to −9.0) of PFR. Subjects having the PSE TKA experienced more normal axial rotation patterns. Nine subjects having the PSE TKA experienced condylar lift-off (maximum = 1.9 mm), while only 4/10 having the PSL TKA experienced condylar lift-off (maximum = 2.7 mm). Discussion: This is the first study to determine the in vivo contact position of the cam/post mechanism. Subjects having a PSE TKA experienced earlier cam/post engagement than subjects having the PSL TKA. Some subjects did not experience any cam/post engagement throughout knee flexion. Subjects having the PSE TKA experienced more PFR and better axial rotation patterns, but subjects having a PSL TKA experienced lesser incidence of condylar lift-off. Results from this study suggest that there may be an advantage to early cam/post engagement, which leads to more normal axial rotation patterns caused by the medial condyle moving in the anterior direction as the lateral condyle rolls in the posterior direction

Purpose: A growing body of literature confirms that idiopathic OA is frequently caused by subtle, and often radiographically occult, abnormalities at the femoral head-neck junction or acetabulum that result in abnormal contact between the femur and acetabulum. This condition, known as femoroacetabular impingement, is a widely accepted cause of early OA of the hip. MRI is the imaging modality that is most sensitive in detecting cam morphology. There is currently little published data regarding the prevalence of abnormalities of the femoral head-neck junction in patients without hip pain or previous hip pathology. The primary aim of this project is to examine the incidence of cam morphology in a population without hip pain or pre-existing hip disease using non-contrast MRI. Method: Two hundred asymptomatic volunteers underwent magnetic resonance imaging targeted to both hips. Subjects were examined at the time of MRI to document internal rotation of the hips at 90 degrees flexion and to assess for a positive impingement sign. The mean age was 29.4 years (range 21.4–50.6); 77.5% were Caucasian and 55.5% female. The Nötzli alpha angle was measured on oblique axial images through the middle of the femoral neck for each hip. A value greater than 50 degrees was considered consistent with cam morphology. Measurements were performed independently by two musculoskeletal radiologists. Results: Twenty-six percent of volunteers had at least one hip with cam morphology: 20% had an elevated alpha angle on either the right or the left side, and 6% had bilateral deformity. The average alpha angle was 42.6 degrees on the right (SD=7.9) and 42.4 degrees on the left (SD=7.7). Internal rotation was negatively correlated with alpha angle (p< .05). Patients with an elevated alpha angle on at least one side tended to be male (p< .01). Conclusion: The high prevalence of cam morphology in asymptomatic individuals is critical information in determining the natural history of FAI as well as establishing treatment strategies in patients presenting with pre-arthritic hip pain

Purpose of the study: The purpose of this work was to search for a relationship between the size of the femoral cam, the presence of cup retroversion, and the presence of labral or chondral lesions on the arthroscan in patients with an asymptomatic femoroacetabular impingement. Material and method: Fifty arthroscans were obtained to explore impingements. The patients complained of groin or trochanteric pain limiting their physical activities. Generally signs of an anterosuperior impingement were demonstrated with flexion-adduction-internal rotation. The localization, dimensions and depth of the cartilage lesions were measured on the arthroscan. The sagittal slice was used to describe the acetabular chondral lesions anteriorly to posteriorly in clockwise manner. Presence of an associated labral lesion was noted. A second operator measured the hip joint anomalies causing the impingement: Notzli’s alpha angle was measured to search for a cam effect and the femoral offset was noted. Results: The presence of a femoral cam or a decreased femoral offset were found in all cases. Mean alpha angle was 65°; mean offset was 0.09. Acetabular retroversion was identified in 24 patients (48%). Chondral lesions were a constant finding and were superficial (type 1& 2) in 32 patients (64%) and deep (type 3& 4) in 18 patients (36%). Labral lesions were found in 28 patients (56%). The depth of the chondral lesions, like the presence of a labral lesion, were correlated significantly with increased alpha angle and patient age. There was conversely no correlation with the presence of acetabular retroversion. Discussion: This study confirmed the close relationship between femoroacetabular impingement by a cam effect and the severity of labral lesions and acetabular cartilage lesions. These lesions can favour degeneration, explaining the early centred or posterinferior damage observed in young patients with satisfactory acetabular cover

Purpose: Femoroacetabular impingement (FAI) has recently been described as a cause of adult hip pain and a precursor of hip osteoarthritis. Pincer type is secondary to acetabular retroversion or coxa profunda and Cam type is secondary to lack of concavity/offset of the antero-lateral femoral head-neck junction. Purpose of this study was to determine the prevalence of bilateral deformity in patients with cam type FAI as well as the presence of associated acetabular abnormalities. Method: One hundred and thirteen patients with symptomatic cam impingement (alpha (α) angle of Notzli > 55.5°) of at least one hip were evaluated. Eighty-two males, 31 females with an average age of 37.9 yrs (16–55). Standardized AP pelvis and bilateral Dunn views were reviewed. Alpha angle of Notzli was measured on Dunn views. Cam impingement was defined by α angle > 55.5 on the Dunn view and Pincer impingement was defined by the presence of either acetabular retroversion or coxa profunda. Statistical analysis was done using the two tailed paired t-test, chi-square test and intra-class correlation coefficient. Odds Ratios were calculated using conditional logistic regression. Results: Eighty-eight patients (77.8%) had bilateral deformity and 27% had symptoms in both hips. Mean α angles were higher for bilateral impingement deformity than for the impingement side only when unilateral deformity was present (72.10 versus 64.50, p< 0.001). Forty-four percent of hips with an impingement deformity also had a pincer deformity, either acetabular retroversion or coxa profunda. Painful hips had a statistically significant higher mean alpha angle than asymptomatic ones (69.70 versus 63.10, p< 0.001)). Comparing hips with α angles of 61–70 with those < 60 found an odds ratio of being painful of 2.59 (95% CI: 1.32–5.08, p=0.006). Hips with α angles > 71 had an odds ratio of being painful of 2.54 (95% CI: 1.3–4.96, p=0.007). Conclusion: The majority of patients with cam type FAI have bilateral deformities and an associated acetabular deformity less commonly. The severity of the deformity at the femoral head neck junction is a significant determining factor for the development of hip symptoms. This information is important as we better define the natural history of this deformity as well as devise effective treatment strategies

This study evaluates the outcome of arthroscopic femoral osteochondroplasty for cam lesions of the hip in the absence of additional pathology other than acetabular chondral lesions. We retrospectively reviewed 166 patients (170 hips) who were categorised according to three different grades of chondral damage. The outcome was assessed in each grade using the modified Harris Hip Score (MHHS) and the Non-Arthritic Hip Score (NAHS). Overall, at the last follow-up (mean 22 months, 12 to 72), the mean MHHS had improved by 15.3 points (95% confidence interval (CI), 8.9 to 21.7) and the mean NAHS by 15 points (95% CI, 9.4 to 20.5). Significantly better results were observed in hips with less severe chondral damage. Microfracture in limited chondral lesions showed superior results. Arthroscopic femoral osteochondroplasty for cam impingement with microfracture in selected cases is beneficial. The outcome correlates with the severity of acetabular chondral damage

Introduction: The conversion of the fused hip to a total hip replacement poses a challenging reconstructive problem. The technical pitfalls depend on the aetiology of the arthrodesis, the surgical technique used and the available bone stock. Indications include painful pseudo arthrosis, disabling back or ipsilateral knee pain and malposition of the arthrodesed hip. There are often difficulties restoring appropriate biomechanics and providing a functionally useful outcome. We present a short series where a custom CAD/CAM femoral prosthesis was used to accommodate the anatomical problems caused by previous spontaneous and operative arthrodesis. Patients and Method: 5 patients (4 female, 1 male) with primary diagnoses of septic arthritis, TB, trauma and DDH were reviewed. The average age at the time of conversion was 43.6 years (Range 20–62 years). The patients were reviewed with a mean follow up of 82 months (Range 24–110 months). All the patients were evaluated by an independent observer radiologically and clinically using Harris, WOMAC and Oxford hip scores. Results: The patients improved from preoperative HHS 55 (Range 39–73), Oxford 40 (Range 37–46) and WOMAC 80 (Range 65–92) to postoperative HHS 73 (Range 44–94), Oxford 26 (Range 17–42) and WOMAC 45 (Range 24–79). These results compare poorly to a large series of age and sex matched cases undergoing primary and revision hip arthroplasty. Nevertheless, 4 patients were extremely satisfied with the results of their operation. 1 patient showed no improvement in his scores although he reports that his spinal symptoms are better. His operation was complicated by non-union of the greater trochanter. Conclusion: Most series report poor results after the conversion of arthrodeses to total hip replacements. The commonest problems include instability, sepsis, fractures, limited mobility of the hip replacement and poor function. Careful planning is required to accommodate the atypical anatomy. The use of CAD/CAM femoral stems in the conversion of the arthrodesed hip has allowed preservation of valuable bone stock in anatomically abnormal femora whilst optimising biomechanics and improving function

Purpose: The purpose of this study was to evaluate the outcome of arthroscopic femoral osteochondroplasty for cam lesions of the hip with respect to the severity of acetabular chondral damage. Methods: The study is a retrospective review of 170 patients (35 females, 135 males) who underwent surgery for symptomatic cam femoroacetabular impingement (FAI) between the years 2003 to 2008. The patients were categorized according to three different grades of chondral damage. No patients had evidence of labral pathology. Microfracture of the acetabular chondral damage was also performed when indicated. The clinical results in each grade were measured preoperatively and postoperatively with the modified Harris Hip Score (MHHS) and Non Arthritic Hip Score (NAHS). Results: The mean follow-up time was 22 months (range 12 to 72 months). At the last follow-up, significantly better results were observed in hips with less chondral damage. The mean MHHS improved from 74.1±17.1 to 89.8±11.6 in grade 1 whereas it improved from 62.3±14.3 to 77.4±18.3 in grade 3 (p=0.02). The mean NAHS improved from 70.7±13.5 to 87±16.2 in grade 1 whereas it improved from 60.5±16.2 to 78±17.8 in grade 3 (p=0.04). Microfracture in limited zones of ace-tabular chondral damage had shown superior results. Conclusions: Arthroscopic femoral osteoplasty for hip cam impingement with acetabular chondral damage provides a significant improvement in symptoms. Microfracture of the chondral lesion in selected cases has been demonstrated to be safe and benifical

A robust frame of reference is required to accurately characterize pathoanatomy in the proximal femur and quantify the femoral head-neck relationship. A three dimensional (3D) femoral neck axis (FNA) could serve such a purpose, but has not yet been established in the current literature. The primary aim of this study was to develop and evaluate a reliable method of determining the 3D femoral neck axis. Secondly, we wanted to quantify the translational relationship between the femoral head and neck in normal and cam type hips. Pelvic computed tomographic scans (CT) and radiographs were retrieved from our database of patients who had undergone navigated hip surgery or CT colonography. All patients had given informed consent for their medical files and imaging to be used for research purposes, as approved by the institutional review board. Pre-operative scans were performed using the Siemens Sensation 64 slice scanner (Siemens Medical Solutions, Erlangen, Germany). The Imperial Protocol developed at the authors’ orthopaedic unit was applied, allowing acquisition of Digital Imaging and Communications in Medicine (DICOM) files of 0.75mm thickness. Normal and cam type hips (n=30) were identified for analysis. ‘Normal’ hips (n=15) were defined in asymptomatic patients with no previous history of hip disease, and, no obvious abnormality on radiographs or CT. The ‘cam’ hip type (n=15) was defined by the presence of an anterior osseous bump at the head-neck junction, and an alpha angle greater than 50° on hip radiographs. DICOMs were converted to 3D stereolith (STL) images using validated commercial image processing and analysis software (3-Matics, Materialise Group, Leuven, Belgium). In order to determine the 3D-FNA, a best fit sphere was applied to the femoral head with a root mean square error of less than 0.5mm. The border between sphere and femoral neck defined the head -neck junction. The bone surface was marked here (including the anterior bump in cam hips) and at the neck base, providing two anatomical rings that defined the superior and inferior limits of the femoral neck. The centre point of each ring was calculated. A line connecting these points defined the femoral neck axis, and was verified on a DICOM viewer in sagittal, axial and coronal planes. The offset between the femoral head centre and neck axis was measured. The 3D image and axis were further analysed to examine the femoral head-neck relationship, using customized software developed at our institution and previously validated in previous research projects. To standardize rotational alignment, the femoral neck was aligned vertically in two planes by creating an axis between the tip of the greater trochanter and the center of the lesser trochanter. The aligned proximal femur was viewed end on, and the version of the head relative to the neck determined by calculating the angle between the head centre and a vertical marker placed at the 12 o’clock position. Angles below 180° demonstrated anteversion, while those above 180° demonstrated retroversion

Introduction. Alpha angles have been used to identify the precise area on the femoral head/neck junction that causes cam-type FAI. Now, computer programs are available to calculate the precise motion pattern of a hip joint and identify areas of FAI, dysplasia and other morphological abnormalities. We hypothesise that one cannot rely on the alpha angle alone to predict the precise area of resection required to remove cam impingement. Methods. We used Clinical Graphics software to analyse a cohort of 142 hips. We recorded the alpha angle at 12, 1, 2 and 3 o'clock and whether resection was recommended by the software at these points. We then removed the patients with acetabular influences on potential FAI (pure cam group). Results. At the points recommended for resection alpha angles were found to be significantly higher than those where resection was not advised (52.88° v 49.29°, p=0.0001). However, of the alpha angles greater than 50°, resection was recommended in only 49%. Of the alpha angles less than 50°, resection was still recommended in 36%. In the pure cam-type FAI patients we found no statistically significant association between alpha angle and whether resection was or wasn't indicated (p=0.0536). We further analysed each point on the femoral head/neck. Alpha angles were highest at the 1 and 2 o'clock position which would fit with the anatomical variation that most surgeons would associate with the area of impingement. However, the most common recommended area for resection was between 3 and 5 o'clock. Conclusion. Alpha angle is a poor predictor of cam resection to remove FAI. The suggested location of osteochondroplasty required to remove impingement appears to be further anterior and inferior on the femoral neck than many surgeons might predict. Motional analysis software is a valuable tool in assisting surgeons to understand the morphological abnormalities that may affect the hip