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

The frequency of severe femoral retroversion is unclear in patients with femoroacetabular impingement (FAI). This study aimed to investigate mean femoral version (FV), the frequency of absolute femoral retroversion, and the combination of decreased FV and acetabular retroversion (AR) in symptomatic patients with FAI subtypes.

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

Background. Over 30 million people run marathons annually. The impact of marathon running on hips is unclear with existing literature being extremely limited (only one study of 8 runners). Aim and Objectives. We aimed to better understand the effect of marathon running on the pelvis and hip joints by designing the largest MRI study of asymptomatic volunteers. The objectives were to evaluate the pelvis and both hip joints before and after a marathon. Materials and Methods. This was a prospective cohort study, Fig.1. We recruited 44 asymptomatic volunteers who were registered for the Richmond Marathon. They were divided into novice and experienced marathoners, Fig.2. All volunteers underwent 3T MRI of pelvis and hips with Dixon sequences 4 months before, and within 2 months after the marathon. Outcome measures were: 1. change in radiological score of each hip joint structure and muscle from the pre- to the post-marathon MRI; 2. change in the self-reported hip function questionnaire score (HOOS) between the two timepoints. Results Pre-marathon, Asymptomatic novice marathoners' hips showed few joint abnormalities (cartilage, bone marrow, labrum), while minimal fatty muscle atrophy of the abductors and CAM-type hip impingement were common (68%; 34%, respectively). Experienced marathoners had no cartilage lesions and slightly lower prevalences of abnormalities than novice runners. Post-marathon, Hip joint cartilage, bone edema and labrum did not worsen in neither novice nor experienced marathoners. Abductor muscles were unaffected post-marathon. Self-reported hip outcomes were not significantly different after the run for both groups. Conclusion. This is the largest MRI study of long-distance runners. We showed that marathon running has no negative impact on the pelvis and hip joints. For any figures or tables, please contact the authors directly

Cam-type femoroacetabular impingement (FAI) is a common cause for athletic hip injury and early hip osteoarthritis. Although corrective cam FAI surgery can improve patient reported outcome measures (PROMs), it is not clear how surgery affects muscle forces and hip joint loading. Surgery for FAI may redistribute muscle forces and contact forces at the hip joint during routine activities. The purpose of this study was to examine the muscle contributions and hip contact forces during gait in patients prior and after two years of undergoing surgery for cam FAI. Kinematics and kinetics were recorded in 11 patients with symptomatic cam FAI as they completed a gait task. Muscle and hip contact forces during the stance phase were estimated using musculoskeletal modelling and static optimization in OpenSim. All patients reported improvements in PROMs. Post-operatively, patients showed reduced forces in the long head of the biceps femoris at ipsilateral foot-strike and in the rectus femoris at the contralateral foot-strike. The reduced muscle forces decreased sagittal hip moment but did not change hip contact forces. This was the first study to evaluate hip muscle and contact forces in FAI patients post-operatively. Although hip contact forces are not altered following surgery, muscle forces are decreased even after two years. These findings can provide guidance in optimizing recovery protocols after FAI surgery to improve hip flexor and extensor muscle forces

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

Surgical management of cam-type femoroacetabular impingement (FAI) aims to preserve the native hip, restore joint function, and delay the onset of osteoarthritis. However, it is unclear how surgery affects joint mechanics and hip joint stability. The aim was to examine the contributions of each surgical stage (i.e., intact cam hip, capsulotomy, cam resection, capsular repair) towards hip joint centre of rotation and microinstability. Twelve fresh, frozen cadaveric hips (n = 12 males, age = 44 ± 9 years, BMI = 23 ± 3 kg/m2) were skeletonized to the capsule and included in this study. All hips indicated cam morphology on CT data (axial α = 63 ± 6°, radial α = 74 ± 4°) and were mounted onto a six-DOF industrial robot (TX90, Stäubli). The robot positioned each hip in four sagittal angles: 1) Extension, 2) Neutral 0°, 3) Flexion 30°, and 4) Flexion 90°, and performed internal and external hip rotations until a 5-Nm torque was reached in each direction, while recording the hip joint centre's neutral path of translation. After the (i) intact hip was tested, each hip underwent a series of surgical stages and was retested after each stage: (ii) T-capsulotomy (incised lateral iliofemoral capsular ligament), (iii) cam resection (removed morphology), and (iv) capsular repair (sutured portal incisions). Eccentricity of the hip joint centre was quantified by the microinstability index (MI = difference in rotational foci / femoral head radius). Repeated measures ANOVA and post-hoc paired t-tests compared the within-subject differences in hip joint centre and microinstability index, between the testing stages (CI = 95%, SPSS v.24, IBM). At the Extension and Neutral positions, the hip joint centre rotated concentrically after each surgical stage. At Flexion 30°, the hip joint centre shifted inferolaterally during external rotation after capsulotomy (p = 0.009), while at Flexion 90°, the hip joint centre further shifted inferolaterally during external rotation (p = 0.005) and slightly medially during internal rotation after cam resection, compared to the intact stages. Consequently, microinstability increased after the capsulotomy at Flexion 30° (MI = +0.05, p = 0.003) and substantially after cam resection at Flexion 90° (MI = +0.07, p = 0.007). Capsular repair was able to slightly restrain the rotational centre and decrease microinstability at the Flexion 30° and 90° positions (MI = −0.03 and −0.04, respectively). Hip microinstability occurred at higher amplitudes of flexion, with the cam resection providing more intracapsular volume and further lateralizing the hip joint during external rotation. Removing the cam deformity and impingement with the chondrolabral junction also medialized the hip during internal rotation, which can restore more favourable joint loading mechanics and stability. These findings support the pathomechanics of cam FAI and suggest that iatrogenic microinstability may be due to excessive motions, prior to post-operative restoration of static (capsular) and dynamic (muscle) stability. In efforts to limit microinstability, proper nonsurgical management and rehabilitation are essential, while activities that involve larger amplitudes of hip flexion and external rotation should be avoided immediately after surgery

Cam-type femoral acetabular impingement (FAI), is a common structural hip deformity and thought to be a leading cause of early hip osteoarthritis. Although patients who undergo surgical correction notice improved clinical function it is unclear what impact this has on the overall health of the cartilage. T1rho MRI cartilage mapping has been shown to be a reliable imaging technique to assess the proteoglycan (PG) content potentially serving as a biomarker. This study analyses post surgical changes in T1rho levels in hip joints treated with cam FAI. Eleven patients with a mean age of 38 (all males) underwent pre and post T1Rho Cartilage mapping of their hips at a mean time of 20 months post surgical intervention. The acetabulum was spatially divided into 4 main regions of interest (ROI), with levels of T1Rho in cartilage quantified as a whole and in each spatial segment. T1Rho signal is inversely correlated with level of PG content. All patients demonstrated loss of PG content on pre-op imaging with a T1Rho of 33.5ms+2.6ms. Preop T1rho levels were found to significantly correlated with the difference between pre-op and post-op T1rho in entire hip cartilage (R: 0.73; p=0.016). This correlation was reflected both in the anterolateral quadrant (R: 0.86; p=0.002), and in the posteriosuperior quadrant (R:0.70; p=0.035). Additionally, significant correlation was found between improvement of WOMAC pain score over time, and difference of T1rho values over time in the most lateral 3mm slice of the anterolateral quadrant (R: 0.81; p=0.045). Significant correlation was found between pre-op alpha angle at 1:30 and difference between pre-op and post-op total cartilage T1rho content (R: −065;p=0.038). T1Rho Cartilage mapping of the hip is a useful biomarker in the assessment of the surgical management of Cam type FAI. This preliminary data provides some evidence that surgical correction of the deformity can help minimise disease progression

Background. Cam-type femoro-acetabular impingement (FAI) is increasingly recognised as a cause of mechanical hip symptoms in young adults. It is likely that it is a cause of early hip degeneration. Ganz et al have developed a therapeutic procedure involving trochanteric flip osteotomy and dislocation of the hip, and have reported good results. We have developed an arthroscopic osteochondroplasty to reshape the proximal femur and relieve impingement. Methods. Fifty patients who presented with mechanical hip symptoms and had demonstrable cam-type FAI on radially-reconstructed MR arthrography, were treated by arthroscopic osteochondroplasty. Ten patients had a post-operative CT; from these images flexion and internal rotation range was tested in a virtual reality (VR) model to determine adequacy of resection. All patients were followed up for a minimum of one year, and post-operative Non-Arthritic Hip Scores (NAHS, maximum possible score 100) compared with pre-operative NAHS. Results. Mean operating time was 110 minutes. 31 patients were discharged on the day of surgery, the remainder on the following day. There were no complications. All patients were asked to be partially weight-bearing with crutches for four weeks but most returned to work within two weeks. The VR models showed satisfactory resection, although there was clear evidence of improved precision with practice. Symptoms improved in all but two patients, with mean NAHS improving from 54 pre-operatively to 87 at one year. The two patients who did not improve, were both found to have unexpectedly extensive acetabular articular cartilage damage. Conclusion. Arthroscopic femoral 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 the arthroscopic procedure avoids the prolonged disability and the complications associated with trochanteric flip osteotomy

Background: Cam-type femoroacetabular impingement (FAI) is becoming more recognized. Cartilage lesions of the acetabulum and labral tears are frequently encountered. The goal of this study was to accurately describe and communicate these injuries and thus providing a standard for reporting injury, management, and outcome. Methods: We evaluated acetabular cartilage lesions and labral tears found during hip arthroscopy in 52 patients with radiological signs of cam-type FAI. They were graded according to the morphology and extent of the lesion. The labral tears were described according to the classification by Lage. Results: Eleven patients (21.2%) had normal cartilage, 14 (26.9%) had a grade 1, 17 (32.7%) a grade 2, 6 (11.5%) a grade 3, and 4 (7.7%) a grade 4 lesion. Labral tears were found in 31 patients (59.6%). There was a high correlation between age and the presence and extent of acetabular cartilage and labral lesions (r=0.70; p< 0.0001 and r=0.45; p< 0.001 respectively). There was also a high correlation between the extent of the acetabular cartilage lesion and the presence of labral lesions (r=0.62; p< 0.0001). Conclusion: In our study there was a high prevalence of associated injuries (86.5%) in cam-type FAI. Despite the recognized consequences of associated lesions on treatment and outcome, no classification system includes this aspect of FAI. Based on our findings, we developed a system to grade acetabular cartilage lesions according to their morphology and extent. This should provide the surgeon with a standardized tool to better describe the full extent of the injury and treat it accordingly

Introduction: Cam-type femoroacetabular impingement (FAI) is a pre-osteoarthritic condition causing premature joint degeneration. Cam-deformities are characterised by decreased cranial offset of the femoral head/neck junction and aspherity of the femoral head causing delamination of the acetabular cartilage and detachment of the acetabular labrum. To asses the epidemiological aspects of cam-type FAI we evaluated Nötzlis alpha angle and our own Triangular Index (TI) for use on plain AP pelvic radiographs. Materials and Methods: Cam malformation was assessed in 2.803 pelvic radiographs by the alpha (α) angle and the TI to define pathological cut off values. The α-angle and TI were assessed in AP and lateral hip radiographs of 164 patients scheduled for THR and the influence of varying rotation on the α-angle and TI was assessed in femoral specimens. The distribution of Cam-deformities was assessed in 3.712 standardized AP pelvic radiographs using the α-angle and TI. Results: Mean AP α-angle male/female was 55°/45°. The α-angle and TI was highly interrelated, OR 8.6–35 (p< 0.001). Almost all cam-malformations were identifiable in AP projections, sensitivity 88–94% compared to axial view. The TI proved robust for cam identification during rotation (± 20°) compared to the α-angle (−10° to +20°). The distribution of pathologic TI and α-angle (Right/Left) were 11.6/12.5% and 6.1/7.4% in males and 2.2/3.2% and 2.1/3.8% in females. We found a pronounced sexrelated difference in cam-deformity distribution, OR 2.0–6.3 (p< 0.001). Conclusion: The triangular index and the α-angle were found reliable for epidemiological purpose. Overall prevalence of definite cam-deformity was app. 10% in men and 2,5% in women

Introduction. Bracing, a strategy employed by humans and robotic devices, can be generally described as a parallel mechanical link between the actor, the environment, and/or the workpiece that alters the mechanical impedance between the tool and workpiece in order to improve task performance. In this study we investigated the potential value of bracing in the context of bone milling to treat cam-type femoroacetabular impingement (FAI) lesions. The goal of this study was to evaluate whether a proposed bracing technique could enable a user to perform a cam resection more accurately and quickly than a currently employed arthroscopic technique. Materials/Methods. Test samples consisted of white urethane plastic reproductions of a commercially available adult proximal femur, which were laser scanned to obtain ground-truth surface information. A black cam lesion was then cast onto the surface of the femur in the anterosuperior region of the femoral neck, creating a clear visual resection boundary for the simulated osteochondroplasty. Test subjects were 4 adult males (25 +/− 3 years) with no surgical experience. Test conditions included two binary factors: (1) Braced vs. Unbraced – The braced case introduced a spherical bearing tool support mounted in the approximate anterolateral arthroscopic portal position. (2) Speed vs. Accuracy – The subject was instructed to perform the resection as quickly as possible or as accurately as possible with a moderate regard for time. Following the removal of the lesion, femurs were laser scanned to acquire the post-resection surface geometry, with accuracy being reported as RMS deviation between the pre- and post-resection scans over the anterosuperior neck region. Results. In both accuracy and speed cases, bracing tended to reduce errors (on the order of 7–14%) and task duration (on the order of 32–52%), although given the small number of subjects in this pilot study, these differences were not statistically significant. Conclusion. These results provide some encouragement that our hypothesis that bracing can improve both speed and accuracy of cam lesion resection by untrained subjects may be true. The standard deviations between subjects are high and are likely due to both the difficulty of the task and differences in experience using handheld power tools, so additional subjects would be needed to verify the trends identified here

Introduction: Abnormal hip morphology, seen with conditions such as slipped capital femoral epiphyses and femoral head necrosis, can lead to repetitive contact between the femoral neck and the acetabular rim. Impingement is a significant cause of hip pain in young adults and may be a mechanism for the development of early osteoarthritis. The senior surgeon has modified a technique to debride the pathology responsible for femoroacetabular impingement through a mini anterior approach, obviating the need to dislocate the hip. We describe this technique and present early clinical outcomes. Method: Between Jan 2006 and June 2008, ‘notchplasty’ for the surgical treatment of femoroacetabular impingement was performed by the senior author (AHN) or directly under his supervision in 38 hips. There were 17 male patients and 21 female patients with an average age of 31 years. Patients have been followed according to a prospective protocol with Oxford and Iowa hip scores obtained pre-operatively, at 3 months and at 1 year. Results: This study is still in progress. Twenty nine patients have had 3 month follow up and 13 of these have now been followed up to one year. Four patients are still less than 3 months post op. Data was unobtainable for 5 patients. 1 patient was excluded from the study. The overall Oxford hip score improved significantly from a mean pre-operative value of 35 to a mean post operative value of 22.9 at 3 months (p< 0.001). The mean score at 1 year increased slightly to 27.3 points but this remains lower than the pre operative average. We report no cases of osteonecrosis. One patient has since been scheduled to undergo resurfacing arthroplasty. Conclusions: The technique described is a new method for managing these patients whilst avoiding the pit-falls of current operative methods. The method avoids detaching the straight head of rectus, thereby tremendously improving postoperative mobilisation. However, the long term benefit of debridement of the head-neck junction for Cam-type femoroacetabular impingement remains to be seen

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

This systematic review examines the current literature regarding surgical techniques for restoring articular cartilage in the hip, from the older microfracture techniques involving perforation to the subchondral bone, to adaptations of this technique using nanofractures and scaffolds. This review discusses the autologous and allograft transfer systems and the autologous matrix-induced chondrogenesis (AMIC) technique, as well as a summary of the previously discussed techniques, which could become common practice for restoring articular cartilage, thus reducing the need for total hip arthroplasty. Using the British Medical Journal Grading of Recommendations, Assessment, Development and Evaluation (BMJ GRADE) system and Grade system. Comparison of the studies discussed shows that microfracture has the greatest quantity and quality of research, whereas the newer AMIC technique requires more research, but shows promise.

Cite this article: W. E. Hotham, A. Malviya. A systematic review of surgical methods to restore articular cartilage in the hip. Bone Joint Res 2018;7:336–342. DOI: 10.1302/2046-3758.75.BJR-2017-0331.

The April 2012 Children’s orthopaedics Roundup³⁶⁰ looks at osteonecrosis of the femoral head and surgery for dysplasia, femoral head blood flow during surgery, femoroacetabular impingement and sport in adolescence, the Drehmann sign, a predictive algorithm for septic arthritis, ACL reconstruction and arthrofibrosis in children, spinal cord monitoring for those less than four years old, arthroereisis for the flexible flat foot, fixing the displaced lateral humeral fracture, and mobile phones and inclinometer applications