Can combining femoral and acetabular morphology parameters improve the characterization of femoroacetabular impingement?

BACKGROUND: Femoroacetabular impingement (FAI) presupposes a dynamic interaction of the proximal femur and acetabulum producing clinical symptoms and chondrolabral damage. Currently, FAI classification is based on alpha angle and center-edge angle measurements in a single plane. However, acetabular and femoral version and neck-shaft angle also influence FAI. Furthermore, each of these parameters has a reciprocal interaction with the others; for example, a shallow acetabulum delays impingement of the femoral head with the acetabular rim. QUESTIONS/PURPOSES: We introduce the new parameter "omega zone," which combines five parameters into one: the alpha and center-edge angles, acetabular and femoral version, and neck-shaft angle. We sought to determine whether the omega zone could differentiate patients with FAI from (1) normal control subjects (alpha < 55°), but also from (2) control subjects with elevated alpha angles (≥ 55°). METHODS: We evaluated CT data of 20 hips of male patients with symptomatic cam-type FAI and of 35 male hips extracted from 110 anonymized CT scans for vascular diagnosis. We excluded hips with osteoarthritis, developmental dysplasia, or coxa profunda (center-edge angle 20°-45° on AP pelvic view or corresponding coronal CT views). With dedicated software, femoral and pelvic orientation was standardized; we tested the omega zone in four hip positions in three distinct groups: patients with cam-type FAI (alpha > 60°) and control subjects with normal (< 55°) and high alpha angles (≥ 55°). RESULTS: The omega zone was smaller in patients with cam-type FAI than normal control subjects (alpha angle < 55°) at 60° and 90° of flexion (mean, 12%; 95% confidence interval [CI], 7-17; p = 0.008; Cohen's d = 9%; 95% CI, 4-13; p = 0.003). Furthermore, the omega zone was smaller in all positions in patients with cam-type FAI than control subjects with high alpha angles (0° p = 0.017, 30° p = 0.004, 60° p = 0.004, 90° p = 0.007). In contrast, the omega zone did not differ between control subjects with normal or high alpha angles. In all hips, the omega zone decreased with flexion, corresponding to a decrease in remaining impingement-free motion with flexion. CONCLUSIONS: The omega zone visualizes and quantifies the interaction of the proximal femur and acetabulum. The omega zone differed between patients with cam-type FAI and control subjects with high alpha angles (≥ 55°), who could not be distinguished based on alpha angle alone. For hip-preserving surgery, it can help surgeons decide whether to address the femur, the acetabulum, or both.

What ape proximal femora tell us about femoroacetabular impingement: a comparison.

BACKGROUND: Human hip morphology is variable, and some variations (or hip morphotypes) such as coxa profunda and coxa recta (cam-type hip) are associated with femoroacetabular impingement and the development of osteoarthrosis. Currently, however, this variability is unexplained. A broader perspective with background information on the morphology of the proximal femur of nonhuman apes is lacking. Specifically, no studies exist of nonhuman ape femora that quantify concavity and its variability. QUESTIONS/PURPOSES: We hypothesized that, when compared with modern humans, the nonhuman apes would show (1) greater proximal femoral concavity; (2) less variability in concavity; and (3) less sexual dimorphism in proximal femoral morphology. METHODS: Using identical methods, we compared 10 morphological parameters in 375 human femora that are part of the Hamann-Todd collection at the Cleveland Museum of Natural History with 210 nonhuman ape femora that are part of the collection of the Royal Museum for Central Africa, Tervuren, Belgium, and the Muséum National d'Histoire Naturelle, Paris, France. RESULTS: The nonhuman apes have larger proximal femoral concavity than modern humans. This morphology is almost uniform without large variability or large differences neither between species nor between sexes. CONCLUSIONS: Variability is seen in human but not in nonhuman ape proximal femoral morphology. An evolutionary explanation can be that proximal femoral concavity is more important for the nonhuman apes, for example for climbing, than for modern humans, where a lack of concavity may be related to high loading of the hip, for example in running.

Where is the neck? Alpha angle measurement revisited.

BACKGROUND AND PURPOSE: The alpha angle is the most used measurement to classify concavity of the femoral head-neck junction. It is not only used for treatment decisions for hip impingement, but also in cohort studies relating hip morphology and osteoarthritis. Alpha angle measurement requires identification of the femoral neck axis, the definition of which may vary between studies. The original "3-point method" uses 1 single point to construct the femoral neck axis, whereas the "anatomic method" uses multiple points and attempts to define the true anatomic neck axis. Depending on the method used, the alpha angle may or may not account for other morphological characteristics such as head-neck offset. METHODS: We compared 2 methods of alpha angle measurement (termed "anatomic" and "3-point") in 59 cadaver femora and 83 cross-table lateral radiographs of asymptomatic subjects. Results were compared using Bland-Altman plots. RESULTS: Discrepancies of up to 13 degrees were seen between the methods. The 3-point method had an "equalizing effect" by disregarding femoral head position relative to the neck: in femora with high alpha angle, it resulted in lower values than anatomic measurement, and vice versa in femora with low alpha angles. Using the anatomic method, we derived a reference interval for the alpha angle in normal hips in the general population of 30-66 degrees. INTERPRETATION: We recommend the anatomic method because it also reflects the position of the femoral head on the neck. Consensus and standardization of technique of alpha angle measurement is warranted, not only for planar measurements but also for CT or MRI-based measurements.

The short external rotators in the anterior approach hip arthroplasty: do the tendons heal or not? A prospective MRI study.

INTRODUCTION: Release of some of the short external rotator tendons may be needed in the direct anterior approach (DAA) for Total Hip Arthroplasty (THA). It is unknown if these tendons heal. The purpose of this prospective study is to examine short external rotator tendon healing after release and the associated effect on muscle volume. In addition, we examined the relation with external rotation force and patient reported outcome measures (PROMs). METHODS: In 21 DAA THA patients, preoperative MRI was compared with postoperative MRI at 6 weeks and 12 months. PROMs and rotation force of both hips were assessed. Tendon integrity and muscle volume of the obturator internus and piriformis were assessed on MRI using dedicated software. RESULTS: In 5 patients all tendons remained intact, in 4 patients only the conjoined tendon was released and in 12 patients both the conjoined and piriformis were released. Obturator externus remained intact in all patients. In patients with tendon release, mean volume of obturator internus and piriformis muscle decreased 27% (SD 11) and 23% (SD 16) 6 weeks after surgery, respectively. Released tendons and muscle volume loss did not recover 12 months after surgery. We found no relation between tendon release and hip rotation force or PROMs. CONCLUSIONS: We found absent tendon healing and muscle volume loss when the conjoined or piriformis tendons were released. Although we found no relation between tendon detachment and hip force or PROMs, we have adapted our operative technique to make it more preserving for the piriformis.

Hip ontogenesis: how evolution, genes, and load history shape hip morphotype and cartilotype.

BACKGROUND: Developmental hip disorders (DHDs), eg, developmental dysplasia of the hip, slipped capitis femoris epiphysis, and femoroacetabular impingement, can be considered morphology variants of the normal hip. The femoroacetabular morphology of DHD is believed to induce osteoarthritis (OA) through local cumulative mechanical overload acting on genetically controlled patterning systems and subsequent damage of joint structures. However, it is unclear why hip morphology differs between individuals with seemingly comparable load histories and why certain hips with DHD progress to symptomatic OA whereas others do not. QUESTIONS/PURPOSES: We asked (1) which mechanical factors influence growth and development of the proximal femur; and (2) which genes or genetic mechanisms are associated with hip ontogenesis. METHODS: We performed a systematic literature review of mechanical and genetic factors of hip ontogeny. We focused on three fields that in recent years have advanced our knowledge of adult hip morphology: imaging, evolution, and genetics. WHERE ARE WE NOW?: Mechanical factors can be understood in view of human evolutionary peculiarities and may summate to load histories conducive to DHD. Genetic factors most likely act through multiple genes, each with modest effect sizes. Single genes that explain a DHD are therefore unlikely to be found. Apparently, the interplay between genes and load history not only determines hip morphotype, but also joint cartilage robustness ("cartilotype") and resistance to symptomatic OA. WHERE DO WE NEED TO GO?: We need therapies that can improve both morphotype and cartilotype. HOW DO WE GET THERE?: Better phenotyping, improving classification systems of hip morphology, and comparative population studies can be done with existing methods. Quantifying load histories likely requires new tools, but proof of principle of modifying morphotype in treatment of DDH and of cartilotype with exercise is available.

Validation of the Super Simple Hip score combined with the University of California, Los Angeles activity scale for younger patients.

INTRODUCTION: Patient-reported outcome measures (PROMs) are used increasingly, but for young patients with hip complaints, traditional scoring systems have a ceiling effect that limits their usability. We developed and validated the Super Simple Hip (SUSHI) score, a PROM specifically targeted at younger patients with hip complaints. Although the SUSHI measured hip problems adequately, the responsiveness of its activity rating component was considered inadequate. Consequently, we replaced the activity rating component by the University of California, Los Angeles (UCLA) activity scale. The aim of this study was to validate the resulting new 10-item SUSHI-UCLA score. METHODS: A prospective multicentre observational cohort study was performed. Patients between 18 and 59 years, who visited the Orthopaedic Department with hip complaints, completed the SUSHI-UCLA and hip osteoarthritis outcome score (HOOS) twice before their 1st appointment, and once 16 months after. RESULTS: 142 patients were included (mean age 49 years; SD 8.8). The SUSHI-UCLA score correlated well with the HOOS, both before and after treatment (Spearman's rho = 0.739 and 0.847, respectively, both p < 0.001). The responsiveness of both the SUSHI-UCLA score and the UCLA activity scale was high (standardised response mean = 2.51 and 1.35 respectively). The reproducibility was good (interclass correlation coefficient for agreement = 0.962). The minimal important change was 21.2. No significant floor or ceiling effect was observed. CONCLUSION: The SUSHI-UCLA score is an adequate PROM to measure hip complaints in younger patients and includes a validated activity rating.

Evolution of the hip and pelvis.

Man's evolution features two unique developments: growing a huge brain and upright gait. Their combination makes the pelvis the most defining skeletal element to read human evolution. Recent revival in joint preserving hip surgery have brought to attention morphological variations of the human hip that appear similar to hips of extant mammals. In man, such variations can produce hip osteoarthrosis through motion. We reviewed the evolution of the hip and pelvis with special interest in morphology that can lead to motion induced osteoarthrosis in man. The combination of giving birth to big brained babies and walking upright has produced marked differences between the sexes in pelvis and hip morphology, each having their characteristic mode of hip impingement and osteoarthrosis.

Femoroacetabular impingement causes osteoarthritis of the hip by migration and micro-instability of the femoral head.

Femoroacetabular impingement is the condition whereby parts of the proximal femur mechanically collide with the acetabular rim leading to adjacent and contrecoup acetabular damage. Evidence is growing that at least for cam impingement, and perhaps less so for pincer impingement, there is a relation to the development of osteoarthritis. It has been demonstrated that surgery for impingement can improve function and decrease pain. Intuitively, it would then make sense that surgical intervention would prevent further degeneration. However, available literature to date cannot assure that it does. Therefore, the impingement itself seems not a sufficient cause to consistently cause osteoarthritis. For many years we have observed a phenomenon whereby the femoral head 'migrates' anteriorly and superiorly in the acetabulum in patients with cam impingement. The same, but less constant, can be observed in pincer impingement, where the head may migrate posteriorly and medially. Migration of the femoral head is known in the literature and seen as caused by, or as part of, osteoarthritis of the hip. We suggest that the migration is caused by the impingement, and that the femoral head wanders into the impingement-related area with cartilage damage. In cam impingement this may be anterolateral, in pincer impingement posteromedial. The effect must be a huge increase in compression forces, especially in cam impingement. The migration may even lead to, or be a sign of, micro-instability of the femoral head in the acetabulum, which may produce an increase in shear forces. We therefore hypothesise that impingement may lead to osteoarthritis by means of migration and the possible existence of micro-instability of the femoral head. Detecting and quantifying these phenomena seem of uttermost importance and may add a new dimension to conservative hip surgery.

Evolution of the human hip. Part 2: muscling the double extension.

Part 1 of this article outlined the extensive osseous adaptations around the hip that occurred in the development of a habitual bipedal gait in modern humans. The shortest summary of these osseous changes is 'double extension', i.e. extension of both the hip joint and the lumbar spine. Not surprisingly, these osseous changes went hand in hand with major muscular changes. The primary changes that accompanied the double extension were changes in relative muscle volume for the quadriceps, gluteus maximus and hamstrings, changes in moment arms for the iliopsoas, gluteus maximus and hamstrings, a change in function for the gluteus medius and minimus, while the functional anatomy of the adductors and hip rotators changed only slightly. The effect of these osseous and muscular changes was improved energy efficiency of human bipedal walking and (long distance) running. However, this occurred at the expense of maximum power, characteristic for activities such as tree climbing (in the apes), but equally so for sprinting. Recognizing these changes and their consequences may help us better understand and treat soft-tissue disorders around the hip.

Combining femoral and acetabular parameters in femoroacetabular impingement: the omega surface.

The concept of femoroacetabular impingement (FAI) proposes the development of hip osteoarthritis through motion-induced damage to the acetabular cartilage and labrum. Thus, dynamic interaction of the proximal femur and acetabulum is the crux of FAI. Several types of FAI can be distinguished, but FAI classification is mostly done with separate parameters for acetabular and femoral morphology on planar images, without direct representation of the femoroacetabular interaction. Five main parameters influence impingement between the proximal femur and the acetabular rim: alpha and center edge angles, acetabular and femoral version, and neck-shaft angle. We attempted to integrate these five parameters in order to reflect their interaction and derive a signal comprehensive parameter, the omega surface, to characterize the severity of FAI. The omega surface is a CT-based delineation of the femoral head surface that represents the area for impingement-free motion. The omega surface is determined with dedicated software (Articulis™) and can be determined for various positions of the hip joint. We determined the omega surface in a pilot study for five different hip morphotypes and found the omega surface was smaller in FAI morphotypes than in a normal hip. Furthermore, the omega surface was smaller in symptomatic versus control subjects with FAI morphotypes. The omega surface may therefore help in improved differentiation between symptomatic and asymptomatic FAI hips.

Selective joint denervation promotes knee osteoarthritis in the aging rat.

Osteoarthritis is the most common joint disorder with aging, but its cause is unknown. Mice lose joint afferents with aging, and this loss precedes development of osteoarthritis. We hypothesized a loss of joint afferents is involved in the pathogenesis of osteoarthritis. To test this hypothesis, we denervated knee joints of 16 rats at age 2 months, by intra-articular injection of an immunotoxin. The immunotoxin killed neurons after retrograde axonal transport to the cell body. At 16 or 24 months follow-up, each joint was histologically assessed and assigned an osteoarthritis score. At follow-up, the number of joint afferents had spontaneously decreased by 42% in control knees and 69% in denervated knees. We found that control knees developed osteoarthritic changes with aging. However, denervated knees had far more severe changes, as evidenced by a 54% higher average osteoarthritis score than control knees (P = 0.0016, both groups 16 knees). These results suggest a loss of afferents predisposes a joint to osteoarthritis. We propose the spontaneous loss of neurons with aging may be a normal developmental process. To explain the mechanism causing osteoarthritis, we suggest denervation permits aberrant joint loading, either by disturbing neuromuscular joint control, or by inducing joint laxity after neurogenic loss of tissue homeostasis.

Changes in bone scans after anterior cruciate ligament reconstruction: a prospective study.

BACKGROUND: Whether anterior cruciate ligament reconstruction retards the progression of osteoarthrosis is not established. Bone scintigraphy can be useful for monitoring the course of osteoarthrosis. Bone scan findings are abnormal in the majority of patients with anterior cruciate ligament deficiency. Three uptake patterns can be distinguished. HYPOTHESIS: Reconstruction corrects the three abnormal bone scan patterns seen in patients with anterior cruciate ligament deficiency. STUDY DESIGN: Prospective cohort study. METHODS: We performed bone scintigraphy in 80 patients, before and 2 years after anterior cruciate ligament reconstruction. RESULTS: Reconstruction consistently corrected type 2 bone scan pattern (meniscus scan) but not type 1 and 3 patterns (osteoarthrosis and cartilage ulcer scan). Correction of all three patterns decreased among patients who had longer duration of anterior cruciate ligament deficiency and was more reliable for the combined uptake of all three patterns among patients who had less than 6 months of deficiency. CONCLUSION: These findings indicate anterior cruciate ligament reconstruction protects the menisci. Reconstruction may be best performed within 6 months after injury.

A potential animal model for creating a controlled and reversible anterior cruciate ligament insufficiency.

We developed and tested a device to manipulate the axial position of the tibial anterior cruciate ligament (ACL) insertion in vitro to create a potential animal model that could simulate both ACL insufficiency and 'optimal' ACL reconstruction. This model is based on the concept that controlled incremental proximal displacement of the tibial ACL insertion simulates ACL insufficiency. Replacing the insertion at the joint level and then adjusting its position until the forces recorded equaled those in the ACL-intact knee can simulate 'optimal' ACL reconstruction. Anterior tibial translation (ATT) was quantified in vitro in 24 sheep cadaver knees with the ACL intact and after the ACL was cut or detached (ACL insufficiency). In 8 knees, a bone plug including the tibial ACL insertion was detached, mounted in a specially designed device, and adjusted to reproduce ATT of the ACL-intact knee. ATT was then measured after proximal displacement of the tibial ACL insertion in calibrated 1 mm increments. The results revealed that detaching the ACL increased ATT by 132-700%. Controlled 3 mm proximal displacement of the insertion using this device increased ATT by more than 100%. Comparing the increase in ATT due to controlled displacement of the ACL insertion to that due to detaching the ACL, in only one case was the same magnitude of ACL insufficiency reproduced. Despite the variability between knees, the device was able to reproduce ATT of the ACL-intact knee and to substantially increase ATT with controlled proximal displacement of the tibial ACL insertion. Use of this device, if successful in an in vivo ACL reconstruction model, could help define any quantitative association between altered joint kinematics and degenerative changes in the joint.

Evolution of the human hip. Part 1: the osseous framework.

Extensive osseous adaptations of the lumbar spine, pelvis, hip and femur characterize the emergence of the human bipedal gait with its 'double extension' of the lumbar spine and hip. To accommodate lumbar lordosis, the pelvis was 'compacted', becoming wider and shorter, as compared with the non-human apes. The hip joint acquired a much more extended position, which can be seen in a broader evolutionary context of verticalization of limbs. When loaded in a predominantly vertical position, the femur can be built lighter and longer than when it is loaded more horizontally because bending moments are smaller. Extension of the hip joint together with elongation of the femur increases effective leg length, and hence stride length, which improves energy efficiency. At the hip joint itself, the shift of the hip's default working range to a more extended position influences concavity at the head-neck junction and femoral neck anteversion.

Mammal hip morphology and function: coxa recta and coxa rotunda.

Using 15 parameters, we provide a systematic description of mammal proximal femoral morphology. We established two types of proximal femoral morphology, termed coxa recta and coxa rotunda, characterized by low versus high concavity of the head-neck junction. Concavity is a measure of the sphericity of the femoral head as it meets the femoral neck that can be quantified by angular measurements. We asked whether the parameter of concavity corresponds with the classification of mammal proximal femoral morphology based on coalesced versus separate ossification patterns and locomotor patterns. Statistical analysis demonstrated a distinction between coxa recta and coxa rotunda with significant differences between the two groups in all but 3 of the 15 parameters examined. We found the most discriminating measurement between mammal hips to be the concavity of the posterior head-neck junction (beta angle). Coxa recta (small concavity) and coxa rotunda (large concavity) relate to the ossification pattern seen in proximal femoral development, and species-specific patterns of locomotion. We interpret the two hip types to reflect optimization for strength (recta) versus mobility (rotunda). Conceptually, both hip types can be recognized in humans, where coxa recta can be related to the development of osteoarthritis.

Coxa recta, coxa profunda and abductor ratio: hip morphology variants compared in an arthroplasty and control population.

Morphology variants of the hip such as coxa recta (aspherical femoral head and/or reduced head-neck concavity) or coxa profunda (overcoverage, or "deep" socket) are associated with cam and pincer impingement respectively, and may ultimately lead to coxarthrosis. Several population studies have documented the prevalence of hip morphotypes, but few studies have examined this prevalence in total hip arthroplasty (THA) patients, or persons without hip symptoms or signs.
We reviewed whether coxa recta and profunda morphotypes were more prevalent in THA patients compared to normal controls. Further, we explored differences in hip abductor mechanism related to hip morphology.
We examined 113 THA patients and 83 normal controls with anteroposterior pelvic and lateral hip radiographs. Coxa recta and profunda were classified with alpha and lateral CE-angle, respectively. The abductor ratio (AR) was measured on AP pelvic radiographs.
Both coxa recta and profunda were more prevalent in THA patients than normal controls (coxa recta: male 42% vs 8%, female 15% vs 5%, respectively and coxa profunda: male 20% vs 1%, female 19% vs 6% respectively). AR was higher in females than males, both in THA patients (1.66 vs 1.47) and normal controls (1.68 vs 1.57). Coxa profunda was associated with a lower AR (1.54 vs 1.61).
The higher prevalence of coxa recta and profunda in arthroplasty patients supports the theory of a role of these morphotypes in the development of coxarthrosis. The higher AR in females signifies the need for increased abductor work. Coxa profunda may be an adaptation to lower the AR.

SUSHI: the Super Simple Hip score for younger patients.

We describe the development of a simple patient-based score for young patients with hip problems which concentrates on activities that are difficult for someone with a hip problem and includes an activity rating scale that measures the highest level of physical activity reached during the past year. We compared the super simple hip score (SUSHI) with the more extensive hip osteoarthritis outcome score (HOOS) and evaluated the validity, sensitivity to change and floor and ceiling effects of the SUSHI score. We found that the SUSHI score is an adequate score to measure hip problems and that this score was preferred to the HOOS score by patients.

[Shoulder surgery using only regional anaesthesia]. / Schouderoperaties onder locoregionale anesthesie.

Effective intra-operative anaesthesia and peri-operative analgesia are important aspects of patient care in orthopaedic surgery. The interscalene regional anaesthetic block technique, performed with the patient lying in a lateral decubitus position, is new for arthroscopic shoulder surgery conducted in the Netherlands. The combination of the interscalene block (without general anaesthesia) and the lateral decubitus position results in better peri-operative conditions for the patient. Better analgesia, increased patient satisfaction and fewer complications in comparison to general anaesthesia have been reported for these types of surgery.