Hip Abductor Function Research Articles

Short-Term Complications of Relative Femoral Neck Lengthening Combined with Extra-Articular Osteotomies of the Proximal Femur.

Relative femoral neck lengthening (RNL) is a newer technique to correct coxa breva and coxa vara to relieve a femoro-acetabular impingement and improve hip abductor function without changing the position of the head on the shaft. Proximal femoral osteotomy (PFO) changes the position of the femoral head relative to the shaft. We studied the short-term complications of procedures that combined RNL with PFO. All hips that underwent RNL and PFO using a surgical dislocation and extended retinacular flap development were included. Hips that were treated only with intra-articular femoral osteotomies (IAFO) were excluded. Hips that underwent RNL and PFO, with IAFO and/or acetabular procedures were included. Intra-operative evaluation of the femoral head blood flow was performed with the drill hole technique. Clinical evaluation and hip radiographs were obtained at 1week, 6weeks, 3months, 6months, 12months and 24months. Seventy two patients (31 males, 41 females, 6-52years of age) underwent 79 combined RNL and PFO. 22 hips underwent additional procedures like head reduction osteotomy, femoral neck osteotomy, and acetabular osteotomies. There were 6 major and 5 minor complications noted. Two hips developed non-unions, both with basicervical varus-producing osteotomies. Four hips developed femoral head ischemia. Two of these hips avoided collapse with early intervention. One hip had persistent abductor weakness requiring hardware removal and three hips, all in boys developed symptomatic widening of the hip on the operated side from varus-producing osteotomy. One hip had asymptomatic trochanteric non-union. RNL is routinely performed by releasing the short external rotator muscle tendon insertion from the proximal femur to raise the posterior retinacular flap. Though this technique protects the blood supply from direct injury, it seems to stretch the vessels with major corrections in the proximal femur. We recommend evaluating the blood flow intraoperatively and postoperatively and taking necessary steps early to decrease the stretch on the flap. It may be safer to avoid raising the flap for major extra-articular proximal femur corrections. The results of this study suggest ways to improve the safety of procedures that combine RNL and PFO.

How to Assess Proximal Femoral Shortening after Nailing of Proximal Femoral Fractures? A Short Review

AbstractProximal femoral fractures (PFFs) are considered one of the most frequent situations faced by orthopaedic surgeons. Many lines of management had been described. Although management of PFFs with cephalomedullary nails (CMNs) is now considered the gold standard with many mechanical and biological advantages, this technique may have some disadvantages such as residual peritrochanteric pain, limping, limited walking distance, and difficulty with stairs. These complications may be attributed to fracture malreduction with shortening, which may result in either malunion or nonunion and ultimately implant failure. The resultant proximal femoral shortening (PFS) with alteration of the proximal femoral mechanics may affect both the hip abductor function and the daily patient activities. The purpose of this short review is to discuss the assessment and secondary effects of PFS after treating femoral fractures with CMNs.

Static and dynamic abductor function are both associated with physical function 1 to 5 years after total hip arthroplasty

BackgroundA subset of total hip arthroplasty patients experience functional impairments past the first postoperative year. Poor hip abductor function is common before and in the early postoperative period. It is not known if abductor impairment is associated with long-term functional impairment. This study evaluated the relationships between static and dynamic abductor function and performance-based and self-reported function >1 year post-total hip arthroplasty. MethodsEighteen adults 1–5 years post-total hip arthroplasty participated. Static and dynamic abductor function were assessed through dynamometry and gait analysis, respectively. Subjects completed four physical performance tests and two self-report instruments. FindingsHigher peak isometric abductor strength was associated with better performance-based function (P ≤ 0.001–0.030) and with self-reported function (P ≤ 0.001–0.012). Higher peak external adduction moment was associated with better results on 3 of 4 performance tests (P = 0.007–0.026). Together, static and dynamic abductor function predicted 35–77% of the variation in physical function. Abductor strength best predicted walking test results and self-reported function, while dynamic abductor function best predicted tests involving sit-to-stand InterpretationStatic and dynamic abductor function were associated with physical function 1–5 years after total hip arthroplasty. These results support further investigation of interventions targeting abductor function for persons experiencing persistent impairments.

Recurrent internal hip rotation gait in cerebral palsy: Case reports of two patients

Internal hip rotation in cerebral palsy (CP) is typically treated with a femoral derotation osteotomy. This has been shown to be largely a successful procedure but recurrence rates up to 41% have been reported. Reported risk factors include younger age, reduced hip joint impulse and ankle plantar-flexion. We report on two patients with bilateral CP demonstrating recurrent unilateral internal hip rotation despite surgical intervention(s). Both demonstrate a number of the reported risk factors for recurrence. In addition, this case report specifically compared gait kinematic patterns pre and post recurrence. On comparing both patient’s hip rotation and ankle dorsi/plantarflexion kinematics they are seen to be almost identical both pre-operatively and post-operatively. Both patients appear to revert to approximately 30o of internal hip rotation which has been shown to maximise hip abductor function. Therefore, this case report suggests that surgical derotation in isolation is unlikely to be successful in this group and we suggest that this hip and ankle pattern may help predict recurrence in unilateral internal hip rotation.

Surgical repair of gluteus medius muscle in hip replacement surgery

Injury of gluteus medius muscle is a serious often complication after hip replacement surgery followed by pain, claudication and significant deterioration of the quality of life. Prevention of intraoperative injury of this muscle is especially relevant in young patients. Normal function of this muscle provides rapid rehabilitation and early postoperative recovery. However, hip replacement surgery through Hardinge's direct lateral approach is accompanied by fatty degeneration of gluteus medius muscle in 12-20% of cases. Moreover, two or more redo procedures lead to fatty degeneration of almost 70% of anterior and 40% of central muscular segment. Currently, there are many methods of surgical treatment of this complication including transosseous muscle fixation, endoscopic procedures, repair using Achilles tendon, gluteus maximus muscle, lateral head of quadriceps muscle and allografts. However, various publications devoted to this problem have certain disadvantages including short follow-up period, small sample size and often unsatisfactory outcomes. Therefore, the question of surgical repair of hip abductor function remains open.

Testing the Hip Abductor Muscle Strength of Older Persons Using a Handheld Dynamometer.

Objective:To investigate the reliability of a clinically applicable method of dynamometry to assess and monitor hip abductor muscle strength in older persons.Design:Bilateral isometric hip abductor muscle strength measured with a handheld dynamometer, patients supine with the contralateral hip positioned directly against a wall for stabilization. Reliability determined by comparing intra-assessor and inter-assessor results and comparison to a criterion standard (stabilized dynamometer with patients in the standing position).Setting:UniSA Nutritional Physiology Research Centre.Participants:Twenty-one patients older than 65 years were recruited from the Royal Adelaide Hospital.Main Outcome Measures:Intraclass correlation coefficients (ICCs), bias, and limits of agreement calculated to determine reliability.Results:Intra-assessor and inter-assessor ICCs were high (0.94 and 0.92-0.94, respectively). There was no intra-assessor bias and narrow limits of agreement (±2.4%). There was a small inter-assessor bias but narrow limits of agreement (0.6%-0.9% and ± 2.3%, respectively). There was a wide variation comparing results to the criterion standard (±5.0%-5.2% limits of agreement), highlighting problems attributed to difficulties that the test population had with the standing position used in the criterion standard test.Conclusions:Testing older persons’ hip abductor muscle strength while in the supine position with optimal pelvic stabilization using a handheld dynamometer is highly reliable. While further studies must be done to assess patients with specific pathologies, this test has potential application to monitor and evaluate the effects of surgical interventions and/or rehabilitation protocols for a variety of conditions affecting hip abductor function such as hip fractures and arthritis.

Sex-specific hip osteoarthritis-associated gait abnormalities: Alterations in dynamic hip abductor function differ in men and women

BackgroundHip osteoarthritis results in abnormal gait mechanics, but it is not known whether abnormalities are the same in men and women. The hypothesis tested was that gait abnormalities are different in men and women with hip osteoarthritis vs. sex-specific asymptomatic groups. Methods150 subjects with mild through severe radiographic hip osteoarthritis and 159 asymptomatic subjects were identified from an Institutional Review Board-approved motion analysis data repository. Sagittal plane hip range of motion and peak external moments about the hip, in all three planes, averaged from normal speed walking trials, were compared for men and women, with and without hip osteoarthritis using analysis of variance. FindingsThere were significant sex by group interactions for the external peak hip adduction and external rotation moments (P=0.009–0.045). Although asymptomatic women had peak adduction and external rotation moments that were respectively 12% higher and 23% lower than asymptomatic men (P=0.026–0.037), these variables did not differ between men and women with hip osteoarthritis (P≥0.684). The osteoarthritis vs. asymptomatic group difference in the peak hip adduction moment was 45% larger in women than in men. The osteoarthritis vs. asymptomatic group difference in the peak hip external rotation moment was 55% larger for men than for women (P<0.001). Sex did not influence the association between radiographic severity and gait variables. InterpretationNormal sex differences in gait were not seen in hip osteoarthritis. Sex-specific adaptations may reflect different aspects of hip abductor function. Men and women with hip osteoarthritis may require different interventions to improve function.

Hominin Hip Biomechanics: Changing Perspectives

The shape of the human pelvis reflects the unique demands placed on the hip abductor muscles (gluteus medius and gluteus minimus), which stabilize the body in the frontal plane during bipedal locomotion. This morphological shift occurred early in hominin evolution, yet important shape differences between hominin species have led to significant disagreement about abductor function and locomotor capability in these extinct taxa. A static biomechanical model that relies on a close association between skeletal measurements of the pelvis and femur has traditionally been used to reconstruct hip biomechanics in these species. However, experimental biomechanical approaches have highlighted the dynamic nature of mediolateral balance in walking and running, challenging the assumptions of the static hip model. This article reviews traditional approaches for understanding hip abductor function, shows how they have been applied to the fossil hominin record, and discusses new techniques that integrate the dynamic nature of mediolateral balance during human locomotion. Anat Rec, 300:932-945, 2017. © 2017 Wiley Periodicals, Inc.

Hip biomechanics during stair ascent and descent in people with and without hip osteoarthritis.

Hip osteoarthritis (OA) is often associated with pain and impaired function. Understanding biomechanical alterations in patients with hip OA during challenging activities such as stair use is important to inform treatments. The aim of this study was to determine whether kinematics and kinetics during stair ambulation differed between people with hip OA and healthy controls. Fifteen participants with symptomatic and radiographic hip OA and 15 asymptomatic healthy controls underwent 3-D motion analysis during stair ascent and descent. Trunk, pelvis, and hip kinematics as well as hip kinetics were evaluated. Analyses were performed unadjusted and adjusted for speed and leg length. In both the unadjusted and adjusted analyses, participants with hip OA ascended stairs with less hip range of motion in all three planes and a lower peak external rotation moment compared to controls. In the unadjusted analysis, hip OA participants descended stairs with greater ipsilateral trunk lean, less sagittal plane range of motion, lower peak extension moment, lower peak external rotation moment, and greater hip adduction moment impulse compared to controls. In the adjusted results, peak internal rotation moment and hip adduction moment impulse were greater in hip OA participants compared to controls. Findings show that individuals with hip OA display limited range of hip joint movement, particularly during stair ascent, and overall indicate the use of strategies (e.g., trunk lean; lower peak external rotation moment; higher adduction moment impulse) that implicate altered hip abductor function. Future research is required to further understand the implications of these findings on hip OA. © 2017 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 35:1505-1514, 2017.

The strength and function of hip abductors following anterolateral minimally invasive total hip arthroplasty

ObjectiveTo analyze the extent of postoperative hip abductor insufficiency in primary total hip arthroplasty (THA) patients undergoing anterolateral minimally invasive (ALMI) approach, and to investigate whether the clinical outcomes are more favorable in femoral neck fracture (FNF) patients than in non-femoral neck fracture (nFNF) patients. MethodsA total of 48 patients were enrolled in this study. Each patient underwent a clinical examination preoperatively and 6, 12, 24 and 48 weeks postoperatively. The abductor torque, Trendelenburg’s sign, gait velocity, Harris hip score, Oxford hip score, Westren Ontario and McMaster Universities (WOMAC) score and visual analog scale pain score were recorded. Statistical evaluation was performed with SPSS software version 18.0. The significance level was set at P<0.05. ResultsThe abductor torque of the operated hip and the recovery ratio showed a gradual improving tendency from 6 weeks postoperatively until the last follow-up. Gait velocity, Harris hip score, Oxford hip score and WOMAC score improved significantly after the operation until 24 weeks postoperatively. In the FNF group, the abductor torque of the operated side and the recovery ratio were significantly higher than in nFNF group at 6 weeks postoperatively, however, as time passed, this trend tended to disappear. ConclusionThis study demonstrates that patients can obtain good abductor strength and function in the early postoperative period and the hip abductor function of patients who suffer from hip osteoarthritis, rheumatoid arthritis, avascular necrosis of the femoral head could be significantly improved following ALMI THA.

A model dilemma: how assumptions about locomotion and birth have shaped the obstetrical dilemma (335.1)

The obstetrical dilemma posits that the human female pelvis is under antagonistic selection pressures: narrow enough for efficient locomotion, but large enough to pass a large‐brained infant through the birth canal. This adaptive trade‐off is thought to explain the apparent difficulty of human childbirth, the helplessness of human neonates, and sex differences in human locomotor performance. However, core assumptions of the obstetrical dilemma model have gone untested. One assumption, that wider pelves in women increase locomotor cost, is based on a static biomechanical model of hip abductor function. Wider biacetabular width is thought to increase the external torque about the hip by moving the body center of mass farther from the hip joint, thereby increasing hip abductor muscle force and energetic cost to stabilize the pelvis. However, skeletal dimensions are actually poor proxies for the mechanical determinants of hip abductor function measured during locomotion and do not correlate significantly with locomotor cost. While this first assumption of the obstetrical dilemma can be empirically rejected, it is harder to directly assess the bases for and evolutionary history of cephalopelvic disproportion (CPD) that uniquely imperils human birth. A novel hypothesis to be tested suggests that recent environmental conditions have made CPD more common today than through most of human evolutionary history.Grant Funding Source: National Science Foundation BCS#0850841, The Leakey Foundation, The Wenner‐Gren Foundation

Hip abductor function in individuals with medial knee osteoarthritis: Implications for medial compartment loading during gait

BackgroundHip abductor muscles generate moments of force that control lower extremity frontal plane motion. Strengthening these muscles has been a recent trend in therapeutic intervention studies for knee osteoarthritis. The current study investigated the relationship between hip abductor muscle function (strength and activation) and the net external knee adduction moment during gait in those with medial compartment knee osteoarthritis. Methods54 individuals with moderate knee osteoarthritis walked at their self-selected velocity while gluteus medius electromyograms, segment motions and ground reaction forces were recorded. Net external knee adduction moment (KAM) and linear enveloped electromyographic profiles were calculated. Peak KAM was determined and then principal component analyses (PCA) were applied to KAM and electromyographic profiles. Isometric hip abductor strength, anthropometrics and gait velocity were measured. Multiple regression models evaluated the relationship between walking velocity, hip abductor strength, electromyographic variables recorded during gait and KAM waveform characteristics. FindingsMinimal peak KAM variance was explained by abductor strength (R2=9%, P=0.027). PCA-based KAM waveform characteristics were not explained by abductor strength. Overall gluteus medius amplitude (PP1-scores) was related to a reduction in the bi-modal KAM (PP3-scores) pattern (R2=16%, P=0.003). InterpretationThere was no clear relationship between hip abductor muscle strength and specific amplitude and temporal KAM characteristics. Higher overall gluteus medius activation amplitude was related to a sustained KAM during mid-stance. 84 to 90% of the variance in KAM waveform characteristics was not explained by hip abductor muscle function showing hip abductor muscle function has minimal association to KAM characteristics.

Association between hip abductor function, rear-foot dynamic alignment, and dynamic knee valgus during single-leg squats and drop landings

BackgroundPreventing anterior cruciate ligament (ACL) injuries is very important for athletes, and dynamic knee valgus is considered a risk factor for non-contact ACL injury. However, little is known about whether the functions of the hip abductor and rear-foot increase dynamic knee valgus. A two-dimensional (2D) video-based screening test focused on hip abductor and rear-foot functions among factors involved in dynamic knee valgus. The present study determined associations between hip and rear-foot dynamic alignment and dynamic knee valgus. MethodsThis cross-sectional study recruited 130 female basketball players (258 legs) from nine high-school teams. The players performed single-leg squats and single-leg drop landings to provide knee-in (KID) and hip-out (HOD) distances on 2D video images. Hip and rear-foot dynamic alignment was evaluated using a dynamic Trendelenburg test (DTT) and a dynamic heel-floor test (HFT). ResultsThe Chi-square test revealed no significant difference in the prevalence of DTT-positivity between single-leg squats (28.7%) and single-leg drop landings (23.3%). The prevalence of HFT-positivity was significantly greater during landings (51.4%) than during single-leg squats (31.0%, p < 0.01). The KID values for both single-leg squats and single-leg drop landings were greater in the DTT-positive than in the DTT-negative group (15.1 ± 5.4 cm and 20.2 ± 7.5 cm, p < 0.001). The HOD values were similarly greater in the DTT-positive group (15.2 ± 1.9 cm and 17.6 ± 2.8 cm, p < 0.001). The KID values for both single-leg squats and single-leg drop landings were greater in the HFT-positive than in the HFT-negative group (12.2 ± 5.1 cm, p < 0.01; 14.7 ± 7.2 cm, p < 0.001), whereas HOD values for these tasks did not significantly differ between the two groups. ConclusionDynamic hip mal-alignment might be associated with both greater KID and HOD, whereas rear-foot eversion is associated only with greater KID. Hip abductor and rear-foot dysfunction are important factors for dynamic knee valgus and thus evaluating DTT and HFT will help to prevent dynamic knee valgus.

Relationships Among Performance of Lateral Cutting Maneuver From Lateral Sliding and Hip Extension and Abduction Motions, Ground Reaction Force, and Body Center of Mass Height

Basketball players have to move laterally and quickly change their movement directions, especially during defensive moves. This study aimed to investigate how frontal and sagittal plane hip movements relate to fastness and quickness of lateral cutting maneuvers from sliding. Three-dimensional biomechanical data were obtained for 28 female college basketball players while they performed lateral cutting maneuvers using their left leg after 2 lateral sliding steps. The lateral cutting index (LCIndex) expressing fastness and quickness of lateral cutting maneuvers, peak hip abduction and extension velocities immediately before foot contact, hip abduction and extension velocities at foot contact, peak horizontal ground reaction force, frontal plane ground reaction force angle, and sacrum center of mass position were calculated. Simple and stepwise regression analyses were conducted to predict LCIndex. The former showed that greater maximum hip extension velocity (p = 0.03) and lesser hip abduction velocity (p = 0.04) as well as smaller ground reaction force angle (p = 0.001) and lower sacrum center of mass position (p = 0.001) at foot contact led to better LCIndex. The latter showed that sacrum center of mass position at foot contact and hip extension velocity explained 35.3% (p < 0.01) and 7.3% (p = 0.088) of variance in LCIndex, respectively. Our results did not suggest that hip abductor function is important for lateral sliding moves, instead suggesting that faster hip extension motions to kick the ground and lowering the body center of mass are crucial for better lateral deceleration-acceleration motions.

HIP abductor function in individuals with knee osteoarthritis: implications for medial compartment loading during gait

Purpose: Hip abductor muscles generate moments of force that control lower extremity coronal plane motion. Strengthening these muscles has been a recent trend in therapeutic intervention studies for knee osteoarthritis based on the theory that hip abductor strength influences knee joint loading. The current study investigated the relationship between hip abductor muscle function (strength and activation) and the net external knee adduction moment during gait in those with medial compartment knee osteoarthritis. Methods: 54 individuals with moderate knee osteoarthritis walked at their self-selected velocity while gluteus medius electromyograms, lower extremity segment motions and ground reaction forces were recorded. The net external knee adduction moment (KAM) was calculated and amplitude normalized to body mass. Linear enveloped electromyographic profiles were generated and amplitude normalized to maximal voluntary isometric contraction amplitudes. Peak KAM was determined. Principal component analyses were applied to the KAM and electromyographic profiles. Hip abductor strength, subject anthropometrics and gait velocity were measured. Multiple regression models evaluated the relationship between anthropometric, velocity, strength and electromyographic variables and the KAM waveform characteristics. Statistical significance was determined at alpha = 0.05. Results: A significant positive relationship was found between hip abductor strength and peak KAM (R2=16%, P=0.003). Walking velocity, early stance phase gluteus medius activity (PP2-scores) and height were positively associated with an increased difference between early and late stance KAM (PP2-scores)(R2=60%, P<0.001). Greater overall gluteus medius amplitudes were positively related to greater mid-stance net adduction moments (PP3-scores) (R2=16%, P=0.003). Conclusions: Hip abduction muscle strength and gluteus medius activation characteristics explained significant variability in specific KAM variables during gait in individuals with moderate knee osteoarthritis. However; a large percentage of the variability was not explained by these variables, thus altering hip muscle function is only one small contributor to KAM characteristics.

Time course and extent of functional recovery during the first postoperative year after minimally invasive total hip arthroplasty with two different surgical approaches—a randomized controlled trial

While others have reported short-term comparisons between various minimally invasive surgical (MIS) approaches to total hip arthroplasty (THA) and their conventional analogues, longer-term data is lacking, as is information indicating whether MIS approaches to THA provide a biomechanically complete recovery. Furthermore, different MIS approaches have not been compared. Our approaches of interest were a one-incision modified Watson-Jones, and a two-incision approach. Hypotheses: (1) There are significant differences in gait recovery patterns between the two surgical groups and (2) THA subjects have significant differences in function one year after surgery compared to control subjects. To test these hypotheses, THA candidates ( n=26) were randomized to receive one of these MIS approaches and evaluated preoperatively, and postoperatively at 3 weeks, and at 3, 6 and 12 months. Evaluations included three-dimensional gait analysis and 24-hour step-counts. The same data were obtained from 25 control subjects. Recovery time-course was assessed using repeated measures ANOVA. T-tests were used to compare controls with the pooled group of THA subjects. We found no differences between the two THA surgical groups regarding the time-course of recovery ( p≥0.591). Although recovery was statistically complete by 3 months postoperatively for all variables, there were significant differences from controls at 12 months. Most notably, the external hip adduction moment, which reflects hip abductor function, was more than one standard deviation below normal ( p<0.001). THA subject inactivity could not explain the gait differences, since one year after surgery daily step counts were not significantly different from controls ( p=0.346). More work is necessary to determine ways to improve biomechanical outcomes for today’s patients with high expectations for function and implant longevity.

Enhancing Soft Tissue Ingrowth in Proximal Femoral Arthroplasty With Aortograft Sleeve: A Novel Technique and Early Results

Hip abductor function is critical to joint stability after proximal femoral arthroplasty. Normal soft tissue relationships are often violated during this procedure for complete tumor resection. Abductor insufficiency leads to abnormal gait mechanics and poor function. To improve soft tissue stability about a metallic proximal femoral endoprosthesis, we devised a novel use of vascular graft material. Two patients received a proximal femoral arthroplasty using this technique. These patients were followed for an average of 26.5 months. They demonstrated mean active hip abduction of 48°, hip flexion of 90°, mean Musculoskeletal Tumor Society score of 24 (80%), and Toronto Extremity Salvage Score of 80. We believe that this technique may be useful in achieving soft tissue stability about a metal endoprosthesis and may facilitate better function in patients undergoing this surgery.

Experimentally reduced hip abductor function during walking: Implications for knee joint loads

Hip and knee functions are intimately connected and reduced hip abductor function might play a role in development of knee osteoarthritis (OA) by increasing the external knee adduction moment during walking. The purpose of this study was to test the hypothesis that reduced function of the gluteus medius (GM) muscle would lead to increased external knee adduction moment during level walking in healthy subjects. Reduced GM muscle function was induced experimentally, by means of intramuscular injections of hypertonic saline that produced an intense short-term muscle pain and reduced muscle function. Isotonic saline injections were used as non-painful control. Fifteen healthy subjects performed walking trials at their self-selected walking speed before and immediately after injections, and again after 20 min of rest, to ensure pain recovery. Standard gait analyses were used to calculate three-dimensional trunk and lower extremity joint kinematics and kinetics. Surface electromyography (EMG) of the glutei, quadriceps, and hamstring muscles were also measured. The peak GM EMG activity had temporal concurrence with peaks in frontal plane moments at both hip and knee joints. The EMG activity in the GM muscle was significantly reduced by pain (−39.6%). All other muscles were unaffected. Peaks in the frontal plane hip and knee joint moments were significantly reduced during pain (−6.4% and −4.2%, respectively). Lateral trunk lean angles and midstance hip joint adduction and knee joint extension angles were reduced by ⩽1°. Thus, the gait changes were primarily caused by reduced GM function. Walking with impaired GM muscle function due to pain significantly reduced the external knee adduction moment. This study challenge the notion that reduced GM function due to pain would lead to increased loads at the knee joint during level walking.

Explaining the hip adduction moment variability during gait: Implications for hip abductor strengthening

Background There is emerging interest in hip abductor function during gait and its potential relationship to knee joint pathology. During gait, the hip abductor muscles are primarily responsible for generating moments of force to control frontal plane movement. The current study investigated the relationship between hip abductor muscle function and frontal plane hip moments of force during gait. Methods Frontal plane hip moments of force and electromyographic features of gluteus medius were measured during walking in 22 healthy individuals. Hip abductor strength, subject anthropometrics and gait velocity were recorded. Multiple regression models were used to evaluate the relationship between the anthropometric, velocity, strength and electromyographic variables and the initial and mid-stance magnitude of the hip adduction moment. Findings A positive relationship was found between the initial peak moment (Nm), and both body mass and gait speed ( R 2 = 90%). Body mass (positive) and hip abductor strength (negative) explained significant levels of mid-stance magnitude variability ( R 2 = 62.5%). Gait speed (positive) explained significant levels of variability in the normalized initial peak moment (Nm/kg) ( R 2 = 52%). No variables were included in the normalized mid-stance moment model ( P > 0.05). Interpretation Body mass was the key factor associated with high hip adduction moments during initial and mid-stance of the gait cycle. Increased gait velocity was associated with higher initial peaks and higher muscle strength was associated with lower mid-stance magnitude of the external hip adductor moment during walking. These findings suggest that in a healthy adult population, hip abductor strength and activation were not directly related to the hip adduction moment magnitude during gait.

Shortening after Femoral Neck Fracture Fixation

When using parallel screws for treatment of femoral neck fractures, shortening of the femoral neck might occur. Given the high revision surgery rates associated with parallel screws, we developed a questionnaire to explore (1) surgeons' viewpoints on difficulties in the fixation of femoral neck fractures, (2) their perception of the clinical importance of femoral neck shortening after internal fixation, and (3) their opinions regarding the ideal fixation device. Two hundred three surgeons responded. Eighty-three percent believed shortening of the femoral neck is common after screw fixation of femoral neck fractures; 89% believed shortening limits hip abductor function; and 69% believed shortening limits patients' physical function. When asked for features of the ideal implant for treatment of a femoral neck fracture, allowing compression across the fracture site on insertion and providing angular stability with a fixed-angle device to minimize shortening of the femoral neck were favored by 89% and 79% of the respondents, respectively. A plate with multiple nonparallel lag screws that can be locked into the plate might be a solution. However, the findings of this study are surgeons' opinions, which may or may not be confirmed by scientific evidence.