An anatomic consideration of the femoral nerve during direct anterior hip approach: A cadaveric study.

PURPOSE: This study aimed to investigate the distance and correlation between the anatomy of the anterior side of the hip joint and the femoral nerve. METHODS: Using ten fresh-frozen cadavers with twenty hip joints. We dissected and marked the femoral nerve in the inguinal area. Employing the direct anterior approach, we identified and marked study points, including the superior and inferior points of the anterior rim of the acetabulum, » point, half point, and ¾ point along an imagined line connecting the formers, the inferomedial and mid aspect of the femoral neck, and the soft spot. Coronal plane measurements gauged the distance between these points and the femoral nerve. The collected data were analyzed to assess the distance and correlation. RESULTS: In the coronal plane, the median distance between the inferior point of the anterior rim of the acetabulum and the femoral nerve was 0 millimeters (interquartile range [IQR] 0-0). Likewise, the median distance between the mid aspect of the medial side of the femoral neck and the femoral nerve was 0 millimeters (IQR 0-0). Additionally, the mean distance between the soft spot and the femoral nerve was 1.18 cm (SD 0.63). CONCLUSION: Surgeons approaching the hip joint via the direct anterior approach should be cautious at the inferior point of the anterior rim of the acetabulum and the mid aspect of the femoral neck. The soft spot at the anterior rim of the acetabulum remains safe from direct injury when surgeons use the correct technique during anterior retractor insertion.

Intramuscular innervation of the tensor fasciae latae: Application to total hip arthroplasty.

The aims of this study were to clarify the extra- and intramuscular branching patterns of the tensor fasciae latae (TFL) with reference to surface landmarks on the thigh and to thus suggest a safe approach for total hip arthroplasty. Sixteen fixed and four fresh cadavers were dissected and subjected to the modified Sihler's staining method to reveal the extra- and intramuscular innervation patterns, and the findings were matched with surface landmarks. The landmarks were measured from the anterior superior iliac spine (ASIS) to the patella and divided into 20 parts along the total length. The average vertical length of the TFL was 15.92 ± 1.61 cm, which was 38.79 ± 2.73% when converted to a percentage. The entry point of the superior gluteal nerve (SGN) was an average of 6.87 ± 1.26 cm (16.71 ± 2.55%) from the ASIS. In all cases, the SGN entered parts 3-5 (10.1%-25%). As the intramuscular nerve branches traveled distally, they had a tendency to innervate more deeply and inferiorly. In all cases, the main SGN branches were intramuscularly distributed in parts 4 and 5 (15.1%-25%). Most tiny SGN branches were found inferiorly in parts 6 and 7 (25.1%-35%). In three of 10 cases, very tiny SGN branches were observed in part 8 (35.1%-38.79%). We did not observe SGN branches in parts 1-3 (0%-15%). When information on the extra- and intramuscular nerve distributions was combined, we found that the nerves were concentrated in parts 3-5 (10.1%-25%). We propose that damage to the SGN can be prevented if parts 3-5 (10.1%-25%) are avoided during surgical treatment, particularly during the approach and incision.

Sciatic nerve movement in the deep gluteal space during hip rotations maneuvers.

We hypothesize that the sciatic nerve in the subgluteal space has a specific behavior during internal and external coxofemoral rotation and during isometric contraction of the internal and external rotator muscles of the hip. In 58 healthy volunteers, sciatic nerve behavior was studied by ultrasound during passive internal and external hip rotation movements and during isometric contraction of internal and external rotators. Using MATLAB software, changes in nerve curvature at the beginning and end of each exercise were evaluated for longitudinal catches and axial movement for transverse catches. In the long axis, it was observed that during the passive internal rotation and during the isometric contraction of external rotators, the shape of the curve increased significantly while during the passive external rotation and the isometric contraction of the internal rotators the curvature flattened out. During passive movements in internal rotation, on the short axis, the nerve tended to move laterally and forward, while during external rotation the tendency of the nerve was to move toward a medial and backward position. During the isometric exercises, this displacement was less in the passive movements. Passive movements of hip rotation and isometric contraction of the muscles affect the sciatic nerve in the subgluteal space. Retrotrochanteric pain may be related to both the shear effect of the subgluteus muscles and the endoneural and mechanosensitive aggression to which the sciatic nerve is subjected.

Anatomic Relationship of the Femoral Neurovascular Bundle in Patients With Congenital Femoral Deficiency.

BACKGROUND: Congenital femoral deficiency (CFD) is a rare condition that affects the morphology of the hip and surrounding soft tissues. Bony deformity and distorted muscular anatomy are well known, but no studies have described the relationship of the femoral neurovascular (NV) bundle to surgically relevant anatomic landmarks. The authors compared the location of the femoral NV bundle on the affected side in patients with CFD with the unaffected side. The authors hypothesized that the bundle on the pathologic side would be in an abnormal position relative to the unaffected side. METHODS: Thirty-three patients diagnosed with unilateral CFD who had undergone preoperative magnetic resonance imaging of the pelvis were included in our study. The authors identified the femoral NV bundle on the axial cuts and measured its distance from the anterior superior iliac spine (ASIS), anterior inferior iliac spine (AIIS), and lesser trochanter (LT). Anatomic percent change and absolute measurements were then compared and correlated with associated boney deformities and the Paley classification. RESULTS: The distance from the femoral NV bundle to the ASIS, AIIS, and LT was significantly different compared with the unaffected side. The AIIS absolute distance and AIIS percent change significantly correlated with the neck-shaft angle of the proximal femur. CONCLUSIONS: In patients with CFD, the femoral NV bundle seems to be further from the LT and closer to the AIIS on the affected side when compared with the unaffected side. magnetic resonance imaging may be helpful to understand the course of the femoral NV bundle before reconstruction in patients with CFD; however, the authors recommend identification of the femoral NV bundle before transection of the proximal rectus femoris tendon to provide safe surgical care. LEVEL OF EVIDENCE: Level IV-case-control study of diagnostic studies.

Minimally Invasive Therapies for Osteoarthritic Hip Pain: a Comprehensive Review.

PURPOSE OF REVIEW: Osteoarthritis (OA) is a highly prevalent cause of chronic hip pain, affecting 27% of adults aged over 45 years and 42% of adults aged over 75 years. Though OA has traditionally been described as a disorder of "wear-and-tear," recent studies have expanded on this understanding to include a possible inflammatory etiology as well, damage to articular cartilage produces debris in the joint that is phagocytosed by synovial cells which leads to inflammation. RECENT FINDINGS: Patients with OA of the hip frequently have decreased quality of life due to pain and limited mobility though additional comorbidities of diabetes, cardiovascular disease, poor sleep quality, and obesity have been correlated. Initial treatment with conservative medical management can provide effective symptomatic relief. Physical therapy and exercise are important components of a multimodal approach to osteoarthritic hip pain. Patients with persistent pain may benefit from minimally invasive therapeutic approaches prior to consideration of undergoing total hip arthroplasty. The objective of this review is to provide an update of current minimally invasive therapies for the treatment of pain stemming from hip osteoarthritis; these include intra-articular injection of medication, regenerative therapies, and radiofrequency ablation.

A Review of Current Denervation Techniques for Chronic Hip Pain: Anatomical and Technical Considerations.

PURPOSE OF REVIEW: Percutaneous radiofrequency (RF) denervation of articular sensory nerves of the hip joint is a minimally invasive neurotomy technique that can provide pain relief in patients with chronic hip pain. There has been an increase in the number of publications on RF denervation of the hip over the last few years although many questions remain regarding anatomical targets, technical aspects, selection criteria, and evidence for effectiveness. RECENT FINDINGS: For this updated review, publications were identified by searching MEDLINE and other medical literature databases from inception through November 30, 2018. Existing knowledge of hip joint innervation was reviewed and data on patient selection, prognostication of analgesic benefit from ablation by using local anesthetic blocks, current techniques of performing hip joint ablation, analgesic success, functional outcomes, and adverse effects were critically reviewed and analyzed. Sensory denervation of the anterior hip joint using RF current is a viable treatment option for management of chronic hip pain after conservative methods fails to do so. We have synthesized knowledge from papers on techniques of ablation and from recently elaborated anatomical details. We also provide suggestions regarding anticipated outcomes of the procedure. Our review of existing literature indicates evidence for analgesic benefits, improvement in function, and a low incidence of adverse effects of RF ablation of sensory innervation to the hip joint. Future research should focus on refining the technique of ablation and monitoring of long-term outcomes.

Applications and critical evaluation of fascia iliaca compartment block and quadratus lumborum block for orthopedic procedures.

Anterior section of the hip joint capsule is innervated by femoral nerve and obturator nerve, and posterior section is innervated by the nerve to quadratus femoris muscle and occasionally by the superior gluteal (posterolateral region) and sciatic nerve (posterosuperior region). One of the regional anesthesia options for hip surgery is the fascia iliaca compartment block (FICB) that affects nerves important for hip innervation and sensory innervation of the thigh - femoral, obturator and lateral femoral cutaneous nerve. FICB can be easily performed and is often a good solution for management of hip fractures in emergency departments. Its use reduces morphine pre-operative requirement for patients with femoral neck fractures and can also be indicated for hip arthroplasty, hip arthroscopy and burn management of the region. Quadratus lumborum block (QLB) is a block of the posterior abdominal wall performed exclusively under ultrasound guidance, with still unclarified mechanism of action. When considering hip surgery and postoperative management, the anterior QLB has shown to reduce lengthy hospital stay and opioid use, it improves perioperative analgesia in patients undergoing hip and proximal femoral surgery compared to standard intravenous analgesia regimen, provides early and rapid pain relief and allows early ambulation, thus preventing deep vein thrombosis and thromboembolic complications etc. However, some nerve branches responsible for innervation of the hip joint are not affected by QLB, which has to be taken into consideration. QLB has shown potential for use in hip surgery and perioperative pain management, but still needs to be validated as a reliable treatment approach.

Pudendal nerve injury is a relatively common but transient complication of hip arthroscopy.

PURPOSE: Hip arthroscopy is emerging as the standard of care for conditions involving the hip, and has a unique set of complications. The purpose of this review was to identify (1) the crude rate of pudendal nerve injury following hip arthroscopy and (2) the specific factors leading to pudendal nerve injury. METHODS: MEDLINE, EMBASE, and PubMed were searched from database inception to October 2016. Patient demographics, indications, surgical technique, complication rates, treatment approaches, and rehabilitation strategies were extracted. RESULTS: Twenty-four studies (n = 3405) were included, with the majority (66%) of studies being level IV evidence. The mean age was 33.9 ± 9.7 years (range 12-78) and 48.2% were males. Average follow-up was 30.2 ± 19.1 months. 62 patients were reported to have sustained pudendal nerve injury (1.8%) post-operatively, and all resolved within 6 weeks to 3 months. Of the seven studies that reported using a perineal post, 20 patients were diagnosed with pudendal nerve injury (4.3%), in contrast to two studies (189 patients) reporting only 0.5% pudendal nerve injury without the use of perineal post. Two studies commented on time of traction during surgical intervention with mean times of 98 and 68 min with complication rates of 10% and 6.6%, respectively. CONCLUSIONS: Pudendal nerve injury is not uncommon following hip arthroscopy, with a reported rate found in this review of 1.8%. Potential risk factors may include the use of a perineal post and long traction times. All reported cases resolved within 3 months. Patients should be informed of complications related to pudendal nerve injury, which include sexual and urinary dysfunction. LEVEL OF EVIDENCE: Level IV, systematic review of level I-IV studies.

Anatomical study of the articular branches innervated the hip and knee joint with reference to mechanism of referral pain in hip joint disease patients.

INTRODUCTION: Referred pain in the anterior knee joint is the most common symptom in hip disease patients. The development of referred pain is considered to be related to dichotomizing peripheral sensory fibers. However, no gross anatomical findings identify any dichotomizing fibers innervating both the hip and knee joints. We dissected the femoral and obturator nerves in human cadavers to investigate the distribution of the articular branches in the hip and knee joints. Fourteen embalmed left lower limbs from 14 Japanese adult cadavers (five from females, nine from males, average age 73.8 ± 14.1 years) were observed macroscopically. The articular branches of the femoral and obturator nerves were dissected at the anterior margin of the groin toward the thigh region. After dissections of the articular nerves of the hip joints, the femoral and obturator nerves were exposed from proximally to distally to identify the articular nerves of the knee joints. The branching pattern of the articular branches in the hip and knee joints was recorded. In six of 14 limbs (42.9%), the femoral nerve supplied articular branches to the anteromedial aspect of both the hip and knee joints. These articular branches were derived from the same bundle of femoral nerve. These gross anatomical findings suggested that dichotomizing peripheral sensory fibers innervate the hip and knee joints and these could relate to the referred pain confirmed in the anterior knee joints of patients with hip disease. Clin. Anat. 31:705-709, 2018. © 2018 Wiley Periodicals, Inc.

Effect of hip and knee position on nerve conduction in the common fibular nerve.

INTRODUCTION: The aim of this study was to measure the influence that hip and knee position have on routine fibular motor nerve conduction studies. METHODS: Healthy subjects under age 40 were recruited (n = 24) to have fibular nerve conduction studies completed in various positions, using hip extension-knee extension as a control. RESULTS: A mean increase in conduction velocity of 2.5 m/s across the knee (P = 0.020) was seen during hip flexion compared with hip extension. A mean decrease in velocity of 1.6 m/s through the leg segment (P = 0.016) was seen during knee flexion compared with knee extension. CONCLUSIONS: This study shows that the optimal position of the leg during fibular nerve studies is with the hip in flexion and knee in extension, to more accurately reflect nerve length for velocity calculations. This may have implications for other peripheral nerves with respect to proximal joint position affecting calculated velocity. Muscle Nerve 56: 519-521, 2017.

Technical success of the ultrasound-guided supra-inguinal fascia iliaca compartment block in older children and adolescents for hip arthroscopy.

BACKGROUND: Hip arthroscopic surgery is performed on older pediatric patients. Fascia iliaca compartment block has proven efficacy in providing analgesia following hip surgery and can be performed with target location of local anesthetic below or above the inguinal ligament. The reported success of ultrasound-guided infra-inguinal fascia iliaca compartment block is lower when compared to traditional landmark technique, while the reliability of supra-inguinal fascia iliaca compartment block is unreported. AIM: The primary aim was to report the results in obtaining sensory changes in the distribution of the femoral and lateral femoral cutaneous nerves following supra-inguinal fascia iliaca compartment block in patients undergoing arthroscopic hip surgery. Secondary outcomes are the ability to find echogenic landmarks and to report pain scores and opioid consumption. METHODS: We reviewed the electronic medical record and regional anesthesia database of patients receiving ultrasound-guided fascia iliaca compartment block for arthroscopic hip surgery. Sensory changes to the femoral and lateral femoral cutaneous nerves were determined. Identification of echogenic landmarks was quantified. Pain scores and opioid consumption were determined. RESULTS: Seventeen patients of mean age 15.4 years old (SD 1.3; range 13-17 years) were included. Sensory changes to both the femoral and lateral femoral cutaneous nerves occurred in 94% of patients (95% CI: 82%-100%). The average volume of ropivacaine 0.2% was 0.53 mL/Kg (SD 0.11 mL/Kg). Echogenic landmarks were identified in all patients. Pain scores and opioid consumption were generally low. CONCLUSION: A supra-inguinal location for the deposition of local anesthetic when performing fascia iliaca nerve block for hip surgery is reliable in anesthetizing the femoral and lateral femoral cutaneous nerves and should encourage investigation into the clinical efficacy.

Distal Extension of the Direct Anterior Approach to the Hip: A Cadaveric Feasibility Study.

BACKGROUND: The direct anterior approach (DAA) is becoming more popular as the standard surgical approach for primary total hip arthroplasty. However, femoral complications of up to 2.8% have been reported. Therefore, it is important for surgeons to understand the periarticular neurovascular anatomy in order to safely deal with intraoperative complications. METHODS: Anatomic dissections were performed on 20 cadaveric hips. The neurovascular structures anterior to the femur and distal to the intertrochanteric line were dissected and its position was described in relation to anatomic landmarks easily identified through the DAA: anterior superior iliac spine (ASIS), the insertion of the gluteus minimus (GM), and the lesser trochanter (LT). RESULTS: Two clearly distinguishable neurovascular bundles running to the vastus lateralis were seen in 17 of 20 specimens. The average distances to the landmarks were as follows: ASIS-1st bundle = 12.3 cm (range, 9.7-14.5); GM-1st bundle = 3.2 cm (range, 2.2-4); LT-1st bundle = 1.6 cm (range, 0.7-2.8); 1st bundle-2nd bundle = 3.3 cm (range, 1.8-6.1). CONCLUSION: A consistent pattern of 2 clearly distinguishable neurovascular bundles was seen in 85% of the specimens. Knowledge of the position of these neurovascular bundles in relation to the anatomic landmarks makes distal femoral extension of the DAA feasible. Further clinical studies are needed to confirm the safety of the extensile anterior approach.

Inflammatory pain-related traits of sensory DRG neurons innervating the hip joints.

BACKGROUND: Hip pain is transmitted to the dorsal horn of the spinal cord via the dorsal root ganglion (DRG), which contains two types of neurons with differential sensitivity to neurotrophic factors. If either type predominantly innervates the hip joint, it may represent a good target for hip joint pain treatment. METHODS: Inflammation was induced in the left hip joint of rats (n = 10) by using complete Freund's adjuvant. Fluoro-Gold (FG) was applied to the hip joint after 7 days, and T12-L6 DRGs were double-stained for calcitonin gene-related peptide (CGRP) and isolection-IB4 1 week later. RESULTS: FG-labeled neurons in the control group were distributed throughout the left DRG from T13 to L5, primarily in L2 to L4, and CGRP-positive neurons were significantly more frequent than IB4-binding neurons. In the inflammatory group, FG-labeled neurons were similarly distributed, primarily at L3 and L4, and CGRP-positive neurons were significantly more frequent than IB4-binding neurons. The percentage of CGRP-positive neurons was significantly greater in the inflammatory group (P < 0.05). CONCLUSIONS: Most small neurons innervating the hip joint express CGRP. Furthermore, hip joint inflammation caused an increase in CGRP-positive neurons, but not in IB4-binding neurons. Our results suggest that CGRP-expressing nerve growth factor-dependent neurons are primarily responsible for hip joint pain and may represent therapeutic targets.

Influence of the contractile properties of muscle on motor unit firing rates during a moderate-intensity contraction in vivo.

It is suggested that firing rate characteristics of motor units (MUs) are influenced by the physical properties of the muscle. However, no study has correlated MU firing rates at recruitment, targeted force, or derecruitment with the contractile properties of the muscle in vivo. Twelve participants (age = 20.67 ± 2.35 yr) performed a 40% isometric maximal voluntary contraction of the leg extensors that included linearly increasing, steady force, and decreasing segments. Muscle biopsies were collected with myosin heavy chain (MHC) content quantified, and surface electromyography (EMG) was recorded from the vastus lateralis. The EMG signal was decomposed into the firing events of single MUs. Slopes and y-intercepts were calculated for 1) firing rates at recruitment vs. recruitment threshold, 2) mean firing rates at steady force vs. recruitment threshold, and 3) firing rates at derecruitment vs. derecruitment threshold relationships for each subject. Correlations among type I %MHC isoform content and the slopes and y-intercepts from the three relationships were examined. Type I %MHC isoform content was correlated with MU firing rates at recruitment (y-intercepts: r = -0.577; slopes: r = 0.741) and targeted force (slopes: r = 0.853) vs. recruitment threshold and MU firing rates at derecruitment (y-intercept: r = -0.597; slopes: r = 0.701) vs. derecruitment threshold relationships. However, the majority of the individual MU firing rates vs. recruitment and derecruitment relationships were not significant (P > 0.05) and, thus, revealed no systematic pattern. In contrast, MU firing rates during the steady force demonstrated a systematic pattern with higher firing rates for the lower- than higher-threshold MUs and were correlated with the physical properties of MUs in vivo.

Immune response and innervation signatures in aseptic hip implant loosening.

BACKGROUND: Aseptic loosening (AL) of hip prosthesis presents inflammation and pain as sign and symptom similarly to arthritis pathologies. Still, the immune and innervation profiles in hip AL remain unclear and their interplay is poorly explored. Herein, local tissue inflammatory response, sensory and sympathetic innervation as well as associated local mediators were assessed in hip joint microenvironment underlying AL and compared to osteoarthritis (OA). METHODS: Histopathological analysis, immune cells (macrophages, T, B cells and PMNs) as well as sensory and sympathetic nerve fibers (SP(+), CGRP(+), TH(+)) distribution and profiles were analyzed on tissues retrieved from patients with failed hip prostheses due to AL (n = 20) and hip OA (n = 15) by immunohistochemistry. Additionally, transcriptional levels of pro-inflammatory cytokines (TNF-α, IL-1ß, IL-6, IL-12a, iNOS), anti-inflammatory cytokine (IL-10), osteoclastic factor (RANKL) and bone remodeling factor (TGF-ß1) were locally evaluated by qRT-PCR. Serum TGF-ß1 levels were assessed preoperatively by ELISA. RESULTS: Histopathological analysis revealed that tissues, aseptic interface membranes of AL patients had distinct tissue architecture and immune cells profile when compared to OA synovial tissues. Macrophages, T cells and B cells showed significant differences in tissue distribution. In OA, inflammation is mostly confined to the vicinity of synovial membrane while in AL macrophages infiltrated throughout the tissue. This differential immune profile is also accompanied with a distinct pattern of sensory and sympathetic innervation. Importantly, in AL patients, a lack of sympathetic innervation aseptic interface membranes without compensation mechanisms at cellular levels was observed with simultaneous reorganization of sensorial innervation. Despite the different histopathological portrait, AL and OA patients exhibited similar transcriptional levels of genes encoding key proteins in local immune response. Nevertheless, in both pathologies, TGF-ß1 expression was prominent in sites where the inflammation is occurring. However, at systemic level no differences were found. CONCLUSION: These findings indicate that AL patients exhibit different local inflammatory response and innervation signatures from OA patients in hip joint. These insights shed the light on neuro-immune interplay in AL and highlight the need to better understand this crosstalk to unravel potential mechanisms for targeted-therapies to improve hip joint lifetime and treatment.

The relationship between lower limb proprioceptive sense and locomotor skill acquisition.

Sensorimotor integration is essential for controlling movement and acquiring new motor tasks in humans. The aim of this project was to understand how lower limb proprioceptive sense contributes to the acquisition of a skilled walking task. We assessed lower limb joint position and movement detection sense in healthy human subjects using the Lokomat robotic exoskeleton. Subjects walked on a treadmill to practice a skilled motor task (200 trials) requiring them to match their foot height during the swing phase to the height of a virtual obstacle displayed on a monitor in front of them. Subjects were given visual feedback on their error relative to the obstacle height after it was crossed. Lower limb joint position sense was related to the final performance error, but not the learning rate of the skilled walking task. The findings from this study support the role of lower limb proprioceptive sense on locomotor skill performance in healthy adult subjects.

Characterization of the Neural Anatomy in the Hip Joint to Optimize Periarticular Regional Anesthesia in Total Hip Arthroplasty.

The purpose of the current study was to identify and map the periarticular neural anatomy of the hip to optimize periarticular injection techniques in total hip arthroplasty. A literature review of common search engines was performed using terms associated with hip innervation and 17 met the inclusion criteria. The studies addressed both gross and microscopic neural anatomy of the human hip joint, and the findings summarize key areas of hip mechanoreceptors and free nerve endings to provide a framework for targeted periarticular hip infiltration. Grossly, the hip joint is supplied by the femoral, obturator, sciatic, and superior gluteal nerves, as well as the nerve to the quadratus femoris. The greatest concentration of sensory nerve endings and mechanoreceptors is found at the anterior hip capsule, especially superiorly. The labrum is most highly innervated from the 10 to 2 o'clock position. After the cup and liner are placed, periarticular injections should be infiltrated toward the remnant labrum from 10 to 2 o'clock. Before stem insertion, the visible periosteum may then be injected circumferentially about the femur. The anterior and superior capsular tissue, if retained, is routinely infiltrated at the time of capsular repair. Depending on surgical approach, the fascia and incised soft tissue are infiltrated before final closure.

Non-uniform surface electromyographic responses to change in joint angle within rectus femoris muscle.

INTRODUCTION: Our recent studies have demonstrated region-specific neural activation within the rectus femoris (RF) muscle. However, these studies involved a fixed joint angle or posture. In this study we investigated the effect of hip and knee joint angles on neural activation within RF using multichannel surface electromyography (SEMG). METHODS: Eleven healthy men performed isometric maximal voluntary contraction (MVC) during knee extension and hip flexion at different hip or joint angles. During the contractions, SEMG of the RF was recorded using 46 electrode pairs covering most of the superficial area of the muscle. RESULTS: During knee extension MVC, an increase in the hip joint angle was associated with a significant increase in SEMG amplitude in the proximal region and a decrease in the distal region (P < 0.05). Higher SEMG amplitude during hip flexion MVC compared with knee extension MVC was observed in proximal regions with the flexed knee and hip joint angles. This task-dependent spatial distribution of SEMG amplitude was seen at the extended hip, but not at the extended knee. CONCLUSIONS: SEMG amplitudes within the RF muscle are not modified uniformly with changes in joint position.

Hip resurfacing does not improve proprioception compared with THA.

BACKGROUND: Proposed benefits of total hip resurfacing arthroplasty over total hip arthroplasty (THA) include better proprioception, but this has not been rigorously tested or validated. QUESTIONS/PURPOSES: Our purpose was to apply an advanced testing device that objectively quantifies dynamic postural stability to determine if total hip resurfacing is associated with improved proprioception compared with standard or large-head THA. METHODS: Three groups of 25 patients (total hip resurfacing, THA femoral head > 32 mm, THA femoral head ≤ 32 mm) and a matched control group were recruited. All participants had UCLA scores ≥ 5 and Harris hip scores ≥ 90 at the time of testing. Testing was conducted using a commercially available device that uses a multidirectional, powered platform to measure deviations of the center of mass and consisted of trials with both double- and single-limb support. RESULTS: Double-limb testing showed no differences between groups. In single-limb testing, the operative side performed better in patients who had undergone total hip resurfacing versus THA, but this difference disappeared when the operative side was normalized to the nonoperative side. When compared with control subjects who had not had arthroplasty, both operative and nonoperative sides showed significantly worse proprioception for all arthroplasty cohorts, suggesting that decreased proprioception is associated with arthritis of the hip in young adults. CONCLUSIONS: Total hip resurfacing arthroplasty did not result in improved proprioception compared with THA. These results tend to refute the concept that improved proprioception is a rationale for selecting total hip resurfacing over THA in young patients.

The innervation of the human acetabular labrum and hip joint: an anatomic study.

BACKGROUND: The aim of the current study was to evaluate the innervation of the acetabular labrum in the various zones and to understand its potential role in nociception and proprioception in hips with labral pathology. METHODS: A total of twenty hip labrums were tagged and excised intraoperatively from patients undergoing a total hip replacement. After preparation, the specimens were cut to a thickness of 10 µm and divided into four quadrants (zones) using a clock face pattern. Neurosensory structure distribution was then evaluated using Hematoxylin and Eosin (H and E), and immunoreactivity to S-100. RESULTS: All specimens had abundant free nerve endings (FNEs). These were seen predominantly superficially and on the chondral side of the labrum. In addition, predominantly three different types of nerve end organs (NEOs) were identified in all twenty specimens. FNEs and NEOs were more frequently seen in the antero-superior and postero-superior zones. Four specimens had abundant vascularity and disorganised architecture of FNEs in the deeper zones of the antero-superior quadrant suggestive of a healed tear. Myofibroblasts were present in abundance in all the labral specimens and were distributed uniformly throughout all labral zones and depth. CONCLUSIONS: The current study shows that the human acetabular labrum has abundant FNEs and NEOs. These are more abundant in the antero-superior and postero-superior zones. The labrum, by virtue of its neural innervation, can potentially mediate pain as well as proprioception of the hip joint, and be involved in neurosecretion that can influence connective tissue repair.