[The piriformis syndrome-a special indication for botulinum toxin]. / Das Piriformissyndrom ­ eine spezielle Indikation für Botulinumtoxin.

The piriformis syndrome (PiS) is a possible cause of gluteal pain radiating into the legs. From a pathophysiological anatomical point of view a division into primary and secondary PiS is made. A primary PiS is based on variants of the course of the sciatic nerve with respect to the piriformis muscle. A secondary PiS occurs as a result of hypertrophy, tension and hardening of the piriformis muscle. Muscular hypertrophy causes an impingement syndrome with pressure on the sciatic nerve in the infrapiriform foramen more often than course variants. A tentative diagnosis of PiS can be made based on anamnestic information, clinical signs of strain and the flexion adduction internal rotation (FAIR) test. If asymmetry or hypertrophy exists, the tentative diagnosis is substantiated with the representation of the piriformis muscle in computed tomography (CT). Thus, a CT-supported botulinum injection (BTX) into the piriformis muscle is indicated. This is a pathogenetic treatment approach leading to a reduction in volume. In most cases a single treatment is sufficient. Since there are no adverse consequences, the BTX into the piriformis muscle is also justified from a diagnostic and therapeutic point of view in cases of primary PiS if the clinical indications are clear and other causes can be ruled out. In an in-house case series the tentative diagnosis of PiS could be made for 19 patients and the effectiveness of BTX was confirmed.

[Schwannoma of the inferior gluteal nerve as a rare cause of gluteal radiating chronic low back pain]. / Schwannom des Nervus gluteus inferior als seltene Ursache von nach gluteal einstrahlenden chronischen Rückenschmerzen.

This is the first report of a schwannoma of the inferior gluteal nerve (IGN) as a cause of chronic low back pain in a 43-year-old man. The patient suffered from severe pain radiating to the gluteal region. He was treated for months without pain relief and was on long-term disability. Only a targeted sonographic exam revealed a hypoechoic intrapelvic mass along the course of the IGN. By tumor resection, a schwannoma was histologically confirmed. After tumor removal the patient is free of pain with all medication discontinued. He has been fully reintegrated into his professional life.

A randomized double-blind placebo-controlled trial on the effect of local analgesia on postoperative gluteal pain in patients undergoing sacrospinous ligament colpopexy.

BACKGROUND: The incidence of temporary gluteal pain after sacrospinous ligament colpopexy ranges from 6.1% to 15.3%. Gluteal pain may occur as a result of injury to S3 to S5 nerve roots that course over the mid-portion of the coccygeus-sacrospinous ligament complex at the time of suspension suture placement. There are no data on the use of injections to prevent postoperative pain from nerve entrapment at the time of suture placement. OBJECTIVE: The purpose of this study was to determine whether intraoperative local analgesia that is administered at the level of the sacrospinous ligament can lessen the gluteal pain felt by patients postoperatively after sacrospinous ligament colpopexy. STUDY DESIGN: In a randomized double-blind placebo-controlled trial, women with vaginal apex prolapse who were undergoing surgical treatment with sacrospinous ligament colpopexy underwent intraoperative injection with either 0.25% bupivacaine or normal saline solution. Subjects completed visual analog pain scales (0-10) and the Activities Assessment Scale and recorded the use of pain medications over a 6-week period. The primary outcome was postoperative gluteal pain. A sample size of 50 subjects (25 in each arm) was planned to test the hypothesis that local analgesia administration will lessen postoperative pain compared with placebo. RESULTS: Between April 2014 and March 2016, 51 women were enrolled in the study, and 46 women underwent sacrospinous ligament colpopexy. On postoperative day 1, 90.2% of all subjects (n=41) reported gluteal pain. At weeks 1 and 2, 63.8% (n=29) and 44.1% (n=20) women reported pain; at weeks 4 and 6, 33.3% (n=15) and 26.9% (n=12) women continued to have some pain. On day 1, the mean score for gluteal pain was 3.7±2.9. By week 1, the score was 1.8±2.6; by week 6, the mean score was 0.1±0.3. There were no differences in pain scores for patients who had undergone injection with 0.25% bupivacaine and those who were injected with normal saline solution. Patients in the placebo group used significantly more nonsteroidal antiinflammatory drugs than the treatment group: adjusted odds ratio, 1.25; 95% confidence interval, 1.04-1.35; P=.01). By 6 weeks, 87.5% of patients had returned to their baseline "light" activity level. There was no difference in time to return to baseline between the groups. CONCLUSION: Intraoperative administration of local analgesia does not reduce patients' perceptions of postoperative gluteal pain after sacrospinous ligament colpopexy; however, it may reduce the need for pain medication after surgery.

Possible pathogenic mechanism of gluteal pain in lumbar disc hernia.

Recent reported results by Fang et al. published in BMC Musculoskeletal Disorders have added to the weight of evidence supporting association between gluteal pain and lumbar disc hernia. Their clinical finding shows the L4/5 level is the main level responsible for gluteal pain in lumbar disc hernia. Indeed, many possible mechanisms may explain why patients experience pain in the gluteal area. In this Correspondence, we would like to highlight several possible mechanisms of LDH-related gluteal pain based on detailed analysis of the sensory innervation of the gluteal region. We hope this can better explain the phenomenon found by Fang et al. We believe the principle mechanism is compression/irritation of L5 or S1 dorsal rami (intraspinal portion), which produce gluteal pain by irritating superior/medial cluneal nerve and referred pain from facet joints and sacroiliac joints. In addition, the presence of proximal sciatica could also induce gluteal pain. Lastly, fibers in the superior or inferior gluteal nerve could be compressed/irritated in LDH, inducing LDH-related gluteal pain. However, additional studies are needed in the future to delineate the exact mechanism(s).

Point-of-Care Ultrasound Diagnosis of Proximal Hamstring Rupture.

BACKGROUND: Acute proximal hamstring ruptures can be a diagnostic challenge in the emergency department. The revealing sign of large posterior thigh ecchymosis is typically not yet present; the physical examination is limited due to pain, radiographs can be unremarkable, and definitive testing with magnetic resonance imaging is not practical. These avulsions are often misdiagnosed as hamstring strains and treated conservatively. The diagnosis is made after failed treatment, often months after the injury. Surgical repair at that time can be technically challenging and higher risk due to tendon retraction and adhesion of the tendon stump to the sciatic nerve. CASE REPORTS: The first case illustrates an example of how delay in diagnosis can occur in both emergency medicine and outpatient primary care settings. It also shows complications and morbidity potential for patients who warrant and do not receive timely surgical repair. The second case illustrates physical examination findings obtainable during the acute setting, and the use of point-of-care ultrasound (POCUS) in facilitating an expedited diagnosis and treatment plan. WHY SHOULD AN EMERGENCY PHYSICIAN BE AWARE OF THIS?: Timely diagnosis of hamstring rupture is paramount to optimize patient outcomes for this serious injury. The best results are obtained with surgical repair within 3-6 weeks of injury. POCUS evaluation can aid significantly in the timely diagnosis of this injury. If the POCUS examination raises clinical concern for a proximal hamstring rupture, this may allow for earlier diagnosis and definitive treatment of proximal hamstring rupture.

Inferior gluteal and other nerves associated with sacrospinous ligament: a cadaver study.

BACKGROUND: Reported rates of gluteal pain after sacrospinous ligament fixation range from 12-55% in the immediate postoperative period and from 4-15% 4-6 weeks postoperatively. The source of gluteal pain often is attributed to injury to the nerve to levator ani or pudendal nerve. The inferior gluteal nerve and other sacral nerve branches have not been examined thoroughly as potential sources of gluteal pain. OBJECTIVES: The purpose of this study was to further characterize anatomy of the inferior gluteal nerve and other nerves that are associated with the sacrospinous ligament from a combined gluteal and pelvic approach and to correlate findings to sacrospinous ligament fixation. STUDY DESIGN: Dissections were performed in female cadavers that had not been embalmed with gluteal and pelvic approaches. From a pelvic perspective, the closest structure to the superior border of the sacrospinous ligament midpoint was noted, and the sacral nerves that perforated the ventral surface of coccygeus muscle were examined. From a gluteal perspective, the closest distances from ischial spine to the pudendal, inferior gluteal, posterior femoral cutaneous, and sciatic nerves were measured. In addition, the closest distance from the midpoint of sacrospinous ligament to the inferior gluteal nerve and the origin of this nerve were documented. The thickness and height of the sacrospinous ligament at its midpoint were measured. Sacral nerve branches that coursed between the sacrospinous and sacrotuberous ligaments were assessed from both a pelvic and a gluteal approach. Descriptive statistics were used for data analysis. RESULTS: Fourteen cadavers were examined. From a pelvic perspective, the closest structure to the superior border of sacrospinous ligament at its midpoint was the S3 nerve (median distance, 3 mm; range, 0-11 mm). Branches from S3 and/or S4 perforated the ventral surface of coccygeus muscles in 94% specimens. From a gluteal perspective, the closest structure to ischial spine was the pudendal nerve (median distance, 0 mm; range, 0-9 mm). Median closest distance from inferior gluteal nerve to ischial spine and to the midpoint of sacrospinous ligament was 28.5 mm (range, 6-53 mm) and 31.5 mm (range, 10-47 mm), respectively. The inferior gluteal nerve arose from dorsal surface of combined lumbosacral trunk and S1 nerves in all specimens; a contribution from S2 was noted in 46% of hemipelvises. At its midpoint, the sacrospinous ligament median thickness was 5 mm (range, 2-7 mm), and its median height was 14 mm (range, 3-22 mm). In 85% of specimens, 1 to 3 branches from S3 and/or S4 nerves pierced or coursed ventral to the sacrotuberous ligament and perforated the inferior portion of the gluteus maximus muscle. CONCLUSIONS: Damage to the inferior gluteal nerve during sacrospinous ligament fixation is an unlikely source for postoperative gluteal pain. Rather, branches from S3 and/or S4 that innervate the coccygeus muscles and those coursing between the sacrospinous and sacrotuberous ligaments to supply gluteus maximus muscles are more likely to be implicated. A thorough understanding of the complex anatomy surrounding the sacrospinous ligament, limiting depth of needle penetration into the ligament, and avoiding extension of needle exit or entry point above the upper extent of sacrospinous ligament may reduce nerve entrapment and postoperative gluteal pain.

Which level is responsible for gluteal pain in lumbar disc hernia?

BACKGROUND: There are many different reasons why patients could be experiencing pain in the gluteal area. Previous studies have shown an association between radicular low back pain (LBP) and gluteal pain (GP). Studies locating the specific level responsible for gluteal pain in lumbar disc hernias have rarely been reported. METHODS: All patients with lumbar disc herniation (LDH) in the Kanghua hospital from 2010 to 2014 were recruited. All patients underwent a lumbar spine MRI to clarify their LDH diagnosis, and patients were allocated to a GP group and a non-GP group. To determine the cause and effect relationship between LDH and GP, all of the patients were subjected to percutaneous endoscopic lumbar discectomy (PELD). RESULTS: A total of 286 cases were included according to the inclusive criteria, with 168 cases in the GP group and 118 cases in the non-GP group. Of these, in the GP group, 159 cases involved the L4/5 level and 9 cases involved the L5/S1 level, while in the non-GP group, 43 cases involved the L4/5 level and 48 cases involved the L5/S1 level. PELD was performed in both groups. Gluteal pain gradually disappeared after surgery in all of the patients. Gluteal pain recrudesced in a patient with recurrent disc herniation (L4/5). CONCLUSIONS: As a clinical finding, gluteal pain is related to low lumbar disc hernia. The L4/5 level is the main level responsible for gluteal pain in lumbar disc hernia. No patients with gluteal pain exhibited involvement at the L3/4 level.

Ischiofemoral impingement syndrome: A five-case series report.

Gluteal pain is a frequent cause of medical attention in the daily clinical practice. It can be caused by multiple pathologies, being ischiofemoral impingement syndrome among those included in its differential diagnosis. Encompassed within the deep gluteal syndromes, this entity occurs as a consequence of the entrapment of the neuromuscular structures between the lesser femoral trochanter and the ischial tuberosity, causing pain in the root of the lower limb, with irradiation towards the thigh or the gluteal region and poor tolerance to deambulation and sedestation. The magnetic resonance imaging of the hip is fundamental for its diagnosis, and its management consists on medical treatment at onset. Despite not being a frequent diagnosis in the clinical practice in Rheumatology, keeping it in mind helps improving its prognosis by establishing an early and adequate treatment.

Piriformis Syndrome in Pre-monsoon, Monsoon, and Winter: An Observational Pilot Study.

INTRODUCTION:  Piriformis syndrome (PS) is a rare focal soft tissue rheumatic disease. Due to heavy rural work, we questioned whether PS was more prevalent in the rainy monsoon than in other seasons. In this pilot research, we studied the pattern of PS, the frequency of PS over the seasons, and whether there were typical preceding events.  Methods: In this time-series descriptive study, PS cases diagnosed in a community-based clinic between January 2018 and December 2019 were enrolled. PS was diagnosed by clinical features and a 50% immediate pain relief from ultrasonogram-guided lidocaine (2%) injection in the piriformis muscle (PM). PS mimics were excluded. RESULTS:  A total of 38 PS cases (11 males) were enrolled consecutively. In 2018, during dry winter (November-February), pre-monsoon (March-May), and rainy monsoon (June-October), nine, seven, and one PS cases were diagnosed, respectively; in 2019, the numbers were three, eight, and seven, respectively. Thus, over two years, 12 PS patients were diagnosed in dry winter, 15 in pre-monsoon, and eight in rainy monsoon. There was no correlation with the type of preceding events. There were no differences in the pattern of PS between the seasons. CONCLUSIONS:  In this pilot study, over two years more new PS cases were observed in the pre-monsoon and dry winter than in the rainy season; this was not supporting our research question. There was no association with specific preceding events.

Sacral Chordoma Presenting as Back Pain in the Chiropractic Clinic: A Case Report.

Cases of lumbar and gluteal pain are commonly encountered in chiropractic clinics, with a broad differential diagnosis primarily centered on musculoskeletal conditions. This report presents the second documented case of sacral chordoma diagnosed at a chiropractic clinic and emphasizes the importance of considering alternative diagnoses and interdisciplinary collaboration in patient care. A 42-year-old man presented to a chiropractic clinic with complaints of lumbar and gluteal pain. The initial conservative management based on a presumptive musculoskeletal diagnosis was ineffective. Suspicion of an alternative etiology prompted a referral for imaging, which revealed a sacral chordoma. An interdisciplinary collaboration involving orthopedic surgeons, oncologists, radiologists, and other healthcare professionals was initiated to optimize the treatment outcomes of this rare and aggressive tumor. This case report underscores the importance of maintaining a high index of suspicion in cases of musculoskeletal presentations in chiropractic clinics and the critical role of advanced imaging in establishing a definitive diagnosis. Interdisciplinary collaboration is essential for managing complex conditions such as sacral chordomas, ensuring the delivery of the highest quality of care, and optimizing patient outcomes. Chiropractors play a crucial role in identifying, referring, and contributing to the management of patients with complex presentations as part of a comprehensive multidisciplinary treatment plan.

Arthroscopic Lesser Trochanter Osteoplasty, Quadratus Femoris Debridement, and Sciatic Neurolysis via Posterior Approach for Ischiofemoral Impingement.

Ischiofemoral impingement (IFI) syndrome is considered the narrowing of the ischiofemoral space (IFS), leading to pathological changes in the quadratus femoris and sciatic nerve, causing posterior hip and sciatica-like pain. Open or arthroscopic resection of the lesser trochanter to enlarge the IFS is the main surgical procedure. However, there is a lack of research on isolated IFI, and currently known surgical procedures are at risk of weakening the flexion strength of the hip joint. In this study, four patients, who were diagnosed with isolated IFI and had undergone arthroscopic treatment with partial resection of the lesser trochanter, debridement of the quadratus femoris, and decompression of the sciatic nerve, were reviewed. To the best of our knowledge, this is the first study to describe the management of IFI using a series of surgical procedures via a posterior approach as an effective treatment option. The outcomes of this study broadened the strategies for IFI management.

A Retrospective Comparative Study of Modified Percutaneous Endoscopic Transforaminal Discectomy and Open Lumbar Discectomy for Gluteal Pain Caused by Lumbar Disc Herniation.

Introduction: This study aimed to demonstrate the safety and effectiveness of modified percutaneous endoscopic transforaminal discectomy (PETD) in the surgical management of single-segment lumbar disc herniation (LDH) gluteal pain and to determine whether it provides a better clinical outcome than open lumbar discectomy (OD). Methods: A retrospective analysis of patients treated with modified PETD and OD for gluteal pain in LDH from January 2015 to December 2020 was conducted. Sample size was determined using a priori power analysis. Demographic information, surgical outcomes including procedure time (minutes), intraoperative blood loss (mL), hospital days, costs (RMB), fluoroscopy shots, recurrence and complications, etc., were recorded and analyzed. Prognostic outcomes were assessed using the visual analog scale (VAS), the Oswestry Disability Index (ODI), the Japanese Orthopedic Association Score (JOA) and modified MacNab criteria. The preoperative and postoperative VAS, ODI and JOA scores were recorded by two assistants. When the results were inconsistent, the scores were recorded again by the lead professor until all scores were consistently recorded in the data. MRI was used to assess radiological improvement and all patients received follow-ups for at least one year. Results: The sample size required for the study was calculated by a priori analysis, and a total of 72 participants were required for the study to achieve 95% statistical test power. A total of 93 patients were included, 47 of whom underwent modified PETD, and 46 of whom underwent OD. In the modified PETD intragroup comparison, VAS scores ranged from 7.14 ± 0.89 preoperatively to 2.00 ± 0.58, 2.68 ± 0.70, 2.55 ± 0.69, 2.23 ± 0.81, and 1.85 ± 0.72 at 7 days, 1 month, 3 months, 6 months, and 12 months postoperatively. Patients showed significant pain relief postoperatively (P < 0.01). According to the modified MacNab score, the excellent rate in the PETD group was 89.36%. There was no significant difference compared to the OD group (89.13%, P > 0.05). Complication rates were lower (P > 0.05) but recurrence rates were higher (P > 0.05) in the modified PETD group than in the OD group. The modified PETD group had a faster operative time (P < 0.01), shorter hospital stay (P < 0.01), less intraoperative bleeding (P < 0.01), and less financial burden to the patient (P < 0.01) than the OD group. At 7 days postoperatively, the VAS score for low back pain was higher in the OD group than in the modified PETD group (P < 0.01). The VAS and JOA scores at 1, 3, 6, and 12 months postoperatively were not significantly different between the modified PETD and OD groups (P > 0.05), and the ODI was significantly different at 3 months postoperatively (P < 0.05). Conclusion: Modified PETD treatment is safe and effective for gluteal pain due to L4/5 disc herniation and has the advantages of a lower complication rate, faster postoperative recovery, shorter length of stay, fewer anesthesia risks and lower cost of the procedure compared with OD. However, modified PETD has a higher recurrence rate.

Endoscopic Sciatic Neurolysis for Deep Gluteal Syndrome: A Systematic Review.

Deep gluteal syndrome (DGS) is an underdiagnosed condition caused by an extra-spinal entrapment of the sciatic nerve in the deep gluteal space. Symptomatic patients who fail conservative treatment require surgical decompression of the nerve either by an open or endoscopic approach. In recent times, there has been an increasing trend towards minimally invasive surgery performed with endoscopic techniques. This systematic review aimed to assess the effectiveness of endoscopic sciatic nerve decompression in the management of DGS. A comprehensive search of the PubMed, Web of Science, Cumulated Index to Nursing and Allied Health Literature (CINAHL), and SPORTDiscus databases were performed on January 3, 2022. All English-language clinical studies on DGS treated with endoscopic surgical decompression were included. The initial search criteria identified 145 articles, of which four studies were available for the final review. There was one level III evidence, while the remaining three were level IV, comprising 144 patients with a mean age of 46 years. The Coleman methodology score (CMS) was utilized to assess the quality of the studies and the mean score was 62 (range, 52 to 71). The presence of fibrovascular bands and bursal tissue was the most common cause of DGS, followed by musculotendinous structures. The average follow-up of the included studies was 26.3 months (range, 12 to 32 months). Less favorable outcomes were seen in patients with major traumatic sciatic neuropathies after fractures or open reconstructive hip surgeries. Conversion to formal open surgery was recorded in one case of DGS caused by sciatic nerve schwannoma due to poor endoscopic access. One patient developed postoperative recurrent sciatic nerve entrapment due to a foreign body reaction requiring an open decompression. Overall, the available studies reported a high degree of clinical success with a low rate of complications, albeit no high-quality studies could be identified.

Piriformis Syndrome Masquerading as an Ischiofemoral Impingement.

Hip pain can have a number of different etiologies. Ischiofemoral impingement (IFI), an etiology causing extra-articular hip pain, shares many of the same symptoms as other causes of gluteal or inguinal pain, making its diagnosis difficult. We present a case of a young female with persistent deep gluteal pain who was diagnosed with IFI based on radiographic findings; however, a diagnostic injection into the quadratus femoris did not confirm IFI as the primary pain generator. The patient subsequently failed several trials of physical therapy designed to address this diagnosis. The diagnosis was expanded to include piriformis syndrome and the modified treatment approach resulted in complete resolution of her pain. The similarities of these pathologies resulted in a delay of definitive treatment and would have potentially required unnecessary surgery. This case study highlights the diagnostic conundrum clinicians face in the evaluation of gluteal hip pain and provides an algorithm for considering alternate diagnoses when conservative management fails to achieve expected results.

Postoperative Deep Gluteal Syndrome After Hip Arthroscopic Surgery.

BACKGROUND: Deep gluteal syndrome (DGS) is an uncommon source of buttock and groin pain, resulting from entrapment of the sciatic nerve in the deep gluteal space. The incidence and risk factors of postoperative DGS after primary hip arthroscopic surgery are currently unknown. PURPOSE: To investigate the incidence and risk factors of postoperative DGS after primary hip arthroscopic surgery. STUDY DESIGN: Case-control study; Level of evidence, 3. METHODS: This study reviewed 1167 patients who underwent arthroscopic surgery between 2010 and 2018 by a single surgeon at a single center in Japan. DGS was defined using the seated piriformis stretch test, active hamstring test, and evidence of a hypertrophic sciatic nerve on magnetic resonance imaging. Overall, 11 of 1167 patients were diagnosed with DGS postoperatively. The DGS group (n = 11) was compared with the non-DGS group (n = 1156). Patient age, sex, body mass index (BMI), generalized joint laxity (GJL; Beighton score >6), number of hip arthroscopic procedures, and radiographic parameters including lateral center-edge angle, Sharp angle, vertical center anterior angle, Tönnis angle, alpha angle, ischiofemoral distance, ischiofemoral space, and quadratus femoris space were compared. The prevalence of developmental dysplasia of the hip (DDH) and borderline DDH (BDDH) was also compared. Logistic regression analysis was conducted to identify potential predictors for a postoperative DGS diagnosis. RESULTS: The incidence of postoperative DGS in our study was 0.9%. Female sex (male:female ratio: 0:11 in DGS group vs 568:588 in non-DGS group; P < .01), mean number of hip surgical procedures (1.8 ± 0.9 in DGS group vs 1.1 ± 0.4 in non-DGS group; P < .01), and GJL (P < .01) were significantly higher in the DGS group, while the mean BMI was significantly lower in the DGS group (19.8 ± 1.8 vs 22.7 ± 3.6 kg/m2, respectively; P < .01). Radiographic parameters were not significantly different between groups. Logistic regression analysis revealed that female sex (odds ratio [OR], 22.0 [95% CI, 1.29-374.56]), multiple surgical procedures (OR, 7.8 [95% CI, 2.36-25.95]), GJL (OR, 40.9 [95% CI, 8.74-191.70]), lower BMI (OR, 0.77 [95% CI, 0.644-0.914]), and DDH/BDDH (OR, 18.1 [95% CI, 2.30-142.10]) were potential predictors of postoperative DGS. CONCLUSION: The incidence of postoperative DGS in our study was 0.9%. The predictors for postoperative DGS after hip arthroscopic surgery were female sex, GJL, multiple hip surgical procedures, and DDH/BDDH. Although hip arthroscopic surgery can provide favorable clinical outcomes, surgeons should be aware of the risk factors for DGS as a complication of hip arthroscopic surgery.

Sciatic Nerve Injury Secondary to a Gluteal Compartment Syndrome.

Gluteal compartment syndrome (GCS) is extremely rare, with a low index of suspicion among physicians, hence, it is highly overlooked. The underdiagnosis can lead to irreversible tissue ischemia and severe neurological deficits. GCS is a surgical emergency and requires immediate surgical intervention given its high morbidity and mortality. Based on the limited available literature, multiple etiologies have been postulated including traumatic and nontraumatic causes. This article presents a complex and unusual case of GCS after prolonged immobilization in an IV drug abuser who was subjected to initial missed diagnosis.