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Frontiers in Surgery 2022To analyze the effect of percutaneous endoscopic lumbar discectomy in treating lumbar intervertebral infections.
OBJECTIVE
To analyze the effect of percutaneous endoscopic lumbar discectomy in treating lumbar intervertebral infections.
METHODS
A total of 13 patients with lumbar intervertebral infections who underwent percutaneous endoscopic lumbar discectomy combined with external drainage between November 2016 and December 2019 were enrolled in the present study. After the operation, sensitive antibiotics were used based on the results of the bacterial culture. If no pathogens were detected in the biopsy culture of the infected tissues, empirical antibiotics were administrated to these patients. The clinical efficacy was evaluated by using a visual analog scale (VAS), Japanese Orthopaedic Association (JOA), Oswestry Disability Index (ODI), and standard Macnab's evaluation. Postoperative computed tomography (CT) and MRI were also used to evaluate clinical efficacy.
RESULTS
The follow-up time was 10-18 months, and the average time was (13.69 ± 2.63) months. Causative bacteria were isolated in 7 of 13 infected tissue biopsy cultures. Systemic antibiotics and anti-tuberculous chemotherapy were administered according to sensitivity studies for identified. There were no pathogens isolated from the other six patients. Empiric antibiotics were administrated in these patients. One week after the operation, WBC, a fractional fraction of medium granulocytes, ESR and CRP were significantly lower compared to before the operation (all < 0.05). At the last follow-up visit, the above-mentioned markers were all within normal range, which differed compared to the pre-operative data ( < 0.05). The VAS and ODI of the patients at 1 week and 3 months after operation were significantly lower compared to preoperative data (all < 0.05). During the last follow-up visit, seven patients were excellent, five were good, and one was poor according to standard Macnab's evaluation. No serious complications were recorded.
CONCLUSIONS
Percutaneous lumbar discectomy combined with external drainage resulted as an effective method for treating lumbar intervertebral infections and was associated with fewer injuries, less pain, low cost, and low recurrence rate.
PubMed: 36017524
DOI: 10.3389/fsurg.2022.975681 -
International Journal of Spine Surgery Feb 2020The objective was to compare the traditional microdiscectomy with percutaneous endoscopic lumbar discectomy for the treatment of disc herniations regarding pain,...
Percutaneous Endoscopic Lumbar Discectomy Versus Microdiscectomy for the Treatment of Lumbar Disc Herniation: Pain, Disability, and Complication Rate-A Randomized Clinical Trial.
PURPOSE
The objective was to compare the traditional microdiscectomy with percutaneous endoscopic lumbar discectomy for the treatment of disc herniations regarding pain, disability, and complications.
METHODS
Randomized clinical trial with 47 patients with disc herniations treated with 2 different surgical techniques: traditional microdiscectomy or percutaneous endoscopic lumbar discectomy. Forty-seven patients were divided into 2 groups and monitored for 12 months. Irradiated and low back pain were evaluated with the visual analog scale. Surgery complications were recorded.
RESULTS
After surgery, the sciatica and disability improved significantly but without significant differences between the groups. Improvements in back pain were significant until the third month. There were no statistical differences between groups regarding recurrence, infection, and the need for reoperation.
CONCLUSIONS
Endoscopic discectomy results are similar to those of conventional microdiscectomy regarding pain and disability improvement. Postoperative lumbar pain is less intense with endoscopic discectomy than conventional microdiscectomy only during the first 3 months. Endoscopic discectomy is a safe and efficient alternative to microdiscectomy.
CLINICAL TRIALS
Trial protocol registration number: RBR-5symrd (http://www.ensaiosclinicos.gov.br).
PubMed: 32128306
DOI: 10.14444/7010 -
BMC Musculoskeletal Disorders Sep 2022A symptomatic postoperative pseudocyst (PP) is a cystic lesion that is formed in the operation area of the intervertebral disc, leading to worse symptoms. Some minority...
BACKGROUND
A symptomatic postoperative pseudocyst (PP) is a cystic lesion that is formed in the operation area of the intervertebral disc, leading to worse symptoms. Some minority patients who developed PP experienced rapidly aggravating symptoms and could not be treated by any kind of conservative treatment. However, no clinical studies have evaluated the clinical characteristics and surgical strategies of symptomatic PP requiring a revision surgery after full-endoscopic lumbar discectomy (FELD). This study aimed to demonstrate the clinical characteristics and surgical strategies of symptomatic PP requiring a revision surgery after FELD.
METHODS
We retrospectively analyzed the data of patients who received FELD revision surgeries due to symptomatic PP formation between January 2016 and December 2021. Common characteristics, time intervals of symptom recurrence and revision surgery, strategies for conservative treatment and revision surgery, operative time, imaging characteristics, numeric rating scale (NRS) score, Oswestry disability index (ODI) and overall outcome rating based on modified MacNab criteria were analyzed.
RESULTS
Fourteen patients (males = 10, females = 4), with a mean age of 24.4 years, were enrolled. The mean time intervals of symptom recurrence and revision surgery were 43.5 and 18.9 days respectively. While the patients were conservatively managed with analgesics and physical therapy, pain persisted or progressively worsened. In comparison to the initial herniated disc, the PP was larger in 11 cases, and up- or down-migrated in four cases. The PP location included the lateral recess (n = 12), foraminal (n = 1), and centrolateral (n = 1) zones. One of the two cases treated by percutaneous aspiration (PA) was eventually treated by FELD as pain was not relieved. Follow-ups revealed an improved mean NRS score from 7.1 to 1.4, mean ODI from 68.6 to 7.9% and promising overall surgical outcomes.
CONCLUSIONS
The progressively severe pain experienced due to PP might be a result of its enlargement or migration to the lateral recess and foraminal zones. As complete removal of capsule is the goal, we recommend FELD instead of PA.
Topics: Adult; Diskectomy; Diskectomy, Percutaneous; Endoscopy; Female; Humans; Intervertebral Disc Displacement; Lumbar Vertebrae; Male; Pain; Reoperation; Retrospective Studies; Treatment Outcome; Young Adult
PubMed: 36057592
DOI: 10.1186/s12891-022-05791-y -
Pain Physician Jul 2017Herniated intervertebral disc disease (HIVD) is a common cause of lower back and leg pain. Percutaneous endoscopic lumbar discectomy (PELD) is indicated when...
BACKGROUND
Herniated intervertebral disc disease (HIVD) is a common cause of lower back and leg pain. Percutaneous endoscopic lumbar discectomy (PELD) is indicated when non-surgical treatments such as medication and interventions are intractable. Ruptured discs and loose fragments inside discs are removed during PELD. Nerve root decompression is usually assessed by visualizing the free movement of the traversing nerve root or epidural fat, the free passage of a probe into the epidural space, the depression of the annulus, and the removal of the expected ruptured discs and loose fragments based on preoperative magnetic resonance images (MRI). However, these criteria are subjective, and the quantity of the disc removal necessary for successful outcomes after PELD has not been investigated.
OBJECTIVES
The present study investigates the amount of discectomy of PELD and its clinical and radiological outcomes.
STUDY DESIGN
A retrospective case study (IRB Number H-1611-015-803).
SETTING
University Medical Center, Seoul, Korea.
METHODS
PELD was performed in 109 consecutive patients (M:F = 53:56; mean age, 37.4 years) using the transforaminal or interlaminar route. Ruptured disc fragments were first removed in all patients, and the graspable loose fragments under the disc were removed. After surgery, all removed disc fragments were placed into disposable syringes and manually compressed to measure their volume. The volume of herniated disc outside the disc boundary was calculated in MRI. The measured and calculated disc volumes were retrospectively compared. Clinical success was defined as an improvement in both the Oswestry Disability Index (ODI) and leg pain, as well as no recurrent symptoms. Radiological success was defined as the disappearance of herniated disc material outside the disc boundary based on postoperative MRI taken within one day after surgery. The follow-up period was 7.2 ± 5.2 months.
RESULTS
Successful clinical outcomes were obtained in 96/109 (88.1%) patients in a median time of 3 months. Re-operation was performed in 3 patients due to recurrent discs in 2 patients and a residual disc in one patient. Predictors of clinical success were not identified, and the quantity of the removed disc was not associated with the clinical outcome. Radiological success was achieved in 93/109 (85.3%) patients. Of 13 patients with radiological failure, 2 patients showed clinical failure. A logistic regression analysis showed that the relative volume of the removed disc (%) compared with the volume of preoperative herniated disc based on the MRI was the only significant predictor (P < 0.001; OR = 0.96). When 100% of the calculated disc amount was removed during the operation, the probability of residual disc was 30%. When 131% of the calculated disc amount was removed, the probability of residual disc was 10%.
LIMITATIONS
This study employed a retrospective design, and its inherent selection bias and limited statistical power should be considered.
CONCLUSIONS
The amount of disc removal during PELD was not a significant predictor of clinical success after the primary ruptured fragments were removed. The relative volume of the removed disc based on the preoperative MRI might predict the postoperative MRI.
KEY WORDS
Disc, lumbar vertebra, discectomy, surgery, endoscopy, volume.
Topics: Adolescent; Adult; Aged; Arthroscopy; Diskectomy, Percutaneous; Female; Humans; Intervertebral Disc Degeneration; Intervertebral Disc Displacement; Lumbar Vertebrae; Male; Middle Aged; Outcome and Process Assessment, Health Care; Retrospective Studies; Young Adult
PubMed: 28727718
DOI: No ID Found -
Orthopaedic Surgery Feb 2022This retrospective case-control study aimed to evaluate and compare the clinical outcomes of full-endoscopic visualized foraminoplasty and discectomy (FEVFD) with...
OBJECTIVE
This retrospective case-control study aimed to evaluate and compare the clinical outcomes of full-endoscopic visualized foraminoplasty and discectomy (FEVFD) with microdiscectomy (MD) for lumbar disc herniation (LDH).
METHODS
Data from 198 patients who presented with LDH between January 2016 and December 2017 treated by either FEVFD or MD were retrospectively analyzed. The inclusion criteria were single-level LDH, unilateral radiating leg pain with or without positive Lasegue's sign, and failure of standard conservative treatment for at least 12 weeks. The patients were categorized into an FEVFD group (n = 102) or an MD group (n = 96), according to the surgical procedure performed. Operative time, time in bed after surgery, postoperative hospitalization time, complications, and reoperations were recorded. Visual analog scales (VAS) for leg and back pain, Oswestry Disability index (ODI), 36-Item Short-Form Health Survey physical function (SF36-PF), and bodily pain (SF36-BP) scores were assessed and compared between the two groups.
RESULTS
The demographic data and baseline characteristics of the two groups were not significantly different. Operative time for the FEVFD group (73.82 ± 20.73 min) was longer than that for the MD group (64.74 ± 17.37 min) (P = 0.003), and fluoroscopy time for the FEVFD group (1.71 ± 0.58s) was longer than that for the MD group (1.30 ± 0.33s) (P < 0.001). However, time in bed experienced in the FEVFD group (8.51 ± 2.10 h) was less than that in the MD group (9.24 ± 2.01 h) (P = 0.014), and postoperative hospitalization time experienced in the FEVFD group (2.89 ± 0.83d) was also shorter than that in the MD group (4.94 ± 1.35d) (P < 0.001). All patients completed 24 months of follow-up. Postoperative scores at each follow-up for the VAS for leg and back pain, ODI, SF36-PF, and SF36-BP all improved significantly for both groups, as compared to the preoperative data (P < 0.05). The mean preoperative and postoperative scores for the VAS for leg and back pain, ODI, SF36-PF, and SF36-BP were not significantly different between the two groups. According to the modified MacNab criteria, the outcomes of the procedures were rated as excellent or good by 92.16% and 93.75% of the patients in the FEVFD and MD groups, respectively. One patient suffered a nerve root injury during the discectomy, one patient suffered from a dural tear, and two patients suffered from a residual herniation in the FEVFD group. One patient in the MD group suffered from poor wound healing. Moreover, recurrence happened in two cases in the FEVFD group, and in one case in the MD group.
CONCLUSION
FEVFD and MD are both reliable techniques for the treatment of symptomatic LDH. FEVFD resulted in a more rapid recovery and equivalent clinical outcomes after 24 months of follow-up.
Topics: Case-Control Studies; Diskectomy; Diskectomy, Percutaneous; Endoscopy; Humans; Intervertebral Disc Displacement; Lumbar Vertebrae; Retrospective Studies; Treatment Outcome
PubMed: 34914186
DOI: 10.1111/os.13087 -
Orthopaedic Surgery Jan 2022To investigate the feasibility and efficacy of percutaneous transforaminal endoscopic discectomy (PTED) with three-step maneuver for puncture (TSMP) for lumbar herniated...
OBJECTIVE
To investigate the feasibility and efficacy of percutaneous transforaminal endoscopic discectomy (PTED) with three-step maneuver for puncture (TSMP) for lumbar herniated disc (LDH).
METHODS
We performed a retrospective review of 30 patients who underwent PTED using TSMP for LDH and met inclusion criteria from January 2018 to September 2018. The primary outcome, leg or back pain, was assessed using Visual Analogue Scale (VAS). Patient surgical satisfaction was measured at 12 months post surgery using a five-point Likert scale. Potential prognostic factors measured were demographic characteristics, duration of symptom (DOS), and involved levels. Statistical analysis was performed using Fisher exact test and t-test. TSMP is a three-step maneuver that builds on the concept of needle puncture site and trajectory determination based on the principles of Kambin's triangle. First, accurate direction of the puncture is confirmed by inserting the needle horizontally. Then by gradually raising the needle tail in the manner described, the superior articular facet and the intervertebral foramen are sequentially located. Finally, the needle tip slides into the intervertebral foramen to reach the target superior articular facet.
RESULTS
Preoperative mean VAS was 7.6 ± 1.19, which decreased to 1.4 ± 0.97 at 12 months following treatment (P < 0.0001). Rates of surgical satisfaction per Likert scale were as follows: very satisfied and satisfied in 26 patients (86.7%). Three recurrent disc herniations of adjacent segmental levels were observed in the L5-S1 group at eight and 12 months after surgery. VAS scores at 12 months varied significantly between L4-L5 level surgery and L5-S1 level surgery groups (P < 0.01).
CONCLUSION
TSMP is a reliable technique for puncture into the intervertebral foramen.
Topics: Adult; Diskectomy, Percutaneous; Endoscopy; Feasibility Studies; Female; Humans; Intervertebral Disc Displacement; Lumbar Vertebrae; Male; Middle Aged; Pain Measurement; Punctures; Retrospective Studies; Treatment Outcome
PubMed: 34873865
DOI: 10.1111/os.13113 -
BioMed Research International 2017The objective was to investigate the effective and safe range of paramedian CDH by percutaneous posterior full-endoscopy cervical intervertebral disc nucleus pulposus...
The objective was to investigate the effective and safe range of paramedian CDH by percutaneous posterior full-endoscopy cervical intervertebral disc nucleus pulposus resection (PPFECD) to provide a reference for indications and patient selection. Sixteen patients with CDH satisfied the inclusion criteria. Before surgery the patients underwent cervical spine MRI, and the distance between the dural sac and herniated disc was measured. An assessment was performed by MRI immediately after surgery, measuring the distance between dural sac and medial border of discectomy (DSMD). The preoperative average distance between the dural sac and peak of the herniated disc (DSPHD) was 3.87 ± 1.32 mm; preoperative average distance between dural sac and medial border of herniated disc (DSMHD) was 6.91 ± 1.21 mm and an average distance of postoperative DSMD was 5.41 ± 1.40 mm. Postoperative VAS of neck and shoulder pain was significantly decreased but JOA was significantly increased in each time point compared with preoperative ones. In summary, the effective range of PPFECD to treat paramedian CDH was 5.41 ± 1.40 mm, indicating that DSMHD and DSPHD were within 6.91 ± 1.21 mm and 3.87 ± 1.32 mm, respectively. PPFECD surgery is, therefore, a safe and effective treatment option for patients with partial paramedian cervical disc herniation.
Topics: Adult; Diskectomy, Percutaneous; Endoscopy; Female; Humans; Intervertebral Disc; Intervertebral Disc Degeneration; Intervertebral Disc Displacement; Lumbar Vertebrae; Magnetic Resonance Imaging; Male; Middle Aged; Patient Selection; Spinal Canal
PubMed: 29226132
DOI: 10.1155/2017/3610385 -
Pain Physician Nov 2020Microendoscopic discectomy (MED) and percutaneous transforaminal endoscopic discectomy (PTED) are 2 of the most popular minimally invasive spinal surgery techniques. We... (Observational Study)
Observational Study
Microendoscopic Discectomy Combined with Annular Suture Versus Percutaneous Transforaminal Endoscopic Discectomy for Lumbar Disc Herniation: A Prospective Observational Study.
BACKGROUND
Microendoscopic discectomy (MED) and percutaneous transforaminal endoscopic discectomy (PTED) are 2 of the most popular minimally invasive spinal surgery techniques. We are investigating whether minimally invasive early annular closure can achieve a better clinical effect in the treatment of lumbar disc herniation (LDH).
OBJECTIVE
To compare the clinical and imaging outcomes between MED combined with annular suture and PTED in the treatment of LDH.
STUDY DESIGN
A prospective observational study with follow-up of 36 months.
SETTING
The First People's Hospital of Lianyungang in China.
METHODS
A total of 135 prospective consecutive patients underwent MED + annular suture or PTED. Patients were assessed postoperatively at 3 days and 3, 6, 12, 24, and 36 months. The outcome measures were visual analog scales for back pain (VAS-back) and leg pain (VAS-leg) scores, the Oswestry Disability Index (ODI) score, the Medical Outcomes Study 36-Item Short-Form Health Survey bodily pain (SF36-BP), and physical function (SF36-PF) scales, disc height, and recurrence rate.
RESULTS
One hundred and six patients have completed the 3-year follow-up. The operation time and length of stay in the MED + annular suture group were longer than that in the PTED group (P < 0.001 and P < 0.001). VAS-back score, VAS-leg score, ODI score, SF36-BP, and SF36-PF significantly improved at follow-up time points after surgery compared to before surgery, but no significant differences were found at postoperative and 36 months between the groups. The disc height in the MED + annular suture group was significantly greater than that in the PTED group after 3 months. Within 36-month follow-up, imaging re-herniation was reported in 4 patients in the MED + annular suture group, and 9 patients in the PTED group (P = 0.170). Symptomatic re-herniation occurred in one patient in the MED + annular suture group and in 4 patients in the PTED group (P = 0.190).
LIMITATIONS
First, this was not a randomized controlled trail, which could provide more evidence-based conclusions. Second, we did not accurately measure and compare the amount of nucleus pulposus removed, although less nucleus pulposus was removed in MED + annular suture.
CONCLUSION
PTED has the advantages of shorter length of incision, shorter operation time, and shorter length of stay. MED + annular suture is associated with greater preservation of disc height, and showed certain advantages of lower recurrence rate, although there was no statistical difference.
Topics: Adult; Female; Humans; Male; Middle Aged; Diskectomy, Percutaneous; Endoscopy; Intervertebral Disc Degeneration; Intervertebral Disc Displacement; Lumbar Vertebrae; Minimally Invasive Surgical Procedures; Operative Time; Pain Measurement; Postoperative Period; Prospective Studies; Recurrence; Sutures; Treatment Outcome
PubMed: 33185390
DOI: No ID Found -
Revista Da Associacao Medica Brasileira... Feb 2021The objective of this study is to compare the clinical outcome among patients who are surgically treated for lumbar disc herniation by transforaminal and interlaminar...
OBJECTIVE
The objective of this study is to compare the clinical outcome among patients who are surgically treated for lumbar disc herniation by transforaminal and interlaminar endoscopy techniques.
METHODS
For the treatment of lumbar disc herniation, 31 patients were assigned to undergo the interlaminar technique and 24 patients the transforaminal technique. They were evaluated using visual analog scale and Oswestry disability index in the preoperative period, in the first postoperative period, and in the 12th month after the procedure. The clinical results between the two techniques were then compared.
RESULTS
Overall, 89.1% of the patients obtained good results, with 12.5% complications in the transforaminal technique and 9.6% in the interlaminar technique.
CONCLUSION
Although both the endoscopic techniques, compared in this study, are safe and effective for the surgical treatment of lumbar herniated disc, the interlaminar technique presented significantly better results and lower rates of complications than the transforaminal technique.
Topics: Diskectomy, Percutaneous; Endoscopy; Humans; Intervertebral Disc Displacement; Lumbar Vertebrae; Retrospective Studies; Treatment Outcome
PubMed: 34406248
DOI: 10.1590/1806-9282.67.02.20200643 -
BioMed Research International 2019To predict the early recurrence after full endoscopic lumbar discectomy, we analyzed factors related to demographic factor anatomical factors, operative method, and...
PURPOSE
To predict the early recurrence after full endoscopic lumbar discectomy, we analyzed factors related to demographic factor anatomical factors, operative method, and postoperative management, and predicted the possibility of recurrence according to the scoring system.
MATERIALS AND METHODS
In this prospective study, we enrolled 300 patients who underwent 1 out of 3 surgical procedures. The patients were randomized into one of the following groups: group A ( = 100), transforaminal inside-out approach; group B ( = 100), transforaminal outside-in approach; and group C ( = 100), interlaminar approach. The clinical results were evaluated by a visual analogue scale (VAS). Related factors evaluated with points of (A) demographic factors: (1) age, (2) gender, (3) BMI, (B) anatomical factors: (4) disc degeneration scale, (5) modic change, (6) number of involved disc herniation, (7) history of discectomy (first, recurred), (8) herniated disc level, (9) disc height, (10) segmental dynamic motion, (11) disc location, (C) operation factors: (12) annulus preservation along the disc protrusion, (13) approach method (transforaminal inside-out, transforaminal outside-in, interlaminar); (D) postoperative care factors: (14) early ambulation, (15) spinal orthosis (corset) application. Among these, we analyzed statistically significant recurrence risk factors after PELD in all patients and early recurrence predicting score ratio was obtained.
RESULTS
The overall recurrence rate was 9.33%. The recurrence rate was 11%, 10%, and 7% for groups A, B, and C, respectively. Average early recurrence time was 3.26 months. The change in preoperative and postoperative VAS score was from 8.07 to 1.39, 8.34 to 1.34, and 8.14 to 1.86 in groups A, B, and C, respectively. The recurrence rate based on the (1) age was <40 years: 5.22% (6/115), 41-60 years: 16.1% (20/124), and >61 years: 3.07% (2/65); (2) gender was male: 13/139 (9.35%), female: 15/161 (9.32%); (3) BMI was obese: 17.57% (13/74), overweight: 11.6% (9/77), underweight: 6.35% (4/63), and normal weight: 2.33% (2/86); (4) degeneration scale was grades 1-2: 2% (1/50), grade 3: 7.4% (10/135), and grades 4-5: 14.8% (17/115); (5) modic change was type I: 25% (3/12), type II: 14.3% (1/7), type III: 33% (1/3), and no modic change: 8.27% (23/278); (6) number of involved disc herniation was 1 level: 3.9% (5/128), 2 level: 10.4% (13/125), 3 levels: 18.9% (7/37), and 4 levels: 30% (3/10); (7) history of discectomy was first: 8.83% (25/283) and repeated: 17.65% (3/17); (8) herniated disc level was L1-L2/L2-L3/L3-L4: 3.95% (3/76) and L4-L5: 14.6% (18/123); (9) disc height was <80%: 17.14% (6/35), 81%-100%: 8.16% (12/147), and >101%: 8.5% (10/118); (10) segmental dynamic motion was 1-10°: 8.58% (20/233) and 11-20° : 11.9% (8/67); (11) disc location was central: 7.41% (2/27), foraminal: 3.03% (2/66), and inferior/superior/paracentral: 11.59% (24/207); (12) radical annulotomy was 8.05% (7/87) vs. 9.86% (21/213); (13) approach method was transforaminal (inside-out): 11% (11/100), transforaminal (outside-in): 10% (10/100), and interlaminar: 7% (7/100); (14) early ambulation was 16.42% (23/140) vs. 3.13% (5/160); and (15) spinal orthosis application was 7.35% (10/136) vs. 10.98% (18/164). According to the above results, after summation of all scores, the early recurrence predicting score: recurrence rate ratio was 1-4: 0% (0/23), 5-8: 7.1% (13/183), 9-12: 8% (6/75) and 13-16 100% (10/10).
CONCLUSIONS
Early recurrence after PELD is associated with several risk factors such as BMI, degeneration scale, combined HNP, and early ambulation. If we use the predicting score, we can postulate the occurrence of early recurrence after PELD. Knowing the predictive factors prior to surgical intervention will allow us to decrease the early recurrence rate after PELD.
Topics: Adult; Aged; Aged, 80 and over; Diskectomy, Percutaneous; Endoscopy; Female; Follow-Up Studies; Humans; Intervertebral Disc Displacement; Male; Middle Aged; Predictive Value of Tests; Prospective Studies; Recurrence; Risk Factors
PubMed: 31828113
DOI: 10.1155/2019/6492675