Cost-effectiveness of microendoscopic discectomy versus conventional open discectomy in the treatment of lumbar disc herniation: a prospective randomised controlled trial [ISRCTN51857546]

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Cost-effectiveness of microendoscopic discectomy versus conventional open discectomy in the treatment of lumbar disc herniation: a prospective randomised controlled trial [ISRCTN51857546]
Received: 12 February 2006
Accepted: 13 May 2006
Published: 13 May 2006
Mark P Arts1,2 , Wilco C Peul1,2 , Ronald Brand3 , Bart W Koes4 and Ralph TWM Thomeer1
BMC Musculoskeletal Disorders 2006
BioMed Central

1Department of Neurosurgery, Leiden University Medical Center, Leiden, The Netherlands
2Department of Neurosurgery, Medical Center Haaglanden, The Hague, The Netherlands
3Department of Medical Statistics, Leiden University Medical Center, Leiden, The Netherlands
4Department of General Practice, Erasmus Medical Center, Rotterdam, The Netherlands

The electronic version of this article is the complete one and can be found online at: http://www.biomedcentral.com/1471-2474/7/42

© 2006 Arts et al; licensee BioMed Central Ltd.
This is an Open Access article distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/2.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

© 2006 Arts et al; licensee BioMed Central Ltd.
This is an Open Access article distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/2.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

Abstract
Background
Open discectomy is the standard surgical procedure in the treatment of patients with long-lasting sciatica caused by lumbar disc herniation. Minimally invasive approaches such as microendoscopic discectomy have gained attention in recent years. Reduced tissue trauma allows early ambulation, short hospital stay and quick resumption of daily activities. A comparative cost-effectiveness study has not been performed yet. We present the design of a randomised controlled trial on cost-effectiveness of microendoscopic discectomy versus conventional open discectomy in patients with lumbar disc herniation.

Methods/Design
Patients (age 18Ò70 years) presenting with sciatica due to lumbar disc herniation lasting more than 6Ò8 weeks are included. Patients with disc herniation larger than 1/3 of the spinal canal diameter, or disc herniation less than 1/3 of the spinal canal diameter with concomitant lateral recess stenosis or sequestration, are eliglible for participation. Randomisation into microendoscopic discectomy or conventional unilateral transflaval discectomy will take place in the operating room after induction of anesthesia. The length of skin incision is equal in both groups. The primary outcome measure is the functional assessment of the patient, measured by the Roland Disability Questionnaire for Sciatica, at 8 weeks and 1 year after surgery. We will also evaluate several other outcome parameters, including perceived recovery, leg and back pain, incidence of re-operations, complications, serum creatine kinase, quality of life, medical consumption, absenteeism and costs. The study is a randomised prospective multi-institutional trial, in which two surgical techniques are compared in a parallel group design. Patients and research nurses are kept blinded of the allocated treatment during the follow-up period of 2 years.

Discussion
Currently, open discectomy is the golden standard in the surgical treatment of lumbar disc herniation. Whether microendoscopic discectomy is more cost-effective than unilateral transflaval discectomy has to be determined by this trial.

Background
Sciatica due to lumbar disc herniation refractory to conservative treatment is effectively treated by surgery. The primary goal of surgery is retrieval of herniated disc fragments and decompression of the nerve root. Since the first report of lumbar disc surgery in 1934 by Mixter and Barr [1], who performed a laminectomy with transdural disc removal, various less invasive techniques have been developped. With the introduction of the microscope, Yasargil and Caspar refined the original laminectomy into the open microdiscectomy [2,3]. This technique has become the most common procedure worldwide. In 1997 Foley and Smith introduced the transmuscular approach of microendoscopic discectomy (MED) with advanced optics and instruments applicated in laparoscopic surgery [4]. Later, the original endoscopic procedure was modified with the operative microscope which has led to the development of the Microscopic Endoscopic Tubular Retractor System (METRX). This technique is subject of our protocol.

The concept of minimally invasive spine surgery is less tissue damage, while achieving good clinical outcome comparable with conventional open surgery. Patients are expected to have less back pain, shorter hospitalisation and quicker resumption of daily activities. Moreover, the cost-effectiveness is expected to be superior.

The Cochrane review of lumbar disc surgery has shown considerable evidence on the effectiveness of discectomy in patients in whom conservative management has failed [5]. Three studies compared microdiscectomy versus standard open discectomy [6-8]. Use of the microscope lengthened the surgical procedure but there was no significant difference in clinical outcome. The expected earlier return to work was not realised. This could be explaned by the rather small difference in invasiveness between microdiscectomy and the frequently performed unilateral transflaval approach by using loupe magnification. Nowadays, these two procedures are lumped together. A randomised controlled trial (RCT) between microdiscectomy with microscope versus microdiscectomy with loupe magnification has not been performed.

The Cochrane review did not include trials concerning MED. However, MED has proven it's safety and efficiency in multiple studies [4,9-15]. Three of these studies have compared MED with conventional open discectomy [10,12,13], 1 was randomised [12]. There is a trend towards faster recovery and less tissue damage in MED, although due to limited number of patients and methodological flaws, no firm evidence based conclusions can yet be drawn.

The rational of MED is a muscle-splitting approach by using sequential dilators and insertion of a tubular retractor, instead of subperiostal muscle dissection in the conventional open procedure. Iatrogenic devascularisation and denervation of paraspinal muscles is regarded to be one of the causes of poor clinical outcome and failed-back-surgery syndrome [16]. Therefore, the muscle-splitting technique of MED is expected to result in less tissue damage since subperiostal muscle dissection is prevented. However, 1 study of 40 patients failed to show a significant difference in post-operative contrast enhanced magnetic resonance imaging (MRI) with respect to paraspinal muscle damage between MED and conventional open discectomy [11].

Another parameter to analyse post-surgery tissue damage is serum creatine kinase (CK) as indicator of muscle injury. CK increases after spinal surgery and reaches a maximal value 1 day after surgery [17]. Nakagawa et al. have compared CK values on day 1 after MED and conventional open discectomy. They showed a significant difference in postoperative CK in favor of the MED [10]. Whether this is related to clinical outcome is not known.

Minimally invasive spine surgery has limitations as well. One of the disadvantage of MED is potential nerve root injury because of limited exposure. On the contrary, it is shown that MED causes less intraoperative nerve root irritation compared to conventional surgery [12].

Another issue related to limited exposure is recurrent disc herniation. The recurrence rate after MED is not known but it is expected to be higher than after conventional open discectomy since less disc material is retrieved. However, a recent randomised trial has shown superiority of sequesterectomy only, compared to conventional discectomy with regard to recurrence rate [18]. Therefore, the relationship between the extent of disc retrieval and recurrence rate is debated. In our study we will weight the total amount of disc retrieval in both surgical techniques and correlate this with disc recurrency.

Like other new minimally invasive techniques, MED has a learning curve which is related to surgery time, complications, conversion to the open procedure, and recurrent disc herniation. It is demonstrated that a surgeon should perform at least 30 procedures in order to be skilled and know the pitfalls [14]. Skill acquisition of MED is necessary before clinical assessment of MED versus conventional open discectomy can be started. Therefore, in our trial we have selected surgeons with large experience in MED.

Presently, the golden standard in surgical treatment of lumbar disc herniation is the unilateral transflaval discectomy to which all other techniques should be compared. The purpose of our study is to assess whether MED is more (cost)-effective than conventional open discectomy. The cost-effectiveness results will be a trade-off between a quicker relief in leg pain in the MED group versus the advantage of lower costs in the conventional group. Moreover, we will identify possible subgroups of patients who will substantially benefit from one of the allocated surgical treatments. Since MED is hypothesised to have a particularly favorable short term effect, we will set 8 weeks and 1 year as primary measure points.

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