Outcome of Lumbar Spine Surgery in Elite Athletes vs. Untrained : Matched Cohort Study from SWESPINE

- 1 - Örebro University

School of Medicine Degree project, 15 ECTS May 2018

Outcome of Lumbar Spine Surgery in

Elite Athletes vs. Untrained

–

Matched Cohort Study from SWESPINE

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Version 2

Author: Bella Lagrange

Supervisor: Yohan Robinson, MD, PhD, MBA

Associate Professor, Spine Surgery

Uppsala University, Dept. of Surgical Sciences

Co-supervisor: Adad Baranto, MD, PhD

Associate Professor, Consultant Spine Surgeon

Sahlgrenska Academy, Dept. of Clinical Sciences

Abstract

Background:

Low back pain may be treated surgically if a mechanical cause can be identified. In elite athletes, certain spinal adaptations have been described, from the diver’s kyphosis to the gymnast’s spondylolysis. Some of these chronic spinal changes have previously been identified to influence the long-term result of spinal surgery of untrained patients.

Purpose:

The aim of this study is to determine whether elite athletes have a better or worse outcome of spinal surgery compared to physically inactive patients.

Methods:

Data from patients registered in Swedish National Spine Register SWESPINE between 1996-2014 were analyzed. The patient reported outcome measures (PROM: s) preoperatively, after one year, and two years were evaluated with the following instruments: Visual Analogue Scale (VAS) for leg- and back pain, Oswestry Disability Index (ODI) and EuroQol five-dimension scale (EQ5D) for health-related quality of life.

Results:

Surgical treatment was associated with improvements in VAS for leg pain in both groups (-48 for elite athletes vs. -53 for physically inactive patients) with no statistically significant difference between the two groups (p = 0.203). VAS for back pain improved in both groups (-37 vs. -44) without a statistically significant difference between the two groups (p=0.073). ODI improved in both groups (-32 vs. -37) without a statistically significant difference between the two groups (p = 0.142). EQ5D improved the first year for both groups (0.15 vs. 0.11) with a decline the second year (- 0.15 vs. -0.13) for both groups without a statistically significant difference between both groups (p = 0.140). There was no statistically significant difference for AUC VAS leg (p = 0.178) and AUC VAS back (p= 0.99). However, there was a statistically significant difference for ODI (p = 0.017) and EQ5D (p = 0.002).

Conclusion:

Disability, back- and leg pain decreased after spinal surgery. Quality of life increased the first year but decreased the second year. There was only a statistical difference of outcome

Abbreviations

AUC: Area Under the Curve

EQ5D: EuroQol Five Dimension Scale

MCID: Minimally Clinically Important Difference ODI: Oswestry Disability Index

PROM: Patient Reported Outcome Measures

R version 3.3.0: The R Foundation for Statistical Computing, Vienna, Austria SWESPINE: Swedish National Spine Register

Contents

Introduction ... - 1 - Objectives ... - 2 - Research question ... - 2 - Hypothesis ... - 2 - Methods ... - 3 - Study design ... - 3 - Setting ... - 3 - Participants ... - 3 - Variables ... - 4 - Exposures ... - 4 - Outcome measures ... - 4 - Quantitative variables ... - 4 - Statistical methods ... - 5 - Ethical aspects ... - 6 - Results ... - 7 -

Pain reduction in the leg ... - 7 -

Pain reduction in the back ... - 8 -

Improvement of Oswestry Disability Index ... - 8 -

Improvement of EQ5D ... - 8 -

Area under the curve (AUC) ... - 9 -

Discussion ... - 11 -

Strengths and weaknesses of this study ... - 12 -

Conclusion ... - 13 -

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Introduction

Degenerative disc disease is a common musculoskeletal disorder that is related to disability and chronic low back pain. Due to its effect both on workforce and healthcare resource, utilization surgical therapy is promising with regard to outcome and cost- effectiveness [1]. A systematic review by Carreon et al. reports that surgical treatment leads to greater

improvement in function than nonsurgical treatment [2]. In the last decades, there has been an increasing amount of spinal surgery in several countries [3,4]. The aim of spinal surgery is to decompress neural structures and / or stabilize the spine and to reduce lower back pain. Therefore, this treatment is applied to patients with the diagnoses disc herniation, spinal stenosis, spondylolysis or chronic lower back pain where the pain is chronic, severe and rehabilitation has been unsuccessful. However, Gibson and Waddel show that clinical study results are not equivocal [5]. The positive result may not be sustained at a longer follow-up and surgery may therefore not be ideal for all patients [6]. Another study by Ibrahim et al. demonstrates that there is no statistically significant improvement of disability after spinal fusion surgery[7]. In addition, a number of studies have raised the question whether this type of treatment is indeed cost-effective [8] and there might be better treatments regarding that there always is a risk with surgery [9]. It is therefore of importance to further investigate factors that influence outcome of surgical treatment for chronic lower back pain.

There is a higher incidence of back pain amongst elite athletes compared to a control group [10]. Exercise has a great impact on the intervertebral disc. Studies have confirmed that there are short-term changes in the structures of the intervertebral disc shortly after exercise [11]. However, the effect of exercise on long-term changes of the intervertebral discs is unknown. There is evidence that absence of physical activity (sedentary behavior) diminishes the quality of the intervertebral disc [12]. Sports resulting in rotational movements, repetitive motions and with a high impact on the spine may lead to spondylolysis (explained by repetitive spinal stress fractures) or early disc degeneration [13–19]. Sports that involve running have either a positive or no effect on the intervertebral disc[11].

Several studies have evaluated different factors that influence the outcome of spine surgery. Exercise might be one of those factors. The results are inconclusive, showing either no effect or positive consequences of exercise programs after lumbar fusion surgery [20].

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Objectives

The aim of this study is to determine whether the outcome of spinal surgery (operating on the disc and/or fusion surgery) is better or worse for elite-athletes than physically inactive patients prior to surgery.

Research question

Do elite athletes have a better or worse outcome after surgery compared to physically inactive patients?

Hypothesis

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Methods

Study design

This was a national registry-based cohort study. Data was collected from The Swedish National Spine Register (SWESPINE). The diagnoses disc herniation, spinal stenosis, spondylolysis or chronic lower back pain were studied.

Setting

Data collection is performed continuously via SWESPINE. SWESPINE registers the majority of operations performed on the spine on patients in Sweden with a coverage of 98 % (46 of 47 clinics) and a completeness of 75 % (the proportion of patients operated that are included in the register) in 2017[21].

Patients complete questionnaires pre- and postoperatively. The same questionnaires are sent to the patients by post or online as a one- and two-year follow-up. The follow-up rate of answered questionnaires after one year is 75 %. The surgeon includes surgical data (such as diagnosis, type of treatment etc.) in conjunction with the surgery report before discharge from hospital[3].

Participants

Study population were patients included in the register who were surgically treated for disc herniation, spinal stenosis, spondylolysis or chronic lower back pain and who completed the one- and two-year follow-up. Study objects were divided into two groups: elite active patients or physically inactive patients. The groups where determined by the patients answering the question: “Are you physically active?” choosing the alternatives “Yes- on an elite level” or “No”.

Between 1996 and 2014 the register included 67115 patients. 44492 were excluded because of no data of athletic activity. Of the 22623 patients left with data on athletic activity, 398 were elite athletes. These were matched with 398 untrained patients with the most similar

characteristics regarding age, sex, BMI, date of treatment, diagnosis and smoking (see inclusion flow diagram).

- 4 - Variables

Exposures

• Spinal disease (disc herniation, spinal stenosis, spondylolysis or chronic lower back pain)

• Spinal surgery type

• Level of physical activity (in SWESPINE: elite or none).

Outcome measures

• Leg pain (VAS) • Back pain (VAS)

• ODI (Oswestry Disability Index)

• EQ-5D (EuroQol)

Quantitative variables

Back pain (VAS) and leg pain (VAS)

Included was Visual Analog Scale (VAS) for leg- and back pain[3]. VAS is the most sensitive scale for measuring pain[22]. It is a single, 10 cm long, straight line (horizontally or

vertically) with perpendicular lines at the ends. At each end, the extreme of the symptoms are written (such as no pain = 0 points and worst pain imaginable = 100 points). The patient

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marks what they currently experience. Thereafter, the point from “no pain” to the patient’s mark is measured. In this way, a higher score means worse pain[23].

Oswestry Disability Index

The outcome measure Oswestry disability index (ODI) is used for measurement for low back pain. It is a questionnaire with ten sections examining the ability to perform daily activities. Every section is ranked from 0-5 where 5 is the highest level of disability. The index is calculated by adding the patients score, divide them through the highest possible score and thereafter multiply the answer by 100. It is then expressed in percentage[24].

EuroQol Five Dimension Scale

EuroQol Five Dimension Scale (EQ5D) is a standardized generic measurement for self- rated quality of life. EQ5D consists of a questionnaire with five dimensions: mobility, capacity of self-care, conduct of usual activities, pain/discomfort and anxiety / depression. Each category has three levels: none, moderate and severe /extreme. VAS is also part of the EQ5D, a 20 cm long vertical visual analogue scale numbered from 0 (the worst health imaginable) to 100 (the best health imaginable) [25]. EQ5D is then calculated to a single index by using a formula that attaches values to every level of category. This produces an index where 1.00 is perfect health[26,27].

Area under curve

Area under curve (AUC) describes the time it takes to improve during the first two years after surgery. It was calculated for VAS leg, VAS back, ODI and EQ5D.

Statistical methods

The statistic calculations were programmed in R version 3.3.0 (The R Foundation for Statistical Computing, Vienna, Austria). A matched cohort study was performed. Patients training on an elite level were matched against an untrained control group using the software

MatchIT package. Nearest neighbor propensity score matching was performed to minimize

the confounding factors year of birth, sex, diagnosis and type of surgical treatment. The included participants were grouped according to training habits in elite and untrained groups.

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Mean values were presented ± standard deviation. Groups were compared with t-test for normally distributed variables, otherwise the Wilcoxon-test was applied. Differences in group proportions were tested with the 𝜒𝜒2-test. A probability of p<0.05 was considered as

statistically significant.

The values for the minimally clinically important difference (MCID) were taken from SWESPINE database as follows: ≥ 14 for VAS, ≥ 8 for ODI, ≥ 0.2 for EQ5D[3].

Ethical aspects

Patients enter the register voluntarily and can choose to leave the register anytime.

SWESPINE provided anonymized data where the key remains with SWESPINE. An entry cannot be traced back to the patient. The Uppsala Ethical Review Board approved the registry study (no. 2015/145).

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Results

The patients’ baseline characteristics are summarized in Table 1.

Table 1 – Baseline values of included patients.

Untrained Elite athletes p N 398 398 Mean age (sd) 40 (±18) 39 (±18) 0.648 Male gender (%) 111 (28) 112 (28) 1 Diagnosis (%) 0.134 Disc herniation 199 (50) 209 (53) Spinal stenosis 122 (31) 97 (24) Spondylolysis 33 (8) 32 (8)

Chronic Low Back Pain 44 (11) 60 (15)

Smoker (%) 36 (9) 38 (10) 0.903

Previous spine surgery (%) 56 (14) 60 (15) 0.763

Mean BMI (sd) 25 (±4) 25 (±4) 0.774

Treatment (%) 0.054

Discectomy 181 (46) 192 (48)

Decompression 102 (26) 82 (21) Non-instrumented posterolateral fusion 5 (1) 4 (1) Instrumented posterolateral fusion 49 (12) 53 (13) Interbody Fusion 53 (13) 44 (11) Total Disc Replacement 8 (2) 23 (6)

Unemployed (%) 253 (64) 213 (54) 0.005

Pain reduction in the leg

Surgery led to improvements in VAS for leg pain in both groups (-48±35 for elite athletes vs. -53±33 for physically inactive patients) with no statistically significant difference between the two groups (p = 0.203). VAS for leg pain improved for both groups the first year after surgery with only a minimal improvement during year two (Fig. 1). The improvement of leg pain for both groups was above the MCID of 14 and thus of clinical importance.

- 8 - Pain reduction in the back

VAS for back pain improved in both groups (-37±33 vs. -44±32) without a statistically significant difference between the two groups (p=0.073). Patients doing either elite or no sports improved the first year after surgery. There was only a slight improvement during year two (Fig. 1). The improvement of VAS for back pain for both groups were above the MCID of 14 and thus of clinical importance.

Improvement of ODI

ODI improved in both groups (-32 ±23 vs. -37±22) without a statistically significant

difference between the two groups (p = 0.142). The ODI decreases the first year and second year after surgery for both patients doing elite sports or no sports (Fig. 1). The improvement of ODI for both groups were above the MCID of 8.

Improvement of EQ5D

EQ5D improved the first year for both groups (0.15±0.42 vs. 0.11±0.41) with a decline the second year (-0.15 ±0.41 vs. -0.13 ±0.39) for both groups without a statistically significant difference between both groups (p = 0.140) (Fig. 4). The improvement of EQ5D was below the MCID of 0.20.

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Figure 1 – Improvement of VAS (leg), VAS (back), ODI and EQ5D one- and two years after surgery for elite active patients and untrained.

Area under the curve (AUC)

There was no statistically significant difference for AUC VAS leg (p = 0.178) (Fig. 2) and AUC VAS back (p= 0.99) between elite and physically inactive patients (Fig. 3).

Figure 3 – The difference of time to improvement between elite athletes and untrained patients for VAS leg. 44 45 46 47 48 49 50 51 52 elite untrained M ean

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Figure 4 - The difference of time to improvement between elite athletes and untrained patients for VAS back..

However, there was a statistically significant difference for ODI (p = 0.017) (Fig. 4) and EQ5D (p = 0.002) (Fig. 5). 0 10 20 30 40 50 60 70 80 90 100 elite untrained M ean

AUC for VAS back

Figure 4 – The difference of time to improvement between elite athletes and untrained patients for ODI.

Figure 5- The difference of time to improvement between elite athletes and untrained patients for EQ5D.

. 0 0,5 1 1,5 2 elite untrained M ea n

AUC for EQ5D

0 20 40 60 80 100 elite untrained M ean

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Discussion

This matched cohort study confirmed that surgery leads to improvement of leg and back pain (VAS), function (ODI) and health-related quality of life (EQ5D). At each time point no difference between the two groups was found. The improvement over time – as determined by the AUC – revealed significantly less disability (ODI) and higher health-related quality of life (EQ5D) for elite athletes. This means that the time it takes to improvement differs for ODI and EQ5D between elite athletes and untrained. It is unclear why this is the case.

The improvement in VAS for leg pain and VAS for back pain were above the MCID of 14 for both elite athletes and physically inactive groups. The change in ODI was also above the MCID score. These results can therefore be considered being clinically significant and of importance to the patient. The development of EQ5D, on the other hand, is below the MCID. That is, the change in EQ5D is not considered to be of clinical importance for the patient. This means that there is neither a statistically significant difference nor a clinical significant

difference of EQ5D. Even more important than the lack of statistically significant difference between the two groups is that there is no clinical difference in the outcome of spinal surgery between the two groups.

An unexpected finding was the short-term improvement of the EQ5D during the first year, which is lost again during year two with levels below the starting point. These changes have not been seen in VAS for leg pain, VAS for back pain and ODI, which all improve through the first and the second years. These results differ from a previous study. Triebel et al. [28] performed a comparable study to investigate whether the results differ between men and women after lumbar fusion surgery where EQ5D also was used as an outcome measure. In their study EQ5D did not decline the second year. This difference remains unexplained as raw data were collected from the same register. On the other hand, the SWESPINE annual

report[29] shows a similar pattern as regards to EQ5D as our study. The annual report confirms our findings where EQ5D rises the first year and decreases thereafter.

Clark et al [30] investigate how certain major life events influence the subjective wellbeing. They look at life-satisfaction in connection with marriage where an increase in life-

satisfaction is followed by a decrease. The opposite is true for people who are left disabled after an accident, their life- satisfaction deteriorates after the accident but returns to normal thereafter. Even with people who are operated because of pain, one can interpret the findings that the improvement in the subjective judgement of quality of life is not lasting. On the other

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hand, findings for marriage and disability are not necessarily comparable to the impact of pain. Also, as life moves on and the study participants experience less pain, their attention and worries are drawn to other problems. Moreover, the question might be raised if the placebo effect had an impact on the results.

Another possible explanation might be that the athletes expected a full return to sport and felt disappointment two years after surgery when realizing that this was not going to be possible. However, this theory does not explain why non- athletes show similar tendencies.

Our findings show that spinal surgery decrease pain and disability both in elite athletes and untrained controls. The findings suggest that surgery might be a possible treatment for elite active patients. This is in agreement with a systematic review by Nair et al. that shows that 75 to 100 % of elite athletes were able to return to elite competition after lumbar discectomy [31]. However, a systematic review by Sheepers et al.[32] draw the conclusion that there is a lack of evidence about the effectiveness of surgery versus conservative treatment for return to sports in high performance athletes. On the other hand, our study showed a marked decrease

in quality of life the second year after surgery. If the same doesn’t apply to conservative treatment, this might be the better alternative.

Strengths and weaknesses of this study

The group of participants doing exercise on an elite level is certainly rather heterogeneous as the elite athletes engaged in a vast variety of different sports. The effect sports have on the spine vary, and the type of activity the patients perform was not included in the register. This might have an impact on the results as a subgroup analysis was not performed. This could be an explanation for the rather large standard deviations. Moreover, there is no definition of elite athletes in SWESPINE, the patients decided whether they regarded themselves as elite- athletes or not which is a subjective definition. This adds to the heterogenicity of the group. Randomized controlled studies are regarded as more reliable, but in this case randomization for sports or no sports in a blinded fashion is not possible. Patients regarding themselves as athletes might have a different attitude towards pain.

From a dataset of 67, 115 patients, only 398 patients were included in each group. This is only a small but well- matched part of the whole cohort.

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The register is based on patient reported outcome measures, that is the patients themselves report the result. The fact that outcome is a subjective measure can be a possible bias. A systematic review states that athletes in general have a higher pain tolerance compared to a control group [33]. Consequently, physically active patients reported outcome measures (PROM) can differ from physically inactive patients. Moreover, the analgesic treatment postoperatively might vary between patients. If there is a tendency that one group is treated differently, this has an impact on how the patient answers the questionnaires.

SWESPINE collects data over a period of years. During this time the indication for operation might have changed. Also, operation techniques and the population has changed, with a trend towards more obesity and a more sedentary lifestyle. Furthermore, this is a national study meaning that there are different surgeons performing the operation which might lead to different outcomes independent of the patients’ physical activity. Also, included patients were treated for several different diagnoses and with different progression of disease. Subgroup analysis with different diagnoses, operation techniques or sports might lead to different outcomes.

As there was an adjustment for the confounders year of birth, sex, diagnosis and type of surgical treatment, the possibility that other factors influenced the result of this study was minimized. Still, there might be other confounding factors not adjusted for that influenced the results. This applies to the propensity score matching as well – other traits that were not included in the propensity score matching can be a possible bias.

This study only analyzed the two extremes elite active athletes and physically inactive

patients prior to spinal surgery and not patients exercising on a recreational level. As there is a higher incidence of back pain amongst elite athletes, examining the results of spinal surgery on patients with a moderate level of physical activity would be of use in determining the effect of exercise on spine surgery. More studies are needed to evaluate this.

Conclusion

Disability, back pain and leg pain decreased after spinal surgery. Quality of life increased the first year but decreased the second year. There is no statistical difference of outcome between elite-active patients and non-active patients on either one of the variables with the only

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exception being AUC. However, as this study only compared the extremes of elite- active patients to non-active patients, more studies are needed to further determine the influence of physical activity on spinal surgery.

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