Digital Public Defence: Olaf Fjeld

MD Olaf Fjeld at Institute of Clinical Medicine will be defending the thesis "Symptomatic lumbar disc herniation treated in hospitals: Prognosis of unfavourable surgical events and persistent leg-pain" for the degree of PhD (Philosophiae Doctor).

The public defence will be held as a video conference over Zoom.

The defence will follow regular procedure as far as possible, hence it will be open to the public and the audience can ask ex auditorio questions when invited to do so.

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Due to copyright reasons, an electronic copy of the thesis must be ordered from the faculty. In order for the faculty to have time to process the order, it must be received by the faculty no later than 2 days prior to the public defence. Orders received later than 2 days before the defence will not be processed. Inquiries regarding the thesis after the public defence must be addressed to the candidate.

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Adjudication committee

  • First opponent: Professor Wilco C. Peul, Leiden University Medical Centre, the Netherlands
  • Second opponent: Professor Helena Brisby, University of Gothenburg, Sweden
  • Third member and chair of the evaluation committee: Professor II Morten Carstens Moe, Institute of Clinical Medicine, University of Oslo

Chair of defence

Professor II Jens Ivar Brox, Institute of Clinical Medicine, University of Oslo

Principal supervisor

Professor Margreth Grotle, OsloMet


Low-back pain is the single leading cause for disability worldwide causing activity limitation and work absence with subsequently enormous economic burden on individuals, families, communities, industry, health services and governments. In about 5-10% low-back pain is accompanied by nerve root impingement causing radiating pain into one or both legs, described as radiculopathy or sciatica. Patients with severe symptoms or refractory radiating pain are typically offered surgery, making lumbar disc surgery a common procedure worldwide.  Thus, it is important that patients are informed of the different types and rates of unfavorable events that may occur during and after surgery.    

Although the prognosis is generally favorable, some patients unfortunately go on to develop persistent sciatic pain regardless of treatment. It is believed that a combination of biological and psychosocial properties among the patients is responsible for the transition from acute to chronic pain (the biopsychosocial model). However, at present, it is difficult to predict which patients will go on to develop chronic symptoms and which will not. Prognostic factor research enables us to better understand who these patients are and provide insight into what mechanisms are responsible for unsuccessful healing.

The overall aim of the presented work was to assess the frequency of unfavorable surgical events after lumbar disc herniation surgery, and in addition to study potential prognostic factors for the persistence of leg-pain in surgical and non-surgical patients hospitalized with sciatica. 

This was sought through an epidemiological analysis of two large national databases complemented by two in-depth prospective cohort studies.

The aim of Paper I presented in this thesis was to elicit the rates for unfavorable events such as complications, reoperations and readmissions in lumbar disc surgery. 
Paper II was aimed at identifying sociodemographic, lifestyle, psychosocial and clinical prognostic factors for persistent leg-pain at 12 months in both surgically and non-surgically treated patients hospitalized with acute severe sciatica.    

The aim of Paper III was to test whether Conditioned Pain Modulation (CPM) effect measured 6 weeks after hospital discharge could be associated with self-reported leg-pain at 12 months in a cohort consisting of both surgically and non-surgically treated sciatica patients.

Patients and methods
Paper I was a longitudinal observation study. Data were retrieved using a combination of procedure and diagnosis codes from two large medical administrative registries covering all lumbar disc surgeries performed in the public sector in Norway in the years 1999-2013. The impact of age, gender, geographical affiliation, education, civil status, income, and comorbidity on unfavorable surgical events were analyzed by logistic regression.

Paper II was based on data from a cohort study with a total of 210 patients acutely admitted to hospital for either surgical or nonsurgical treatment of sciatica. The patients were consecutively recruited upon hospital admission and received follow-up assessments at 6 weeks, 6 months, and 12 months post hospital discharge. Potential prognostic factors were measured at hospital admission and at 6 weeks. The impact of these factors on leg-pain measured at 12 months was analyzed by multiple linear regression modeling.

Paper III was a prospective cohort study in which CPM effect was measured in 111 patients  who continued to suffer from sciatica 6 weeks after being discharged from hospital. The patients received a follow up assessment of leg-pain 12 months after hospital discharge. The impact of CPM effect on self-reported leg-pain at 12 months was analyzed using logistic regression.

In 34 639 lumbar disc surgeries, 2.7% had a surgical complication, 2.1% had repeat surgery within 90 days, 2.4% had a non-surgical readmission within 90 days and 6.7% experienced at least one of these unfavorable events (in italics). There were no registered mortalities associated with surgery. The most common surgical complications were dural tears/punctures, infections and hemorrhages. Advanced age and comorbidity were associated with a higher rate of complications. 

In patients hospitalised with sciatica as their main complaint, sciatic pain regressed rapidly during the first 6 weeks after discharge, but their pain remained comparatively static after this time point. The following 4 factors were associated with their self-reported leg pain measured 1 year after hospital discharge: 1) High risk according to a psychosocial screening tool, 2) not receiving surgical treatment, 3) not actively employed prior to hospital admission and 4) self-reported leg-pain measured 6 weeks after hospital discharge. 

The prognostic factors: age, sex, smoking, BMI, education, social status, analgesic use, previous lumbar surgery, clinical neurological examination of the lower extremities and CPM effect were all found to have poor predictive capacity.

Less than 7% of patients that undergo simple lumbar disc surgery experience an unfavorable event such as a reoperation, complication, or readmission. Whether the rate of unfavorable events is acceptable must be considered in relation to the health gains achieved by choosing surgical over conservative care, but patients can be informed that simple lumbar disc surgery is safe with low risk of mortality. 

Sociodemographic characteristics, clinical examination, lifestyle factors and CPM effect were found to be poor predictors of long-term leg-pain in patients hospitalised with sciatica. Simply measuring leg-pain 6 weeks after hospital discharge could be an efficient way of establishing prognosis for patients hospitalized with sciatica as their main complaint. A patient’s psychosocial profile was found to have some predictive value in the early stages of disease, but there is still a prognostic void that needs to be filled in order for us to reach the goal of early prognostication in patients hospitalized with sciatica.

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Published Aug. 18, 2021 9:50 PM - Last modified Aug. 31, 2021 10:52 AM