Asymptomatic population reference values for three knee patient-reported outcomes measures: evaluation of an electronic data collection system and implications for future international, multi-centre cohort studies.

OBJECTIVES: The aim was to assess whether the Knee Society Score, Oxford Knee Score (OKS) and Knee Injury and Osteoarthritis Outcome Score (KOOS) were comparable in asymptomatic, healthy, individuals of different age, gender and ethnicity, across two remote continents. The purpose of this study was to establish normal population values for these scores using an electronic data collection system. HYPOTHESIS: There is no difference in clinical knee scores in an asymptomatic population when comparing age, gender and ethnicity, across two remote continents. METHODS: 312 Australian and 314 Canadian citizens, aged 18-94 years, with no active knee pain, injury or pathology in the ipsilateral knee corresponding to their dominant arm, were evaluated. A knee examination was performed and participants completed an electronically administered questionnaire covering the subjective components of the knee scores. The cohorts were age- and gender-matched. Chi-square tests, Fisher's exact test and Poisson regression models were used where appropriate, to investigate the association between knee scores, age, gender, ethnicity and nationality. RESULTS: There was a significant inverse relationship between age and all assessment tools. OKS recorded a significant difference between gender with females scoring on average 1% lower score. There was no significant difference between international cohorts when comparing all assessment tools. CONCLUSIONS: An electronic, multi-centre data collection system can be effectively utilized to assess remote international cohorts. Differences in gender, age, ethnicity and nationality should be taken into consideration when using knee scores to compare to pathological patient scores. This study has established an electronic, normal control group for future studies using the Knee society, Oxford, and KOOS knee scores. LEVEL OF EVIDENCE: Diagnostic Level II.

The outcome of pedicle screw instrumentation removal for ongoing low back pain following posterolateral lumbar fusion.

BACKGROUND: Our aim was to determine whether patients derived benefit from removal of pedicle screw instrumentation for axial pain without other cause using our surgical technique and patient selection. A secondary aim was to investigate factors that were associated with poorer outcomes for this procedure as well as complication rate in this cohort. METHODS: Theater records from a single spinal surgeon's practice were reviewed to identify patients that had undergone lumbar fusion for discogenic back pain with subsequent pedicle screw instrumentation removal (Expedium, DePuy Synthes) in the preceding 3 years with a minimum of 18 months follow-up. Inclusion criteria were persisting midline axial back pain with computed tomography (CT)-confirmed solid fusion with non-radicular symptoms and nil other potential causes found, e.g., infection. Case note review along with pre- and post-operative Oswestry disability index (ODI) questionnaires and visual analog scores (VAS) were assessed for all patients. Surgical technique included re-use of previous midline posterior incision and the Wiltse approach with removal of implants, confirmation of a solid fusion mass, washout and bone grafting of removal sites. RESULTS: From 50 consecutive patients who underwent removal of posterolateral instrumentation for an index elective lumbar fusion for discogenic back pain, 34 patients were identified that met the criteria with a mean follow-up of 25 months (range, 18-36 months). The VAS and ODI improved in 22/34 (65%) of participants. The mean cohort VAS score was 6.6 pre-surgery and 4.3 post-surgery (P=0.04). Preoperative and postoperative mean Oswestry disability scores were 64 and 41, respectively (P=0.05). There was a statistically significant difference in the proportion of patients with poorer compared to satisfactory outcomes with regards to compensable status, preoperative grade II opioid use and shorter time between fusion and removal procedure. Complications were one postoperative hematoma and one superficial wound infection, both of which settled without re-operation. CONCLUSIONS: Approximately two thirds of patients were satisfied with removal of instrumentation for treatment of residual low back pain (LBP) following elective lumbar fusion and recorded reduced VAS and grade II opioid use. A subset of patients remained that did not derive benefit and were associated with compensable status, preoperative grade II opioid use and a shorter time between fusion and removal procedure. A prospective cohort study with preoperative diagnostic injections and standardized imaging and microscopic techniques would strengthen future studies. However, this study suggests that removal of instrumentation is safe and provides modest benefit as a palliative procedure for a subset of patients with significant disability from chronic LBP without an underlying cause following lumbar fusion.