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Titel på arbejdetInvestigation of special imaging studies in patients with knee osteoarthritis
NavnJacob Fyhring Mortensen
Afdeling / StedOrtopædkirurgisk Afdeling, Gentofte Hospital
UniversitetKøbenhavns Universitet
  • Hip and knee surgery
Abstract / Summary

Knee Osteoarthritis is one of the leading causes of knee dysfunction due to debilitating pain and the deterioration of the knee's dynamics, which can lead to less activity and a lower quality of life. When conservative treatment has failed, surgery is possible by implanting a knee replacement, consisting of either a total knee or a partial knee replacement. This thesis focuses on the medial unicompartmental partial knee replacement (mUKR) and the total knee replacement (TKR), and the diagnostic imaging before and after surgery with these treatments.

The thesis has the following purpose:
Study I:
To evaluate if specialized radiographic techniques can assess articular cartilage height similarly by:
- Assessing the inter- and intrarater reliability and agreement of the Rosenberg
view and both varus/valgus stress radiography.
- Comparing measurements of each relevant technique to each other.

Study II:
To assess whether MRi is a better diagnostic tool than specialized radiography in assessing articular cartilage height by:
- Assessing the interrater agreement of MRi.
-Comparing MRi to specialized radiography measurements.

Study III
-To investigate the association of tibial component overhang and local tenderness by:
-Assessing the reliability of ultrasound measurements of overhang on postoperative knee replacements.
-Comparing the incidence of overhang seen on postoperative radiographs to the overhang measured with ultrasound.
-Investigating correlations between overhang measurements and local tenderness.

Study I included seventy-three patients prospectively listed for either a mUKR or TKR, had double measurements of specialized radiography performed with the Rosenberg view and varus/valgus stress. Three knee surgeons measured articular cartilage height on each radiograph in the medial and lateral compartment over three rounds. The results showed substantial reliability and substantial to almost perfect inter/intrarater agreement. A strong to very strong correlation between the Rosenberg view and varus and valgus stress was found. This study concludes that the investigated techniques give similar measurements of articular cartilage height, allowing for the use of both techniques in the clinical setting. Using the Rosenberg view by itself makes it possible to save an extra radiograph and the accompanying radiation, along with the extra equipment and specialized personnel needed for a reliable, standardized stress
radiography setup.
Study II included sixty patients from Study I, which also received an extremity MRi of the same knee. Two radiologists and one orthopedic surgeon measured articular cartilage height in the
medial and lateral compartment on each MRi scan. These results proved fair to substantial interrater agreement. The medians of measurements were used to compare MRi to study I’s median measurements of specialized radiography, which proved negligible to weak correlation medially, and strong to very strong correlation laterally. This study concludes that MRi should not replace specialized radiographs in the workup for mUKR.
Study III included sixty-four patients prospectively, where ultrasound and pressure pain thresholds, i.e., local tenderness, were measured. Measurements were performed at 5 or 10
different knee sites, depending on whether they had a mUKR or a TKR inserted, respectively. The use of ultrasound to measure tibial component overhang proved good reliability indicating
its usefulness in the outpatient department. Comparison with conventional postoperative radiographs proved a systematic underestimation of overhang medially on radiographs,
indicating that tibial component overhang measurements could be underreported. Finally, a positive correlation between overhang local tenderness was found, especially when located
medially, which can irritate the medial collateral ligament.
This thesis investigates and highlights alternative specialized diagnostic tests within knee replacement surgery, helping to guide clinical decision-making and avoid unnecessary imaging
and radiation, buying excess equipment, and ultimately higher costs per patient.

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