BACKGROUND: The source of pain in patellofemoral osteoarthritis is not fully understood. The purpose of this study was to identify the origin of pain using intraosseous pain catheters and to show early results with an osteotomy that is potentially denervating and hydrostatic pressure-relieving.
METHODS: Five patients with patellofemoral osteoarthritis and pain with straight downward patellofemoral compression were included. All underwent arthroscopic placement of two 0.8mm catheters into the medial and lateral patella prior to subsequent patellar facetectomy with an incomplete horizontal patellar osteotomy. The catheters were first flushed with 0.5ml saline, then with local anaesthetic to determine pain response. After a mean of 44months the latest clinical examination was performed.
RESULTS: Instillation of less than 0.5ml of saline provoked sharp pain, which could be localised by all patients as medial or lateral within the patella. Subsequent instillation of local anaesthetic suppressed the mean patellar tenderness during axial compression from VAS 6 to VAS 1. In one of the five patients, patellar osteotomy did not relieve symptoms and further surgical intervention was required. The remaining four patients experienced a clinical improvement with a mean subjective knee value of 55 (range 40 to 65) out of 100.
CONCLUSION: This is the first report on intraosseous catheters applying local anaesthetics into bone. There is a surprisingly precise intraosseous spatial resolution of pain perception in the patella and triggering of pain in osteoarthritis appears at least in part to occur through intraosseous increase of hydrostatic pressure.
LEVEL OF EVIDENCE: Level IV, Case Series.