Tissue mechanics during temporal summation of sequentially cuff pressure-induced pain in healthy volunteers and patients with painful osteoarthritis.

BACKGROUND: The phenomenon of temporal summation to repetitive pressure pain stimuli is an important central neural mechanism for pain intensity encoding. This study evaluated the time-dependent behaviour of mechanical characteristics of soft tissue during repeated cuff stimulation used for eliciting temporal summation of cuff pressure-evoked pain. Such information of tissue mechanics is important for the interpretation of the pain response evoked during sequential stimulations. METHODS: Temporal summation was assessed in 16 subjects separated into two groups (healthy controls and severe knee osteoarthritis patients) using a visual analogue scale during 10 repetitive painful cuff stimuli (1-s duration, 1-s break) of the lower leg. The geometry of the lower leg was constructed based on magnetic resonance image (MRI) data. The loading boundary condition of the finite element model was defined according to the parabolic pattern of the interface pressure around the limb and the time-dependent profile of the cuff pressure during repetitive stimuli. RESULTS: The pain intensity significantly increased with an increasing number of stimuli (p < 0.001), and facilitated temporal summation of pain was observed in patients compared with healthy controls (p < 0.001). The maximal deep tissue stress and strain during stimuli 1-4 varied 43% and 9%, respectively. No variation was observed for stimuli 5-10. CONCLUSIONS: The study concludes that the temporal summation of pain response during sequential cuff pressure is not explicable by a specific time-dependent behaviour of stress and strain in the activated deep tissue and hence not due to changes in tissue biomechanics. SIGNIFICANCE: The temporal summation of pain during sequential cuff stimulation is inexplicable by the time-dependent response of mechanical stress and strain in soft tissue.

Intra-articular fractures at the base of the fifth metacarpal. A clinical and radiographical study of 64 cases.

The treatment of 64 intra-articular fractures at the base of the fifth metacarpal was studied. 11 fractures with minimal displacement had been immobilised in a plaster cast without reduction. The position was improved in five of 25 fractures treated by closed reduction and a plaster cast, six of nine fractures after percutaneous pinning, and 12 of 19 fractures after open reduction and internal fixation. At follow-up after a median of 4.3 years, 19 of 50 patients answering a questionnaire had intermittent pain, especially on firm grip. 43 patients were re-examined clinically and radiographically: 21 (49%) had decreased grip power, and 28 had radiographical signs of osteoarthrosis.

Rolando's fracture.

The relationship between methods of treatment, quality of reduction and the occurrence of late disability and osteo-arthritic changes was studied in 17 Rolando's fractures. Three were undisplaced, 14 were displaced: of these excellent reduction was achieved in five of 11 treated by open reduction and in none of the three treated by percutaneous K wire fixation. After a median interval of 5.8 years, six of 16 reviewed patients had minor symptoms, while nine had no symptoms. Radiographic examination of 11 patients showed signs of osteoarthritis in six. We did not establish a relationship between the quality of reduction and the occurrence of late symptoms and osteoarthritis.

Bennett's fracture.

The relationship between the quality of reduction and the occurrence of arthritic changes, symptoms and disability was studied in 41 Bennett's fractures. Excellent position was obtained in five of nine fractures treated by closed reduction and plaster immobilisation, in four of six fractures treated by percutaneous K wire fixation and in 18 of 26 fractures treated by open reduction. After a median interval of 7.3 years, 15 of 18 reviewed patients with fractures healed in excellent position were free of symptoms, but this was so in only six of 13 fractures with residual displacement. The remainder had intermittent slight pain. Radiographic signs of arthritis was found in ten of 24 patients: three of 14 patients with excellent reduction and seven of ten patients with residual displacement.