The cerebellar cortex is crucial for sensorimotor integration. Sensorimotor inputs converge on cerebellar Purkinje cells via two afferent pathways: the climbing fibre pathway triggering complex spikes, and the mossy fibre-parallel fibre pathway, modulating the simple spike activities of Purkinje cells. We used, for the first time, the mouse whisker system as a model system to study the encoding of somatosensory input by Purkinje cells. We show that most Purkinje cells in ipsilateral crus 1 and crus 2 of awake mice respond to whisker stimulation with complex spike and/or simple spike responses. Single-whisker stimulation in anaesthetised mice revealed that the receptive fields of complex spike and simple spike responses were strikingly different. Complex spike responses, which proved to be sensitive to the amplitude, speed and direction of whisker movement, were evoked by only one or a few whiskers. Simple spike responses, which were not affected by the direction of movement, could be evoked by many individual whiskers. The receptive fields of Purkinje cells were largely intermingled, and we suggest that this facilitates the rapid integration of sensory inputs from different sources. Furthermore, we describe that individual Purkinje cells, at least under anaesthesia, may be bound in two functional ensembles based on the receptive fields and the synchrony of the complex spike and simple spike responses. The 'complex spike ensembles' were oriented in the sagittal plane, following the anatomical organization of the climbing fibres, while the 'simple spike ensembles' were oriented in the transversal plane, as are the beams of parallel fibres.

Iatrogenic nerve injury during fracture surgery of the upper arm is a well-known complication. Prevention of this type of injuries would be of great value. The literature describes several methods to reduce this type of injury, but no perfect solution is at hand. In this study we introduce a new radiographic evaluation of the course and variation of the radial nerve in the distal part of the humerus in relation to bony landmarks as observed on a plain (trauma) radiographs. Aim of this new approach is to reduce the chance of iatrogenic nerve injury by defining of a danger zone in the distal upper arm regarding the radial nerve and hence give an advise for future implant fabrication.Methods and findingsMeasurements were done on both arms of ten specially embalmed specimens. Arms were dissected and radiopaque wires attached to the radial nerve in the distal part of the upper arm. Digital radiographs were obtained to determine the course of the radial nerve in the distal 20 cm of the humerus in relation to bony landmarks; medial epicondyle and capitellum-trochlea projection (CCT). Analysis was done with ImageJ and Microsoft Excel software. We also compared humeral nail specifications from different companies with the course of the radial nerve to predict possible radial nerve damage.ResultsThe distance from the medial epicondyle to point where the radial nerve bends from posterior to lateral was 142 mm on AP radiographs and 152 mm measured on the lateral radiographs. The average distance from the medial epicondyle to point where the radial nerve bends from lateral to anterior on AP radiographs was 66 mm. On the lateral radiographs where the nerve moves away from the anterior cortex 83 mm to the center of capitellum and trochlea (CCT). The distance from the bifurcation of the radial nerve into the posterior interosseous nerve (PIN) and superficial radial nerve was 21 mm on AP radiographs and 42 mm on the lateral radiographs (CCT).ConclusionsThe course of the radial nerve in the distal part of the upper arm has great variety. Lateral fixation is relatively safe in a zone between the center of capitellum-trochlea and 48 mm proximal to this point. The danger zone in lateral fixation is in-between 48–122 mm proximal from CCT. In anteroposterior direction; distal fixation is dangerous between 21–101 mm measured from the medial epicondyle. The more distal, the more medial the nerve courses making it more valuable to iatrogenic damage. The IMN we compared with our data all show potential risk in case of (blind) distal locking, especially from lateral to medial direction.

Abstract. Debridement, antibiotics, and implant retention (DAIR) is a procedure to treat a periprosthetic joint infection (PJI) after total hip arthroplasty (THA) or total knee arthroplasty (TKA). The timing between the primary procedure and the DAIR is likely a determinant for its successful outcome. However, the optimal timing of a DAIR and the chance of success still remain unclear. We aimed to assess the risk of re-revision within 1 year after a DAIR procedure and to evaluate the timing of the DAIR in primary THA and TKA. We used data from the Dutch Arthroplasty Register (LROI) and selected all primary THA and TKA in the period 2007–2016 which underwent a DAIR within 12 weeks after primary procedure. A DAIR was defined as a revision for infection in which only modular parts were exchanged. A DAIR was defined as successful if not followed by a re-revision within 1 year after DAIR; 207 DAIRs were performed <4 weeks after THA, of which 16 (8 %) received a complete revision within 1 year. DAIR procedures performed between 4 and 12 weeks (n=98) had a failure rate of 9 % (n=9). After TKA 126 DAIRs were performed in less than 4 weeks, of which 11 (9 %) received a complete revision within 1 year; 83 DAIRs were performed between 4 and 12 weeks, of which 14 (17 %) were revised. There was no significant difference in 1-year re-revision rate after a DAIR procedure by timing of the DAIR procedure for total hip and knee arthroplasty based on Dutch registry data.