Patient-specific total knee arthroplasty: the importance of planning by the surgeon.

PURPOSE: The purpose of the study was to evaluate the accuracy of the planning of the patient-specific pin guides in total knee arthroplasty (TKA). This planning was performed primarily by a technician of the company and offered to the surgeon. All parameters of the implantation can either be modified or accepted by the surgeon. The hypothesis was that the plan needs preoperative intervention by the surgeon. METHODS: A prospective study in 50 patients was carried out. All patients received the same posterior-stabilised implant with patient-specific instrumentation. All surgical parameters (coronal, sagittal, rotational alignment, femoral and tibial resection levels and implant sizes) were checked by the orthopaedic surgeon and changed if necessary. RESULTS: Preoperatively, the femoral size was changed in 8 patients (16 %), the femoral flexion in 23 patients (46 %), the femoral shift in 34 patients (68 %), the tibial size in 24 patients (48 %) and the tibial rotation in all patients. The epicondylar axis was accepted in 47 patients (94 %) in the technician plan. Mean planning time was 8 ± 4 min. Intraoperatively, the femoral anterior-posterior size was in 50 patients (100 %) the same as in the surgeon and in 42 patients (84 %) the same as in the technician plan (p = 0.003). The tibial component implanted was in 42 patients (84 %) the same as in the surgeon and in 19 patients (38 %) the same as in the technician plan (p < 0.0001). A femoral distal recut was necessary in 31 patients (62 %) and a change of the tibial proximal cut in 17 patients (34 %) during surgery. Intraoperatively, no changes of the femoral and tibial alignment, the femoral anterior-posterior size, the femoral flexion, the femoral shift, the femoral and tibial rotation were necessary. Postoperatively, the coronal mechanical overall axis was within ±3° in 47 patients (94 %) with a maximum deviation of 5.6°. CONCLUSIONS: Significant changes of the technician plan were necessary to get an accurate preoperative plan. Intraoperative changes were significant less compared to the surgeon than to the technician plan. No major changes (alignment, femoral anterior-posterior size and rotation) of the surgeon plan were necessary. Surgeons using patient-specific pin guides in TKA may verify the default plan provided by the technician. A blind reply on the technician plan may be not recommended. LEVEL OF EVIDENCE: Therapeutic study, Level III.

Custom-fit minimally invasive total knee arthroplasty: effect on blood loss and early clinical outcomes.

PURPOSE: Recently, new custom-fit pin guides in total knee arthroplasty (TKA) have been introduced. Use of these guides may reduce operating time. Use of the guides combined with the absence of intramedullary alignment jigs may lead to reduced blood loss and improved early outcomes. Our aim was to evaluate blood loss and early clinical outcomes in patients undergoing minimally invasive TKA using custom-fit magnetic resonance imaging (MRI)-based pin guides. METHODS: A prospective study in 80 patients was carried out. Patients were divided randomly into 2 equal groups. In one group, intramedullary alignment jigs were used. In the second group, custom-fit MRI-based pin guides were used. All patients received the same cemented posterior-stabilized implant through a mini-midvastus approach. The volume in the drain bottles was recorded after 48 h. Hb loss was estimated by subtracting the postoperative from the preoperative Hb level. Transfusion requirements and surgical time were recorded. Outcome measures were Knee Society Scores (KSS), knee flexion, knee swelling and pain. RESULTS: There was lower mean drainage of blood in the custom-fit group (391 ml vs. 603 ml; p < 0.0001). There was no difference in estimated loss of Hb (3.6 g/dl vs. 4.1 g/dl; n.s.) and in transfusion requirements (7.5 % vs. 10 %; n.s.). Surgical time was reduced in the custom-fit group (12 min less; p = 0.001). KSS measured at week 2, 6 and 12 showed no significant difference between groups. Knee flexion measured on days 7, 10 and at week 6, 12 and knee swelling and pain measured on days 1, 3, 10 and at week 6, 12 showed no significant difference between groups. CONCLUSIONS: Using custom-fit pin guides reduces blood drainage, but not the estimated Hb loss in minimally invasive TKA and does not affect transfusion rate. Surgical time is reduced. There is no effect on the early clinical outcomes. LEVEL OF EVIDENCE: Therapeutic study, Level I.

Sexual dimorphisms in the effect of low-level p25 expression on synaptic plasticity and memory.

p25, a degradation product of p35, has been reported to accumulate in the forebrain of patients with Alzheimer's disease. p25 as well as p35 are activators of cyclin-dependent kinase 5 (Cdk5) although p25/Cdk5 and p35/Cdk5 complexes have distinct properties. Several mouse models with high levels of p25 expression exhibit signs of neurodegeneration. On the contrary, we have shown that low levels of p25 expression do not cause neurodegeneration and are even beneficial for particular types of learning and memory [Angelo et al., (2003) Eur J. Neurosci., 18, 423-431]. Here, we have studied the influence of low-level p25 expression in hippocampal synaptic plasticity and in learning and memory for each sex separately in two different genetic backgrounds (129B6F1 and C57BL/6). Surprisingly, we found that low-level p25 expression had different consequences in male and female mutants. In the two genetic backgrounds LTP induced by a strong stimulation of the Schaffer's collaterals (four trains, 1-s duration, 5-min interval) was severely impaired in male, but not in female, p25 mutants. Furthermore, in the two genetic backgrounds spatial learning in the Morris water maze was faster in female p25 mutants than in male transgenic mice. These results suggest that, in women, the production of p25 in Alzheimer's disease could be a compensation for some early learning and memory deficits.

Thermography as a means for quantitative assessment of stump and phantom pains.

Exact differentiation into stump and phantom pain is required when pain is reported after amputation. In a majority of cases appropriate treatment can improve the pain. Thermography is simple and gives a good indication of the circulation in the stump without operative intervention. It provides a key to the nature of the pain in stump and phantom. Although typical patterns occur for pain in the stump or phantom, in this study the thermographic image could confirm the presence of phantom pain, but it could not rule out errors or false statements.