Juan Sánchez-Soler

Use of antibiotic-loaded cement in total knee arthroplasty

Bone cement has the capacity to release antibiotic molecules if any antibiotic is included in it, and these elution properties are improved as cement porosity is increased. In vitro studies have shown high local antibiotic concentration for many hours or few days after its use. Antibiotic loaded bone cement (ALBC) is helpful when treating an infection in total knee arthroplasty (TKA) revision surgery. The purpose of this paper was to review the evidence for the routine use of ALBC in TKA in the literature, its pros and cons. Many authors have recommended the use of ALBC also in primary TKA for infection prophylaxis, but the evidence based on data from National Registries, randomized clinical trials and meta-analysis suggest a protective effect of ALBC against infection when used in hips, but not (or only mild) in knees. A possible explanation to this finding is that the duration and quantity of locally elevated antibiotic levels after surgery are smaller in TKA, due to the smaller amount of cement used for fixation in TKA-only a layer in the bone surface. There are some concerns about the routine use of ALBC in primary TKA as prophylaxis against infection: Firstly, there is a risk of hypersensivity or toxicity even when the chance is highly improbable. Secondly, there is a reduction in the mechanical properties of the cement, but this can be probably neglected if the antibiotic is used in low doses, not more than 1 g per 40 g cement package. Another significant concern is the increased economic cost, which could be overlooked if there were enough savings in treating fewer prosthetic infections. Finally, there is also a risk of selection of antibiotic-resistant strains of bacteria and this could be the main concern. If used, the choice of the antibiotic mixed in ALBC should consider microbiological aspects (broad antimicrobial spectrum and low rate of resistant bacteria), physical and chemical aspects (thermal stability, high water solubility), pharmacological characteristics (low risk to allergic reactions or toxicity) and economic aspects (not too expensive). The most commonly used antibiotics in ALBC are gentamicin, tobramycin and vancomycin. In conclusion, there is a paucity of randomized clinical trials in the use of ALBC in primary TKAs and the actual evidence of the effect of ALBC in reducing the risk of infection is insufficient. This, in addition to concerns about patient safety, risks of increase in the antibiotic resistance of microorganisms and the increase in costs in the procedure, lead us to recommend a cautious use of ALBC, perhaps only in high-risk patients (immunocompromised, morbidly obese, diabetic and patients with previous history of fracture or infection around the knee) unless the benefits of ALBC use were fully proven. Meanwhile, the rigorous use of peri-operative prophylactic systemic antibiotics and adoption of efficient antiseptic procedures and improved surgical techniques must be considered the gold standard in infection prevention in TKA surgery.

Pressure algometry is a useful tool to quantify pain in the medial part of the knee: An intra- and inter-reliability study in healthy subjects

PURPOSE Pain quantification is essential for diagnostic and pain monitoring purposes in disorders around the knee. Pressure algometry is a method described to determine pressure pain threshold (PPT) by applying controlled pressure to a given body point. The purpose of this study was to determine the reliability of this method when it was applied to the medial part of the proximal tibia metaphysis and to evaluate the PPT levels between genders. METHODS Fifty healthy (mean age; 46.9) volunteers were recruited, 25 men and 25 women. Pressure algometry was applied to a 1 cm(2)-probe area on the medial part of the knee by 2 raters. Intra- and interclass correlation (ICC) was obtained and differences between genders were evaluated. Bland-Altman plots were performed to evaluate the variability of the measures. RESULTS The mean values of PPT obtained by rater 1 and 2 were 497.5 Kpa and 489 Kpa respectively. The intrarater reliability values (95% IC) for rater 1 and 2 were 0.97 (0.95-0.98) and 0.84 (0.73-0.90) respectively. With regard to interrater reliability, the ICC (95% IC) for the first measurement was 0.92 (0.87-0.95) and 0.86 (0.78-0.92) for the second one. Women showed significant lower values of PPT than men. The Bland-Altmand plots showed excellent agreement. CONCLUSIONS Pressure algometry has excellent reliability when it is applied to the medial part of the proximal metaphysis of the tibia. Women have lower values of PTT than men. The high reliability of the PA in an individual volunteer makes it a more valuable tool for longitudinal assessment of a given patient than for comparison between them. LEVEL OF EVIDENCE Level III. Prospective study.

Pressure algometry is an excellent tool to measure knee pain relief after a closing-wedge high tibial osteotomy

PURPOSE The aim of this study was to assess the utility of pressure algometry (PA) to measure pain relief in the medial part of the knee after a closing-wedge high tibial osteotomy (CWHTO). METHODS Prospective study including 44 CWHTO. Pain relief was evaluated with the visual analogue scale (VAS) and PA, a radiological study was done and a functional assessment was carried out with the KSS preoperatively, at 6-months and at 1-year after the surgery. PA was applied to the medial and lateral part of the knee and to the infra-clavicular fossa as a control point. RESULTS The mechanical femorotibial angle was changed from 172.2° (SD2.2) to 180.6° (SD2.6) (p=0.00). KSS Knee improved from 53.4 (SD11.2) to 92.8 (SD7.3) (p=0.00), KSS Function from 69.4 (SD9.3) to 93.1 (SD8) (p=0.00). The VAS went from 6.84 (SD1.5) to 2.5 (SD2.1) (p=0.00) at the 1-year follow-up. The pressure pain threshold (PPT), measured with PA in the medial part of the knee also improved from 348.8kPa (SD159.3) to 447.1kPa (SD218.8) (p=0.01). However, the PPT in the lateral part of the knee and in the sub-clavicular fossa remained the same from the preoperative period to 6-months and 1-year, postoperatively. Neither were there any differences between the 6-month and 1-year postoperative values in terms of the different functional, radiological and pain relief obtained. CONCLUSION The pain relief obtained after a CWHTO in the medial part of the knee can be measured by using PA. Furthermore, the functional and pain improvement obtained at 1-year follow-up is no better than those obtained at 6-months postoperatively.

Biomechanics of Meniscal Repair

1. Meniscal repair is feasible and successful in around 75 % of cases when used for the right indications. 2. Different techniques (all-inside, outside-in, and inside-out) should be known to the surgeon disposed to repair a meniscal tear. 3. Suture repair with a vertically oriented suture configuration remains the gold standard in terms of load-to-failure values. Nevertheless, some meniscal repair devices have similar biomechanical properties to suture repairs. 4. It seems that an oblique configuration might be the best way to repair a radial meniscal tear. 5. Although several biomechanical tests have been described, most of studies published lack a thorough biomechanical evaluation. 6. Last but not least, all these aforementioned considerations are based purely on biomechanics. However, the process of meniscal healing is also based on biological aspects that the surgeon who performs a meniscal repair must keep in mind.