Local inflammatory and metabolic response in the knee synovium after arthroscopy or arthroscopic anterior cruciate ligament reconstruction

Younger patients and smokers report a higher level of pain after knee arthroscopy: a clinical and experimental study including synovial metabolism

PURPOSE

Factors associated with post-surgical pain are not fully explored. The aim of this study was to identify determinants of postoperative pain after arthroscopic surgery of the knee. Synovial tissue metabolism was analysed by microdialysis and the association with individual and peri-surgical factors to identify determinants important for pain management and thus patient satisfaction.

METHODS

Cross-sectional study of 57 patients (22 women) with median age of 39 years. All patients were operated on with arthroscopic surgery of the knee and monitored postoperatively with synovial microdialysis. The cross-sectional cohort was investigated to determine local tissue levels of inflammatory and metabolic compounds along with postoperative pain experience.

MEASUREMENTS

pain was determined by visual analogue scale (VAS). Postoperative synovial tissue levels of prostaglandin E₂ (PGE₂), glucose, and glycerol were measured by microdialysis in the knee synovium. Patients reporting VAS ≥ 4 received rescue pain medication with systemic opioids.

RESULTS

Initial results indicated that patients with pain (interpreted as having VAS ≥ 4), i.e. those receiving rescue medication with systemic opioids, were of a younger age (p = 0.04), lower body weight (p = 0.02), had a lower BMI (p = 0.04) and/or were smokers (p = 0.02). A closer analysis using multinomial logistic regression showed a significantly higher amount of pain in smokers (p = 0.01) and patients of a younger age (p = 0.02). A significant correlation was also found between VAS and duration of surgery (p = 0.007). No significant correlation could be found between VAS and synovial levels of PGE₂, glycerol and glucose, but a statistically significant decline with time of PGE₂ in both groups.

CONCLUSIONS

The results from this study show a significantly higher frequency of pain, post-surgery among younger patients (p = 0.02) and smokers (p = 0.01), as well as an association between pain and length of surgery (p = 0.007). These findings point out individual factors useful for the prediction of postoperative pain after arthroscopic surgery and are clinically important for personalized pain management.

LEVEL OF EVIDENCE

II.

Whole-body cryotherapy: empirical evidence and theoretical perspectives

Whole-body cryotherapy (WBC) involves short exposures to air temperatures below −100°C. WBC is increasingly accessible to athletes, and is purported to enhance recovery after exercise and facilitate rehabilitation postinjury. Our objective was to review the efficacy and effectiveness of WBC using empirical evidence from controlled trials. We found ten relevant reports; the majority were based on small numbers of active athletes aged less than 35 years. Although WBC produces a large temperature gradient for tissue cooling, the relatively poor thermal conductivity of air prevents significant subcutaneous and core body cooling. There is weak evidence from controlled studies that WBC enhances antioxidant capacity and parasympathetic reactivation, and alters inflammatory pathways relevant to sports recovery. A series of small randomized studies found WBC offers improvements in subjective recovery and muscle soreness following metabolic or mechanical overload, but little benefit towards functional recovery. There is evidence from one study only that WBC may assist rehabilitation for adhesive capsulitis of the shoulder. There were no adverse events associated with WBC; however, studies did not seem to undertake active surveillance of predefined adverse events. Until further research is available, athletes should remain cognizant that less expensive modes of cryotherapy, such as local ice-pack application or cold-water immersion, offer comparable physiological and clinical effects to WBC.

Temperature-sensitive release of prostaglandin E₂ and diminished energy requirements in synovial tissue with postoperative cryotherapy: a prospective randomized study after knee arthroscopy

BACKGROUND

Local external cooling of the surgical field after joint surgery is intended to enhance recovery and to facilitate the use of outpatient surgery by reducing pain and improving mobility. We hypothesized that the effects of postoperative cooling and compression after knee arthroscopy would be reflected in changes in the concentrations of metabolic and inflammatory markers in the synovial membrane.

METHODS

Forty otherwise healthy patients who were to undergo knee arthroscopy were included in the study, and half were randomized to receive postoperative cooling and compression. Microdialysis of the synovial membrane was performed postoperatively, and the concentrations of prostaglandin E₂ (PGE₂), glucose, lactate, glycerol, and glutamate as well as the ethanol exchange ratio (which indicates blood flow) were measured. The temperature of the knee was monitored, and postoperative pain was assessed by the patient with use of a visual analog scale, a numeric rating scale, and the need for rescue medication.

RESULTS

Application of the cooling and compression device after knee arthroscopy significantly lowered the temperature in the operatively treated knee (as measured on the skin, within the joint capsule, and intra-articularly). The cooling and compression appeared to decrease inflammation, as indicated by a temperature-sensitive decrease in the PGE₂ concentration. The hypothermia also decreased the metabolic rate of the synovial tissue and thus decreased energy requirements, as shown by the stability of the lactate concentration over time despite the decreased blood flow that was indicated by the increasing ethanol exchange ratio. No effect of the compression and cooling on postoperative pain was detected.

CONCLUSIONS

Local cryotherapy and compression after knee arthroscopy significantly lowered the temperature in the knee postoperatively, and the synovial PGE₂ concentration was correlated with the temperature. Since PGE₂ is a marker of pain and inflammation, the postoperative local cooling and compression appeared to have a positive anti-inflammatory effect.

The use of a non-benzodiazepine hypnotic sleep-aid (Zolpidem) in patients undergoing ACL reconstruction: a randomized controlled clinical trial

PURPOSE

Previous studies have addressed post-operative pain management after ACL reconstruction by examining the use of intra-articular analgesia and/or modification of anesthesia techniques. To our knowledge, however, no previous studies have evaluated the effect of zolpidem on post-operative narcotic requirements, pain, and fatigue in patients undergoing outpatient arthroscopic ACL reconstruction. The purpose of this prospective, blinded, randomized, controlled clinical study was to evaluate the effect of zolpidem on post-operative narcotic requirements, pain, and fatigue in patients undergoing outpatient arthroscopic ACL reconstruction.

METHODS

Twenty-nine patients undergoing arthroscopic ACL reconstruction were randomized to a treatment group or placebo group. Both groups received post-operative hydrocodone/acetaminophen bitartrate (Vicodin ES). Patients in the treatment group received a single dose of zolpidem for the first seven post-operative nights. Patients in the placebo group received a gelatin capsule similar in appearance to zolpidem. The amount of Vicodin used in each group, the amount of post-operative pain, and the amount of post-operative fatigue were analyzed.

RESULTS

Following ACL reconstruction, a 28% reduction was seen in the total amount of narcotic consumed with zolpidem (P = 0.047) when compared to placebo. There were no significant differences in post-operative pain or fatigue levels between zolpidem and placebo.

CONCLUSION

Adding zolpidem to the post-operative medication regimen after arthroscopic ACL reconstruction helps to lower the amount of narcotic pain medication required for adequate analgesia.

LEVEL OF EVIDENCE

Randomized controlled clinical trial, Level I.

Intra-articular morphine and bupivicaine for post-operative analgesia in anterior cruciate ligament reconstruction: a prospective randomised controlled trial

Anterior cruciate ligament reconstruction (ACLR) has the potential for significant post-operative pain. Conventional systemic opiate treatment may cause nausea and drowsiness, which may delay recovery. The use of intra-articular local anaesthesia has been shown to be effective. We wished to examine the additional effect of intra-articular morphine. This is a prospective, randomised, double-blind trial. Sixty patients were randomised to receive 20 ml 0.5% bupivicaine (group L, n = 30) or bupivicaine with 10 mg morphine (group M, n = 30) by intra-articular injection at the end of the operation. Visual analogue scores (VAS) were recorded before ACLR (expected pain) and repeated at 6 and 24 h after surgery. Time to first analgesic request and total systemic opiate and other analgesic use in the first 24 h was recorded. Pre-operative VAS measurements did not predict pain or analgesic use post-operatively. There were no significant differences between groups L and M with regard post-operative VAS or time to first analgesic request. Group M required less opiate analgesic post-operatively (oral morphine equivalent 50 mg for group L and 27 mg for group M, P < 0.007). There were no complications associated with the intra-articular analgesic. The simple addition of morphine to the intra-articular injection of bupivicaine gives a significant reduction in opiate analgesic requirement after ACLR.