Shoulder surgery is often associated with substantial postoperative pain1. As a result, many postoperative pain management modalities, often in combination, are in common usage. These include patient-controlled analgesia with intravenous opioids; periarticular injections of morphine or local anesthetic2; nonsteroidal anti-inflammatory drugs, including the cyclooxygenase (COX)-2 inhibitors3; regional nerve blocks4; and oral analgesics.
While effective, each of these modalities has known disadvantages. Most patient-controlled analgesia pump systems require expensive equipment5 as well as the education of patients and monitoring by nursing staff, and they are available only to inpatients. In addition, strong opioid analgesia may cause nausea and vomiting, respiratory depression, and sedation. Potential adverse effects of nonsteroidal anti-inflammatory drug therapy include peptic ulcer disease, platelet dysfunction, hypertension, fluid retention, renal impairment, and delayed tendon-bone healing6,7. Interscalene nerve blocks, while effective, require skilled personnel, have a limited duration unless a catheter and infusion are used, have potential complications including pneumothorax and permanent nerve damage8, and may interfere with postoperative assessment and function9,10.
Recently, a local anesthetic administered directly to the operative site either by continuous infusion or infiltration has been reported to be a potential important advance for orthopaedic postoperative pain management1,11. This technique offers potential advantages over regional anesthetic techniques. The catheter is simple to insert and maintain and is positioned under direct visualization, which reduces the prevalence of nerve and vascular damage. The elastomeric pump is preloaded for single use, runs at a fixed rate, is simple to use, and also reduces nursing time compared with the time associated with the maintenance of patient-controlled analgesia with opioids. Several recent randomized placebo-controlled trials have assessed this modality in shoulder surgery12-18.
While direct comparison between trials is difficult because of differing operative procedures, catheter placement, and local anesthetic used, some trials have found this modality to result in lower postoperative pain and less analgesia use12,14-16,18, while others have found no benefits over placebo13,17. These conflicting results may also be due to methodological issues such as small sample sizes and failure to take into account the potential confounding of multiple surgeons with potentially varying surgical skills12-18.
In Australia, arthroscopic and mini-incision shoulder operations are generally performed as inpatient procedures (one day for a subacromial decompression and one to two days for a rotator cuff repair). Pain management following these procedures in our setting has traditionally consisted of preemptive local anesthetics (ropivacaine [Naropin]; AstraZeneca, North Ryde, New South Wales, Australia) and postoperative opioids administered with patient-controlled analgesia. Recently, intraoperative intravenous parecoxib (Dynastat; Pfizer Australia, West Ryde, New South Wales, Australia), a selective COX-2 inhibitor, and direct operative ropivacaine infusion pumps were introduced concurrently as standard practice, although evidence for their added benefits was limited19. While the addition of parecoxib was relatively cheap (a 40-mg intravenous bolus of parecoxib was A$25 [US$18] at the time of publication), ropivacaine infusion pumps were associated with substantially increased costs (a disposable pump with single or dual catheters ranged from A$300 to A$600 [US$216 to US$432] and ropivacaine cost A$155 [US$112] at the time of publication).
The aim of this randomized placebo-controlled trial was therefore to determine the effectiveness and safety of a continuous infusion of 0.75% ropivacaine at 5 mL/hr, delivered by a pain management system with a single multiorifice catheter (PainBuster; I-Flow, Lake Forest, California) when used following elective arthroscopic or mini-incision rotator cuff surgery. Our hypothesis was that ropivacaine would provide pain relief equivalent to that of a placebo.
Materials and Methods
We performed a randomized, participant and outcome assessor-blinded, placebo-controlled trial at two private hospitals in Melbourne, Australia. Two institutional Ethics Committees approved the study, and all participants provided written informed consent. The trial was registered in the Australian Clinical Trials Register (Number ACTR12606000195550).
The study methodology is presented in detail elsewhere19. In brief, participants were recruited from the private community-based practice of a single orthopaedic shoulder surgeon. All consecutive eligible patients who fulfilled the selection criteria were offered study participation. Inclusion criteria were adults who were eighteen years of age or older for whom elective arthroscopic subacromial decompression or rotator cuff repair was planned. Exclusion criteria were (1) massive or irreparable rotator cuff tears; (2) defects that required filling with grafts; (3) a previous injury or surgery on the shoulder, i.e., a fracture or revision surgery; (4) a previous mastectomy on the affected side; (5) peripheral neuropathy affecting the upper limbs; (6) chronic opioid use; (7) morbid obesity (a body mass index of >35 kg/m2); (8) Parkinson disease; (9) pregnancy; (10) a contraindication to parecoxib, including aspirin-sensitive asthma, a history of recent gastric or duodenal bleeding, severe renal impairment, or sulfonamide allergy; or (11) an inability to understand written and/or spoken English.
Participants were required to cease nonsteroidal anti-inflammatory drugs two weeks prior to surgery but were allowed to take codeine, paracetamol, or dextropropoxyphene hydrochloride-paracetamol. All participants were treated as inpatients. At the time of the operation, the patients received a standardized general anesthesia with 2 to 2.5 mg/kg of propofol and 1 to 2 μg/kg of fentanyl as induction agents and nitrous oxide and oxygen in a ratio of 2:1, with or without isoflurane, and morphine as required to maintain heart rate, blood pressure, and respiratory rate within normal limits. Spontaneous ventilation on a laryngeal mask was maintained unless contraindicated. All participants received a total of 20 mL of 1% ropivacaine, which was injected as a preincision bolus dose into both the glenohumeral joint and the subacromial space fifteen minutes prior to the insertion of the arthroscope, and an intraoperative intravenous bolus of 40 mg of parecoxib.
With the patient in the lateral position with the arm in traction, the arthroscope was initially introduced through a posterior portal. Arthroscopy was then performed with assessment of the glenohumeral and subacromial regions to confirm the presence of impingement and/or a tendon tear and the required operative intervention (arthroscopic subacromial decompression or rotator cuff repair). All patients who had fulfilled the inclusion criteria and had provided written consent were then randomized and stratified by operation type. The randomization sequence with use of random permuted blocks was generated by the study biostatistician. Stratified allocations were sealed in opaque and consecutively numbered envelopes kept in a locked location. These were opened in sequence by an independent administrator who was not involved in eligibility or outcome assessment or in ropivacaine administration.
The subacromial decompression involved arthroscopic division of the coracoacromial ligament with use of bipolar electrosurgical ligament ablation and removal of the anterior and inferior corner of the acromion with a power burr. Repairs were carried out with a so-called mini-incision approach. Through a short lateral incision, a deltoid-splitting approach was made to the subacromial space without detaching the deltoid from the acromion. The tear was repaired back to a freshened greater tuberosity in a footprint manner with a combination of medial anchors with sutures through the rotator cuff and more lateral transosseous sutures. The PainBuster catheter was inserted into the subacromial space by the surgeon at the conclusion of surgery, with the position verified by direct or arthroscopic vision. Portals were closed with interrupted sutures. All participants who had a rotator cuff repair had the wound closed in layers, and they received four doses of 1 g of intravenous Keflin (cephalothin sodium), with one dose given preoperatively and three given postoperatively at six-hour intervals.
A nurse who was not associated with the study attached the elastomeric pump containing 180 mL of either 0.75% ropivacaine or an identical placebo of normal saline solution set to run at 5 mL/hr. All patients had access to alternative analgesia for breakthrough pain. This consisted of a patient-controlled analgesia pump of intravenous morphine, with 2 mg available on demand, a five-minute lockout period, a maximum of 30 mg in four hours, and no background infusion, as well as oral dextropropoxyphene hydrochloride-paracetamol. All medications were recorded.
All outcome assessors were blinded to the treatment allocation. One assessor performed all baseline and two or four-month assessments. Postoperative pain scores, analgesia, and duration of hospital stay were recorded by the hospital nursing staff. Outcomes were assessed postoperatively at fifteen, thirty, and sixty minutes; at two, four, eight, twelve, eighteen, and twenty-four hours; and then at two months for arthroscopic subacromial decompression or four months for rotator cuff repair.
Pain was measured with use of an 11-point verbal analogue pain scale (with 0 indicating no pain and 10, the worst pain imaginable). Preoperatively, participants were instructed in the use of the verbal analogue pain scale as well as the patient-controlled analgesia. The primary end point was average pain at rest over the first twelve-hour postoperative period with use of the verbal analogue pain scale. Average pain scores were calculated as weighted averages, with weighting by the duration of time since the previous measurement. This weighting ensures that the earlier and more frequent measurements are not overrepresented in the average. Secondary end points were the average pain at rest over the second twelve-hour postoperative period and maximum pain over the first and second twelve-hour periods.
All analgesic medication requirements were recorded, with intravenous opioid intake in milligrams and oral analgesic intake as a tablet count.
Variation from standard hospital discharge time was measured as more than a one-night stay for patients who had arthroscopic subacromial decompression and as more than a two-night stay for patients who had rotator cuff repair.
All adverse events, including the presence of infection, were recorded. The amount of postoperative leakage was recorded with use of a three-category ordinal scale of none, minor, or major leakage. Leakage in this study referred to postoperative drainage from the portal sites and not from the infusion device. Minor leakage was defined as requiring a change of dressing, and major leakage, as requiring a change of bed linen; otherwise, leakage was recorded as none. The accuracy of delivery of the infusion and ease of removal of the catheter were also assessed.
Active shoulder movements were measured with use of a standardized and reliable protocol20 at baseline and at two months for the arthroscopic subacromial decompression group or four months for the rotator cuff repair group. The occurrence of a postoperative stiff painful shoulder was defined as the presence of symptoms of shoulder pain and stiffness and restriction of movement of ≥30° in two or more planes.
Sample Size Calculation
Sample size was based on clinical equivalence, which was considered a difference in mean pain scores of ±1 point on an 11-point scale21-23. Statistically, equivalence was declared if the 90% confidence interval for the difference in mean pain scores between the groups lay entirely within the interval of −1 to +1. To have an 80% probability that this equivalence would occur when the two infusion therapies are actually exactly equivalent required seventy patients per arm, assuming a standard deviation of 2 points within each arm (obtained from pilot work). This sample size was also able to detect a difference of 0.95 point with 80% power and a two-sided 5% significance level. Allowing for 10% dropout, the sample size was inflated to seventy-eight patients per group.
The principal analyses involved the comparison of average scores of pain at rest in the first twelve hours postoperatively between the patients who had ropivacaine infusion and those who had the placebo with use of an intention-to-treat analysis. This was performed by multiple regression of each outcome variable with infusion type as the independent variable and adjusted for operative procedure as a covariate. Similar analyses compared maximum pain at rest in the first twelve hours and average and maximum pain at rest in the second twelve-hour postoperative period. The sensitivity of the results from each regression model to a potential baseline imbalance in prognostic factors was assessed by refitting each regression model with adjustment for each slightly imbalanced baseline factor. Since only minimal differences ensued, the results are presented without adjusting for such baseline factors. Further analyses assessed differences between the trial arms in maximum and average pain scores at rest, adjusted for the amount of opioid used.
To assess the impact of non-normality of the outcomes, all analyses were repeated with use of 1000 bootstrap replications24. Since only negligible differences resulted, only the linear regression results are presented. To compare the use of oral analgesia, which was measured on an integer scale, Poisson regression with an identity link function and robust standard errors was used. Poisson regression is a method used for analysis of data in the form of counts, the identity link is used to estimate an effect on a difference scale (rather than a ratio), and robust standard errors allow for the presence of greater variability in counts than is predicted by the Poisson distribution, called overdispersion25. For the comparison of differences between groups in binary outcomes, the chi-square test was used, with regression adjustment for additional factors made with use of logistic regression. For ordinal-scaled outcomes, the proportional odds regression model25 was used for assessment of both unadjusted and adjusted differences between groups. The length of hospital stay and duration of PainBuster catheter insertion were analyzed with the stratified Wilcoxon rank-sum test.
Source of Funding
This study was partially supported by a grant from the Victorian Orthopaedic Research Trust, Melbourne, Australia. The Trust did not have any role in the study other than to provide funding. The placebo PainBuster pumps and catheters were provided gratis by Surgical Synergies, Regents Park, New South Wales, Australia.
The flow of participants through the trial is shown in Figure 1. Two hundred and thirty-three consecutive patients were screened, and 158 participants enrolled in the study. Reasons for noninclusion are shown in Figure 1. Forty-five patients had provided informed consent, but trial enrollment was completed by the time of their surgery, which had been delayed because of social reasons (e.g., postponed because of a holiday) or a delay in receiving Workers' Compensation insurance approval to proceed.
Eighty-eight participants received an arthroscopic subacromial decompression (forty-three in the placebo arm and forty-five in the ropivacaine treatment arm), and seventy participants received rotator cuff repair (thirty-five participants in both the placebo and ropivacaine treatment arms). Follow-up was complete for all participants. The demographic and clinical characteristics of the participants are shown in Table I. Within the arthroscopic subacromial decompression and rotator cuff repair groups, the treatment arms were comparable at baseline for the variables that we assessed.
Compared with the placebo, continuous subacromial ropivacaine infusion resulted in a significant, but clinically unimportant, improvement in average pain in the first twelve hours following both arthroscopic subacromial decompression and rotator cuff repair (the average pain level in the ropivacaine and placebo arms was 1.62 and 2.16, respectively, for the arthroscopic subacromial decompression group and 2.12 and 2.82 for the rotator cuff repair group), with a pooled difference between groups of 0.61 (95% confidence interval, 0.22 to 1.01; p = 0.003) (Table II). There was no significant difference between treatment arms with regard to maximum pain at rest in the first twelve hours or average or maximum pain at rest in the second twelve hours in either the arthroscopic subacromial decompression or rotator cuff repair groups.
Thirty participants in the arthroscopic subacromial decompression group (eighteen [40%] of forty-five in the ropivacaine arm and twelve [28%] of forty-three in the placebo arm) and fourteen in the rotator cuff repair group (six [17%] of thirty-five in the ropivacaine arm and eight [23%] of thirty-five in the placebo arm) did not access opioids with patient-controlled analgesia (p value for pooled difference = 0.55). There was no significant difference in the amount of opioid usage in the first twelve hours between treatment arms in either the arthroscopic subacromial decompression or rotator cuff repair groups (pooled p = 0.12, Table II). In the second twelve hours, opioid usage was strikingly lower in all groups although, on the average, those in the placebo arms used slightly more opioid over the twelve hours (difference = 1.95 mg; 95% confidence interval, 0.17 to 3.72 mg; pooled p = 0.032) (Table II).
When the differences in pain outcomes were adjusted for the amount of opioid use, minimal differences from the results shown in Table II were observed. The only significant difference between the ropivacaine and placebo groups was for average pain in the first twelve hours (pooled difference = 0.49; 95% confidence interval, 0.12 to 0.86; p = 0.009). With respect to oral analgesia use, no significant difference was detected between treatment arms in either operative group for either the first or second twelve hours (pooled p = 0.54 and 0.39, respectively; Table II).
There was no evidence that the effect of ropivacaine differed according to whether opioids were used or not used. The average differences in the effect of ropivacaine between patients who used opioids and those who had not used opioids were −0.3 (95% confidence interval, −2.0 to 1.3) for average pain and −0.8 (95% confidence interval, −3.5 to 1.8) for maximum pain in the first twelve hours, and they were 0.0 (95% confidence interval, –0.9 to 0.9) for average pain and 0.2 (95% confidence interval, −1.0 to 1.5) for maximum pain in the second twelve hours.
There was a slightly greater proportion of patients with nausea and vomiting in the ropivacaine arm in the arthroscopic subacromial decompression group (twenty-nine [64%] of forty-five in the ropivacaine arm and twenty-five [58%] of forty-three in the placebo arm), with a more pronounced difference in the rotator cuff repair group (twenty-six [74%] of thirty-five in the ropivacaine arm and eighteen [51%] of thirty-five in the placebo arm) (Table III); however, the pooled odds ratio across both operative arms was not significant (p = 0.08). No infection occurred in either treatment arm for up to two months in the arthroscopic subacromial decompression operative group and up to four months in the rotator cuff repair operative group. Other adverse events that were reported were contact dermatitis from bed linen in one participant (in the group that had arthroscopic subacromial decompression with ropivacaine), unexplained bruising in the contralateral pectoral area in one participant (in the rotator cuff repair group that had the placebo), and the need for a cardiac stent four days postoperatively in one participant (in the rotator cuff repair group that had the placebo).
Leakage occurred in 127 (80%) of 158 subjects (Table III). There was no significant difference in the amount of leakage across treatment arms (pooled p = 0.37). Delays in hospital discharge were similar for the treatment arms in both operative groups (pooled p = 0.18). The reasons included persistent nausea and vomiting (four in the ropivacaine arm and seven in the placebo arm of the arthroscopic subacromial decompression group); persistent pain (one in the ropivacaine arm and two in the placebo arm of the arthroscopic subacromial decompression group and one in the ropivacaine arm and three in the placebo arm of the rotator cuff repair group); pain, nausea, and vomiting (one in the ropivacaine arm and one in the placebo arm of the arthroscopic subacromial decompression group and two in the ropivacaine arm of the rotator cuff repair group); a medical reason (one in the placebo arm of the arthroscopic subacromial decompression group had hemoptysis on warfarin therapy and was kept for observation); breathlessness requiring a cardiac stent for a blocked coronary artery (one in the placebo arm of the rotator cuff repair group); other (one in the placebo arm and one in the ropivacaine arm of the arthroscopic subacromial decompression group and one in the ropivacaine arm of the rotator cuff repair group who were elderly or had multiple comorbidities and had preplanned an extra night); and transportation difficulties due to distance to residence in the country requiring an extra night (one in the placebo arm of the arthroscopic subacromial decompression group). There was no difference between treatment groups in the proportion of patients who had postoperative stiff painful shoulder develop in either the arthroscopic subacromial decompression or rotator cuff repair groups (p value for pooled difference = 0.32) (Table III).
The PainBuster catheter was in the subacromial space for an overall median duration of 17.75 hours (range, 0 to 23.75 hours), and it differed little across operative groups or treatment arms (pooled p = 0.30). In one patient (from the placebo arm of the rotator cuff repair group), the clamp had not been opened and so the participant received no infusion. The rate of delivery of the infusion varied greatly. When the PainBuster was removed, we expected it to be about half full (approximately 90 mL); however, in 148 (94%) of 158 participants, it was one-quarter full or less. This did not differ significantly across treatment arms and operative groups (pooled p = 0.79).
We demonstrated that ropivacaine infusion provides no clinically important additional benefit over a preoperative bolus ropivacaine injection into the operative site and an intravenous dose of parecoxib following arthroscopic and mini-incision rotator cuff surgery. While there was a small but significant improvement in the average pain in the first twelve hours following surgery compared with the placebo, no observable benefit was seen with respect to maximum pain in the first twelve hours, average or maximum pain in the second twelve hours, reduction in opioid or oral analgesia use, duration of hospital stay, or the proportion with a postoperative stiff painful shoulder. These findings imply that, in this setting, the continued use of ropivacaine infusion is not worth the substantial additional costs.
It is likely that these findings would be equally applicable when these procedures are performed on an outpatient basis where slow-release oral opioid medication is provided to patients on discharge. While it is true that the placebo group had more opioid in the second twelve-hour period overall when the arthroscopic subacromial decompression and rotator cuff repair groups were pooled, neither displayed significant differences from ropivacaine individually (p = 0.13 for both), and, as shown in Table II, the differences were small and likely to be clinically unimportant (a mean of 1.53 mg over twelve hours for the arthroscopic subacromial decompression group and a mean of 2.47 mg for the rotator cuff repair group over twelve hours). Furthermore, the total amount of opioid usage in the second twelve-hour period was markedly lower than in the first twelve-hour period.
Our study has many strengths. In contrast to previous studies12,15-17, we stratified participants into two arms according to the operation performed, analyzed these groups separately, and pooled the results. The involvement of a single surgeon ensured the consistency of the surgical approach and reduced the risk of confounding by differences in surgical skill, technique, and management. The surgeon, participants, single outcome assessor, and nursing staff caring for the participants postoperatively were all blinded to treatment allocation, and all participants had complete follow-up.
There were also several limitations to our study. It was not designed to examine the efficacy of postoperative ropivacaine infusion as the sole pain management modality or the efficacy of parecoxib compared with that of ropivacaine infusion. At the time that our study protocol was developed, each of these treatment modalities had been introduced concurrently into standard care. Therefore, in our study, all participants received a combination of a preoperative injection of a bolus dose of ropivacaine into the operative site and an intravenous dose of parecoxib, in addition to the ropivacaine or saline solution infusion. Possibly as a result, one-third of the participants in the arthroscopic subacromial decompression group and one-fifth of the participants in the rotator cuff repair group did not access the available patient-controlled analgesia with opioids at all, and postoperative pain scores were generally low in all groups. As well as the use of concurrent modalities for pain, electrocautery and electrothermy were used rather than the older surgical technique of a chisel and file13, and this may also have contributed to the relatively low overall postoperative pain levels observed.
This was a partially pragmatic trial and so the protocol did not dictate that the catheter be removed at a certain time point. However, the variation in the timing of catheter removal observed in the trial reflects a common practice in our setting. While leaving the catheter in longer could theoretically favor the ropivacaine group in the twenty-four to thirty-six-hour period, on the basis of our findings in the first and second twelve-hour periods and the low level of overall pain in the second twelve-hour period in both groups in any case, we think that it would be highly unlikely that there would have been a substantial improvement in pain scores in the ropivacaine group if the catheters had stayed in longer. Moreover, the infusion rates were faster than the intended 5 mL/hr, with 94% of patients having a quarter or less of the fluid remaining when the catheter was removed. Thus for this conjecture to be true, the remaining ropivacaine would have to exert a remarkably strong effect.
Technical issues also hampered our trial. While flow rates were similar between treatment arms, they varied greatly. The majority of participants received infusions at greater than the programmed 5 mL/hr, although no side effects as a result of more rapid infusion of local anesthetic were observed. Previous reports have estimated that approximately one-third of documented incidents with continuous infusion pumps relate to unexpected flow rates26. However, in contrast to previous studies17,27-29, we did not observe any difficulties in removing the catheter or with regard to breakage of catheter tips, impaired wound-healing, or infection.
There is always leakage following arthroscopic shoulder surgery30,31, and leakage has been reported to be a major issue with continuous infusion devices26. While leakage may have affected the efficacy of the ropivacaine infusion, this was an effectiveness trial assessing ropivacaine infusion as it is used in routine clinical care. It is not practically possible to design a trial where there is no leakage. Minor leakage, whereby a change in dressing was required, occurred in 80% of our trial participants. As the catheter was always inserted with use of the same technique and the amount of leakage was similar in both treatment groups, the leakage that occurred may be related more to the amount of fluid in the soft tissues from the arthroscopy rather than to ropivacaine leakage.
In conclusion, we found that ropivacaine infusion provides no clinically important additional benefit over a preemptive bolus of local anesthetic and intravenous parecoxib for arthroscopic and mini-incision shoulder surgery. There were also important technical issues with its use, including an increased rate of delivery and leakage, although these were not associated with any important adverse events. The substantial additional cost of ropivacaine infusion does not appear to be justified.
NOTE: The authors thank Dr. Mark Crowther for his assistance in the administration of the randomization sequence. The placebo PainBuster pumps and catheters were provided gratis by Surgical Synergies, Regents Park, New South Wales, Australia.
Disclosure: In support of their research for or preparation of this work, one or more of the authors received, in any one year, outside funding or grants of less than $10,000 from the Victorian Orthopaedic Research Trust, Melbourne, Australia, and funding of less than $10,000 from an Australian National Health and Medical Research Practitioner Fellowship. Neither they nor a member of their immediate families received payments or other benefits or a commitment or agreement to provide such benefits from a commercial entity. No commercial entity paid or directed, or agreed to pay or direct, any benefits to any research fund, foundation, division, center, clinical practice, or other charitable or nonprofit organization with which the authors, or a member of their immediate families, are affiliated or associated.
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Investigation performed at the Cabrini Institute and Monash University, Victoria, Australia
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