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Patient Safety Authority
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Harrisburg, PA 17120

Phone: 717-346-0469
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Quarterly Update: Progress in Preventing Wrong-Site Surgery in Pennsylvania
Pa Patient Saf Advis 2011 Mar;8(1):39-40. 

Is the Pennsylvania Patient Safety Authority Preventing Wrong-Site Surgery Project making progress?

To answer this question, the Authority did a comprehensive review of all Incident and Serious Event reports from December 31, 2010, back to the inception of mandatory reporting by all hospitals and ambulatory surgical facilities on June 28, 2004. To ensure uniform criteria, the Authority analysts applied retrospectively the most recent and comprehensive search strategy. The current search strategy is another expansion of two earlier search strategies. The analysts initiated the expansions to ensure capture of reports missed by earlier searches, but detected by systematic case reviews.

In addition to the 11 reports from the fourth quarter of 2010 and a belated report from the third quarter, the comprehensive search found 14 other reports missed by the more restricted earlier searches (one each from 2004, 2006, and 2007, two from 2008 and 2010, and seven from 2009). These cases were classified in unsuspected event types, such a “preparation inadequate” and “accidental laceration.” One previous report was removed from the count when two separate previous reports were confirmed to be the same event. The final count as of December 31, 2010, is 416, an average of 16 per quarter or 64 per year.

Readers who have been following the quarterly updates in the Pennsylvania Patient Safety Advisory may have noticed the unexplained two-year cycles. To represent any possible trends resulting from the Preventing Wrong-Site Surgery Project, the Authority analysts calculated a rolling average, as Pelczarski et al. did for a regional collaborative in the greater Philadelphia region led by the Health Care Improvement Foundation’s Partnership for Patient Care.1 Because of the previously known two-year cyclicity, the Authority chose to use a two-year rolling average, beginning with the period from July 2004 through June 2006 (the first report was made in July 2004). The Figure shows those rolling averages for each monthly interval since, associated with the 95% confidence intervals. The first 12 rolling averages represent the yearly averages before program interventions began at the end of June 2007 with the first comprehensive Advisory article about the topic.2 The rolling averages between numbers 12 and 36 represent a mixture of months before and after program interventions began. The rolling averages from number 36 on represent months during which interventions regularly occurred. The 95% confidence intervals for the rolling averages for all periods starting after July 2010 are lower than those for any period before the program interventions began.

Figure. Pennsylvania Patient Safety Authority Wrong-Site Surgery Rolling Averages

  Figure. Pennsylvania Patient Safety Authority Wrong-Site Surgery
  Rolling Averages


A more sophisticated time-series analysis was done to determine the statistical reliability of the apparent decrease. The program interventions were modeled to be continuous, beginning at the end of June 2007 with the first comprehensive Advisory article about the topic.2 Time intervals of every month were used to obtain more than 50 data points, with a minimum of empty cells. An auto regression integration of a moving average (ARIMA) model was used for the time-series analysis. The model assumed no correlation of time intervals, no trend without interventions, and no correlation with the random shock of prior time intervals. Given the expectation that the program intervention could
only have a salutary effect, a one-tailed p = 0.05 was used to define 90% confidence intervals for the trend associated with the intervention. To be statistically reliable, the trend would have to be negative within the entire range of the confidence interval.

The results of the ARIMA did not confirm that the correlation of the trend with the program intervention was statistically significant. The baseline prior to the introduction of the program interventions was 5.5 reports per month. The cumulative effect of the program interventions to date was a decrease of 0.73 reports per month to a new baseline of 4.8 reports per month. However, the confidence interval of the trend (-.73) was not totally within the negative range (-2.03 to +0.57). Therefore, the reduction did not meet the predefined threshold for statistical significance; random variation was greater than the small trend toward improvement.

The results were unchanged with more data points using a two-week window, by including an auto regression to assume a correlation between time intervals, or by assuming a correlation with the random shock of prior time intervals.

Is the Pennsylvania Patient Safety Authority Preventing Wrong-Site Surgery Project making progress? The Authority is encouraged that consultation through its patient safety liaisons and its collaborative learning programs1 are creating a noticeable trend. However, the trend does not yet meet the rigorous test of a time-series analysis. More importantly, the Commonwealth has yet to experience a month, let alone a quarter, without wrong-site surgery. The Authority believes Pennsylvania facilities are on the right path to prevent wrong-site surgery, but have not yet reached the goal of zero.

This quarterly Advisory article will also discuss additional special considerations for orthopedic procedures on the knee.

Orthopedic Procedures on the Knee

A review of wrong-site orthopedic procedures involving the knee from July 2004 through June 2010 was done for a presentation to the Pennsylvania Orthopaedic Society in October 2010. Forty patients had wrong-site procedures. Twenty of the 40 (50%) had wrong-side blocks by anesthesiologists. Another 11 (28%) had wrong-side local anesthetic injections by orthopedic surgeons. Nine patients had wrong-site procedures: eight were wrong-site procedures and one was a wrong procedure on the correct knee. Five of the wrong-site procedures were complete wrong-site procedures and four were incomplete, corrected before completion. Seven of the nine wrong-site procedures were specified: three were arthroscopies and three others were arthroscopies with meniscectomies. Seven of the nine wrong-site procedures were described in sufficient detail to determine causal factors. One of the wrong-site procedures resulted from misinformation on the schedule. Six resulted from loss of orientation in the operating room (OR): two from miscues prompted by tourniquets on the wrong sides, one by a leg holder on the wrong side, one by a provider lifting the wrong leg for prepping and draping, another one by the wrong leg being prepped and draped, and one by loss of orientation intraoperatively while reconstructing the collateral ligaments of the knee.

Based on the review of wrong-site orthopedic procedures on the knee, the following suggestions can be made:

  • The most likely wrong-site procedure involving knee surgery is the administration of localized anesthetic by either the anesthesiologist or the surgeon (78% in this review). To prevent wrong-site procedures, injections of local or regional anesthetics should be treated as separate procedures requiring time-outs, unless the injections are done in continuity with the incisions after the time-outs for the principal procedures.
  • Most wrong-site knee operations resulted from following prior erroneous cues—five of seven identified causal factors in this review. To prevent right-left confusion in the OR, the operative sites should be marked consistent with the relevant documents and the patients’ understanding before the patients enter the OR; the marks should be visible at all times before the operations and specifically referenced in the prepped and draped fields during the time-outs.


  1. Pelczarski KM, Braun PA, Young E. Hospitals collaborate to prevent wrong-site surgery. Patient Saf Qual Health 2010 Sep-Oct:20-6.
  2. Doing the “right” things to correct wrong-site surgery. PA PSRS Patient Saf Advis [online] 2007 Jun [cited 2011 Jan 29]. Available from Internet:
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