What is a 'good' result after a joint replacement arthroplasty and how it can it be predicted?

Age and Preoperative Knee Society Score Are Significant Predictors of Outcomes Among Asians Following Total Knee Arthroplasty.

While this paper is about knees, its substance is relevant to important questions about shoulder arthroplasty: what is a good result and how can it be predicted?

These authors extracted registry data from 2006 to 2010. Outcomes were evaluated using the Oxford Knee Score (OKS)(higher scores indicate greater disability) and the Short Form (SF)-36 physical component summary (PCS)(higher scores indicate better physical function). Follow-up data were available for 3,062 patients who underwent primary TKA (mean age of 66.4 years; 79.5% female).

A "good outcome" at 5 years was defined in two ways:

(1) as an improvement in scores of greater than or equal to the minimal clinically important difference (MCID) in the primary analysis. The MCID for the OKS was 5, and the MCID for the PCS was 10. 

(2) as an OKS of <30 and a PCS score of >50. 

Age and preoperative Knee Society score (KSS) were found to be significant predictors. 

When outcomes were assessed by the MCID, lesser age and lower (worse) preoperative KSS predicted a good outcome at 5 years. 

When outcomes were assessed by absolute criteria (postoperative scores measured against OKS and PCS thresholds), a higher (better) preoperative KSS predicted a good outcome at 5 years. The effect of age was not significant.

Body mass index, preoperative flexion range, SF-36 mental component summary (MCS) score, mechanical alignment, sex, education level, ethnicity, operative side, number of comorbidities, type of anesthesia, and type of implant were found not to be significant predictors.

The authors concluded that the majority (85%) of their patients with osteoarthritis had good outcomes according to the MCID criterion and benefitted from primary TKA.

Older patients with a lower (worse) preoperative KSS can be informed that they have a high likelihood of improvement but a lower likelihood of achieving as good a functional outcome as those with better scores.

Comment: This paper is informative.
First, many of the factors that one might think would infuence the quality of the result did not have a significant effect (BMI, preoperative flexion range, SF-36 mental component summary (MCS) score, mechanical alignment, sex, education level, ethnicity, operative side, number of comorbidities, type of anesthesia, and type of implant).

Second, they showed that patients who were more functional before surgery realized the best function after surgery, whereas those who were less functional before surgery realized the most improvement.

These outcomes can be emulated by the chart below that uses data for three hypothetical patients.

We will all agree that the patient represented by the circle did poorly (as would be the case for any patient below the line). But did the diamond patient or the square patient get the better result? The diamond patient improved more but the square patient wound up with 90% of normal function and improved by half of the preoperative functional deficit (whereas the diamond improved only 33% of the preoperative functional deficit).

Rather than arguing whether the amount of improvement or the absolute value of the postoperative function is better, we should acknowlege that both may be useful in explaining the likely result of surgery to the patient.

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Do surgical results keep getting better with increasing experience?

Trend Toward High-Volume Hospitals and the Influence on Complications in Knee and Hip Arthroplasty

These authors used data from the National Inpatient Sample (2000 to 2012) to quantify trends in total hip arthroplasty (THA) and total knee arthroplasty (TKA) volume. They identified elective primary THAs and TKAs and grouped them by hospital by utilizing the hospital identifier, which indicated the geographic location of the hospital. They obtained county geographic and population data from the U.S. Census, and calculated the distances between hospitals and the centroids of counties. They obtained risk-standardized surgical complication rates for hospitals (2009 to 2012)  from Medicare Hospital Compare and grouped them by hospital volume.

They found a marked increase in the number of hospitals that performed a combined volume of ≥400 elective primary THAs and TKAs. The number of elective primary TKAs and THAs performed annually increased from 343,000 to 851,000.

In 2012, 65.5% of the arthroplasties were performed in high-volume hospitals (≥400 arthroplasties annually), and 26.6% of the arthroplasties were performed in very high-volume hospitals (≥1,000 procedures annually). The proportion of arthroplasties performed in low-volume hospitals (<100 arthroplasties annually) shrank from 17.9% to 5.4%. 

Very high-volume hospitals had the lowest complication rates (2.745 per 100; 95% confidence interval [CI], 2.56 to 2.93), and low-volume hospitals had the highest complication rates (3.610 per 100; 95% CI, 3.58 to 3.64; p < 0.0001) (odds ratio, 1.327; 95% CI, 1.26 to 1.40). Each successively higher hospital volume category manifested a lower complication rate.

Using 50 miles as a radius, the percentage of the U.S. population living near a high or very high-volume hospital was still 81.9%, well above the 65.5% of procedures performed at high-volume hospitals. Their data indicated that approximately 130,000 patients annually forwent an arthroplasty procedure at a high-volume hospital despite there being a high-volume center available in their geographic area. 

Comment: The relation between the quality of the result and surgical experience is an important topic - see this recent post (link). While this study is about hips and knees and hospital rather than surgeon volume, it is important because it suggests that the effect of volume may not have a 'threshold for an optimal result', in other words, there is no obvious level above which results stop improving. If a golfer that hits 200 balls per year is not as good as one who hits 500 per year who is not as good as one who hits 1000 per year, how much better are golfers who hit 2000 per year? The answer suggested by this study is that more (volume) is more (fewer complications).

The authors also pose the interesting question - what percent of patients are willing to drive 50 miles to lower their complication rate?  The observation 130,000 patients annually forwent an arthroplasty procedure at a high-volume hospital despite there being a high-volume center available in their geographic area may be due to patient unawareness of the data relating volume to complications, to their high degree of comfort with their local provider, or to the fact that for some, 50 miles of travel may remain a substantial barrier.

Our view is that patients need to ask about the experience of their surgeon in terms of volume, results and complications so that their decisions can be well informed.

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Patient-specific Instrumentation - No Functional Benefit

The John Insall Award: No Functional Benefit After Unicompartmental Knee Arthroplasty Performed With Patient-specific Instrumentation: A Randomized Trial.

The authors hypothesized that unicompartmental knee arthroplasty (UKA) performed with Patient-specific Instrumentation (PSI) would result in improved level gait as ascertained with three-dimensional analysis, implant positioning, and patient-reported outcomes measured by a validated scoring system when compared with conventional instrumentation 3 months and 1 year after surgery.

They randomized 60 patients into two groups using either the PSI technique or a conventional technique. All patients were operated on using the same technique and the same cemented metal-backed implant.

For the patients allocated to the PSI group,MRIs were obtained after randomization. All patients had their MRI completed  using a standardized protocol validated by the protocol manufacturer (MaterialiseTM , Leuven, Belgium). After segmentation, the engineers planned the UKA and submitted the plan to the surgeon. Based on the clinical examination and standing full-length hip-to-ankle radiographs, the plan was scrutinized and modified by the surgeon to set the appropriate depth of the distal femoral and tibial cuts, flexion of the femoral implant, and slope of the tibial plateau.

One year after surgery, there were no differences between the two groups in the analyzed gait spatiotemporal parameters, in terms of lower limb alignment,  implant positioning on mediolateral and anteroposterior radiographs, or in the functional scores.

Their observations suggest that PSI may confer small, if any, advantage in alignment, pain, or function after UKA. This argument can therefore not be used to justify the extra cost and uncertainty related to this technique.

Comment: When new technologies are brought forward, it is important to ask 'who will benefit'? The possibilities might include the manufacturer, the designer, the product champion, the medical center, the surgeon and/or the patient. In that the incremental cost of these technologies is ultimately borne by the patient and the patient's insurance, their use should be justified in term of benefit to the patient.This Level I randomized controlled study was unable to determine a value of PSI to the patient.

We include this total knee article in the Shoulder Blog because it shows the type of high quality clinical research that is necessary to evaluate the value of new technologies, including the many different forms of patent specific instrumentation, that are being introduced yearly to the shoulder marketplace.

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Propionibacterium periprosthetic infections of hip, knee and shoulder

Treatment of prosthetic joint infections due to Propionibacterium

These authors conducted a retrospective cohort study to evaluate treatment success at 1- and 2-year follow-up after treatment of 60 Propionibacterium-associated prosthetic joint infections (PJI) of the shoulder, hip, and knee at a median duration of 21 (0.1-49) months  39 patients received rifampicin combination therapy, with a success rate of 93% (95% CI: 83-97) after 1 year and 86% (CI: 71-93) after 2 years. The success rate was similar in patients who were treated with rifampicin and those who were not.

Most of the blood tests for inflammation were unremarkable. On average 6 specimens were sent for culture and on average 3 of these were positive for Propi. The specifics of the culturing protocol for Propi is not explained.

An open debridement and prosthesis retention was performed if an early postoperative or acute hematogenous PJI was diagnosed. Those patients with a late chronic infection were managed with a 2-stage exchange arthroplasty. Patients who, preoperatively, were not suspected of having an infection, e.g. with aseptic loosening, polyethylene wear, instability, or prosthesis dysfunction, were treated with a 1-stage exchange arthroplasty. In these patients, a PJI was therefore diagnosed from positive intraoperative cultures.

The combination of surgery and long-term antibiotic treatment postoperatively resulted in an overall success rate of 93% at 1-year follow-up and 86% at 2-year followup. At two year followup 7 of 36 patients had failed - four with evidence of ongoing infection with Propionibacterium and 3 with an infection by a different organism.

Comment: One of the first things to catch our eye was the number of Propionibacterium periprosthetic infections identified for the hip and knee. Up until recently, Propi infections were thought to be primarily in the shoulder. Most of the patients presented with the 'stealth' mode typical of Propi:  49 of the 60 patients with pain and 25 with stiffness.

The results of this series combining three different joints are quite similar to those we have previously note for the shoulder. Perhaps our hip and knee colleagues should consider the possibility of Propionibacterium periprosthetic infections in those patients with apparently 'aseptic' joint pain and stiffness.

In that this was not a prospective study, it is difficult make robust conclusions about the role of Rifampin in the management of these infections. There is no question that Rifampin can complicate the postoperative course by interfering with the action other medications the patient may need.



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Shoulder Joint Replacement Arthroplasty - transexamic acid - topical vs IV? Will it work in the shoulder as well as in TKA and THA?

Topical Tranexamic Acid Was Noninferior to Intravenous Tranexamic Acid in Controlling Blood Loss During Total Knee Arthroplasty

These authors sought to determine how the safety and efficacy of topical tranexamic acid (TXA) compares with intravenous (IV) TXA. They conducted a blinded, controlled, randomized trial of  89 patients ≥18 years of age (mean age, 64.8 years; 74% women) who were undergoing elective unilateral primary total knee arthroplasty for osteoarthritis by an individual surgeon. 42 patients received topical and 47 IV TXA
42 patients were allocated to topical (2.0 g of TXA in 100 mL of normal saline solution directly into the surgical site, which was left undisturbed for 2 minutes before tourniquet release).  47 patients were allocated to IV TXA (a single 10-mg/kg dose of TXA 10 minutes before tourniquet release).

The topical and IV TXA groups did not differ in terms of the decrease in hemoglobin levels or  in terms of total drain outputs. 1 patient in the topical group required a blood transfusion. Postoperative complications included acute kidney injury (1 patient), myocardial infarction (1 patient), and death (1 patient) in the topical group and acute kidney injury (1 patient) in the IV group. There were no cases of deep-vein thrombosis or pulmonary embolism at 18.3 weeks postoperatively.

Comment: While  the current literature indicates that the use of TXA in total hip and knee arthroplasty is widespread, its use in shoulder arthroplasty is uncommonly reported.

Some papers at the AAOS did describe its use:

The Effectiveness of Tranexamic Acid in Reducing Blood Loss after Total Shoulder Arthroplasty

compared the effect of 100 cc of normal saline or 100 cc of normal saline with 2 g TXA by topical application into the wound at the completion of the case and found that the average blood loss recorded after surgery was 170 mL in the placebo group and 108 mL in the TXA group (p = 0.017). The average change in hemoglobin was 2.6 g/dL in the placebo group and 1.7 g/dL in the TXA group (p < 0.001).There were no transfusion requirements or postoperative complications noted in either group.

The authors of Tranexamic Acid Decreases Blood Loss Following Total Shoulder Arthroplasty used a dose of 20mg/kg IV given at the time of skin preparation. One-hundred-twenty-two consecutive patients were done between then and December 2012 and all received TXA and were included in this study (Group A). They were compared with the previous consecutive 108 patients done without TXA (Group B).

The mean dose was 1657 mg, resulting in a mean cost of $68. Statistically significant differences in both Hb loss (Group A change = 2.22 vs. Group B change 2.58, p=0.04) and Hct loss (Group A change = 6.67 vs. Group B change = 8.09, p < 0.01) were seen in the TXA group compared to the non TXA group. In patients receiving TXA, there were statistically significant decreases in the time spent in the recovery room (mean, Group A 68 mins vs. Group B 94 mins, p < 0.01) and total length of hospitalization (mean, Group A 1.16 days vs. Group B 1.36 days, p=0.03). Two patients in Group A received a blood transfusion while six patients in Group B received transfusions

A clinical trial Tranexamic Acid in Reverse Total Shoulder Arthroplasty (TXA) has been registered.


So it looks as though interest is rising in the use of this agent. Stay tuned.

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Postoperative chondrolysis after intra-articular pain pump infusion of an anesthetic medication - now in the knee as well as the shoulder. JBJS

Previous posts on this blog from 3/25/11, 4/7/11, 10/1/11, 11/3/11, 11/9/11, 11/10/11, 11/29/11, 12/31/11, 1/23/12, 2/18/12 and 4/11/12 have dealt with the development of postoperative glenohumeral chondrolysis after intra-articular pain pump infusion of an anesthetic medication.

The JBJS recently published an article regarding the same complication of pain pumps when used in the knee: "The Development of Postoperative Knee Chondrolysis After Intra-Articular Pain Pump Infusion of an Anesthetic Medication: A Series of Twenty-One Cases". 

In each of 17 knees in this most recent report, 0.5% bupivacaine was infused and in one 0.25% bupivacaine was infused.

This article provides additional independent evidence supporting the causation of chondrolysis by pain pumps, even though this causational relationship has been termed 'speculative' by some authors.

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