Protocols, techniques may help overcome effects of surgeon volume on THA outcomes

Studies dating back nearly 20 years have shown a correlation between surgeon volume and the rate of complications in total hip arthroplasty, with higher-volume surgeons yielding lower complication rates.

“There are a fair number of studies now that establish pretty clearly that volume matters — independent of the volume done by the hospital,” said Jeffrey N. Katz, MD, MSc, professor of medicine and orthopedic surgery at Harvard Medical School and Brigham & Women’s Hospital in Boston.

In this Cover Story, Orthopedics Today explores the practices of high-volume total hip arthroplasty (THA) surgeons and provides pearls low-volume surgeons can use to improve outcomes.

In 1995, Carlos Lavernia, MD, medical director at The Center for Advanced Orthopedics at Larkin Hospital in Miami, and Jose F. Guzman, MS, BE, were some of the first researchers to show that patients of surgeons with a low volume of primary total hip and total knee arthroplasty cases (classified as fewer than 10 cases per year) had a significantly higher mortality rate and an increased average length of hospital stay.

“I looked at a small database, about 20,000 cases,” Lavernia said. “It was not as robust as today’s databases, but nevertheless, I did find some interesting results in terms of mortality rates. So almost 20 years ago, we already knew that volume and outcome go together. There have been a number of other papers since then that show that practice is not perfect, but it is better.”

“There may be a stepwise decrease in the incidence of complications for every additional five to 10 cases a surgeon performs each year up to about 50 cases,” Matthew S. Austin, MD, associate professor of orthopedic surgery at Thomas Jefferson University Hospital/Rothman Institute in Philadelphia, told Orthopedics Today. “Some studies have shown an increase in dislocation rate, an increase in infection [and] an increase in venous thromboembolic events related to low volume. But it is important to note that some studies have not found a difference in some of those variables between low-volume and high-volume surgeons.”

Despite a surgeon’s yearly volume, following protocols and continuing to improve one’s technique are paramount in avoiding complications.

“The message is not just that you do a high volume of surgery, but that you do it well and you follow the right protocol in the processes,” Lavernia said. “However, the statistics are clear that doing somewhere between 30 and 50 total hip arthroplasties a year leads to better outcomes.”

Newer data

More robust studies since Lavernia’s 1995 paper have continued to show that surgeon volume is related to patient outcomes.

Most recently, in Canada, Ravi and colleagues evaluated outcomes of nearly 38,000 patients who underwent primary THA. At 2 years postoperatively, they found that patients of surgeons who performed fewer than 35 cases per year had higher rates of dislocation (1.9% vs. 1.3%) and revision (1.5% vs. 1%) compared with patients of surgeons who performed more than 35 cases per year. However, Ravi and his colleagues did not find a relationship between surgeon volume and infection, periprosthetic fracture, venous thromboembolism or death.

In one of the earliest studies, Katz and his colleagues analyzed claims data of 58,512 Medicare recipients who underwent primary THA. Fifty-two percent of the primary THAs were performed by surgeons who did 10 or fewer THAs in Medicare recipients each year. Their study showed that patients treated by higher-volume surgeons (50 or more THAs per year) had a lower risk for dislocation compared with those treated by surgeons who performed five or fewer. Those patients who went to higher-volume hospitals (100 or more THAs per year) also had a lower risk for death compared with patients who underwent THA at a low-volume hospital.

A study of 57,488 Medicare beneficiaries, by Losina and his colleagues, revealed higher rates of revision THA for patients of low-volume surgeons (in this study, classified as fewer than 12 elective primary THAs per year) compared with those of high-volume surgeons (4.9% vs. 3.3%, respectively). The researchers noted this increased revision rate was most pronounced within the 18 months after the primary surgery.

In another study of Medicare beneficiaries, Solomon and his colleagues stated the volume of THAs performed by an individual surgeon is the most important determinant of orthopedic complications. They analyzed data from 5,211 Medicare patients and found 69% fewer events occurred in hospitals where more than 100 THAs were performed annually compared with those where 25 or fewer were performed per year. When they added surgeon volume to the models, it was the strongest predictor of adverse events.

“If you extrapolate these Medicare data to an all-payer practice, we know that surgeons who do more than 50 Medicare procedures a year have better outcomes than surgeons who do less than five,” said Kevin J. Bozic, MD, MBA, William R. Murray, MD, endowed chair and professor and vice chair in the Department of Orthopaedic Surgery at University of California, San Francisco. It is not a linear relationship, but the higher the volume of procedures a surgeon and a team — and it is a team — does, the more predictable their outcomes are.”

In a 2010 analysis of more than 180,000 consecutive patients who underwent total joint arthroplasty, Bozic and his colleagues found patients whose surgeons were in the lowest quartile for THA volume had a higher complication rate (OR = 1.50), readmission rate (OR = 1.24) and reoperation rate (OR = 1.55), as well as a higher likelihood of being discharged home, rather than to an inpatient facility for further rehabilitation (OR = 1.32), and a nearly 9% longer hospital stay. However, mortality rate was not associated with surgeon volume, although it was associated with hospital volume.

Data behind the mechanisms for better outcomes among higher-volume surgeons are lacking. “Surgical technique differs in ways that are hard to measure,” Katz said. “However, the data we have suggest that experience and developing systematized approaches — having algorithms that dictate care so that important things are not forgotten, such as when to give antibiotics — can lead to better patient outcomes.”

“It is the overall efficiency with which the procedure is done, and you improve as you do more surgeries,” Austin said. “Having a standard operating team can certainly help, because it is not just the surgeon — it is the surgical team, the surgical environment, the hospital and the patient. When you look at complications, you always have to look at the health of the patient. There are so many factors that go into this other than surgical volume.”

Bozic also suggested that high-volume surgeons are more adept at patient selection. “Some surgeons may fail to identify the patient who is most likely to benefit from the surgery in the first place,” he said. “A higher-volume surgeon is more likely to have a sense of which patients are most likely to benefit from the procedure based on experience. One of the more common things that I see is pain after hip replacement surgery because of failure to set appropriate expectations and/or identify which patients are most likely to benefit from surgery.”

The experience of the surgical team, such as the scrub nurse and surgical technician, also plays into the success of a surgery. “The surgeon is indeed the captain of the ship, but your assistants, where they put the retractors and how they handle things are key,” Lavernia said. “I would encourage folks who are not high-volume surgeons that if they have access to personnel who work with high-volume surgeons, they try to schedule the cases with that team.”

“Surgeons in hospitals with high volume have enough resources to have a specialized team, which could include dedicated nurses, anesthesiologists, physical therapists, possibly internists,” Bozic said. “That combination results in a more predictable outcome when there is communication among members of the team and they are used to working together.”

For low-volume surgeons who economically cannot work with a specialized team, Bozic suggested they and other surgeons in the area try to perform all THAs at one site where they can gain enough critical mass with other surgeons to develop a specialized surgical team.

Low-volume surgeons can also improve their outcomes by implementing evidence-based clinical care pathways. “Most high-volume surgeons have implemented clinical care pathways where they have the same treatment pathways for all patients,” Bozic said. “It is possibly modified based on patient risk factors.”

In their 2010 study, Bozic and his colleagues evaluated the influence of process standardization on patient outcomes. They found that following evidence-based processes of care, such as antibiotic-related process measures, led to improved clinical outcomes and shorter length of hospital stay, independent of hospital or surgeon procedure volume.

“Standardization of protocols and algorithms through the perioperative care of the patient can reduce the likelihood of complications,” Austin said. “In other words, handle patients in a similar fashion preoperatively, intraoperatively and postoperatively. Identify problems that patients may have and optimize them before surgery — it is all part of the process.”

Austin added that more data are needed to identify the optimum clinical care pathways to reduce complications “so that lower-volume centers can adopt an ideal clinical care pathway from a higher-volume center and achieve lower complication rates.”

Consistency is key to avoiding postoperative complications. “Part of a successful THA relates to what type of implant you are using and how often you change to a new implant that gives you new technical demands,” said Henrik Malchau, MD, PhD, Allen Gerry professor of orthopedic surgery at Harvard Medical School and an attending orthopedic surgeon at Massachusetts General Hospital in Boston and Sahlgrenska University Hospital in Mölndal, Sweden. “It is not a static issue, but it is probably more related to the fact that you use a surgical technique you are familiar with, you have developed a routine to use and you do not change too often.”

A surgeon’s handling of tissues and the length of surgery are major factors influencing the risk for complications after THA. “The amount of blood loss, tissue handling, tissue damage and the need for transfusion are all related to how adept a surgeon is in doing a procedure,” Lavernia said.

To avoid recurrent dislocations, “ensure optimal implant precision that takes specific anatomical features of the patient into account,” Malchau said. “Plan your surgery ahead of time and perform templating. That is an important educational effort and is important to let your assistants know what is going on. The combination of how you position your patient and how secure the patient is positioned on the table will give you a higher chance to obtain an optimal implant precision and thus avoid dislocations.”

Component malpositioning has been shown to be a factor in higher-volume surgeons yielding better outcomes. Barrack and colleagues found that low-volume surgeons were 2.16-times more likely to miss the target component position compared with high-volume surgeons.

“This is one of the rationales for using robotics,” Lavernia said. “The robot does not get tired, so after 10 cases, even the best surgeon in the world gets tired, and at some point, your accuracy and your skill set starts to get a little dull. There is a big future for robotics in joint replacement.”

Obtaining an X-ray of a trial component in the operating room can also help to improve accuracy of component placement and therefore reduce the potential for complications postoperatively. “I would recommend that if you are a surgeon who performs THA two to three times per month, you get an X-ray with a trial component in place before placing the final components,” Lavernia said.

Regardless of the number of THAs a surgeon performs per year, surgeons should always try to improve their techniques and skill sets. “Most importantly, surgeons should be critical of their results,” Bozic said. “You have to measure your outcomes and identify areas for improvement.”

“Although there is a big association between high volume and quality, high volume does not necessarily imply quality,” Lavernia said. “There are some high-volume sloppy things that are done in day-to-day life that we know about, but when it comes to being the best surgeon, it is that search for excellence, the ability to want to get better.”

Lavernia recommends surgeons continue to do cadaver work and travel to other institutions to learn from other surgeons. “I do cadaver work at least three to eight times a year, and I have been a surgeon for 25 years,” he said. “You have to operate with other surgeons on a twice-a-year basis. Practicing in a cadaver environment and working with other surgeons to refine and observe your techniques are key.”

Finally, Lavernia recommends surgeons videotape themselves during surgery to then study how to improve their skills and the skills of the entire operating team.

Value purchasing

A future concern is that payers may start to dictate that patients go to higher-volume centers with higher-volume surgeons — what Lavernia referred to as “value purchasing.”

“Those who are paying for these surgeries — i.e., the insurance companies — are encouraging patients to go to high-volume centers because it is cheaper for the insurance company to have someone fly to a high-volume center for a hip replacement. They may have fewer complications, stay for a shorter time in the hospital, receive fewer transfusions and, in general, may have a better outcome than they would in their local area,” he said.

“Right now patients are not getting switched to higher-volume centers at a high rate, but it is something that may happen in the future,” Austin said. “Although it may sound good on the surface, it may reduce patient access to care.”

If payers start to dictate that patients switch to high-volume centers for THA, another concern is that patients in more rural areas or areas with low-volume centers may not get the necessary procedures. “If you steer people to high-volume surgeons, do you then have some folks who simply do not get the operation and therefore remain in pain?” Katz said. “And for those who do go to a high-volume center, do they experience better outcomes? That would be a complicated, but useful study.”

“We have to better define how to take care of patients, and that gets back to the question of how can low-volume surgeons avoid complications during THA,” Austin said. “It is by standardizing care inside the operating room as well as before and after surgery that minimizes the risk for a complication.” – by Tina DiMarcantonio

References:

Barrack RL. J Bone Joint Surg. 2013;doi:10.2106/JBJS.L.01704.

Bozic KJ. J Bone Joint Surg. 2010;doi:10.2106/JBJS.I.01477.

Katz JN. J Bone Joint Surg. 2001;83:1622-1629.

Lavernia CJ. J Arthroplasty. 1995;doi:10.1016/S0883-5403(05)80119-6

Losina E. Arthritis & Rheum. 2004;50:1338-1343.

Ohmann C. J Bone Joint Surg. 2010;doi:10.2106/JBJS.H.01436.

Ravi B. BMJ. 2014;doi:10.1136/bmj.g3284.

Solomon DH. Arthritis & Rheum. 2002;46:2436-2444.

For more information:

Matthew S. Austin, MD, can be reached at Rothman Institute at Jefferson, 925 Chestnut St., 5th Fl., Philadelphia, PA 19107; email: matt.austin@rothmaninstitute.com.

Kevin J. Bozic, MD, MBA, can be reached at the Department of Orthopaedic Surgery, University of California, San Francisco, 1500 Owens St., San Francisco, CA 94158; email: bozick@orthosurg.ucsf.edu.

Jeffrey N. Katz, MD, MSc, can be reached at Brigham & Women’s Hospital, 75 Francis St., Boston, MA 02115; email: jnkatz@partners.org.

Carlos J. Lavernia, MD, can be reached at The Center for Advanced Orthopedics at Larkin Hospital, 7000 S. W. 62nd Ave., Suite 600, Miami, FL33143; email: c@drlavernia.com.

Henrik Malchau, MD, PhD, can be reached the Orthopedic Department, Massachusetts General Hospital, 55 Fruit St., GRJ 1126, Boston, MA 02114; email: hmalchau@mgh.harvard.edu.

Disclosures: Austin receives royalties from Zimmer and is on the speakers bureau for DePuy. Bozic is chair of the AAOS Council on Research and Quality. Katz has no relevant financial disclosures. Lavernia is a developer of the robotic arm for Stryker and is a consultant for and receives royalties from MAKO/Stryker. Malchau is a paid consultant for MAKO and receives research support from Biomet and DePuy; he is also share owner and board member for RSA Biomedical.

 

Do navigation and robotics play a role in the prevention of complications for a high- vs. a low-volume surgeon in primary THA?

Navigation and robotics can benefit low-volume surgeons

Publilius Syrus, a first-century B.C. Roman author, said, “Practice is the best of all instructors.” This mantra holds true for total hip arthroplasty (THA), with studies demonstrating that higher-volume surgeons have lower rates of revision within the first 2 years of the index procedure as compared with lower-volume surgeons. It stands to reason that a higher-volume surgeon, with greater experience performing THA, would be able to execute the operation faster and more accurately. The ability to perform the surgery more expeditiously should benefit the patient with less blood loss and a lower infection rate. Performing the surgery more accurately with regard to acetabular cup position and restoration of hip biomechanics (leg lengths and offset) should result in a lower rate of dislocation and quicker return to function.

On the other hand, the well-known football coach Vince Lombardi said, “Only perfect practice makes perfect.” In other words, a surgeon cannot perfect a THA without performing it without fault. Tools such as computer navigation and robotics can facilitate a better, more flawless execution of a THA — precise placement of the acetabular component to avoid impingement or dislocation, restoration of leg lengths and hip offset. In this regard, these tools would help improve results without requiring the experience of a high-volume surgeon. In looking at the early complications after THA, the major issues are: infection, dislocation, periprosthetic fracture, leg-length discrepancy and failure of implant fixation. Arguably, with the exception of infection, these are all technical errors that could be mitigated by surgeon experience. Therefore, computer navigation and robotics can be of greater benefit to a low-volume surgeon in achieving a better procedural outcome.

Of course, the issue of early complications after THA is not so simple as to be solved by a tool such as navigation or robotics. Problems such as infection and venous thromboembolism are persistent concerns whose incidence may be affected by a hospital’s overall experience with total joint arthroplasty. Thus, although the surgeon is an important factor in reducing complications after THA, the surgeon is not the sole element in determining a good result.

Edwin P. Su, MD, is an associate professor of clinical orthopedics at the Hospital for Special Surgery and Weill Cornell Medical Center.
Disclosure: Su is a consultant for and receives research support from Smith&Nephew. He holds stock options/equity in OrthAlign.

References:

Katz J. J Bone and Joint Surg. 2012;doi:10.2106/JBJS.K.00569.

Losina E. Arthritis Rheum. 2004;50:1338–1343.

Use of navigation improves precision for all surgeons

Postoperative complications occur in two categories: early and late. Early complications include dislocation, infection, periprosthetic fractures, nerve paralysis and impingement pain. Late complications include wear, osteolysis and loosening. Human nature likes instant gratification, which results in surgeons’ prime concern being to avoid early complications. Although nerve palsy and infection are the worst complications for patients (they destroy the benefits of an operation), the one that torments a hip surgeon is dislocation. Surgeons will change implants, their approach to the hip and postoperative care if they believe the change will reduce the risk for this complication. But one such change is improvement in the precision of their operations — which a computer can achieve — and surgeons have not embraced this high-technology tool. Lawrence D. Dorr

Better component position improves outcomes of total hip replacement, both intuitively and by literature evidence. Computer use in the operating room provides quantitative knowledge of implant position (most commonly the acetabulum), which reduces significantly the number of outliers of position (increased precision). In studies comparing computer use to manual implantation of the cup, there is no difference in mean inclination or anteversion. The advantage is the reduction of outliers. The computer improves precision by providing the surgeon with the knowledge of pelvic tilt, which improves accuracy of cup placement to the target number the surgeon selects. Correct cup position leads to better biomechanical reconstruction, which is the foundation of fewer complications, improved comfort and longevity.

The computer has low acceptance among surgeons because there is no body of evidence that proves this advantage of precision. The advantage is 10% to 15% for high-volume surgeons and more than 50% for low-volume surgeons. There is proof that the computer affects precision so the main objections are time and money (although surgeons will convert to the direct anterior approach to avoid dislocation, even though it takes nearly twice as long to perform the operation). The evidence needs to be forthcoming as follow-up gets longer. We just submitted our 10-year results with a posterior mini-incision and computer use. Clinically significant wear did not occur, but we used highly cross-linked polyethylene. In 93 of 100 hips with known results, 96% of patients graded themselves excellent, 3% very good and 1% fair so impingement pain did not occur. There was one dislocation at 1 year and two late dislocations secondary to weakening of the gluteus medius muscle. The 1% acute dislocation was an improvement over my publications of the 1990s with 4% dislocation. Ninety-six percent of patients still had their original components (two liners changed for dislocation, one cup for loosening and one stem for fracture).

The ultimate test of computer benefit will be 20-year results with a direct comparison of those hips with correct component position vs. those that were outliers of position. An 18-year study confirmed the importance of reconstruction of the center of rotation of the hip to longevity of the operation. Other than waiting for these long-term results, a multicenter study that permits entry of a high volume of cases will need to be done to prove any advantage for short-term complications. I continue to use a computer in the operating room for total hip replacement because in my practice, it contributes to a paucity of complications, high satisfaction of patients and wonderful 10-year results.

Lawrence D. Dorr, MD, is professor of orthopedics at USC Keck School of Medicine in Los Angeles.
Disclosure: Dorr has no relevant financial disclosures.

References:

Callanan MC. Clin Orthop Relat Res. 2011;doi:10.1007/s11999-010-1487-1.

Dorr LD. Clin Orthop Relat Res. 2007;465:92–99.

Karachalios T. Clin Orthop Relat Res. 1993;296:140–147.

Poehling-Monaghan KL. Clin Orthop Relat Res. 2014;doi:10.1007/s11999-014-3827-z

Ulrich SD. Int Orthop. 2008;32:597–604.

von Knoch M. J Bone Joint Surg. 2002;84:1949–1953.