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Second National Joint Registry report issued
It contains data on more than 93,000 hip/knee surgeries done with a wide range of prostheses.
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BIRMINGHAM, England — With hospital participation in the National Joint Registry for England and Wales steadily improving, steering committee officials who oversee the registry said its biggest weakness was an inability to link primary hip and knee replacements with subsequent reoperations or revisions involving the same implant.
“All the hospitals now, except two very low volume units, are submitting at least some records,” said Paul J. Gregg, FRCS, vice chair of the National Joint Registry (NJR) steering committee, who presented data from the second annual report at the British Orthopaedic (BOA) Association Annual Meeting, here.
Linking primary with subsequent surgeries in the same joint would allow registry officials to “produce survivorship tables, which would inform us about long-term outcomes of joints and perhaps performance of hospitals and surgeons. [Linkability is] still only 27%, although it has improved from 2003,” Gregg said.
“Until we can improve on this linkable percentage, the long-term aims of this registry still remain in doubt. I can’t emphasize that point too strongly.”
Data from 381 medical centers
The data collection system, which started in April 2003, now includes 44,000 primary total hip replacements and 42,000 primary total knee replacements, according to the latest report. Recent data analysis conducted by the Royal College of Surgeons Clinical Effectiveness Unit looked at those hip and knee replacements done from Jan. 1, 2004 to Dec. 31, 2004 and entered in the NJR by Feb. 28, 2005.
Analysis revealed that 64.5% of the operations were performed in National Health Service (NHS) hospitals. “Independent hospitals provided 31.5% of the operations,” said Gregg, a past BOA president. He is a consultant orthopaedic surgeon at The James Cook University Hospital, Middlesborough, and professor of Orthopaedic Surgical Science at the University of Durham, England.
In all, 381 centers participated in the registry last year, which was 41 more than in 2003.
Case ascertainment rates, a statistic indicating the completeness of the data, totaled 60% for NHS facilities an increase from 51% in the last report. Case ascertainment is the proportion of total joint replacement (TJR) surgeries included in the registry from among all those estimated to be done in England and Wales.
Since NHS procedures typically require using patient identifier numbers, officials expect that higher NHS case ascertainment rates might improve the linkability of those records for NJR tracking purposes. “In the event of a prosthesis in use being found to perform unsatisfactorily, there is a serious danger that patients implanted with the prosthesis will not be traceable through the NJR system unless these key patient identifiers are consistently and invariably entered,” officials wrote in the summary report.
Patient consent rates need improvement, Gregg said. Consent was obtained in just 65% of cases; most of it came from independent sector hospitals. Surgeons in Wales obtained consent for 78% of operations compared to 64% in England. The 2003 consent rate was 63%.
Consent is critical to the NJR program’s success because, according to the report summary, patient identifier numbers can only be included when there is NJR patient consent. Although some hospitals failed to achieve any consent, 31 hospitals achieved 100% consent, Gregg said.
Concerning primary total hip replacements (THR) done last year, 54% were cemented, 20% were cementless and 14% were hybrid. Hip resurfacing accounted for 12% of them. Consultants were the lead surgeons performing 82% of THR procedures, while specialist surgical registrars, or SPRs, operated on hips 9% of the time. “Whether this is due to the European Work Time Directive and they push cases through more quickly … I don’t know.”
Based on NJR data, Gregg wondered if THR surgeons were confused about the best prostheses to use on patients who are younger than 55 years.
“It’s interesting — 46% had resurfacing, 25% cementless, 18% cemented and 12% hybrid, only indicating this needs further work,” he said.
Low mortality rates
As with the hips, primary total knee replacement (TKR) was done cemented (81%), 7.3% were uncemented, and 6% were completed with a minimally invasive (MIS) technique. Unicondylar prostheses were implanted during 9% of primary TKRs.
Using available NJR linkability data for TKR, surgeons performed 35% of revisions on primary TKS done with cementless implants compared to 20% for cemented ones. They revised TKRs more frequently when the primary surgery was done using MIS techniques (10% vs. 6.5%). The most common indications for revisions were aseptic loosening and infection.
For hip replacement, the three-month postop mortality remained low at 0.64% (range, 0.56% to 0.73%), based on some 31,000 procedures that could be traced to the Office of National Statistics. It was greater in men and those older than age 85, which held true for TKR mortality, which was also extremely low at 0.49%.
Impressive results
Results from the Patient Reported Outcomes Measurement Studies (PROMS) done in the first half of 2005 were very good, Gregg said. The PROMS involved mailing questionnaires to patients to determine their Oxford hip and knee scores. Patients answered questions using a 1-to-5 rating scale. Their answers were totaled for an overall score (12=no problems; 60=severe problems). The PROMS instrument, which requested information about the patients’ operative experiences, had an 88% response rate. “Patients really are very enthusiastic,” he said.
Mean Oxford hip scores were 20.5; 28.5% of respondents scored 12 or 13, and 6% of patients scored 40 or more. By comparison, the 1996 National THR Outcome Study reported Oxford hip scores at 23.4.
Mean Oxford knee scores from the PROMS analysis were 25, with about 8.6% of patients scoring 13 and 11% scoring 40 or more.
For more information:
- Gregg, PJ. National Joint Registry — Launch of 2nd annual report. Presented at the British Orthopaedic Association Annual Congress. Sept. 20-23, 2005. Birmingham, England.