Journal of Rehabilitation Medicine 51-10 | Page 57

Joint replacement rehabilitation and role of funding source
Study limitations
This study has several limitations. One limitation is
the representativeness of the study participants. While
the study captured geographical diversity, study par-
ticipation was voluntary and thus presents potential
for selection bias. It was not possible to analyse dif-
ferences between responders and non-responders to
determine the extent of such bias. As noted, the NZJR
captures more than 95% of joint replacements in New
Zealand, but only samples 20% of this larger group
for follow-up collection of patient-reported outcome
data (5). An even smaller proportion of this 20% was
sampled, taking into account NZJR response rates.
However, when we considered the demographic and
clinical features of the wider NZJR population, role
of rehabilitation sample appears very similar in terms
of variables, such as age, sex, comorbidity burden and
procedure type.
It is also possible that our sampling method and
frame resulted in systematic bias regarding those
participating in our study, under-representing the expe-
riences of certain subsections of our target population.
Important subgroups within New Zealand’s population,
such as Māori, may not have been captured. Partici-
pants responding to our survey were predominantly
New Zealand European and rates across ethnicity
categories were inconsistent with general New Zea-
land population statistics (4, 19), and other studies
examining rates of TJR among Māori and non-Māori
(20). We can only speculate on the reasons for lack of
ethnic diversity in our sample. It has been well demon-
strated that Māori have the poorest health status of any
ethnic group in New Zealand (20), although there is
limited evidence to suggest lower rates of TJR among
Māori compared with non-Māori in publicly funded
systems in New Zealand (4, 10). There is, however,
good evidence to suggest that Māori may be difficult
to reach in terms of participation in health research
and intentional strategies are required by researchers
achieve recruitment equity (21, 22).
There is a possibility that referral bias underpins,
to some extent, differences in rehabilitation between
groups. For example, some surgeons may have been
more likely to have referred patients to rehabilita-
tion than others. This study did not capture particular
surgeons operating on participants, and so any such
patterns or potential for bias were not examinable.
In addition, our study is not able to shed light on the
impacts of incentives/disincentives in either public or
private systems, or optimal levels of rehabilitation to
determine whether the public system under-provides or
the private system over-provides rehabilitation services.
These are issues that should be a focus of future studies.
777
Finally, we asked participants to recall details re-
garding access to rehabilitation extending back many
months and the reliability of the survey itself has not
been examined. This raises a concern about the accuracy
of data collection as a result of recall bias. This may
be reflected in variability evident in the self-reported
data, most notably with regard to pre-surgical variables.
None­theless, this analysis drew on the experiences of
more than 500 participants, which makes this study one
of the larger published studies seeking to characterize ac-
cess to rehabilitation before and after joint replacement.
Conclusion
This study investigated whether the source of funding
for surgery (private vs public funding) was associated
with use of rehabilitation and outcomes following hip
and knee joint replacements. The findings suggest that
factors already known to affect health outcomes, such
as length of time on a surgical waiting list, satisfaction
with rehabilitation, and self-efficacy, were associated
with funding source. Those with private funding for
their joint replacements and associated rehabilitation
also tended to be younger, have higher levels of educa-
tion, be in employment, and have fewer comorbidities,
than their publicly-funded counterparts. These findings
suggest that socio-economic differences and inequities
based on funding source exist and are consistent with
prior research, although previous research is limited.
Clinically significant differences in pain and function
outcomes between the groups based on funding
source were not identified in this sample. Prospective
randomized trials that examine pain and functional
outcomes will help to clarify whether funding source
directly impacts on outcomes.
ACKNOWLEDGEMENTS
The authors would like to thank research assistant Caroline
Norris for her assistance with recruitment and data collection.
We acknowledge and thank the staff at the New Zealand Joint
Registry who assisted with recruitment and provision of ad-
ditional data. We also acknowledge the Burwood Academy
of Independent Living (BAIL) for hosting the research grant.
Funding. This research was supported by a Project Grant from
the Canterbury Medical Research Foundation (Grant no 14/07).
The authors have no conflicts of interest to declare.
REFERENCES
1. Collins N, Roos E. Patient reported outcomes for total hip
and knee arthroplasty: Commonly used instruments and
attributes of a “good” measure. Clin Geriatr Med 2012;
28: 367–394.
2. Jeffery A, Wylde V, Blom A, Horwood J. “It’s there and
I’m stuck with it”: patients’ experiences of chronic pain
J Rehabil Med 51, 2019