The shortening of the length of stay implies rethinking the perioperative management (around the operative period), which precedes and immediately follows the operation, in order to ensure a good preparation of the patient and an adequate postoperative follow-up.

The aim of this study is to evaluate the effect on the length of stay of adding an individualized preoperative preparation and education session to the current protocol in the musculoskeletal department at the CHUV in patients undergoing total hip or knee replacement surgery.

The implementation of a targeted, low-impact immediate postoperative follow-up could contribute to improving the detection of complications, preventing avoidable readmissions, improving the management of pain and adverse events, supporting the patient and responding to difficulties encountered in the patient's living environment. However, the actual added value for the patient and for the healthcare system has yet to be specified. As patients' needs and resources vary, it would also be useful to better determine the profile of patients for whom a pre- and postoperative session provides significant added value.

In Switzerland, in 2017,12.4% of the Swiss population suffered from osteoarthritis. In 2019, the SIRIS hip and knee implant registry recorded 20,077 total hip replacement (THR) and 15,453 total knee replacement (TKR) implants in Switzerland.

The placement of THR and TKR is one of the major activities of the Department of the Musculoskeletal System of the CHUV (DAL-CHUV), with respectively 282 THR and 218 TKR placed in 2019.

The improvement of global practices in prosthetic surgery, the pressure on health costs and the shift to ambulatory care have led to a shortening of the length of stay.

The shortening of the length of stay implies rethinking the perioperative care (around the operative period), which precedes and immediately follows the operation, in order to ensure good preparation of the patient and adequate postoperative follow-up.

Currently, patients of the DAL-CHUV participate in a pre-operative information session (only before the operation) in a group that informs patients about the procedure, its preparation and its implications in general.

Pre-operative management is described in the literature as a multidisciplinary approach to cover all aspects to be taken into consideration in the patient, and thus prepare him/her in an optimal way for the operation and the recovery phase that will follow. Pre-operative or peri-operative rehabilitation is a broader concept of optimized recovery, which involves addressing the entire peri-operative process. Thus, the patient's health status, nutritional status, the operative and immediate postoperative process, pain management, prevention of complications and definition of relevant criteria for return home are all elements to be taken into account in an interdisciplinary manner to optimize the entire perioperative process.

The main objective of the study is to evaluate in patients undergoing total hip (THR) or knee (TKR) replacement surgery whether the addition of an individualized pre- and peri-operative preparation and education session to the existing protocol in the DAL-CHUV, provided by physiotherapists and nursing staff, has an effect on length of stay, hospital indicators, and objective and subjective clinical indicators.

The main hypothesis is that targeted pre- and peri-operative information adapted to the needs of patients would contribute to a decrease in length of stay.

The secondary indicators are readmission rate, discharge destination, postoperative pain, complications, joint function and mobility, anxiety and depression, pain representation, expectations of the prosthesis, satisfaction with care and quality of life. The hypothesis is that these indicators will be improved by the intervention.

The 1st secondary objective of the study is to evaluate in patients operated on for a total hip or knee prosthesis who have benefited from the preparation and education session whether the addition of a remote postoperative follow-up (3 telephone interviews or videoconferences during the 1st postoperative week after discharge) has additional effects on the measured indicators. The hypothesis is that the intervention will provide an additional beneficial effect for these indicators.

The 2nd secondary objective is to identify whether the effect of the pre- and postoperative interventions differs according to the characteristics of the population and the operation (THR or TKR). This secondary analysis will help to better identify the categories of populations for which the proposed peri-operative interventions are useful. The hypothesis is that the effects are dependent on patient characteristics, such as age, education level, or comorbidities for example.

Recruitment was carried out within the DAL-CHUV, based on consultation of the list of patients scheduled for a primary THR or TKR operation, and then consultation of their medical records by the study's scientific collaborator, who is also a collaborating physiotherapist at the CHUV, to verify the inclusion and exclusion criteria.

At the pre-operative information session (PIS), the important points of the study are presented orally and the consent forms of the patients who have made their decision are collected. An individual discussion will take place with those who wish to have more information about the study. The consent form is kept as part of the study files.

Those who wish to have time to reflect after the PIS will be contacted again the following week to find out their decision. They will hand in their approved consent form at the time of the pre-surgical consultation (PSC).

Once their decision is known, patients will be assigned to their group according to the randomization list.

The information of the intervention group A and B (preop and postop) does not imply any additional travel for the patient, there is only additional time dedicated to them during the PSC for the preop (group A and B) and postop (group B). The time for filling in the forms is essentially included in the consultation time (waiting time for the PSC and 6th week control), the hospital stay (day of discharge), as well as at home (2 weeks post-operatively).

The duration of the study per participant is approximately 10 weeks, PSC intervention approximately 3 weeks before the intervention, last follow-up 6 weeks after the intervention during the routine follow-up consultation at DAL-CHUV.

Descriptive statistics will be carried out for all quantitative variables of the study (means and standard deviation or medians and interquartile ranges, frequency, depending on the continuous, ordinal or nominal nature of the data), as well as graphical representations (box plot, histograms, pie chart).

The qualitative data collected will be grouped by theme and their frequency of occurrence will be analyzed (e.g. nature and frequency of occurrence of difficulties at home) For the main analysis, a Student's t test comparing the length of hospitalization between control and intervention groups will be applied. Linear regression models will then be used to adjust the difference between the groups for various potentially confounding factors (e.g. age, comorbidities, etc.). A sample size of N=200 allows for many adjustments to be included, with up to 13 parameters being estimated using the 15 observations per parameter rule.

To assess group differences in post-hospitalization measured values, linear mixed models will be used. This allows for repeated measurements (3 measurements per patient) while adjusting for various confounding factors.

A stratified analysis will be performed to differentiate the effects of the interventions in the various subpopulations of interest (e.g. age, comorbidities...), in order to identify those who particularly benefit from the tested interventions.

Inclusion Criteria:

• male and female patients admitted to the CHUV musculoskeletal department during the study period
• primary total hip replacement or primary total knee replacement
• a Risk Assessment and Prediction Tool (RAPT) score >6

Exclusion Criteria:

• a RAPT score <6,
• knee/hip arthroplasty revision surgery
• inability to give informed consent or answer questionnaires knowledgeably due to language or cognitive impairment as reported in the medical record