Abstract
Objective:
To investigate the effect of combining conventional rehabilitation nursing with targeted noise control during the key sleep period on clinical outcomes in elderly patients with knee osteoarthritis (KOA) after knee arthroplasty.
Methods:
This retrospective study included 100 elderly patients with KOA who underwent knee arthroplasty at the Orthopedics Department of the Second Affiliated Hospital of Zhejiang University School of Medicine, between May 2023 and September 2024. According to the actual nursing records and ward noise management implemented during hospitalization, patients were divided into a control group (n = 50), which received conventional orthopedic rehabilitation nursing and routine noise control, and an observation group (n = 50), which received conventional orthopedic rehabilitation nursing plus additional targeted nighttime noise control during key sleep period. Propensity score matching was used to exclude baseline confounding. The incidence and duration of postoperative delirium, Sedation-Agitation Scale (SAS) scores, ward noise levels (LAeq, LAmax), and Richards–Campbell Sleep Questionnaire (RCSQ) scores were compared between the two groups.
Results:
The observation group showed a significantly lower postoperative delirium incidence and a shorter duration of delirium than the control group (both P < 0.05). During the key sleep period (02:00–04:00), both LAeq and LAmax values were significantly lower in the observation group (both P < 0.05). The observation group also had lower SAS scores and higher RCSQ scores (both P < 0.05). Moreover, postoperative recovery was superior in the observation group, as reflected by earlier first out-of-bed mobilization, greater knee flexion at discharge, and a shorter length of hospital stay (all P < 0.05).
Conclusion:
In this retrospective study, conventional orthopedic rehabilitation nursing combined with targeted nighttime noise control during key sleep periods was significantly associated with a lower incidence of postoperative delirium, better sleep quality, and faster functional recovery in elderly patients after knee arthroplasty.
Keywords: noise, knee osteoarthritis, rehabilitation, postoperative delirium, sleep quality
KEY MESSAGES
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(1)
A nursing protocol combining conventional orthopedic rehabilitation with targeted ward noise management during the key sleep period was associated with reduced postoperative delirium incidence and shorter delirium duration in elderly patients after knee arthroplasty.
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(2)
This protocol was associated with better sedation-agitation scores and enhanced sleep quality.
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(3)
This protocol was also associated with better functional recovery, including earlier ambulation, greater knee flexion at discharge, and a shorter hospital stay.
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(4)
This study provides a nurse-led management framework incorporating continuous assessment, rhythmic activity–rest scheduling, and targeted noise control.
INTRODUCTION
Knee osteoarthritis (KOA) is a chronic degenerative disease characterized by degeneration of the articular cartilage and secondary changes in bone structure, with high prevalence among the elderly population.[1,2] As the disease progresses, patients often experience persistent knee pain, stiffness, and limited mobility, which seriously affect their activities of daily living and quality of life. For patients with end-stage KOA, knee arthroplasty has become an important treatment for improving joint function and relieving pain.[3,4,5] However, elderly patients often have reduced functional reserves of multiple systems and weakened neuroregulatory function, placing them at a higher risk of perioperative complications. Postoperative delirium is one of the most common complications following knee arthroplasty in elderly patients with KOA.[6] It is a neuropsychiatric syndrome characterized by acute onset, fluctuating level of consciousness, attention deficit, and cognitive impairment. Studies have shown that the occurrence of delirium not only prolongs hospital stay but also associated with falls, delayed functional recovery, increased nursing dependence, long-term cognitive decline, and increased risk of mortality.[7,8,9] Therefore, identifying and controlling the relevant influencing factors of postoperative delirium in elderly patients undergoing knee arthroplasty is of great clinical significance for improving patient prognosis.
Postoperative delirium in elderly patients is associated with neurofunctional instability and sleep architecture disruption, which are synergistically affected by both internal physiological stress and external environmental stimulation.[10] Modern orthopedic rehabilitation nursing targets internal physiological regulation through rhythmic activity arrangement, targeted pain management, and circadian rhythm guidance, which can reduce nociceptive stimulation, stabilize autonomic nerve function, and maintain the continuity of sleep–wake cycles.[11] Ward noise, a common but often overlooked environmental stressor, can indirectly induce or aggravate postoperative cognitive dysfunction by affecting sleep architecture, aggravating psychological stress response and interfering with circadian rhythm. Elderly patients have a lower tolerance for environmental changes, and continuous or intermittent noise stimulation is more likely to cause sleep disruption and mood fluctuations, thereby increasing the risk of delirium.[12,13] Targeted nighttime noise control during key sleep period may reduce nocturnal environmental interference, minimize sleep interruption and awakening events, and help maintain the integrity of sleep structure. When combined with conventional orthopedic rehabilitation nursing, targeted nighttime noise control may provide complementary internal regulation and external protection, thereby helping to maintain the stability of neurological function, reduce the incidence of acute cognitive impairment, and reduce the risk of postoperative delirium.
Therefore, this study retrospectively analyzed the clinical and nursing data of elderly patients with KOA who underwent knee arthroplasty between May 2023 and September 2024. It investigated the association between conventional orthopedic rehabilitation nursing combined with additional targeted nighttime noise control during key sleep period and the clinical outcomes of these patients. The findings may provide objective evidence and reference for optimizing the nursing management of elderly patients after knee arthroplasty.
MATERIALS AND METHODS
Study Design and Patient Selection
This retrospective study included 156 elderly patients with KOA who underwent knee arthroplasty in the Orthopedics Department of the Second Affiliated Hospital of Zhejiang University School of Medicine between May 2023 and September 2024. All data were extracted from the hospital’s electronic medical record system and nursing documentation. Ward noise measurement data were collected from the environmental monitoring records of the orthopedic ward during the same period. The study was approved by the Medical Ethics Committee of the Second Affiliated Hospital of Zhejiang University School of Medicine (ethics approval number [2025-1523]. Written informed consent was obtained from all patients or their legal guardians before enrolment in this study. All relevant nursing staff have received standardized nursing assessment training organized by the hospital. Clinical care and the nursing records followed the department’s routine procedures to ensure the accuracy and reliability of the data.
Among the initial 156 patients, 28 were excluded due to preoperative cognitive impairment or dementia, 12 due to severe organ dysfunction or perioperative instability, 8 due to incomplete medical records or acoustic monitoring data, and 6 due to reoperation or transfer to intensive care unit within 72 h postoperatively. After these exclusions, 102 patients remained. A propensity score matching (PSM) was then performed, and two additional patients were further excluded due to poor covariate balance. After PSM, 50 matched pairs (100 patients) were included in the final analysis.
Inclusion and Exclusion Criteria
Inclusion Criteria
① Age ≥ 60 years; ② diagnosis of KOA confirmed clinically and by imaging examination, with treatment by knee arthroplasty; ③ complete medical records and nursing records during hospitalization; ④ clear preoperative consciousness, a Mini-Mental State Examination (MMSE) score > 27 points, no obvious delirium, and the ability to cooperate in completing routine preoperative assessments; and ⑤ complete ward acoustic measurement records during the hospitalization.
Exclusion Criteria
① Patients with a clear preoperative diagnosis of dementia, cognitive impairment, or other severe mental illnesses; ② patients with a history of recurrent delirium or long-term use of antipsychotic medications; ③ patients with severe hearing or visual impairment affecting agitation/sedation and sleep quality assessment; ④ patients with severe heart, lung, liver, kidney, or other vital organ dysfunction, or unstable perioperative condition; ⑤ patients who develop severe perioperative complications (e.g., severe infection, stroke, or shock); ⑥ patients who require reoperation or were transferred to the intensive care unit within 72 hours postoperatively; and ⑦ patients with incomplete medical records, nursing records, or outcome indicators.
Methods
Control Group
Patients in the control group underwent conventional orthopedic rehabilitation nursing plus routine noise control, including prohibiting loud talking in the ward, implementing wheelchair and nursing cart noise reduction, and verbal reminders to keep quiet. Conventional orthopedic rehabilitation care comprised the following components:
(1) Responsibility-based nursing and continuous assessment: After admission, each patient was assigned to a fixed responsible nurse. The responsible nurse recorded the patient’s age, underlying diseases, previous sleep status, and preoperative mental state in detail during the first assessment. Patients were identified as requiring enhanced postoperative observation in the nursing assessment form. During the postoperative nursing period, the responsible nurse continuously recorded the patient’s level of consciousness, communication response, orientation changes, and nighttime behavior in the nursing record daily. These observations were highlighted during the nursing shift handovers.
(2) Rhythmic nursing of postoperative activities and rest: Nursing staff arranged the patient’s daytime activities and nighttime rest in a rhythmic manner according to the patient’s postoperative recovery plan. During the daytime, dressing changes, functional exercises, treatment operations, and health education were arranged in a concentrated manner to avoid repeated interruptions to the patient’s rest. In the early postoperative period, nursing staff assisted the patient with adjusting the bed position and repositioning every 2–3 hours. According to the patient’s tolerance, nurses guided patients to complete ankle pump exercises and quadriceps isometric contraction training, and documented the start time, duration, and patient cooperation in the nursing record. Nighttime care focuses on maintaining rest. Except for necessary vital sign monitoring and medical order procedures, unnecessary visits to the ward were minimized.
(3) Dynamic monitoring of consciousness and agitation/sedation: In addition to routine rounds, nurses closely monitored patients’ consciousness, speech coherence, and limb movement after surgery. For patients who exhibited agitation, repeated attempts to turn over or get out of bed, or disordered speech, nurses used the Sedation-Agitation Scale (SAS) to assess patients’ consciousness. For patients with significant fluctuations in SAS scores, the frequency of nighttime rounds was increased, and their condition was highlighted during nursing shift handovers.
(4) Pain and nighttime comfort care: Nurses assessed patients’ pain level by asking them about their subjective feelings and observing changes in body position and facial expressions. For patients with severe pain and frequent changes in body position during nighttime, nurses should assist in adjusting the patients’ limbs to comfortable positions and documented the nighttime discomfort in the nursing record. For patients who repeatedly call out or wake up due to discomfort, nurses should first use non-pharmacological methods to soothe them, such as verbal comfort and assisting in adjusting their posture, and record the treatment process.
Observation Group
The observation group received additional targeted nighttime noise control during the key sleep period, based on the same routine orthopedic rehabilitation care and noise control implemented in the control group. The specific measures are as follows:
(1) Integration of nursing processes and standardized workflow management: Nursing staff completed the operations such of medication, intravenous fluid replacement, vital sign monitoring, and basic nursing during the night nursing period, to reduce the environmental noise generated by repeated entry and exit from the ward and nursing activities, and to minimize the interference with the continuity of patients’ sleep. The frequency of elective knee arthroplasties was controlled to ≤3 cases per operating room per day. Ward rounds were standardized to four times daily (08:00, 12:00, 18:00, and 22:00), and no additional ward rounds were performed unless necessary. The volume of verbal communication in the ward was strictly limited to ≤35 dB(A) (measured by a sound level meter).
(2) Additional layered identification and standardized control of ward noise sources: In order to ensure the objectivity of environmental management, noise data were obtained in three representative periods—daytime (14:00–16:00) reflecting routine ward activity, pre-management baseline (22:00–23:00) as pre-sleep baseline, and post-management assessment (02:00–04:00) for core sleep-stage noise control effect, which are most correlated with postoperative delirium and sleep quality. Morning high-activity periods (06:00–10:00) were not included as this study focused on sleep-related nocturnal noise.
Based on the monitoring results and the characteristics of noise generation, ward noise sources were divided into operational noise (e.g., nursing operations and cart movement), communication noise (e.g., nursing handovers and conversations), and environmental noise (e.g., door/window closing and bed rail collisions). Specific control measures included: ① When moving nursing carts and treatment carts in the ward, the operation procedures should be standardized, the speed should be reduced, and collisions with bed rails, door frames and hard facilities should be avoided; ② Night nursing handovers should be conducted at the nursing station in principle. If it is necessary to enter the ward, the nursing staff should actively control the volume of communication below 35 dB(A) and avoid unnecessary communication; ③ For nursing operations performed in the ward, relevant items should be prepared in advance to minimize procedure duration and reduce the exposure to environmental noise.
(3) Continuous recording and key marking of nighttime sleep status: On the basis of routine rounds, the night-shift nurses should continuously observe and record the nighttime sleep status of patients, including sleep onset time, the number of nocturnal awakenings, and the reasons for awakening. For patients who wake up repeatedly at night or complain of poor sleep quality, key marks should be made in the nursing records and fed back to the day-shift nurses as special content during handovers.
(4) Daytime activity rhythm regulation based on sleep feedback: The day-shift nurses should make targeted adjustments to the patients’ daytime activities and rehabilitation training arrangements based on the nighttime sleep records and guide patients to avoid long periods of bed rest during daytime and to reasonably arrange functional exercises and rest time to promote the gradual recovery of the sleep–wake rhythm.
(5) Team collaboration and process supervision in the noise management: The responsible nurse was responsible for the implementation of nighttime noise management and sleep records. The head nurse regularly checked and provided feedback on the completeness of nursing records and the implementation of noise management measures to ensure that these strategies were applied continuously and in a standardized manner. The head nurse conducted random noise spot checks three times a week in the three representative periods, and the noise measurements were recorded in the ward environmental management log to form a closed-loop management of noise control.
Observation Indicators
Incidence of Postoperative Delirium
Postoperative delirium was assessed using the Confusion Assessment Method (CAM: k = 0.82–0.94, sensitivity 94%–100%, specificity 90%–95%) at 24 h postoperatively for the first screening,[14] then once every 24 h for 7 consecutive days (until discharge), primarily based on the following four core characteristics: ① acute onset and fluctuations in condition; ② attention deficit; ③ disordered thinking; and ④ altered level of consciousness. A patient was diagnosed with postoperative delirium when exhibiting characteristics ① and ②, and also having at least one of characteristics ③ and ④. All CAM assessors completed a standardized 4-hour training course on delirium assessment, with a theoretical and practical assessment pass rate ≥95% before independent assessment. Incidence rate = (number of delirium cases / total number of cases) × 100%. The assessment for postoperative delirium was conducted by a uniformly trained responsible nurse or attending physician.
Duration of Postoperative Delirium
The first screening time for postoperative delirium was set within 24 hours after surgery. It is identified by the responsible nurse or attending physician who participated in the clinical care at that time, based on the medical records and bedside observation. The endpoint of delirium remission was defined as two consecutive negative CAM assessments with stable conscious state for ≥24 hours. For patients who showed delirium in the first assessment, daily follow-up assessment was carried out until the delirium symptoms were completely relieved in accordance with the above remission standard.
Assessment of Agitation/Sedation Status
The agitation/sedation status was assessed using the SAS (ICC = 0.85–0.92, Cronbach’s α = 0.88, and construct validity r = –0.89) at 6 hour postoperatively.[15] The patient’s state of consciousness was quantified by a nine-level scale (1–7 points). The meaning of each score is as follows: 1 point (unable to be awakened): no response to strong stimuli; 2 points (deep sedation): only slight response to physical stimuli; 3 points (moderate sedation): can be awakened by sound but unable to communicate; 4 points (quiet and cooperative): awake and cooperative with treatment; 5 points (mild agitation): anxious or agitated, requiring verbal reassurance; 6 points (moderate agitation): frequent aimless movements, requiring restraint; and 7 points (severe agitation): aggressive behavior, threatening the safety of medical staff.
Comparison of Noise Levels in Wards
Ward noise was measured using a calibrated sound level meter (AWA6228, Hangzhou Aihua Instruments, China). Acoustic measurements were recorded during three predefined time periods on three consecutive postoperative days, three times per period daily, performed by two specially trained nurses. The sound level meter was placed 1.2 m above the floor and 0.5 m away from the patient’s bed. The measurement methods and locations of the two groups were the same. Recorded indicators included equivalent continuous A-weighted sound pressure level (LAeq) and maximum sound pressure level (LAmax). Mean values from repeated measurements were used for analysis.
Sleep Quality Assessment
Sleep quality was assessed using the Richards–Campbell Sleep Questionnaire (RCSQ: Cronbach’s α = 0.86–0.91, ICC = 0.84, and concurrent validity r = 0.78). The RCSQ is a scale specifically designed for short-term sleep quality assessment of hospitalized patients. It is applicable to perioperative and intensive care settings and can reflect the patient’s actual sleep experience the previous night. The scale contains five items: sleep depth, sleep latency, nighttime awakening frequency, difficulty in falling back asleep, and overall sleep quality. Each item is assessed using the 0–100 mm visual analogue scale. The average of the five items constitutes the total score, with a maximum score of 100 and the lowest score being 0 point. The higher the total score, the better the sleep quality. In this study, patients were assessed using the RCSQ on the nights of postoperative days 1–3. The responsible nurses who were involved in the nighttime care assisted the patients in completing the assessment during the morning rounds and recorded the specific assessment dates. The average RCSQ score on postoperative day 3 was used as the patient’s short-term postoperative sleep quality.[16,17]
Postoperative Recovery
Postoperative recovery was evaluated using the time to first ambulation, knee flexion angle before discharge, and length of hospital stay. Knee flexion angle was measured by a qualified rehabilitation therapist using a standard goniometer. During measurement, the patient was placed in the supine position with the hip joint in a neutral position. The maximum active flexion angle of the operated knee was measured with the greater trochanter of the femur as the axis. Each measurement was repeated twice, and the mean value was taken as the final result.
Statistical Methods
Data analysis was performed using SPSS 26.0 (IBM Corporation, Armonk, New York, USA) statistical software and R 4.5.1 software (R Foundation for Statistical Computing, Vienna, Austria) with the “MatchIt” package for PSM. Propensity scores were estimated using a logistic regression model incorporating age, sex, body mass index, and underlying diseases. Patients were matched using a 1:1 nearest-neighbor matching algorithm without replacement, with a caliper width of 0.02. Standardized mean differences (SMDs) were calculated to assess the balance of covariates before and after matching, with an SMD of < 0.1 indicating a good balance. Before statistical analysis, continuous variables underwent a normality test using the Shapiro–Wilk test to determine the data distribution characteristics; Levene’s test was performed to assess whether the variances of the data in each group were homogeneous. Continuous variables that conformed to a normal distribution and had homogeneous variance were expressed as mean ± standard deviation (x̄ ± s). Independent sample t-tests are used for inter-group comparisons, whereas paired sample t-tests were used for comparisons within two groups before and after. Categorical variables were expressed as number (n) and percentage (%), and χ2 tests were used for comparisons between groups; when the expected frequency was < 5, a continuity-corrected χ2 test or Fisher’s exact test was used. All ward noise measurement data (LAeq, LAmax) conformed to normal distribution and homogeneous variance and were compared between groups using independent samples t-tests. All statistical tests were two-tailed, and a P-value < 0.05 was considered statistically significant. Binary logistic regression analysis was performed with postoperative delirium (yes = 1, no = 0) as the dependent variable; grouping (observation group = 1, control group = 0) as the independent variable; and anesthesia type, operation time, intraoperative blood loss, analgesia regimen, and blood transfusion as confounding variables to calculate adjusted odds ratio (OR) and 95% confidence interval (95% CI) for the independent protective effect of the observation group’s regimen (conventional orthopedic rehabilitation nursing plus additional targeted nighttime noise control during key sleep period) relative to the control group’s regimen (conventional orthopedic rehabilitation nursing plus routine noise control) on postoperative delirium.
RESULTS
Comparison of Baseline Data
After PSM, there were no significant differences in baseline characteristics between the two groups of patients (P > 0.05), and the SMDs for all covariates were less than 0.1, indicating a good balance and comparability between the groups (Table 1).
Table 1.
Comparison of Baseline Data between the Two Groups
| Material | Control group (n = 50) | Observation group (n = 50) | t/χ2 | P | |
|---|---|---|---|---|---|
| Sex (n, %) | Male | 21(42.00) | 23(46.00) | 0.162 | 0.687 |
| Female | 29(58.00) | 27(54.00) | |||
| Age(x̄±s) | 72.81 ± 5.64 | 73.24 ± 6.16 | 0.364 | 0.717 | |
| Body mass index (x̄±s) | 24.13 ± 2.35 | 24.44 ± 2.56 | 0.631 | 0.530 | |
| Underlying diseases (n, %) | Hypertension | 28(56.00) | 30(60.00) | 0.164 | 0.685 |
| Type 2 diabetes | 17(34.00) | 18(36.00) | |||
| Coronary heart disease | 9(18.00) | 10(20.00) | |||
| COPD | 6(12.00) | 7(14.00) | |||
| Anesthesia type (n, %) | Spinal anesthesia | 41(82.00) | 43(86.00) | 0.321 | 0.571 |
| General anesthesia | 9(18.00) | 7(14.00) | |||
| Operation time (min, x̄±s) | 89.56 ± 12.34 | 91.22 ± 11.87 | 0.658 | 0.512 | |
| Analgesia regimen (n, %) | Patient-controlled intravenous analgesia (PCIA) | 32(64.00) | 30(60.00) | 0.218 | 0.640 |
| Epidural analgesia | 18(36.0) | 24(40.00) | |||
| Intraoperative blood transfusion (n, %) | 7(14.00) | 6(12.00) | 0.102 | 0.746 |
Comparison of Postoperative Delirium Incidence
The incidence of postoperative delirium in the observation group was significantly lower than that in the control group (P < 0.05; Table 2).
Table 2.
Comparison of Postoperative Delirium Incidence between the Two Groups (n, %)
| Group | n | Patients with delirium | No delirium | Incidence (%) |
|---|---|---|---|---|
| Control group | 50 | 14(28.00) | 36(72.00) | 28.00 |
| Observation group | 50 | 5(10.00) | 45(90.00) | 10.00 |
| χ 2 | 5.263 | |||
| P | 0.022 |
Comparison of Postoperative Delirium Duration
The duration of delirium in the observation group was significantly shorter than that in the control group (P < 0.05; Table 3).
Table 3.
Comparison of Postoperative Delirium Duration between the Two Groups (x̄±s, hour)
| Group | n | n (delirium occurs) | Duration of delirium |
|---|---|---|---|
| Control group | 50 | 14(28.00) | 38.52 ± 10.08 |
| Observation group | 50 | 5(10.00) | 24.96 ± 8.04 |
| t | 2.700 | ||
| P | 0.015 |
Comparison of SAS Scores
The SAS score in the observation group was significantly lower than that in the control group (P < 0.05; Table 4).
Table 4.
Comparison of Postoperative SAS in the Two Groups of Patients (x̄±s, Points)
| Group | n | SAS score |
|---|---|---|
| Control group | 50 | 4.38 ± 0.51 |
| Observation group | 50 | 4.13 ± 0.34 |
| t | 2.884 | |
| P | 0.005 |
Note: SAS, Sedation-Agitation Scale.
Comparison of Ward Noise Levels
LAeq and LAmax differed significantly between the two groups only during the key sleep period (02:00–04:00), with both parameters being lower in the observation group than in the control group (both P < 0.05). Following the nighttime noise control measures, all LAeq values in the observation group met the national hospital environmental noise standard (LAeq ≤ 45 dB(A)), whereas the corresponding values in the control group exceeded this threshold (Table 5).
Table 5.
Comparison of Ward Noise Levels between the Two Groups [x̄±s, dB(A)]
| Group | n | LAeq (14:00-16:00) | LAmax (14:00-16:00) | LAeq (22:00-23:00) | LAmax (22:00-23:00) | LAeq (02:00-04:00) | LAmax (02:00-04:00) |
|---|---|---|---|---|---|---|---|
| Control group | 50 | 58.51 ± 3.25 | 66.24 ± 4.09 | 55.15 ± 2.92 | 65.83 ± 3.87 | 52.85 ± 3.50 | 62.57 ± 4.23 |
| Observation group | 50 | 58.27 ± 3.53 | 65.95 ± 4.12 | 54.64 ± 2.88 | 65.36 ± 4.16 | 42.54 ± 2.13 | 48.77 ± 3.23 |
| t | 0.452 | 0.361 | 0.785 | 0.602 | 18.625 | 16.837 | |
| P | 0.652 | 0.719 | 0.434 | 0.549 | <0.001 | <0.001 |
Note: Continuous variables were presented as x̄±s and compared using independent-samples t-test.
Comparison of RCSQ Scores
The RCSQ score of the observation group on postoperative day 3 was higher than that of the control group (P < 0.05; Table 6).
Table 6.
Comparison of RCSQ Scores between the Two Groups of Patients (x̄±s, Points)
| Group | n | Before management | After management | t | P |
|---|---|---|---|---|---|
| Control group | 50 | 55.36 ± 3.08 | 69.62 ± 2.14 | –25.327 | <0.001 |
| Observation group | 50 | 55.58 ± 3.12 | 77.04 ± 1.84 | –37.975 | <0.001 |
| t | –0.355 | –18.077 | |||
| P | 0.723 | <0.001 |
Comparison of Postoperative Recovery
The observation group had significantly shorter time to first ambulation, larger knee flexion angle before discharge, and shorter length of hospital stay than the control group (all P < 0.05; Table 7).
Table 7.
Comparison of Postoperative Recovery between the Two Groups of Patients (x̄±s)
| Group | n | Time to first ambulation (h) | Knee flexion angle (°) | Length of hospital stay (days) | |
|---|---|---|---|---|---|
| Preoperative | Postoperative | ||||
| Control group | 50 | 42.61 ± 8.93 | 89.72 ± 7.86 | 96.31 ± 8.25 | 12.44 ± 2.68 |
| Observation group | 50 | 34.84 ± 7.62 | 88.59 ± 8.22 | 105.94 ± 7.08 | 10.98 ± 2.13 |
| t | 4.680 | 0.703 | 6.264 | 3.016 | |
| P | <0.001 | 0.484 | <0.001 | 0.003 | |
Correlation Analysis
Nighttime LAeq (02:00–04:00) was negatively correlated with RCSQ score (r = −0.72, P < 0.001). Nighttime LAeq was positively correlated with postoperative delirium incidence (r = 0.65, P < 0.001).
Binary Logistic Regression Analysis of Risk Factors for Postoperative Delirium
After adjusting for anesthesia type, operation time, intraoperative blood loss, analgesia regimen, and blood transfusion, the nursing regimen in the observation group remained independently associated with a lower risk of postoperative delirium (adjusted OR = 0.27, 95% CI: 0.09–0.78, P = 0.015); none of the adjusted confounding variables were significantly associated with postoperative delirium (all P > 0.05).
DISCUSSION
Multifactorial Stressors Contributing to Delirium after Knee Arthroplasty in Elderly Patients
In the early stages after knee arthroplasty, elderly patients are often exposed to multiple stressors, including pain, limited mobility, environmental changes, and sleep disruption. These factors may overlap and induce or aggravate postoperative delirium, agitation, and sleep disorders. In the present study, multivariate logistic regression analysis revealed that the nursing protocol in the observation group was independently associated with a lower risk of postoperative delirium (adjusted OR = 0.27, 95% CI: 0.09–0.78, P = 0.015). Postoperative delirium is a common neuropsychiatric complication in elderly patients and is associated with an increased risk of falls, delayed functional recovery process, prolonged hospital stay, and greater nursing demands.[18,19] Therefore, the nursing management of elderly patients after knee arthroplasty is no longer limited to routine vital sign monitoring and wound care, but needs to build a more systematic, refined, and continuous nursing support model addressing patients’ neurobehavioral state, sleep rhythm, and environmental factors.[20] As a quantifiable environmental stressor, ward noise may contribute to the development of postoperative delirium, and objective acoustic measurements provide a crucial basis for evaluating the effectiveness of noise management.
Limitations of Conventional Orthopedic Rehabilitation Nursing in Neurobehavioral Management of Elderly Patients
Conventional orthopedic rehabilitation nursing is established for ensuring basic perioperative safety and completing routine nursing tasks; however, it remains insufficient in the management of postoperative neurobehavioral changes and control of environmental factors in elderly patients.[21] On the one hand, conventional nursing procedures are mostly centered on implementing medical orders and basic operations, with limited coordination of daytime activities and nighttime rest. This may lead to frequent nighttime nursing operations and repeated interruptions. On the other hand, the assessment of the patient’s consciousness level and behavioral changes mostly relies on subjective experience judgment, with limited use standardized scales for continuous monitoring. Mild agitation or brief fluctuations in consciousness are easily overlooked. More importantly, routine noise management only has basic nighttime measures, such as prohibiting loud talking and reducing wheelchair noise, without incorporating a standardized protocol of targeted nighttime noise control or objective acoustic measurement indicators. As a result, nighttime ward noise level of the control group in present study was as high as 52.8 ± 3.5 dB(A), far exceeding the national standard, which may adversely affect patients’ sleep quality and inducing delirium. The above defects are particularly evident in the recovery stage of elderly patients after knee arthroplasty. Kraonual et al.[22] reported that inadequate nursing interventions for elderly patients after orthopedic surgery were associated with an increased risk of postoperative delirium. Ding et al. [23] also demonstrated a correlation between ward acoustic environment, sleep architecture, and neurobehavioral stability. Therefore, the above-mentioned nursing and environmental management deficiencies may jointly increase the risk of postoperative agitation and decrease sleep quality.
The Mechanism of Action of Conventional Orthopedic Rehabilitation Nursing in the Prevention of Postoperative Delirium
Conventional orthopedic rehabilitation nursing mainly focuses on patients’ functional recovery process and is characterized by the continuity, rhythm, and multi-dimensional assessment of nursing.[24] In the nursing care of elderly patients after knee arthroplasty, conventional nursing pays more attention to the balance between postoperative activity and rest, pain and comfort management, changes in consciousness and behavior, and continuous observation of sleep status. By combining nursing care with patients’ physiological status, it helps to reduce unnecessary stimulating factors and enable patients to complete postoperative recovery in a relatively stable state, thereby providing a nursing basis for reducing the risk of delirium.[25] When combined with standardized noise management, this nursing model can further reduce environmental stressors, creating a synergistic effect that is associated with a lower incidence of postoperative delirium.
Effect of Targeted Nighttime Noise Control during Key Sleep Period on Postoperative Delirium
Targeted nighttime noise control during key sleep period refers to a nursing management strategy designed to identify, record, and control manageable ward noise to reduce noise interference during patients’ key sleep period. For elderly patients, continuous or intermittent noise stimulation can affect the stability of the nervous system by disrupting sleep structure, aggravating psychological stress response and interfering with circadian rhythm.[26] The present study showed that the incidence of postoperative delirium in the observation group was significantly lower than that in the control group (P < 0.05), which may be associated with the additional targeted nighttime noise control measures during key sleep period. In addition, the nighttime (02:00–04:00) LAeq of the observation group was 10.3 dB(A) lower than that of the control group. Pearson correlation analysis revealed a positive correlation between LAeq (02:00–04:00) and the incidence of delirium (r = 0.65, P < 0.001). These findings suggest that noise management during the key sleep period may be associated with sleep quality and postoperative delirium in elderly patients. Although full-day integrated noise metrics were not used, the noise control targeted key sleep period still provided a stable sleeping environment, and the data do not support overall ward noise reduction. This stable low-noise environment may be associated with reduced sleep disturbances and nervous system irritation. Nursing records showed that by reducing nighttime sound stimulation, the observation group had reduced risk of acute altered consciousness due to frequent awakening and disorientation. From the perspective of previous nursing management studies, a stable acoustic environment is associated with the maintenance of time and space perception and a reduced risk of postoperative delirium in elderly patients.[27,28] The classification of ward noise sources into operational noise, communication noise, and environmental noise may facilitate the implementation of targeted noise-control measures, including equipment transformation, operation standardization, and communication volume control.
Effect of Continuous Nursing Records and Responsibility-Based Nursing Management on Shortening the Duration of Delirium
In patients who developed postoperative delirium, the duration of delirium in the observation group was significantly shorter than that in the control group (P < 0.05). This may be attributed to the responsibility system management and continuous recording of consciousness. When patients showed delirium-related symptoms, the nursing staff gave key reminders during shift handovers and adjusted the frequency of nighttime nursing care in a timely manner, reduced stimulating operations, and thereby provided patients with a relatively quiet and stable recovery environment. This nursing management model, characterized by continuous monitoring and dynamic adjustment of treatment, may be associated with a reduction in recurrent exacerbation of delirium symptoms, a shortened duration of delirium, and a faster recovery of consciousness.[29]
Effect of Dynamic Assessment of Agitation/Sedation in Postoperative Behavioral Management
This study showed that the SAS score was lower in the observation group than in the control group, indicating that the patients’ consciousness and behaviors were more stable. The reason may be closely related to the dynamic assessment of agitation/sedation by the nurses. By using the SAS scale, nurses can more objectively identify the tendency of patients to be agitated or oversedated, rather than relying solely on experience. In addition, the observation group prioritized non-pharmacological soothing methods at night, such as verbal communication, body position adjustment and environmental control, to reduce agitation caused by overstimulation or discomfort. The low-noise environment created by noise management is an important part of non-pharmacological strategies, which reduces the external stimulation that causes patients’ agitation and further stabilizes their consciousness and behavior state. The quality improvement project implemented by Reppas-Rindlisbacher et al.[30] in orthopedic inpatients also confirmed that a systematic multi-component intervention strategy centered on nursing behavior adjustment can effectively reduce the incidence of delirium, thereby helping to maintain the relative stability of patients’ consciousness and behaviors.
Effect of Additional Targeted Nighttime Noise Control during Key Sleep Period and Sleep Rhythm Regulation on Improving Sleep Quality
Sleep quality is an important part of the recovery after knee arthroplasty in the elderly. This study showed that the RCSQ score of the patients in the observation group was significantly higher than that of the control group (P < 0.05). Pearson correlation analysis revealed a negative linear correlation between nighttime LAeq (02:00–04:00) and RCSQ score (r = −0.72, P < 0.001), indicating that lower nighttime noise during this period was associated with better perceived sleep quality. This result may be related to the systematic recording and adjustment of sleep-related factors by nursing staff. By recording patients’ sleep time and wakefulness during night rounds, nursing staff can make corresponding adjustments to patients’ daytime activities, avoiding excessive bed rest during the day, which may lead to difficulty falling asleep at night. Meanwhile, implementing targeted noise reduction measures during key sleep period was associated with a reduction in noise stimulation, an improvement in sleep continuity, and an enhancement in RCSQ scores.
Limitations
This study has several limitations. First, as a single-center retrospective non-randomized study, it inevitably introduces potential selection bias despite PSM for baseline covariates, given that grouping was based on actual clinical nursing and environmental management rather than random allocation. Second, key confounding factors, including anesthesia type, analgesic use, and perioperative complications, were not adjusted in the multivariable analysis for all outcomes, which may lead to residual confounding and compromise the rigor of any causal inferences drawn from the observed associations. Third, noise measurements only covered daytime (14:00–16:00), pre-nighttime (22:00–23:00), and late-night (02:00–04:00) periods, without including high-activity morning periods (06:00–10:00). This measurement scheme may reduce the representativeness of overall ward noise assessment; significant differences were limited to 02:00–04:00, and no 24-hour integrated metrics were available, so all noise-related conclusions of this study are confined to the observed associations between targeted nighttime noise control during key sleep period and the outcomes measured. Not applicable to the overall full-day ward noise environment.
CONCLUSION
This retrospective study showed that for elderly patients with KOA undergoing knee arthroplasty, implementing targeted nighttime noise control during key sleep period in addition to routine rehabilitation care was associated with lower nighttime noise levels, lower incidence and duration of postoperative delirium, better sleep quality, and faster functional recovery. The above findings suggest that noise management during key sleep period may be a noteworthy aspect of perioperative care, but its causal relationship needs to be further validated through prospective studies.
Availability of Data and Materials
The original contributions presented in the study are included in the article. Further inquiries can be directed to the corresponding authors.
Author Contributions
LiHong Lai contributed to the study conceptualization, core knowledge content definition, and research design. HuanTing Hu conducted literature retrieval. Li Li was responsible for data collection, including extracting patient clinical and nursing records. JiaJiang Jiang performed statistical analysis. GuoPing Xu took charge of manuscript preparation, synthesizing findings and structuring the academic writing. Authors read and approved the final manuscript, took public responsibility for appropriate portions of the content, and agreed to be accountable for all aspects of the work in ensuring that questions related to the accuracy or completeness of any part of the work were appropriately investigated and resolved.
Ethics Approval and Consent to Participate
The study was approved by the Medical Ethics Committee of the Second Affiliated Hospital of Zhejiang University School of Medicine (ethics approval number [2025-1523]. Informed consent was obtained from all patients.
Conflicts of Interest
The authors declare no conflict of interest.
Acknowledgments
The authors express gratitude to all participating patients for their cooperation. They also acknowledge the ethical approval and clinical support from the Second Affiliated Hospital of Zhejiang University School of Medicine, as well as the nursing team for their diligent clinical record-keeping and data collection.
Funding Statement
This study was supported by the Medical and Health Science Program of Zhejiang Province (Project No.: 2025HY0387).
REFERENCES
- 1.Johnson DS, Dhiman N, Badhal S, Wadhwa R. Effects of intra-articular platelet rich plasma on cartilage thickness, clinical and functional outcomes in knee osteoarthritis. Cureus. 2022;14:e32256. doi: 10.7759/cureus.32256. [DOI] [PMC free article] [PubMed] [Google Scholar]
- 2.Sun YT, Xiang XN, Yang J, Peng JL, He HC. Platelet-rich plasma improves pain and function in knee osteoarthritis: a retrospective study. Front Physiol. 2025;16:1678037. doi: 10.3389/fphys.2025.1678037. [DOI] [PMC free article] [PubMed] [Google Scholar]
- 3.Teimouri M, Salehi A, Shahsavan M, Rezaei H, Dayani Dardashti A. effectiveness of total knee arthroplasty on pain reduction and functional improvement in elderly patients: a quasi-experimental study. Adv Biomed Res. 2025;14:86. doi: 10.4103/abr.abr_409_24. [DOI] [PMC free article] [PubMed] [Google Scholar]
- 4.Clark GP. Treatment options for symptomatic knee osteoarthritis in adults. JAAPA. 2023;36:1–6. doi: 10.1097/01.JAA.0000979536.73946.98. [DOI] [PubMed] [Google Scholar]
- 5.Aftab S, Ali HN, Saeed B, Sarwar S, Dawood MH, Pervez M. Early physiotherapy for post-total knee arthroplasty recovery: a systematic review of randomized controlled trials on quality of life, pain, and range of motion outcomes. Musculoskeletal Care. 2025;23:e70158. doi: 10.1002/msc.70158. [DOI] [PubMed] [Google Scholar]
- 6.Chen X, Wang X, Liu Y, et al. Impact of tourniquet application on postoperative delirium in elderly patients undergoing total knee arthroplasty: a randomized clinical trial. Int J Surg. 2025;111:6191–9. doi: 10.1097/JS9.0000000000002762. [DOI] [PMC free article] [PubMed] [Google Scholar]
- 7.Khan IA, Cozzarelli NF, Hohmann AL, et al. Undergoing cartilage procedures before total knee arthroplasty is not associated with worse postoperative functional outcomes, readmission rates or complication rates. Knee Surg Sports Traumatol Arthrosc. 2025;33:2136–43. doi: 10.1002/ksa.12529. [DOI] [PubMed] [Google Scholar]
- 8.Kitsis P, Zisimou T, Gkiatas I, et al. Postoperative delirium and postoperative cognitive dysfunction in patients with elective hip or knee arthroplasty: a narrative review of the literature. Life (Basel) 2022;12:314. doi: 10.3390/life12020314. [DOI] [PMC free article] [PubMed] [Google Scholar]
- 9.Knebel A, Singh M, Rasquinha R, et al. Postoperative delirium following total joint arthroplasty: epidemiology, risk factors, and associated complications. Hip Int. 2025;35:150–8. doi: 10.1177/11207000241305771. [DOI] [PubMed] [Google Scholar]
- 10.Pettit RJ, Gregory B, Stahl S, Buller LT, Deans C. Total joint arthroplasty and sleep: the state of the evidence. Arthroplast Today. 2024;27:101383. doi: 10.1016/j.artd.2024.101383. [DOI] [PMC free article] [PubMed] [Google Scholar]
- 11.Betts JA, Bowden Davies KA, Smith HA, Hawley JA. Physiological rhythms and metabolic regulation: shining light on skeletal muscle. Exp Physiol. 2025;110:976–83. doi: 10.1113/EP091890. [DOI] [PMC free article] [PubMed] [Google Scholar]
- 12.Long G, Duo W, Man L, et al. The impact of post-traumatic stress on the clinical outcome in a cohort of patients with knee osteoarthritis and knee arthroplasty: a prospective study. J Orthopedic Sci. 2024;29:847–53. doi: 10.1016/j.jos.2023.03.017. [DOI] [PubMed] [Google Scholar]
- 13.Yang C, Zhuang MY, Chen X, et al. Effect of noise isolation on postoperative delirium in elderly patients undergoing hip surgery: protocol for a randomized controlled trial. BMJ Open. 2025;15:e088092. doi: 10.1136/bmjopen-2024-088092. [DOI] [PMC free article] [PubMed] [Google Scholar]
- 14.Hoffmann AJ, Tin AL, Vickers AJ, Shahrokni A. Preoperative frailty vs. cognitive impairment: which one matters most for postoperative delirium among older adults with cancer? J Geriatr Oncol. 2023;14:101479. doi: 10.1016/j.jgo.2023.101479. [DOI] [PMC free article] [PubMed] [Google Scholar]
- 15.Wei Y, Zhang Q, Bi H, et al. Assessment and management of analgesia and sedation in critically ill patients in intensive care units in Guizhou Province. Chin J Crit Care Med. 2025;37:861–5. doi: 10.3760/cma.j.cn121430-20240723-00624. [DOI] [PubMed] [Google Scholar]
- 16.Kamdar BB, Shah PA, King LM, et al. Patient-nurse interrater reliability and agreement of the Richards-Campbell sleep questionnaire. Am J Crit Care. 2012;21:261–9. doi: 10.4037/ajcc2012111. [DOI] [PMC free article] [PubMed] [Google Scholar]
- 17.Ritmala-Castren M, Axelin A, Richards KC, Mitchell ML, Vahlberg T, Leino-Kilpi H. Investigating the construct and concurrent validity of the Richards-Campbell Sleep Questionnaire with intensive care unit patients and home sleepers. Aust Crit Care. 2022;35:130–5. doi: 10.1016/j.aucc.2021.04.001. [DOI] [PubMed] [Google Scholar]
- 18.Qu L, Li Y, Hong D. Effectiveness of refined nursing on postoperative recovery in elderly hip fracture patients: a retrospective study. Medicine (Baltimore) 2025;104:e43870. doi: 10.1097/MD.0000000000043870. [DOI] [PMC free article] [PubMed] [Google Scholar]
- 19.Zhou Q, Zhou X, Zhang Y, et al. Predictors of postoperative delirium in elderly patients following total hip and knee arthroplasty: a systematic review and meta-analysis. BMC Musculoskelet Disord. 2021;22:945. doi: 10.1186/s12891-021-04825-1. [DOI] [PMC free article] [PubMed] [Google Scholar]
- 20.Karimijashni M, Yoo S, Barnes K, Lessard-Dostie H, Ramsay T, Poitras S. Prehabilitation in patients at risk of poorer outcomes following total knee arthroplasty: a systematic review. J Arthroplasty. 2025;40:1367–76. doi: 10.1016/j.arth.2024.10.132. [DOI] [PubMed] [Google Scholar]
- 21.Kaya C, Seyman CC, Kaya Y. Determination of the effect of preoperative knee joint function on postoperative quality of life in patients with total knee arthroplasty. J Orthop Res. 2024;42:2189–96. doi: 10.1002/jor.25876. [DOI] [PubMed] [Google Scholar]
- 22.Kraonual S, Thongpeth W, Thongpet T. The effectiveness of nursing interventions for preventing postoperative delirium in older adults undergoing major orthopedic surgery: a systematic review. BMC Nurs. 2026;25:676. doi: 10.1186/s12912-026-04821-7. [DOI] [PMC free article] [PubMed] [Google Scholar]
- 23.Ding Y, Sun X, Yin J, et al. Impact of white noise on sleep quality across age groups and in critically ill/non-critically ill patients: a systematic review and meta-analysis of randomized controlled trials. Sleep Med. 2025;136:106869. doi: 10.1016/j.sleep.2025.106869. [DOI] [PubMed] [Google Scholar]
- 24.Ji CY, Yang LR. Perioperative nursing care for hip arthroplasty patients with concomitant hypertension: a minireview. World J Clin Cases. 2023;11:8440–6. doi: 10.12998/wjcc.v11.i36.8440. [DOI] [PMC free article] [PubMed] [Google Scholar]
- 25.Pu YL, Li WT, Zhi XX, Meng AF. The impact of individualized care after artificial knee replacement surgery for patients with valgus deformity of the knee. Front. Nurs. 2020;7:103–9. [Google Scholar]
- 26.Qureshi O, Arthur ME. Recent advances in predicting, preventing, and managing postoperative delirium. Fac Rev. 2023;12:19. doi: 10.12703/r/12-19. [DOI] [PMC free article] [PubMed] [Google Scholar]
- 27.Neale S, McKnight E, Dixon R, Hitch D. Evaluation of a multidimensional occupational therapy environmental checklist for people experiencing delirium during hospital admission: a quasi-experimental study. Australas J Ageing. 2026;45:e70165. doi: 10.1111/ajag.70165. [DOI] [PMC free article] [PubMed] [Google Scholar]
- 28.Lee HJ, Jung YJ, Choi NJ, Hong SK. The effects of environmental interventions for delirium in critically ill surgical patients. Acute Crit Care. 2023;38:479–87. doi: 10.4266/acc.2023.00990. [DOI] [PMC free article] [PubMed] [Google Scholar]
- 29.Gómez Tovar LO, Henao Castaño AM. Dynamic delirium—nursing intervention to reduce delirium in patients critically Ill, a randomized control trial. Intensive Crit Care Nurs. 2024;83:103691. doi: 10.1016/j.iccn.2024.103691. [DOI] [PubMed] [Google Scholar]
- 30.Reppas-Rindlisbacher C, Siddhpuria S, Wong EK, et al. Implementation of a multicomponent intervention sign to reduce delirium in orthopaedic inpatients (MIND-ORIENT): a quality improvement project. BMJ Open Qual. 2021;10:e001186. doi: 10.1136/bmjoq-2020-001186. [DOI] [PMC free article] [PubMed] [Google Scholar]
Associated Data
This section collects any data citations, data availability statements, or supplementary materials included in this article.
Data Availability Statement
The original contributions presented in the study are included in the article. Further inquiries can be directed to the corresponding authors.