The inclusion criteria were as follows: (1) end-stage medial compartment osteoarthritis which was was clinically and radiographically diagnosis and met the surgical indications for unicompartmental knee arthroplasty (UKA); (2) American Society of Anesthesiology(ASA) classes 1 to 2, or class 3 but assessed could tolerate UKA; (3) those have a responsible caregiver and can stay with them for at least 4 days after operation; (4) patients and their caregiver can adequately understand the process of outpatient operation and post-operative analgesia regimen; (5) adequate home environment for postoperative recovery. Exclusion criteria included: (1) rheumatoid arthritis or suppurative arthritis;; (2)patients with systemic diseases and can not tolerate major surgical operation (ASA 3-5); (3) opioid consumption (4)patients with contraindications of spinal anesthesia or femoral nerve block (FNB); (5)refused to participate in this study or not willing to finish regular follow-up.
After approved by the Ethics Committee of our institution (KY2020124) , a randomized controlled trial was conducted on the basis of pre- and postoperative outpatient clinical charts. From October 2017 to June 2018, 64 consecutive and unselected patients who underwent primary, medial UKA in our institution were involved in our study. All patients were operated with cementless mobile bearing Oxford Ⅲ UKA system with a minimal invasive technique as described by the manufacturer. A single senior surgeon performed more than 200 primary UKAs, in which the outpatient procedures was employed in 26.7% of cases. After assessed by the senior surgeon, patients who met the inclusion criteria for day-time UKA operation could be involved in our study. 64 patients were equally divided into two groups using random number method:32 patients with spinal anaesthesia(group A) and 32 with general anaesthesia(group B). All patients participating in the trial gave written informed consent.
Patients and procedures
Patients who met the inclusion criteria could be scheduled for the operation. Written informed consent was obtained before inclusion in the study.
- Two weeks preoperatively: Comprehensive educational material would be provided by our surgeon, and the degree of preoperative pain was evaluated by visual analog score (VAS). Patients with VAS score ≥ 4 either at rest or in motion were prescribed with oral analgesia: NSAIDs (celecoxib), pregabalin, or buprenorphine for external use.
- One week preoperatively: Senior surgeon and anaesthesiologist should reassess and confirm if patient met the inclusion/exclusion criteria. Patients were contacted by the protocol nursing, who would provide the introductions about the surgical procedure, anaesthesia techniques, risks and recovery procedures. Further preoperative education, including strict prohibition of smoking and alcohol, ankle pump exercise and quadriceps muscle contraction training, schedule of rehabilitation plan and daily goals of functional exercise after operation should also be informed to help them establish a reasonable psychological expectation, and make them fully understand and participate in recovery process.
- Three days preoperatively: Chest X-ray, electrocardiogram and other auxiliary examinations should be implemented. Patients with anemia (HB: female < 110g/L, male < 120g/L) or hypoalbuminemia (< 30 g/L) should be delayed until their HB/albumin returned to normal level; For patients with hypertension and diabetes mellitus, the blood glucose and blood pressure should be adjusted to the normal range, then the operation could be scheduled again.
- Day of operation: When arrived at surgical department, all patients were randomized arranged into one of two groups(Group A or Group B). After confirmed no absolute contraindication, related documents could be signed. Fasting solid food 6 hours before induction; 2 hours before induction, 600 ~ 800 ml high concentration carbohydrate were given orally. Prophylactic antibiotic and a single dose (1 g) of tranexamic acid was given intravenously 30 minutes before skin incision.
Types of anaesthesia
The senior surgeon performed THA on all patients by using the same surgical technique and peri-operative protocol for both groups. And all anesthetic procedures(SA and GA) were under the management of an experienced anesthetist. All patients were given femoral nerve block (FNB) preoperatively.
Spinal anaesthesia
Under aseptic conditions, spinal anaesthesia was performed in a midline approach. The anaesthetist identified the L3 to L4 interspace in the lateral decubitus position. After local infiltration anaesthesia(LIA), the subarachnoid space was sought. Free-flowing cerebrospinal fluid(CSF) and no reflux of blood indicated correct needle position, then 2 mL 0.5% hyperbaric bupivacaine was injected in the absence of paraesthesia. Blood pressure and heart rate should be carefully observed. After induction patients were immediately transferred to the operating room and positioned. Optionally, by request, patients were given propofol until a mild level of sedation was achieved (Richmond Agitation Sedation Scale 1 to 2). Sensory block and motor block were evaluated 3 min after injection. Sensory block was tested using a toothpick to elicit pinprick starting caudally and moving cephalad.
General anaesthesia
After pre-oxygenation, sufentanil (0.2 ~ 0.5mg/kg) and propofol (2 to 3 mg/kg) were intravenously injected. Laryngeal mask (LM) was provided according to body weight. For difficult or impossible ventilation that could not be resolved by replacement or re-insertion of the LM, an endotracheal tube would be provided with an inner diameter of 7.0 mm for women and 7.5 mm for men. The nondepolarising neuromuscular blocking agent atracurium was administered for orotracheal intubation. Ventilation was managed by pressure-controlled mode at a frequency to achieve an end tidal PCO2 of 35 ~ 40 mmHg. Anaesthesia was maintained by continuous propofol infusion through a perfusor pump, with the infusion rate set 8 ~ 12 mg kg/body weight/h, and could be adjusted according to the individual condition. To ensure prompt recovery, the infusion of propofol was stopped 5 min before completion of skin closure. If necessary, the anaesthetist would administer repetitive sufentanil doses according to clinical need. Indicated by the Apfel score, patients at risk of PONV received granisetron (1 mg) and dexamethasone (4 mg) as prophylaxis.
Surgical technique
After a satisfactory anaesthesia, all patients were put in hanging leg (HL) position, then an iodised incision drape (Ioban 3M®) was applied after conventional draping. All the surgical incisions were performed by minimally invasive surgical incision near the patella. Oxford Ⅲ UKA prostheses were utilized in all patients. The senior doctor with a fixed surgical team performed operation according to the Oxford III UKA system operation manufacturer. Before skin suture, all patients received local infiltration analgesia (LIA) with 20ml "cocktail" (ropivacaine 200mg, epinephrine 5mg, triamcinolone acetonide 5mg) injected in the posterior capsule, periarticular tissues, and subcutaneous tissue. No intra-articular suction drain or urinary catheter was placed in all patients. The fluoroscopy with a C-arm X-ray machine should be conducted to ascertain that the prostheses were satisfactory. Once the procedure was finished, all patients were immediately transferred into the postanesthesia care unit(PACU). After pain and PONV were controlled, patients were orally provided with 200ml high concentration carbohydrate and sent back to the ward after active bleeding disappeared.
Postoperative management
All patients were treated by multimodal analgesia once sent back to ward, in combination with PCIA (Patient control intravenous anesthesia) pump. 2 hours after surgery, patients were orally given celecoxib (200mg/12h), Tylenol (650mg/8h) and gabapentin (300mg/8h). If the pain symptoms were still obvious (VAS score ≥ 5, and the pain affected postoperative functional exercise), tramadol and buprenorphine were given additionally. 1 h, 3 h and 24 h postoperatively, single dose of tranexamic acid (1g) was given separately.
Postoperative functional exercise was initiated and evaluated by the therapists in day-time operation team. After the effect of anesthesia subsided, the functional exercise should be started, including CPM, ankle pump, knee flexion and extension exercise. 2 hours after operation, all patients were required to sit and stand up. Then with the walking aid, they were required to try to walk independently with adjustable lower limb brace. The therapists ensured that all patients can walk safely and, meanwhile, assessed their gait and pain level. 4 hours after the operation, they walked on the floor again and tried to walk up and down stairs independently.
The discharge criteria were as follows: 1) Mobilizes in and out of bed independently; 2) walk 30 m independently; 3) walk up and down stairs independently; 4) obvious relief of pain; 5) has minimal or no wound wound exudation; 6) HB ≥ 90; 7) patient feel comfortable and confident to go home.
Only patients met the discharge criteria can they be discharged. Anticoagulation with low molecular weight heparin was given every day from 12 hours after operation, and rivaroxaban was given orally after discharge until 3 weeks after operation;
All discharged patients were maintained contact via Wechat, a social networking application (Tencent Inc., China) and telephone. They were followed up by a doctor on regular basis.
The primary outcome measures included the length of stay (LOS), the total hospitalization cost. Early post-operative complications and reasons for delayed discharge were recorded. And the operation time, intraoperative blood loss and VAS at the time of discharge were recorded. Patients were followed up regularly1, 3, 6, 12 month(s) and then annually after the operation, to record the complications, including periprosthetic infection, thromboembolic event, prosthesis dislocation and aseptic loosening. And the hospital for Special Surgery knee score (HSS) and Oxford knee score (OKS) were used to assess the knee function.
Study size and statistical methods
The sample size was calculated according to the primary outcome (the length of stay) using the SAS software package (version 9.0, SAS Institute Inc., Iowa, IA, USA). We presumed that a difference of 2h between the two groups would be clinically important. Assuming a SD of 4h, a 5% significance level and a 90% power using a two-sided test, we obtained a total sample size of n=22 for each group. As we were not able to ensure that these data would be normally distributed, we enhanced the sample size to n= 32 patients per group.
SPSS 22.0 statistical software was employed for statistical analysis. Measurement data were expressed as mean±standard deviation (SD). Repeated analysis of variance was used for comparison between time points before and after surgery in the groups. Paired t-test was used for pairwise comparison. Independent sample t test was utilized for comparison between groups. Comparison of count data between groups was made by using χ 2 test. Inspection level was set at α = 0.05.
Results
A total of 64 patients were involved, consisting of 20 males and 42 females, with an average age of 60.4 ± 3.8 year-old at the time of surgery. The demographics are shown in Table 1. There existed no significant differences in demographics between the two groups, including sex (P = 0.59), age (P = 0.96), BMI (P = 0.83), ASA (P = 0.74), and preoperative HSS (P = 0.47).
Tab.1 Comparison of Patient Demographics. ()
Group
|
n
|
Sex
male/female
|
Age
|
BMI
|
ASA
|
Preoperative HHS
|
A
|
32
|
9/23
|
60.1±6.3
|
22.80±4.45
|
2.0±0.4
|
46.81±7.37
|
B
|
32
|
11/21
|
60.2±5.5
|
23.03±5.52
|
1.9±0.3
|
48.44±4.92
|
Statistic
|
|
P=0.590
|
t=-0.052
P= 0.959
|
t=-0.213
P= 0.833
|
t=0.330
P= 0.751
|
t=-1.009
P= 0.321
|
The length of stay(LOS) and total cost were significantly less in group A than in group B (P < 0.05). The patients in group A were followed up for 6–16 months (mean time: 9.7 months) and 6–18 months (mean time: 9.3 months) in group B. In terms of postoperative satisfaction, the numeric rating scales (NRS) of group A was (8.87 ± 0.83), which was slightly higher than that of group B (8.59 ± 0.84), and the difference was not statistically significant (P > 0.05) (see Table 2).
Tab.2 Comparison of clinical indexes when discharge between 2 groups ()
Group
|
n
|
LOS(h)
|
Expense(¥)
|
NRS
|
VAS(at rest)
|
VAS(in motion)
|
A
|
32
|
17.7±3.9
|
40356.5±652.8
|
8.87±0.83
|
2.06±0.31
|
3.15±0.48
|
B
|
32
|
21.4±6.4
|
44131.8±191.7
|
8.59±0.84
|
2.13±0.49
|
3.25±0.58
|
Statistic
|
|
t=-0.052
P=0.590
|
t=-0.052
P= 0.959
|
t=-0.213
P= 0.833
|
t=0.330
P= 0.751
|
t=-1.009
P= 0.321
|
Among all patients, 51 patients (80%) were not discharged on the day of operation (DOS), with 53 patients(83%) discharged on POD-1, and 95% on POD-2. In group A, 24 patients were not discharged on the day of operation (DOS), with 27 patients discharged on POD-1, and 30 on POD 2; In group B, 27 patients were not discharged on the day of operation (DOS), with 26 patients discharged on POD-1, and 31 on POD 2. There was no significant difference between two groups on the discharge day (P>0.05). Lack of mobilization (84%), pain (23%), and PONV (17%) were the main reasons for patients not meeting the discharge criteria on DOS (Table 3). There was no significant difference between two groups on the reasons for not discharge on DOS (P>0.05).
Tab.3 count and percentage of total amount of patients still hospitalized on day of surgery (DOS), postopertive day 1 (POD 1) and postopertive day 2 (POD 2)
group
|
Not discharged on
|
DOS
|
POD 1
|
POD 2
|
N=51
|
N=11
|
N=3
|
S
G
|
24
27
|
5
6
|
2
1
|
χ2
P
|
1.463
0.226
|
0.110
0.704
|
0.350
1.000
|
Patients with spinal anaesthesia underwent a longer surgery time than those with GA.(P<0.05); And the blood loss in two groups had no significant difference(P=0.727). Meanwhile, Patients in the Group A had a significantly earlier oral fluid intake and walking unaided(P<0.05); Pain occurred significantly earlier in the Group B(P<0.05; Table 4).
Tab.4 Duration of procedures and recovery times from start of intrathecal injection ()
Group
|
A
|
B
|
P value
|
Operation time (min)
|
70.8±7.1
|
60.1±9.1
|
0.000
|
Blood loss (ml)
|
121.3±15.8
|
122.3±19.1
|
0.727
|
Occurrence of pain (min)
|
108.8±10.0
|
71.8±8.4
|
0.000
|
Food intake (min)
|
55.4±4.5
|
91.8±5.3
|
0.000
|
Walking unaided (min)
|
119.7±15.5
|
139.3±13.9
|
0.000
|
Time spans marked with an M are measured from the end of induction; median (range) are given.
Figure 1 showed the comparison of HSS score and OKS score between the two groups preoperatively and post-operatively: the HSS score and OKS score of both groups were significantly improved at 1, 3 and 6 months after operation, and the differences between two groups were not statistically significant (P > 0.05).
There was no significant difference in VAS scores between the two groups at the time of discharge (P > 0.05), suggesting that while the LOS was significantly reduced, the pain symptoms could still be well controlled by both types of analgesia. At latest follow-up, no periprosthetic infection, aseptic loosening of prosthesis, deep vein thrombosis (DVT), pulmonary infection and other complications were found in all patients.( see Fig.2)