Introduction

Total knee arthroplasty (TKA) represents an effective treatment for end-stage osteoarthritis.1 At present, posterior-stabilized (PS) and posterior cruciate retaining (CR) prostheses are the most commonly used TKA prostheses. However, the superiority of each prosthesis type in terms of functional outcome, range of motion, kinematics, and long-term survival rates remains controversial.2 However, 10–36% of patients experience moderate-to-severe postoperative pain, leading to patient dissatisfaction following TKA and increasing hospital utilization.3 Postoperative pain can even cause chronic pain syndrome.4 Therefore, treating postoperative pain is crucial for patient management and has been a focal point of research for decades.

Many studies have focused on postoperative pain associated with the use of different types of prostheses. Wang et al.5 compared the incidence of postoperative knee pain between PS and medial pivot (MP) prostheses. The results showed that six patients in the PS group and three patients in the MP group had postoperative pain, indicating that the incidence of postoperative knee pain in the PS group was higher than that in the MP group. Moreover, Frank et al.6 compared postoperative knee pain between patients with PS and CR prostheses. After 60 months of follow-up, two 65-year-old men had postoperative knee pain in the CR group. Both of them received adequate pain relief with analgesic medications. Notably, all previous studies on knee pain after the use of different prostheses reported long-term follow-up outcomes, and there is a lack of comparative data in the perioperative period. Therefore, we decided to explore the perioperative analgesia effect of PS and CR prostheses, so as to provide a reliable clinical basis for optimizing the postoperative analgesia program of TKA.

Researchers hold different views on the effect of perioperative pain on postoperative functional recovery of patients with TKA. In a recent study by Harmer et al.7, no relationship between in-hospital postoperative pain and decreased range of motion (ROM) was noted. In contrast, Mikko et al.8 found that perioperative pain is a critical etiological factor in stiffness. The study included 391 TKA patients, 39 patients developed knee joint stiffness after surgery, with an incidence of 10%. During the perioperative period, these patients experienced excruciating pain and consumed large amounts of opioids. In order to improve ROM, 3 months after operation, they received manipulation under anesthesia.Therefore, adequate analgesic management in perioperative period is essential for functional recovery after TKA. In the study of Mikko et al.8, all patients received multi-mode analgesia, patients could self-administer intravenous oxycodone via the patient-controlled analgesia (PCA) pump combined with oral analgesics. Although oral and intravenous opioids can relieve moderate to severe pain after TKA. However, due to their unfavorable side-effect profile9, such as nausea, vomiting, constipation, etc. Therefore newer alternative therapy combinations, such as periarticular injections (PAI) in combination with peripheral nerve blocks (PNB) are being used instead of frequent opioid usage10. When adjuvants such as dexamethasone are added to local anesthetics, the analgesic time can be extended effectively.

As an early peripheral nerve block, femoral nerve block (FNB) is gold standard for pain relief following TKA. However, recently, the analgesic effect of adductor canal block (ACB) has been found to be equivalent to that of FNB following TKA in terms of the reported pain scores and opioid consumption. An advantage of ACB is the relatively universal absence of quadriceps weakness compared with FNB, this muscle-sparing quality of ACB facilitates early ambulation and recovery11. Thus, ACB has largely replaced FNB for regional analgesia and constitutes an element of multimodal analgesia regimens. The combined use of ACB along with periarticular infiltration (PAI) yields considerably better postoperative visual analog scale (VAS) scores, knee ROM, and ambulation distances compared with ACB alone12. Therefore, in the present study, the multimodal analgesia scheme of ACB + PAI was used for all patients to compare the perioperative analgesia effects between the PS and CR groups.

Methods

This study was approved by the Ethics Committee of the Fourth Hospital of Baotou (BSYLL2022016) and all methods were performed in accordance with the relevant guidelines and regulations. This study included 120 consecutive patients who underwent TKA at Baotou Fourth Hospital from January 2021 to September 2022. The participants were divided into PS and CR groups according to the type of prosthesis used. The inclusion criteria were patients who had signed the informed consent, had undergone unilateral elective TKA, were aged 50–80 years, and met the American Society of Anesthesiologists classification I–III. The exclusion criteria included previous surgery on the same knee, liver or kidney failure, allergy or intolerance to one of the study drugs, chronic opioid use, infection at the puncture site, and communication impairment. The PS and CR groups included 60 patients each, with 14 men and 46 women in the former and 13 men and 47 women in the latter.

All patients underwent TKA performed by the same senior surgeon and were managed by the same team during the perioperative period. After ensuring that the test piece was suitable, the prosthesis was installed and no drainage tube was placed.

Anesthesia and analgesia

All patients received 1.5–2 ml/kg normal saline preoperatively. Spinal anesthesia was administered with the patient in the lateral recumbent position. A 27-gage needle was inserted in the L3–4 intervertebral space. After ensuring that clear cerebrospinal fluid was freely flowing, 15 mg ropivacaine (Registration Number: H20140763, AstraZeneca AB, Specification: 100 mg/10 ml) was administered to achieve sensory block at or above the T8 dermatome. There was no drastic fluctuation in circulation in any patient during the perioperative period. After placing the patient in the supine position, a linear ultrasound probe (13–6 MHz) was moved from the cephalad to the caudal and the superficial femoral artery was visualized in the short axis, medial to the vastus medialis, lateral to the sartorius muscle, and anterior to the adductor magnus muscle. A 22 gage × 50 mm needle (Braun® Stimuplex) was guided from lateral to medial to the adductor canal using an in-plane technique. A mixture of 10 ml 1% ropivacaine and 5 mg dexamethasone (1 ml diluted in 9 ml 0.9% normal saline) was administered along with periarterial spread following negative aspiration under sterile conditions. The PAI cocktail (50 ml) comprising 0.2% ropivacaine, 5 mg morphine, and 10 mg dexamethasone was prepared in the operating room. The PAI was administered in two stages. Following bone surface preparation and before component placement, the cocktail (50% of the total volume) was injected into the posterior capsule. Aspiration was performed before injection into the posterior region of the knee. The second PAI cocktail injection (remaining 50% of total volume) was administered following component insertion but before wound closure while the cement was curing in the suprapatellar pouch, collateral ligament, fat pad, and retinacular and subcutaneous tissues. At the end of the surgery, the surgeon covered the entire knee with compression bandages. For all patients, a cold pack (gel ice) was applied as a standard treatment for 20 min every 2 h for 3 days postoperatively, starting 1 h after surgery. At 3 h after surgery, patients received an intravenous infusion of lornoxicam (8 mg) (Approval No.: H20043685, Zhejiang Zhenyuan Pharmaceutical Co., Ltd. Specification: 8 mg/pc) every 12 h for 3 days.

Postoperative pain at rest and during movement (knee extension and flexion exercises) was measured using VAS at 6, 12, 24, 48, and 72 h after surgery. Simultaneously, the extents of osteotomies on the medial and lateral sides of the femur and tibia were measured using calipers. The preoperative hospital for special surgery (HSS) knee scores and lower extremity tourniquet durations were recorded. The postoperative doses and administration frequencies of opioid analgesics were also recorded.

Statistical analysis

Qualitative data, such as sex and ASA classification, were analyzed using the chi-square test. Quantitative data, such as height, weight, amount of osteotomy, and VAS score, were expressed as mean ± standard deviation, and compared using independent t-tests. A P-value of < 0.05 was considered statistically significant. All statistical analyses were performed using the Statistical Package for the Social Sciences (SPSS, IBM, USA) 19.0 software. PASS11.0 software was used for power analysis and bilateral Mann–Whitney test was used. Group sample sizes of 60 and 60 the power of postoperative VAS score comparison between the two groups was 88.5% at 12h rest, 81.4% at 12h exercise, and 83.5% at 24h rest, respectively. The power of lower extremity tourniquet time comparison between the two groups was 99.9%.

Results

Overall, 120 consecutive patients were included in this study. There were no significant differences between groups in terms of demographic data, including gender, age, height, weight, body mass index, and ASA classification (Table 1).

Table 1 Patient demographic data.
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Perioperative data are shown in Table 2. No statistically significant differences in preoperative VAS scores at rest or during movement were detected between groups. In addition, no significant differences in preoperative HSS knee scores were detected between groups (PS 54.88 ± 10.74 vs. CR 55.26 ± 13.41, P > 0.05). To obtain a clear vision of the surgical field, a thigh tourniquet was applied in all patients throughout the operation. The pressure of the lower extremity tourniquet was 260 mmHg and the duration of its application in the PS group was significantly longer than that in the CR group (P < 0.05). No significant differences in the extents of osteotomies on the medial and lateral sides of the femur and tibia were detected between groups.

Table 2 Perioperative data.
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The postoperative VAS scores of the groups are summarized in Figs. 1 and 2. The 12-h postoperative VAS scores at rest and during movement and the 24-h VAS scores at rest in the CR group were significantly lower than those in the PS group (0.71 ± 1.36 vs. 1.36 ± 0.95, P = 0.01; 2.02 ± 1.85 vs. 2.81 ± 1.25, P = 0.03; 1.85 ± 1.40 vs. 2.47 ± 0.97, P = 0.02). However, there was no significant difference in the VAS scores between groups at other timepoints at rest or during movement (P > 0.05). No opioid analgesics had been used in either group for 72 h after surgery.

Fig. 1
Fig. 1
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Rest.

Fig. 2
Fig. 2
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Movement (knee extension and flexion exercises).

Discussion

A total of 120 patients were continuously enrolled, including 93 female patients and 27 male patients. Although there was no significant difference in demographic data between the two groups (P > 0.05), the incidence of knee osteoarthritis in elderly women was significantly higher than that in men.This phenomenon is similar to those reported by other scholars13. Patients in the PS group were older and heavier, obesity is a risk factor for the development of knee and hip osteoarthritis, particularly knee osteoarthritis13. This may also be the cause of the increased VAS score after surgery, but further studies are needed to confirm it.

We found that the 12-h postoperative VAS scores at rest and during movement and the 24-h VAS scores at rest in the CR group were significantly lower than those in the PS group (P < 0.05). There are several reasons for the decreased VAS scores in the CR group. First, compared with the CR group, patients in the PS group used tourniquets for a significantly longer period (P < 0.05). The PS group preoperative VAS scores at rest or during movement were both higher than those in the cr group, while the HSS score was lower than that in the CR group. Although the differences in these scores were not statistically significant (P > 0.05), it can be seen that the osteoarthritis of patients in the ps group were more severe, so the operation time was longer. Peker et al.14 demonstrated that skeletal muscle ischemia–reperfusion following tourniquet application can result in tissue ischemia, hypoxia, and a massive production and accumulation of oxygen free radicals. Oxygen free radicals efficiently induce proinflammatory cytokines, thereby releasing a large number of intracellular inflammatory factors into the blood.

Not only that, but other researchers have found that tourniquet compression leads to release of prostaglandins by the injured cells15. These prostaglandins increase pain perception by sensitizing and exciting pain receptors. Also, limb ischemia causes central sensitization via N-methyl D-aspartate receptor activation due to repeated nociceptive afferent input from the affected limb. And there was significant association between tourniquet inflation time and pain15. Tourniquet use has been associated with increased postoperative pain and diminished short-term functional outcomes that disappear after 1 month.16 However, Goel et al.17 have reported that tourniquets decrease intraoperative blood loss, which can consequently improve the surgical field of vision and shorten operation durations. A previous meta-analysis revealed that early tourniquet release was associated with greater perioperative blood loss than tourniquet release following wound closure.18 Therefore, in this study, tourniquets were used from the beginning of the surgery until incision closure to maintain the clean of the surgical field and decrease intraoperative blood loss. However, no consensus has been reached regarding the advantages and disadvantages of using tourniquets in TKA.

The VAS scores only differed significantly between groups at rest and during movement 12 h after surgery and at rest 24 h after surgery (P < 0.05). No significant differences were observed at the other timepoints (P > 0.05). All patients received spinal anesthesia, a cold pack (gel ice) 1 h after surgery, and intravenous 8 mg lornoxicam 3 h after surgery. Therefore, there was no significant difference in the VAS scores between groups at 6 h following surgery. Compared with single ACB, continuous ACB can provide more complete analgesia for patients following TKA.11 Nevertheless, catheter usage may create various difficulties during placement and in the postoperative period. In patients with excess subcutaneous adipose tissue, strict follow-up of the catheter and confirmation of location are required. However, patients who have undergone TKA need rapid postoperative mobilization and the rotational movement of the tissue around the femur may displace the catheter tip. Hence, the additional effort in placing and managing the ACB catheter may not support the rapid mobilization of patients who have undergone TKA. Consequently, a single ACB was used in this study.

An important limitation of single-shot nerve blocks is the short duration of analgesia. Researchers are therefore constantly searching for strategies to prolong the duration of peripheral nerve block analgesia without resorting to indwelling perineural catheters.19,20,21 Various adjuvants have been employed to enhance the duration and quality of local anesthesia. Dexamethasone, a high-potency, long-acting corticosteroid, is commonly used to reduce postoperative nausea and vomiting. When combined with a local anesthetic, dexamethasone enhances the duration of local anesthetic blocks by preventing nociceptive impulse transmission along myelinated C fibers.21 Therefore, herein, a single ACB was performed using a mixture of dexamethasone and ropivacaine. The duration of the analgesic effect of this mixture was ~ 24 h. Thus, no significant differences in the VAS scores at rest and during movement at 48 and 72 h were detected between groups (P > 0.05). Compared with ropivacaine alone, dexamethasone and ropivacaine significantly prolonged the duration of analgesia for a single ACB for up to ~ 24 h,22 consistent with the results of the present study.

However, a limitation of this study is its single-center design. Multicenter trials are warranted to determine the manner in which individualized and complete postoperative analgesia can be provided to patients undergoing TKA.

The present study provides new ideas and a reliable clinical basis for solving the problem of postoperative analgesia following TKA. Compared with the PS group, multimodal analgesia with ACB and PAI was more effective in the CR group 24 h after TKA. Therefore, in the future, we will focus on improving postoperative analgesia in patients undergoing TKA with PS prosthesis.