Comparison of patient satisfaction and function outcomes between restricted kinematic alignment and mechanical alignment: An early follow-up study

doi:10.21203/rs.3.rs-5001048/v1

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Comparison of patient satisfaction and function outcomes between restricted kinematic alignment and mechanical alignment: An early follow-up study

https://doi.org/10.21203/rs.3.rs-5001048/v1

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Background

Mechanical alignment (MA) is the gold standard for total knee arthroplasty (TKA). However, MA will inevitably modify the patient's native knee anatomy. Another alignment option is kinematic alignment (KA), which aims to restore the original anatomy of the knee. In recent years, restricted kinematic alignment (rKA), which aims to restore native knee kinematics without reproducing the extreme knee phenotype, has been developed as an alternative to unrestricted KA. This study was designed to evaluate the clinical outcomes and satisfaction scores between patients who underwent rKA and those who underwent MA during TKA.

Methods

We retrospectively analyzed the clinical data of 45 patients who were diagnosed with osteoarthritis and underwent MA-TKA and 45 patients who underwent rKA-TKA from January 2022 to January 2023. Demographic, perioperative, and radiological data were collected and compared. Unpaired two-sample t tests for continuous variables and χ² tests for categorical variables were used to compare various measurements between two groups. The patient-reported outcome measures at baseline(T0) and at 3 (T3), 6 (T6), and 12 (T12) months after surgery were recorded and statistically analyzed.

Result

Forty-five robotic-assisted rKA-TKAs were performed, and 45 conventional MA-TKAs were performed. The changes in the hospital for special surgery score (HSS), visual analogue scale (VAS), forgotten joint score (FJS-12), knee society score (KSS), patient satisfaction, and complications from T0 to T12 for patients who underwent rKA were equal to those who underwent MA (86.58 vs. 86.22, P > 0.05 (KSS-Clinical, T12), 73.40 vs. 75.00, P > 0.05 (KSS-Function, T12), 86.11 vs. 85.28, P > 0.05 (HSS, T12), 0.87 vs. 0.82, P > 0.05 (VAS, T12), 83.29 vs. 83.38, P > 0.05 (FJS-12, T12), and 4.57 vs. 4.43, P > 0.05 (Satisfaction, T12)). The net change in the hip-knee-ankle (HKA) and medial proximal tibial angle (MPTA) for the constitutional varus was greater (P < 0.05) than that for the constitutional valgus knee in the rKA group. Both groups have a good range of motion (ROM). No revision was performed in the two groups at the one-year follow-up.

Conclusion

rKA is safe for short-term TKA and is a valid alternative to MA.

mechanical alignment

restricted kinematic alignment

total knee arthroplasty

Total knee arthroplasty (TKA) has been shown to be successful in relieving pain and improving function in patients with end-stage knee osteoarthritis (OA)[1]. An increasing number of surgeries are performed each year, and the number is expected to increase by 565% in the United States over the next 3 decades[2]. However, the dissatisfaction rate after TKA is as high as 20%[3–5]. Furthermore, neither the use of assistive techniques[6, 7] to improve the accuracy of implant placement nor new implant designs[8] can improve patient satisfaction. An increasing number of surgeons are turning their attention to the alignment of the lower limbs. They belived different alignment strategies can affect the extent of osteotomy and the degree of soft tissue release, and changes in the anatomical structure of the knee joint directly affect patient satisfaction.

Freeman et al.[9] proposed the mechanical axis vertical osteotomy method in 1973. Since 1976, mechanical alignment (MA)[10] has gradually become the gold standard for TKA. However, MA has many inherent limitations: it creates a nonphysiological knee joint by altering the inherent anatomical structure, physiological ligament balance, and kinematic characteristics of the knee joint, altering the original tension of soft tissue and breaking the original balance of motion, resulting in limited improvement in patient function and symptoms. It is possible that the modification of the normal anatomy of the knee may be responsible for those unsatisfactory results[11]. Some large-sample clinical studies conducted at James Cook University[12] and the Mayo Clinic[13] have challenged whether mechanical alignment in total knee arthroplasty is the superior method.

Howell et al. proposed the kinematic alignment (KA)[14] method in 2006, which aims to fully restore the anatomical structure to that before arthritis. KA-TKA has shown impressive clinical results[15], and it has also been appreciated by many surgeons[11]. However, the anatomy of the lower limb varies widely[5], and pathological changes due to trauma, tumors, childhood deformities or previous surgeries further increase this variability[16]. The mechanical stability of the knee joints in this population is inherently poor. If these abnormal anatomical structures are reconstructed using the kinematic alignment technique, they may have potential adverse effects on the survival of the prosthesis[16]. Therefore, restricted kinematic alignment (rKA)[17], which is a combination of KA and MA, theoretically improves patient function and satisfaction while avoiding extreme situations that may affect the survival of the prosthesis, was proposed.

This trial was designed to compare robotic-assited rKA-TKA and conventional MA-TKA under the hypothesis that there would be no difference in pain, function or range of movement (ROM), satisfaction rate or postoperative scores at 1 year between the two groups.

General information

This was an Institutional Review Board-approved retrospective cohort analysis (SPHFJP-S2021096-01). All patients who underwent cemented TKA for OA at the Second Affiliated Hospital of Fujian Traditional Chinese Medical University between January 2022 and January 2023 were considered for enrollment in the study. A total of 45 patients (45 knees) underwent robotic rKA-TKA, and 45 patients (45 knees) underwent conventional MA-TKA by one author (Jian Li) who was trained in both approaches.

Inclusion criteria:

Primary, unilateral or bilateral TKA for end-stage osteoarthritis, inflammatory arthritis, or posttraumatic osteoarthritis

No previous TKA at a different location

Written informed consent

Exclusion criteria:

Previous femoral, tibial, or patellar fracture; healing of femoral or tibial extraarticular deformities; and any planar deformity greater than 15°

Previous joint replacement or osteotomy involving the knee or a medical condition precluding surgery

Previous Grade 3 posterior lateral or lateral collateral ligament injury

Previous medial collateral ligament injury with relaxation exceeding level 2

Active infection or serious illnesses of other systems

Baseline clinical assessment

All patients underwent clinical examination approximately 1 week before surgery. The patient’s history and etiology of orthopedic, alignment and knee joint pathology were recorded. Sociodemographic and clinical data, including sex, age, weight, height, body mass index (BMI), Anaesthesiologists Score (ASA), implant alignment, and hip-knee-ankle (HKA) angle were collected. The clinical examination included global knee pain assessment on a 0–10 visual analogue scale (VAS) (10: worst possible pain), range of active flexion, flexion contracture, Hospital for Special Surgery score (HSS, 0 to 100 worst to best), Knee Society clinical score (KSS-Clinical, 0 to 100 worst to best), Knee Society function score (KSS-Function, 0 to 100 worst to best)[18], Forgotten Joint Score[19] (FJS-12, 0 to 100 worst to best), satisfaction (5, very satisfied; 4, satisfied; 3, neutral; 2, dissatisfied; 1, very dissatisfied) [20, 21] and complications.

Key angle measurements, such as the HKA, lateral distal femoral angle (LDFA), and medial proximal tibial angle (MPTA), were measured on weight-bearing, long leg alignment radiographs[22]. They were measured using the PACS (Centricity™, GE Healthcare, Chicago, IL, USA).

Operation procedure

A posterior-stabilized, fully cemented total knee prosthesis (Vanguard Premier; Zimmer Biomet, Warsaw, Indiana, USA) was used for all patients. MA-TKA was performed using conventional instruments; rKA-TKAs was performed using a robotic-assisted system (ROSA® Knee System; Zimmer Biomet, Warsaw, Indiana, USA). All the implants were aligned according to the group allocation. During the trial, the surgeon determined the most suitably sized tibial insert.

In the control group (MA), resected femoral and tibial bones were positioned perpendicular to the mechanical axis of each bone and at an HKA angle of 0°[23]. The femoral component was rotated and set parallel to the surgical transepicondylar axis with secondary rotational referencing perpendicular to the anteroposterior sulcus axis and 3° externally rotated to the posterior condylar axis.

In the intervention group (rKA), the procedure was as follows[17]: (1) the combined lower limb coronal orientation was set ± 3° neutral; (2) the coronal alignment of the joint line was oriented within ± 5° neutral; (3) the tension/laxity of the soft tissues of the knee were preserved/restored; (4) preservation of the femoral anatomy was prioritized; and (5) the unloaded/most intact knee compartment was resurfaced and used as the pivot point when anatomical adjustment was needed. If the preoperative plan required LDFA and MPTA resections that would lead to an HKA outside the safe zone, then the LDFA and MPTA were incrementally adjusted until the final HKA did not exceed the boundaries of the safe zone. The angles bounding these safe zones were centered at the means of the normally distributed angles [24], as aligning with studies examining implant alignment in the context of survivorship[25]. Femoral component rotation was initially set parallel to the native posterior condylar axis. If the planned tibial resection angle was reduced to bring it within the safe zone, the femoral component was externally rotated by the same amount to rebalance the flexion gap. Postoperative management was identical for both groups.

The physiotherapists and nurses were blinded to the method of alignment used, as were the surgeons who recorded the HSS, VAS score, FJS-12 score and KSS. The limits of active extension and flexion were measured with a long-arm goniometer with the patient in the supine position.

Evaluation of curative effect

The surgeon or a fellow performed postoperative clinical assessment at 3, 6, and 12 months. Each consultation included an assessment of global pain (VAS score, 0–10), range of active flexion, flexion contracture, and implant alignment (HKA, LDFA, MPTA), and the satisfaction rates of the HSS, FJS-12, and KSS were recorded.

Statistical analyses

The data are presented as numbers, percentages, means, and standard deviations (SDs). The differences in the means of the primary outcome measures between the groups were determined using the Wilcoxon signed-rank test for nonnormally distributed data, an unpaired t test for normally distributed data. Categorical data were expressed as [n(%)]. Group differences were assessed through the chi-square tests or Fisher’s exact test. In the comparison of measurement data of the same type of alignment in different follow-up timepoint, the repeated measure anova was employed. The data underwent analysis using statistical software (SPSS Inc. v20, IBM Corp., USA). A significance level of α = 0.05 (P < 0.05) indicated statistical interpretation of differences.

Comparison of the preoperative characteristics of the two groups

Age, sex, BMI, American Society of Anesthesiologists (ASA) class, preoperative alignment of the knee, ROM, HSS, Knee Society Score, and VAS score were similar (p > 0.05) between the two groups (Table 1).

Table 1

Comparison of the preoperative characteristics of the two groups
Characteristics	rKA	MA	P-value
Demographic
Age(years)	69.64 ± 5.61	72.16 ± 8.08	0.09
Female	39(86.7%)	38(84.4%)	0.76
Male	6(13.3%)	7(15.6%)	0.76
BMI(Kg/m²)	25.18 ± 1.88	25.01 ± 2.08	0.68
ASA	2.00 ± 0.48	2.02 ± 0.40	0.81
Range of motion
Flexion Contracture	6.22 ± 6.58	5.62 ± 6.10	0.71
Flexion	111.22 ± 18.86	112.67 ± 14.98	0.69
Alignment
LDFA	89.83 ± 3.75	89.81 ± 3.53	0.98
MPTA	85.72 ± 3.36	84.80 ± 3.17	0.15
HKA Clinical measure scores	8.41 ± 7.65	9.61 ± 7.53	0.42
KSS-Clinical	50.76 ± 13.20	49.27 ± 16.16	0.63
KSS-Function	55.82 ± 13.63	52.36 ± 10.12	0.18
HSS Scores	66.16 ± 9.38	65.11 ± 11.24	0.63
VAS Scores	6.47 ± 0.16	6.49 ± 0.87	0.91

Comparison of lower limb alignment between the two groups

Several radiographic measurements (HKA, LDFA, and MPTA) regarding lower limb alignment were calculated and recorded. Compared to the preoperative HKA, the postoperative HKA significantly differed in two groups (P < 0.05). Compared to the preoperative LDFA, the postoperative LDFA did not significantly differ between the two groups (p > 0.05). Compared to the preoperative MPTA, the postoperative MPTA for two groups was significantly higher (P < 0.05) (Table 2).

Table 2

Comparison post-operative to pro-operative alignment of the two groups
Alignment	rKA			MA
Alignment	pro-operative	post-operative	P-value	pro-operative	post-operative	P-value
HKA	8.41 ± 7.65	1.42 ± 2.41	0.00	9.61 ± 7.53	0.05 ± 0.93	0.00
LDFA	89.83 ± 3.75	90.30 ± 2.30	0.48	89.81 ± 3.53	89.52 ± 1.63	0.63
MPTA	85.72 ± 3.36	89.21 ± 1.34	0.00	84.80 ± 3.17	89.36 ± 1.41	0.00

The HKA for the rKA group was a mean of 1.42° more varus than that for the MA group (P < 0.05), with a mean of 0.05° (Table 3). Femoral component alignment, tibial component alignment, the ΔLDFA and the ΔMPTA were similar between the two groups (P > 0.05). Moreover, seven patients in the rKA group were outside the HKA range of 3°.

Table 3

Comparison of post-operative alignment of the two groups
Alignment	rKA	MA	P-value
Post-operation HKA	1.42 ± 2.41	0.05 ± 0.93	0.00
ΔHKA	9.28 ± 5.34	10.55 ± 6.25	0.30
Post-operation LDFA	90.30 ± 2.30	89.53 ± 1.63	0.07
ΔLDFA	4.18 ± 3.07	4.84 ± 3.32	0.33
Post-operation MPTA	89.21 ± 1.34	89.36 ± 1.41	0.62
ΔMPTA	4.25 ± 3.11	4.79 ± 3.26	0.42
ΔHKA: The net change between pro-operation HKA and post-operative HKA; ΔLDFA: The net change between pro-operation LDFA and post-operative LDFA; ΔMPTA: The net change between pro-operation MPTA and post-operative MPTA

In the rKA group, there were 38 patients with varus knees, and 7 patients with valgus knees. The net change in constitutional varus for the HKA and MPTA was greater (P < 0.05) than that for the constitutional valgus knee (Table 4).

Table 4

Comparison of net change for alignment in rKA group
	Varus(n = 38)	Vaglus(n = 7)	P-value
Pro-operation HKA	11.35 ± 5.43	-4.42 ± 3.24	0.00
Post-operation HKA	1.56 ± 2.92	0.56 ± 2.83	0.41
ΔHKA	10.07 ± 5.21	4.98 ± 4.07	0.02
Pro-operation LDFA	85.51 ± 2.97	90.93 ± 3.47	0.00
Post-operation LDFA	88.51 ± 2.66	88.15 ± 1.24	0.73
ΔLDFA	4.45 ± 3.04	2.69 ± 3.07	0.17
Pro-operation MPTA	85.18 ± 3.34	88.65 ± 1.49	0.01
Post-operation MPTA	89.21 ± 1.36	89.22 ± 1.35	0.98
ΔMPTA	4.69 ± 3.15	1.91 ± 1.46	0.03
ΔHKA: The net change between pro-operation HKA and post-operative HKA; ΔLDFA: The net change between pro-operation LDFA and post-operative LDFA; ΔMPTA: The net change between pro-operation MPTA and post-operative MPTA

Comparison of postoperative patient-reported outcome measures (PROMs) between the two groups

Compared to the preoperative PROMs, the postoperative PROMs (KSS, HSS, VAS score) significantly differed in the two groups (P < 0.05) (Table 5). The results of different follow-up timepoints after surgery showed sustained improvement(Additional file 1, Additional file 2).

Table 5

Comparison post-operative to pro-operative PROMs of the two groups
PROMs	rKA			MA
PROMs	pro-operative	post-operative	P-value	pro-operative	post-operative	P-value
KSS-Clinical	50.76 ± 13.20	86.58 ± 9.07	0.00	49.27 ± 16.16	86.22 ± 10.15	0.00
KSS-Function	55.82 ± 13.63	73.40 ± 10.91	0.00	52.36 ± 10.12	59.90 ± 14.92	0.01
HSS	66.16 ± 9.38	86.11 ± 5.13	0.00	65.11 ± 11.24	85.28 ± 7.06	0.00
VAS	6.47 ± 0.16	0.87 ± 0.73	0.00	6.49 ± 0.87	0.82 ± 0.86	0.00

There was no statistically significant difference (P > 0.05) between the two groups for any of the PROMs (Table 6).

Table 6

Comparison of PROMs between the two groups
PROMs	rKA	MA	P-value
KSS-Clinical	86.58 ± 9.07	86.22 ± 10.15	0.86
ΔKSS-Clinical	35.82 ± 16.87	36.96 ± 18.19	0.76
KSS-Function	73.40 ± 10.91	75.00 ± 11.39	0.50
ΔKSS- Function	17.58 ± 14.44	18.64 ± 12.81	0.45
HSS	86.11 ± 5.13	85.28 ± 7.06	0.52
ΔHSS	19.95 ± 11.49	20.16 ± 11.58	0.85
VAS	0.87 ± 0.73	0.82 ± 0.86	0.59
FJS-12	83.29 ± 4.33	83.38 ± 4.93	0.93
Satisfaction	4.57 ± 0.73	4.43 ± 1.02	0.47
ΔKSS-Clinical: The net change between pro-operation KSS-Clinical and post-operative KSS-Clinical; ΔKSS- Function: The net change between pro-operation KSS- Function and post-operative KSS- Function; ΔHSS: The net change between pro-operation HSS and post-operative HSS

Comparison of the ROM between the two groups

The mean degrees of active extension and active flexion were similar for the two groups (P > 0.05) (Table 7).

Table 7

Comparison of postoperation ROM of the two groups
ROM	rKA	MA	P-value
Mean Extension	0.44 ± 1.20	0.87 ± 1.71	0.18
Mean Active Flexion	106.00 ± 10.95	107.22 ± 8.63	0.56

3.5 Comparison of complications between the two groups

No revision was performed in the two groups at the one-year follow-up. No patients in either group had any complications, such as infection, loosening or periprosthetic fracture, that required further surgery during the most recent follow-up (Table 8). Ten patients in the rKA group and eighteen patients in the MA group (P > 0.05) experienced limb swelling one month after surgery. Some patients (sixteen in the MA group and four in the rKA group, P < 0.05) needed to take oral analgesics due to pain one month after surgery.

Table 8

Comparison of complications between the two groups
Complication	rKA	MA	P-value
Revision	0	0	-
Limb swelling	10(22.2%)	18(40.0%)	0.07
Analgesic for pain	4(8.9%)	16(35.6%)	0.00

Many authors have correlated outcomes with alignment after TKA, but the optimal alignment when performing TKA remains unclear[26]. In the past few decades, MA has become the gold standard for TKA, aiming to ensure implant generation rate and reproducibility[27]. However, the dissatisfaction[4] and residual symptoms[28] after MA-TKA are always present. Moreover, one in four patients reported that they would not undergo the same surgery again[29], and there were numerous patients don’t report a “forgotten knee”[30]. The main reason is that the neutral femoral and tibial cuts, which lack respect for the wide range of normal anatomy of the kne[31], inevitably change knee joint kinematics[32].

Howell has advocated for kinematic alignment (KA)[33] which aims to fully restore the anatomical structure of patients before arthritis and rarely requires soft tissue release, since 2010[34, 35]. However, the anatomy of the human knee varies widely, and pathological changes further increase these variations[24, 31]. Without boundary restrictions in KA, most patients experience excessive varus tibia competent placement and leg alignment[36], which is considered related to a decrease in patient satisfaction[37]. Moreover, these good clinical results of KA are based on Western populations, and these results may not be generalizable to Asian populations due to differences in anatomy[38].

The rKA[39] protocol was developed as an alternative to unrestricted KA for patients with an atypical knee anatomy. Restoration of the knee anatomy without modification may[31] result in relatively undesirable alignment in nearly half of the patients who may be prone to component loosening and early failure. rKA may be suitable for extreme or pathological anatomies as it may lead to good long-term outcomes and does not involve excessive correction or ligament release[40].

In our study, we examined both joint-specific and generic health scores (KSS, HSS, VAS scores, FJ-12 scores, and satisfaction scores) to assess outcomes. The most important finding of the present study was that there was no significant difference (P > 0.05, Table 6) in the postoperative outcomes between robotic rKA-TKA and conventional MA-TKA at the 12-month follow-up. Both groups showed significant improvements at the 1-year postoperative follow-up (P < 0.05, Table 5). Compared with the MA-TKA patients, the rKA-TKA patients demonstrated equal outcomes(P > 0.05, Table 6)in terms of FJ-12 score and patient satisfaction at the early postoperative follow-up (1 year). In the present study, fewer patients (P < 0.05, Table 7) in the rKA group needed oral analgesics due to pain one month after surgery.

The clinical outcomes of rKA and MA in this study were equivalent to those in other studies similar to the findings of other studies[41, 42]. Two network meta-analyses[43, 44] and a systematic review[45] also revealed no significant superiority of rKA-TKA over MA-TKA in terms of PROMs. Even some studies[46–48] described a significantly better postoperative FJS in patients treated with rKA than in those treated with MA. MacDessi et al.[41] reported that the FJS in the rKA group was similar to that in the MA group. And studies[48–50] reported that the patients in the rKA group were significantly more satisfied than those in the MA group. The possible explanation for improvement in outcomes of rKA is the reduction in the need for soft tissue releases with a rKA approach compared to MA[41]. Another possible explanation is less gap imbalance of rKA[51], and less modifications of knee joint anatomy in rKA[31].

In addition, 15.6% (7/45) of rKA patients were outside the HKA range of 3°, which is slightly higher than the 12% (12/100) reported by Hutt et al.[35] and lower than the 27%[52], 33.3%[47] and 35%[53]. Outliers from our safe range probably occurred as a result of slight imprecision in the navigation system or small variations during bone cuts or implant cementation. The clinical impact of being aligned outside the range of three degrees for rKA patients appears to be negligible at the early follow-up; however, long‐term evaluation of these patients is needed. It seems logical that significant clinical differences between rKA and MA may be absent in this patient population, as the component alignment may differ only slightly, and thus, the clinical impact may decrease as well. Similar to the study by MacDessi et al.[43], our study revealed only small preoperative deviations in neutral leg alignment, which may explain the absence of additional significant clinical differences between the groups.

We found equal variability in the preoperative (P > 0.05, Table 1) and postoperative (P > 0.05, Table 3) HKA, LDFA and MPTA in both groups. Compared to the preoperative HKA, the postoperative HKA was significantly greater (P < 0.05, Table 2) in the rKA group than in the MA group, indicating an increase in varus alignment. The net change in the HKA and MPTA were greater (P < 0.05, Table 4) for the constitutional varus knee than for the constitutional valgus knee. Risitano et al.[43] reported low variation in the HKA, LDFA and MPTA values in the rKA group. Conversely, other studies have shown different results. MacDessi et al.[41] and Sappey-Marinier et al.[42] described that the postoperative LDFA in rKA patients was more valgus than that in MA patients. The authors also reported that the femoral component was slightly valgus in patients treated with rKA compared with those treated with MA, and the tibial component was slightly more varus. Winnock de Grave et al.[49] reported that the net change in the HKA in the constitutional varus knee was less than that in the constitutional valgus knee. Almaawi et al.[44] reported greater variability in the preoperative HKA, LDFA and MPTA compared to the preoperative HKA, LDFA and MPTA in the patients who underwent MA than in the patients who underwent rKA. The original anatomy was better preserved in the rKA group. The main reason for the different results may be due to the lack of a standardized gap balancing technique in rKA. Our experience suggests that the tibia-first, but there is no consensus on whether the tibia or femur should be prioritized.

Despite the growing enthusiasm in rKA, concerns remain about longevity of implant survival. We found no revision in either the rKA group or the MA group (Table 8) during this follow-up period, which was similar to the findings of four studies[35, 41, 46, 49] in which rKA was performed. Nevertheless, a systematic review[45] revealed an overall revision rate of 3.4% among the rKA patients after a mean follow-up of 2.3 years. The main reason for revision was aseptic loosening. Abhari et al.[48] reported no statistically significant differences in the revision rate between patients who underwent rKA and those who underwent MA. The authors performed three revision TKAs due to tibial component loosening within one year after the TKA (4.3%), nine knees (7.8%) in the MA group and 7 knees (6.1%) in the rKA group with stiffness requiring manipulation under anesthesia or arthrolysis. The above studies, including our study, have shown that the rKA does not increase the risk of short- to middle-term implant failure.

Limitations

Several limitations should be considered in this study. First, this was a retrospective study with only 12 months of follow-up, and longer-term outcomes at 24 and 60 months still need to be confirmed. Second, the sample size of the study was small. Third, different surgical protocols were used. rKA-TKAs were performed with robotic assistance, whereas MA-TKA was performed with conventional instruments. Finally, there was no standardization in the PROMs used to evaluate TKA patients. The HSS, KSS, FJS, and VAS score were used in this study. The WOMAC score, KOOS, OKS and EQ-5D-5L were used in other studies.

rKA is a safe method for TKA, the patient satisfaction and function outcomes of rKA-TKA were not inferior to MA-TKA. However, it is necessary to perform additional large-sample studies to confirm the superiority of rKA over MA in terms of clinical outcomes and safety.

Body mass index (BMI), anaesthesiologists score (ASA), mechanical alignment (MA), total knee arthroplasty (TKA), kinematic alignment (KA), restricted kinematic alignment (rKA), hospital for special surgery score (HSS), visual analogue scale (VAS), forgotten joint score (FJS-12), knee society score (KSS), hip-knee-ankle (HKA), lateral distal femoral angle (LDFA), medial proximal tibial angle (MPTA), range of motion (ROM), osteoarthritis (OA)

Ethics Declarations

Ethics approval and consent to participate

This study was approved by the Ethics Committee of the Second Affiliated Hospital of Fujian Traditional Chinese Medical University (SPHFJP-S2021096-01) in accordance with regulatory and ethical guidelines pertaining to retrospective research studies. Written informed consent was obtained from patients to participate in the study.

Consent for publication

Written informed consent was obtained from the patients for this study.

Availability of data and materials

The authors confirm that all the data supporting the findings of this study are included in this published article.

Competing interests

The authors declare that they have no competing interests.

Funding

Research funds were provided by Fujian Medical Innovation Project Funding Program (2021CXA039) and Fujian Province Middle aged Teacher Education Research Project(JAT210144).

Author information

Shiluan Liu and Zhengyu Cao contributed equally to this work.

Authors and Affiliations

Department of Sport’s Medicine, The Second Affiliated Hospital of Fujian Traditional Chinese Medical University, 282 Wusi Street, Fuzhou City, Fujian Province, 350000, PR China

Shiluan Liu, Zhengyu Cao, Saijiao Lan, Chongjing Zhang, Lin Pan, Wenjin Luo & Jian Li

Contributions

Study design: J.L., S.L.L. Administrative support: J.L. Surgery performance: J.L. Data collection: S.L.L., Z.Y.C.,S.J.L.,L.P.,W.J.L. Data analysis: Z.Y.C.,C.J.Z. Writing of the manuscript: S.L.L., Z.Y.C., Approving the final version of manuscript: J.L.. All authors read and approved the final manuscript.

Corresponding author

Correspondence to Jian Li., Email: [email protected]

Declarations

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I declare that the authors have no competing interests as defined by BMC, or other interests that might be perceived to influence the results and/or discussion reported in this paper.

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Data availability

This manuscript does not report data generation or analysis.

Clinical Trial Number

Clinical trial number: not applicable.

Acknowledgements

The authors express their appreciation to staff in the Second Affiliated Hospital of Fujian Traditional Chinese Medical University, for their technical assistance.

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Comparison of patient satisfaction and function outcomes between restricted kinematic alignment and mechanical alignment: An early follow-up study

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Baseline clinical assessment

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Evaluation of curative effect

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Comparison of the preoperative characteristics of the two groups

Comparison of lower limb alignment between the two groups

Comparison of postoperative patient-reported outcome measures (PROMs) between the two groups

Comparison of the ROM between the two groups

3.5 Comparison of complications between the two groups

Discussion

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