Predictors of improved and decreased range of motion after medial pivot total knee arthroplasty: A multicenter retrospective analysis

Tsuneari Takahashi; Kazuhisa Hatayama; Masahiro Nishino; Tatsuya Kubo; Hironari Hai; Yuichiro Yamada; Kosuke Suzuki; Katsushi Takeshita

doi:10.1016/j.jor.2025.04.002

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63 (); 201-205

doi:

10.1016/j.jor.2025.04.002

Predictors of improved and decreased range of motion after medial pivot total knee arthroplasty: A multicenter retrospective analysis

Tsuneari Takahashi^a,b,, Kazuhisa Hatayama^c,, Masahiro Nishino^d, Tatsuya Kubo^e, Hironari Hai^f, Yuichiro Yamada^g, Kosuke Suzuki^h, Katsushi Takeshita^a

a Department of Orthopaedics, School of Medicine, Jichi Medical University, Shimotsuke, Japan

b Department of Orthopaedic Surgery, Ishibashi General Hospital, Shimotsuke, Japan

c Department of Orthopaedic Surgery, Japan Community Health Care Organization, Gunma Central Hospital, Maebashi, Japan

d Department of Orthopaedic Surgery, Hokusuikai Memorial Hospital, Mito, Japan

e Department of Orthopaedic Surgery, Shin Oyama City Hospital, Oyama, Japan

f Department of Orthopaedic Surgery, Toyokawa City Hospital, Toyokawa, Japan

g Department of Orthopaedic Surgery, Nagoya Kyoritsu Hospital, Nagoya, Japan

h Department of Orthopaedic Surgery, Seirei Hamamatsu Hospital, Hamamatsu, Japan

⁎Corresponding author: Tsuneari Takahashi. tsuneari9@jichi.ac.jp

⁎⁎Corresponding author: Kazuhisa Hatayama

Received: 2025-3-23, Accepted: 2025-4-13, Published: 2025-4-14

Professor P K Surendran Memorial Education Foundation

Disclaimer:
This article was originally published by Reed Elsevier India Pvt. Ltd. and was migrated to Scientific Scholar after the change of Publisher.

Abstract

No study has identified predictors of improvement and decrease in postoperative range of motion (ROM) after medial pivot (MP) total knee arthroplasty (TKA) compared to preoperative ROM. This multicenter study aimed to identify predictors of improved postoperative range of motion (ROM) after MP-TKA.

The study included 107 consecutive patients who underwent MP-TKA for knee osteoarthritis at six different centers. Data on patient age, gender, hip knee angle, and pre- and postoperative ROM in extension and flexion were collected. A 9° improvement or decrease in postoperative knee flexion was considered positive. Patients were divided into three groups according to whether knee flexion improved by more than 9° (group I; 35 patients), changed within the minimal clinically important difference (MCID) (group M; 54 patients), or decreased by more than 9° (group D; 18 patients) one year after surgery.

Significant differences in preoperative ROM for flexion were observed between the groups (P < 0.001). Multivariate and receiver operating characteristic (ROC) curve analyses revealed that preoperative flexion less than 118.0° (area under the curve (AUC): 0.957, 95 % confidence interval (CI): 0.924–0.990) was a significant positive prognostic factor for improved postoperative ROM one year postoperatively (odds ratio (OR): 0.75, 95 % CI: 0.66–0.85, P < 0.001) and that preoperative flexion greater than 128.0° (AUC: 0.899, 95 % CI: 0.836–0.961) was a significant positive prognostic factor for decreased postoperative ROM one year postoperatively (OR: 1.14, 95 % CI: 1.07–1.22, P < 0.001).

The results showed that a preoperative knee flexion ROM of less than 118° was a significant positive predictor of an improvement in knee flexion ROM of MCID or greater after MP-TKA, and a knee flexion ROM of 128° or greater was a significant positive predictor of a decrease in knee flexion ROM of MCID or greater one year after surgery.

Keywords

Total knee arthroplasty

Knee osteoarthritis

Medial pivot

Range of motion

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1 Introduction

Total knee arthroplasty (TKA) is an established surgical treatment for end-stage osteoarthritis of the knee, relieving pain and improving activities of daily living.¹ However, about 20 % of patients reported being dissatisfied with the intervention.²^,³ Previous studies have reported that postoperative flexion angle has a significant impact on knee function and that improvement in flexion angle has a significant impact on patient satisfaction.⁴ Furthermore, the cutoff postoperative flexion angle for good knee function has been reported to be 120°. accurate surgical technique, including component alignment and soft tissue balance, and patient intrinsic factors are critical to achieving a stable knee joint and good postoperative range of motion (ROM) after TKA. The medial pivot (MP) implant was designed to mimic natural knee joint motion by employing a “ball and socket” construct that selectively constrains the medial tibiofemoral joint.⁵^,⁶ The articulation in the lateral compartment is less congruent with that in the medial compartment during flexion, allowing rollback of the femur here rather than in the medial compartment.⁷ Despite its morphological characteristics, previous systematic reviews and meta-analyses have compared conventional and MP knee prosthesis designs and failed to reach clear conclusions about the clinical performance of the MP knee prosthesis.⁸^,⁹ Kato and colleagues compared the clinical outcomes of the MP design with those of conventional posterior stabilized (PS) design¹⁰ and reported that ROM one year postoperatively was comparable in both groups. In contrast, Takahashi et al. compared the clinical outcomes of the MP design with those of conventional modern CR bearings and reported that 1-year postoperative ROM in the MP group was superior to that of the CR group.¹¹ To the best of our knowledge, no study has identified predictors of improvement or decrease in postoperative ROM after MP-TKA compared with preoperative ROM. Therefore, this multicenter study aimed to identify predictors of improvement in postoperative ROM after MP-TKA.

2 Materials and methods

This study is a retrospective study of MP-TKA (Evolution, MicroPort Orthopedics, Inc, Arlington, TN, USA) performed between August 2019 and December 2021 at 6 facilities in 5 prefectures in Japan with complaints of continuous pain and functional decline despite conservative treatment. This retrospective study included 107 consecutive patients with knee arthritis and knee varus deformity. Surgery was performed according to the manufacturer's instructions for mechanically aligned TKA; the decision to undergo TKA was made by an experienced knee surgeon based on clinical (e.g., loss of ROM) and radiographic findings (grade 3 or 4 on Kellgren-Lawrence classification).¹² Exclusion criteria included prior TKA, knee osteotomy, anterior cruciate ligament (ACL) reconstruction, or posterior cruciate ligament (PCL) reconstruction. Patient age, gender, hip-knee angle (HKA), and preoperative and postoperative ROM in extension and flexion were obtained ROM was measured using a bilateral arm goniometer. The thickness of the distal femur, dorsal femur, and proximal tibia medial and lateral osteotomies was measured using a Vernier caliper.¹³

According to previous studies on clinically significant minimal difference in knee flexion (MCID), a 9° improvement or decrease in knee flexion after surgery was considered positive.¹⁴ Patients were divided into three groups one year after surgery according to whether knee flexion improved more than 9° postoperatively (Group I; 35 patients), changed within the MCID (Group M; 54 patients), or decreased more than 9° postoperatively (Group D; 18 patients).

2.1

2.1 Surgical procedure

All TKAs were performed with cemented prostheses. Both ACL and PCL were completely resected in all cases. No patients underwent patellar resurfacing. Mechanical alignment TKA was performed to achieve neutral coronal alignment of the mechanical limb by cutting the femur and tibia so that the rectangular flexion and extension gap was perpendicular to the mechanical axis. Cutting of the distal femur was performed using an intramedullary alignment system. Posterior femoral cuts were made using a guide to set the osteotomy line parallel to the surgical epicondyle line and perpendicular to Whiteside's line.¹⁵ The proximal tibial cut was made using an extramedullary alignment system. The definitive components were introduced with cement fixation.

2.2

2.2 Postoperative physiotherapy

All patients in this study began a physical therapist-assisted rehabilitation protocol at 3–4 weeks postoperatively. The supervised physical therapy protocol consisted of three exercises: seated pedaling, knee extension stretches, and heel-to-toe walking exercises, which were recommended to be performed at least three times per day if the patient felt comfortable.¹⁶ Patients received individually supervised outpatient physical therapy after discharge. Supervised physical therapy was patient-centered, and the supervising physical therapist determined the type of intervention, duration, and frequency of sessions.

2.3

2.3 Statistical analysis

Data were presented as mean and standard deviation. All statistical analyses were performed using EZR software.¹⁷ The primary outcome was preoperative knee ROM. A priori sample size calculations for the primary outcome were performed for one-way analysis of variance (ANOVA); a P value < 0.05 indicated statistical significance. A post hoc power analysis determined a beta error of 0.01 (i.e., power of 0.99) and an effect size of 0.70. A univariate analysis across groups was conducted to construct the initial model. Predictors included in the final model were selected using stepwise backward elimination.¹⁸ Receiver operating characteristic (ROC) curve analysis was also performed.

3 Results

The mean age of the patients was 74.1 (6.5) years, and 82.3 % were female. Mean preoperative HKA was 11.1° (5.6°), knee extension and flexion ROM were −7.7° (6.5°), and 117.8° (19.4°). Mean postoperative knee ROM was 122.8° (10.4°) and correlated significantly and moderately with preoperative knee flexion ROM (R = 0.637, 95 % confidence interval (CI): 0.508–0.737, P < 0.001).

There were no significant differences among three groups in age, gender, preoperative extension ROM, preoperative HKA, operative time, or osteotomy width, except for the dorsal medial femur (Table 1). Furthermore, there were no significant differences in knee joint ROM at 1 year postoperatively among the three groups (120.8° (14.0°) in Group I, 124.6° (8.1°) in Group M, and 121.3° (7.6°) in Group D). Furthermore, the percentage of patients with knee joint ROM of 120° or greater at 1 year postoperatively did not differ among the three groups (80.0 % in group I, 81.5 % in group M, and 72.2 % in group D) (Table 2). However, one-way analysis of variance revealed significant differences in preoperative ROM of flexion between the groups (99.6° (21.3°) in group I, 123.9° (9.3°) in group M, and 134.8° (7.7°) in group D; P < 0.001). post hoc analysis using Bonferroni correction showed that there was a significant difference between groups I and M, M and D, and between Group I and Group D (Fig. 1). Furthermore, one-way analysis of variance revealed significant differences in medial dorsal femoral osteotomy width between the groups (Group I, 11.0 mm (2.5 mm); Group M, 10.9 mm (1.7 mm); Group D, 9.4 mm (2.1 mm); P = 0.018). post hoc analysis with Bonferroni correction showed significant differences between Group M and Group D (P = 0.025) and Group I and Group D (P = 0.028).

Table 1 Patient demographics.

Parameters		Group I (n = 35)	Group M (n = 53)	Group D (n = 19)	P value
Preoperative ROM for extension (°)		−9.1 (7.2)	−7.2 (6.3)	−6.2 (5.4)	N.S.
Preoperative ROM for flexion (°)		99.6 (21.3)	123.9 (9.3)	134.8 (7.7)	<0.001
Preoperative HKA (°)		10.6 (5.1)	10.7 (5.6)	13.5 (6.0)	N.S.
Surgical duration (min)		87.7 (12.3)	90.0 (12.0)	91.1 (10.9)	N.S.
Width of femoral resection (mm)	Distal-medial	7.7 (1.2)	7.9 (1.2)	7.6 (1.1)	N.S.
	Distal-lateral	7.7 (1.5)	7.9 (1.3)	7.2 (1.1)	N.S.
	Dorsal-medial	11.0 (2.5)	10.9 (1.7)	9.4 (2.1)	0.018
	Dorsal-lateral	8.6 (2.2)	8.8 (1.6)	8.4 (1.6)	N.S.
Width of proximal tibial resection (mm)	Medial	4.0 (2.4)	3.7 (2.2)	3.2 (2.6)	N.S.
Width of proximal tibial resection (mm)	Lateral	10.5 (2.1)	10.9 (1.3)	11.0 (1.6)	N.S.

Table 2 Postoperative ROM of patients in the three groups.

Parameters	Group I (n = 35)	Group M (n = 54)	Group D (n = 18)	P value
ROM one year postoperatively^a	120.8 (14.0)	124.6 (8.1)	121.3 (7.6)	0.19
Rate of ROM 120° or more one year postoperatively (%)^b	80.0	81.5	72.2	0.73

a Comparison between groups using one-way ANOVA.

b Comparison between groups using Fisher's exact test.

Preoperative flexion ROM. Comparison between groups using one-way ANOVA followed by post hoc analysis with Bonferroni correction. ROM range of motion.

For improvement in postoperative ROM, multivariate analysis and ROC curve analysis revealed that preoperative flexion was less than 118.0° (area under the curve (AUC): 0.957, 95 % CI: 0.957, 95 % CI: 0.957): 0.957, 95 % CI CI: 0.924–0.990) was a significant positive prognostic factor for improved ROM at 1 year postoperatively (Fig. 2) (odds ratio (OR): 0.75, 95 % CI: 0.66–0.85, P < 0.001). Furthermore, when the preoperative flexion cutoff of <118° was applied to this patient cohort, the sensitivity, specificity, positive predictive value, and negative predictive value were 88.6 %, 87.5 %, 77.5 %, and 6.0 %, respectively.

ROC curve for postoperative ROM improvement of more than 9°.

For postoperative ROM reduction, multivariate and ROC curve analysis revealed that preoperative flexion of 128.0° or greater (AUC: 0.899, 95 % CI: 0.836–0.961) was a significant positive prognostic factor for ROM reduction at 1 year after surgery (Fig. 3) (OR: 1.14, 95 % CI: 1.07–1.22, P < 0.001). Furthermore, when preoperative flexion cutoff values of 128° or greater were applied to this patient cohort, the sensitivity, specificity, positive predictive value, and negative predictive value were 77.8 %, 86.5 %, 53.8 %, and 95.1 %, respectively.

ROC curve for postoperative ROM decrease of more than 9°.

4 Discussion

This study showed that preoperative flexion ROM was a significant predictor of improved or decreased ROM after MP-TKA. A preoperative knee flexion ROM of less than 118° was a significant predictor of improved postoperative knee flexion ROM over MCID. Furthermore, having a preoperative knee flexion ROM greater than 128° was a significant positive predictor of having a postoperative knee flexion ROM less than the MCID. Knee joint ROM at 1 year postoperatively was not significantly different among the three groups compared to preoperatively, and Arbuthnot et al. reported that PS-TKA produced better and more reliable results for maximum flexion ROM than CR-TKA.¹⁹ In addition, Kato et al. described that the MP design was clinically superior to the conventional PS bearing, with a significantly better Forgotten Joint Score. They also reported that knee joint ROM at 1 year postoperatively was comparable between the PS and MP groups (128.4° vs. 125.2°).¹⁰ These results are consistent with our study. Similarly, Ueyama et al. reported significantly better postoperative knee flexion range of 127° (80°–140°) for Evolution MP-TKA and 118° (90°–135°) for its predecessor, Advance MP-TKA.²⁰ In addition, Takahashi et al. reported that in a propensity-matched cohort, Evolution MP-TKA had better knee ROM at 1 year postoperatively compared to CR-TKA (123.7° vs. 115.3°).¹¹ They also report that an inadequate flexion gap due to PCL retention may affect the relatively tight flexion gap, resulting in a smaller flexion ROM. In this study, all patients underwent PCL resection, which may have influenced the similar flexion ROM at 1 year postoperatively despite the preoperative flexion ROM. The results of this study indicate that MP-TKA is a surgical procedure with predictable postoperative ROM. Postoperative knee flexion ROM was estimated to be approximately 120°, which indicates good knee joint function, and improvement in flexion angle affects patient satisfaction.⁴

4.1

4.1 Limitation

This study has several limitations. First, although all patients included in this study were Japanese, they underwent their respective surgeries at six different centers in Japan. This likely introduced bias because the surgeries were performed by different surgeons. However, a multicenter comparison accurately reflects general practice patterns and may reduce the bias introduced by the single-center design. Furthermore, surgeons at all six centers held consensus meetings and adopted a uniform technique. Second, the proportion of females in the present study was more than 80 %. Female gender has been reported to be a significant predictor of poor ROM requiring manipulation after TKA.²¹ Therefore, gender-specific analysis is of future interest. Third, treatment failures were excluded from the outcome analysis. Thus, there may be selection bias. However, by excluding treatment failures, a confounding effect of TKA on outcomes was avoided. Finally, this study reports short-term results with limited number of patients. Therefore, further long-term follow-up studies are needed to make meaningful comparisons.

5 Conclusion

A preoperative knee flexion ROM of <118° was a significant positive predictor of an improvement in knee flexion ROM of ≥MCID after MP-TKA, and a knee flexion ROM of ≥128° was a significant positive predictor of a decrease in knee flexion ROM of ≥MCID one year postoperatively.

CRediT authorship contribution statement

Tsuneari Takahashi: Conceptualization, Data curation, Formal analysis, Investigation, Methodology, Project administration, Supervision, Validation, Visualization, Writing – original draft, Writing – review & editing. Kazuhisa Hatayama: Conceptualization, Data curation, Formal analysis, Investigation, Methodology, Project administration, Supervision, Validation, Writing – review & editing. Masahiro Nishino: Conceptualization, Data curation, Formal analysis, Investigation, Methodology, Project administration, Writing – review & editing. Tatsuya Kubo: Conceptualization, Data curation, Formal analysis, Investigation, Methodology, Project administration, Writing – review & editing. Hironari Hai: Conceptualization, Data curation, Formal analysis, Investigation, Methodology, Project administration, Writing – review & editing. Yuichiro Yamada: Conceptualization, Data curation, Formal analysis, Investigation, Methodology, Project administration, Writing – review & editing. Kosuke Suzuki: Conceptualization, Data curation, Formal analysis, Investigation, Methodology, Project administration, Writing – review & editing. Katsushi Takeshita: Conceptualization, Project administration, Writing – review & editing, Conceptualization, Data curation, Formal analysis, Funding acquisition, Investigation, Methodology, Project administration, Resources, Software, Supervision, Validation, Visualization, Writing – original draft, Writing – review & editing.

Ethical approval

This research was conducted following the Declaration of Helsinki and was sanctioned by the Ishibashi General Hospital Bioethics Committee for Medical Research (Approval ID: 25-NO.12). It involved a retrospective study. All patients underwent standard treatment, and obtaining informed consent from individual participants was not required.

Patients consent

Guardian/Patient's consent; Individual patient's consent was waived due to retrospective nature of this study.

Funding statement

Not applicable.

References

Achakri H., Ben-Shlomo Y., Blom A., et al . The National Joint Registry 20th Annual Report. 2023
[Google Scholar]
Baker P.N., van der Meulen J.H., Lewsey J., Gregg P.J., . National Joint Registry for E, Wales. The role of pain and function in determining patient satisfaction after total knee replacement. Data from the National Joint Registry for England and Wales. J Bone Joint Surg Br. 2007;89:893-900.
[Google Scholar]
Bourne R.B., Chesworth B.M., Davis A.M., Mahomed N.N., Charron K.D., . Patient satisfaction after total knee arthroplasty: who is satisfied and who is not? Clin Orthop Relat Res. 2010;468:57-63.
[Google Scholar]
Kubo M., Maeda T., Kumagai K., Amano Y., Kawasaki T., Imai S., . Good postoperative flexion angle improves knee function and improvement of flexion angle increases patient satisfaction after total knee arthroplasty. J Arthroplast. 2021;36:3137-3140.
[Google Scholar]
Iwaki H., Pinskerova V., Freeman M.A., . Tibiofemoral movement 1: the shapes and relative movements of the femur and tibia in the unloaded cadaver knee. J Bone Joint Surg Br. 2000;82:1189-1195.
[Google Scholar]
Blaha J.D., . The rationale for a total knee implant that confers anteroposterior stability throughout range of motion. J Arthroplast. 2004;19:22-26.
[Google Scholar]
Cassar-Gheiti A.J., Jamieson P.S., Radi M., Wolfstadt J.I., Backstein D.J., . Evaluation of the medial stabilized knee design using Data from national joint registries and current literature. J Arthroplast. 2020;35:1950-1955.
[Google Scholar]
Tso R., Smith J., Doma K., Grant A., McEwen P., . Clinical and patient-reported outcomes of medial stabilized versus non-medial stabilized prostheses in total knee arthroplasty: a systematic review and meta-analysis. J Arthroplast. 2021;36:767-776 e762.
[Google Scholar]
Nisar S., Ahmad K., Palan J., Pandit H., van Duren B., . Medial stabilised total knee arthroplasty achieves comparable clinical outcomes when compared to other TKA designs: a systematic review and meta-analysis of the current literature. Knee Surg Sports Traumatol Arthrosc. 2022;30:638-651.
[Google Scholar]
Kato M., Warashina H., Mitamura S., Kataoka A., . Medial pivot-based total knee arthroplasty achieves better clinical outcomes than posterior-stabilised total knee arthroplasty. Knee Surg Sports Traumatol Arthrosc. 2023;31:998-1010.
[Google Scholar]
Takahashi T., Hatayama K., Nishino M., et al . Comparison of postoperative clinical outcome in medial‐pivotal and gradually reducing radius design cruciate‐retaining total knee arthroplasty—a multicenter analysis of propensity‐matched cohorts. J Exp Orthopaed. 2024;11
[Google Scholar]
Kohn M.D., Sassoon A.A., Fernando N.D., . Classifications in brief: kellgren-lawrence classification of osteoarthritis. Clin Orthop Relat Res. 2016;474:1886-1893.
[Google Scholar]
Takahashi T., Sugimoto K., Ae R., et al . Can tibia-first total knee arthroplasty using computer-assisted system improve anterior and posterior knee stability? Technol Health Care. 2022;30:1147-1154.
[Google Scholar]
Guzik A., Druzbicki M., Wolan-Nieroda A., Turolla A., Kiper P., . Estimating minimal clinically important differences for knee range of motion after stroke. J Clin Med. 2020;9
[Google Scholar]
Vanin N., Panzica M., Dikos G., Krettek C., Hankemeier S., . Rotational alignment in total knee arthroplasty: intraoperative inter- and intraobserver reliability of Whiteside's line. Arch Orthop Trauma Surg. 2011;131:1477-1480.
[Google Scholar]
Sattler L.N., Walker A.T., Kan A.J., Hing W.A., Vertullo C.J., . Stratification of outpatient physical therapy following total knee arthroplasty: knee arthroplasty physical therapy pathways (KAPPA) nonrandomized controlled trial. J Arthroplast. 2024;39:1685-1691.
[Google Scholar]
Kanda Y., . Investigation of the freely available easy-to-use software 'EZR' for medical statistics. Bone Marrow Transplant. 2013;48:452-458.
[Google Scholar]
Morozova O., Levina O., Uuskula A., Heimer R., . Comparison of subset selection methods in linear regression in the context of health-related quality of life and substance abuse in Russia. BMC Med Res Methodol. 2015;15:71.
[Google Scholar]
Arbuthnot J.E., Wainwright O., Stables G., Rathinam M., Rowley D.I., McNicholas M.J., . Dysfunction of the posterior cruciate ligament in total knee arthroplasty. Knee Surg Sports Traumatol Arthrosc. 2011;19:893-898.
[Google Scholar]
Ueyama H., Kanemoto N., Minoda Y., Yamamoto N., Taniguchi Y., Nakamura H., . Comparison of postoperative knee flexion and patient satisfaction between newly and conventionally designed medial pivot total knee arthroplasty: a 5-year follow-up matched cohort study. Arch Orthop Trauma Surg. 2022;142:2057-2064.
[Google Scholar]
Areti A., Ratcliff T., Perake V., Sambandam S.N., . Factors predicting manipulation under anaesthesia after total knee replacement. Arch Orthop Trauma Surg. 2025;145:138.
[Google Scholar]