Long-term effects of non-weight bearing and immobilization after anterior cruciate ligament reconstruction on joint contracture formation in rats

ABSTRACT

Purpose

Non-weight bearing improves and immobilization worsens contracture induced by anterior cruciate ligament reconstruction (ACLR), but effect persistence after reloading and remobilization remains unclear, and the combined effects of these factors on ACLR-induced contracture are unknown. We aimed to determine 1) whether the effects of short-term (2-week) non-weight bearing or immobilization after ACLR on contracture would be sustained by reloading or remobilization during a 10-week observation period, and 2) how the combination of both interventions compared to the outcome of either alone.

Methods

We divided 88 ACL-reconstructed male rats into four groups: non-intervention, non-weight bearing, joint immobilization, and both interventions. Interventions were performed for 2 weeks, followed by rearing without intervention. Twelve untreated rats were used as controls. At 2, 4, and 12 weeks post-surgery, we assessed range of motion (ROM) and histological changes.

Results

ACLR resulted in persistent loss of ROM, accompanied by synovial shortening, capsule thickening, and osteophyte formation. Two weeks of non-weight bearing increased ROM and reduced osteophyte size, but the beneficial effects disappeared within 10 weeks after reloading. Two-week immobilization decreased ROM and facilitated synovial shortening. After remobilization, ROM partially recovered but remained below non-intervention levels at 12 weeks. When both interventions were combined, ROM was similar to immobilization alone.

Conclusions

The beneficial effects of 2-week non-weight bearing on contracture diminished within 10 weeks after reloading. The adverse effects of 2-week immobilization on contracture persisted after 10 weeks of remobilization. The effects of the combined use of both interventions on contracture were primarily determined by immobilization.

KEYWORDS:

• ACL reconstruction
• rehabilitation
• non-weight bearing
• immobilization
• joint contracture

Disclosure statement

No potential conflict of interest was reported by the author(s).

Author Contributions

Akinori Kaneguchi: Conceptualization, Formal analysis, Funding acquisition, Investigation, Methodology, Project administration, Writing - original draft, Writing - review & editing.

Nanami Masuhara: Formal analysis, Investigation, Writing—original draft.

Ryo Okahara: Formal analysis, Investigation.

Yoshika Doi: Formal analysis, Investigation.

Kaoru Yamaoka: Writing—original draft, Writing—review & editing.

Takuya Umehara: Formal analysis, Writing—review & editing.

Junya Ozawa: Investigation, Methodology, Writing—original draft, Writing—review & editing.

Supplemental data

Supplemental data for this article can be accessed online at https://doi.org/10.1080/03008207.2024.2331567.

Additional information

Funding

This study was supported by the Japanese Physical Therapy Association [Grant Number 006] and JSPS KAKENHI [Grant Number 22K17625].