Relationship Between Mechanoreceptors in the Posterior Cruciate Ligament and Patient Age or Osteoarthritis Severity

Abstract

Background: Mechanoreceptors in the posterior cruciate ligament (PCL) can produce proprioception, which is an important reason why patients choose cruciate-retaining total knee arthroplasty (TKA). The number of mechanoreceptors in the PCL of patients with knee osteoarthritis (OA) is unknown.

Purpose: To provide a theoretical basis for estimating the number of mechanoreceptors in the PCL by evaluating the relationship between this number and patient age or OA severity.

Study design: Cross-sectional study; Level of evidence, 3.

Methods: An overall 28 PCLs from patients with knee OA were collected at the time of TKA and grouped according to patient age (group A, 60-69 years [n = 8]; group B, 70-79 years [n = 12]; group C, ≥80 years [n = 8]) and OA based on Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC) score (group I, ≤80 [n = 8]; group II, 81-120 [n = 10]; group III, >120 [n = 10]). Hematoxylin and eosin and S-100 immunohistochemical staining were performed on the slices near the tibial attachment of the PCL, and the number of mechanoreceptors in each slice was counted. Multifactor analysis of variance was used to evaluate the relationship between the number of mechanoreceptors and patient age or WOMAC score.

Results: The number of mechanoreceptors (mean ± SD) in groups A, B, and C was 24.00 ± 15.19, 30.92 ± 11.41, and 23.38 ± 11.39, respectively, with no significant between-group differences. The number of mechanoreceptors in groups I, II, and III was 43.50 ± 4.99, 25.00 ± 5.27, and 15.20 ± 5.61, with significant differences between groups I and II, groups I and III, and groups II and III (P < .001 for all).

Conclusion: In patients with knee OA, age had no significant effect on mechanoreceptor count, but the number of mechanoreceptors in the PCL decreased significantly with higher (worse) WOMAC score. These findings suggest that in patients of any age with high WOMAC scores, there may be little value as it relates to knee proprioception in performing a PCL-retaining TKA.

Keywords: PCL; TKA; WOMAC; Western Ontario and McMaster Universities Osteoarthritis Index; age; mechanoreceptor; osteoarthritis; posterior cruciate ligament; total knee arthroplasty.

Figure 1.

(A) The femoral intercondylar fossa and the posterior cruciate ligament were exposed after osteotomy. (B) Sharp separation of the posterior cruciate ligament.

Figure 2.

Examples of Pacinian corpuscles (PCs; arrows). S-100 protein staining: (A) a degenerated PC and sparse stained nerve tissue; (B) a PC with better morphology. Hematoxylin and eosin staining: (C) the same PC in panel A, with multiple layers of atrophied membranes; (D) the same PC in panel B, with multiple layers of membranes and a clearer and denser structure. All slides are shown at 1000 × magnification.

Figure 3.

Examples of Ruffini endings (REs; arrows). (A, B) S-100 protein staining shows oval REs with a monolayer membrane. (C) Hematoxylin and eosin staining of the same RE in panel B at the adjacent section. All slides are shown at 500 × magnification.

Figure 4.

Examples of free nerve endings (arrows) with S-100 protein staining. They are loosely arranged without any membranes. Slides are shown at 500 × magnification.

Figure 5.

Examples of Golgi tendon organ–like endings (GTOEs) with a monolayer membrane (arrows). S-100 protein staining: (A and B) curled and deformed GTOEs and (C) a more regular GTOE. Hematoxylin and eosin staining: (D) the same GTOE in panel C, which is fusiform. All slides are shown at 250 × magnification except for panel B at 500 × magnification.

Figure 6.

S-100 protein staining: examples of unclassified nerve fiber tissue (arrows). (A-C) Tissues have a layer of membrane. (C) The tissue has a slightly irregular membrane and (D) the tissue has no membrane. All slides are shown at 500 × magnification.

Figure 7.

Mean number of mechanoreceptors at the tibial attachment of the posterior cruciate ligament (PCL). Error bars indicate 95% CI. FNE, free nerve ending; GTOE, Golgi tendon organ–like ending; PC, Pacinian corpuscle; RE, Ruffini ending.

Figure 8.

Mean number of mechanoreceptors in the tibial attachment of the posterior cruciate ligament (PCL) by (A) age group and (B) WOMAC score group. Error bars indicate 95% CI. WOMAC, Western Ontario and McMaster Universities Osteoarthritis Index.