Bone Plug Versus Suture-Only Fixation of Meniscal Grafts: Effect on Joint Contact Mechanics During Simulated Gait

Abstract

Background: Meniscus allograft transplantation (MAT) is primarily undertaken to relieve the symptoms associated with meniscal deficiencies. However, its ability to restore normal knee joint contact mechanics under physiological loads is still unclear.

Purpose: To quantify the dynamic contact mechanics associated with 2 commonly used fixation techniques in MAT of the medial compartment: transosseous suture fixation via bone plugs and suture-only fixation at the horns.

Study design: Controlled laboratory study.

Methods: Physiological loads to mimic gait were applied across 7 human cadaveric knees on a simulator. A sensor placed on the medial tibial plateau recorded dynamic contact stresses under the following conditions: (1) intact meniscus, (2) MAT using transosseous suture fixation via bone plugs at the anterior and posterior horns, (3) MAT using suture-only fixation, and (4) total medial meniscectomy. A "remove-replace" procedure was performed to place the same autograft for both MAT conditions to minimize the variability in graft size, geometry, and material property and to isolate the effects of the fixation technique. Contact stress, contact area, and weighted center of contact stress (WCoCS) were quantified on the medial plateau throughout the stance phase.

Results: Knee joint contact mechanics were sensitive to the meniscal condition primarily during the first half of the gait cycle. After meniscectomy, the mean peak contact stress increased from 4.2 ± 1.2 MPa to 6.2 ± 1.0 MPa (P = .04), and the mean contact area decreased from 546 ± 132 mm2 to 192 ± 122 mm2 (P = .01) compared with the intact meniscus during early stance (14% of the gait cycle). After MAT, the mean contact stress significantly decreased with bone plug fixation (5.0 ± 0.7 MPa) but not with suture-only fixation (5.9 ± 0.7 MPa). Both fixation techniques partially restored the contact area, but bone plug fixation restored it closer to the intact condition. The location of WCoCS in the central cartilage region (not covered by the meniscus) shifted peripherally throughout the stance phase. Bone plug fixation exhibited correction to this peripheral offset, but suture-only fixation did not.

Conclusion: Under dynamic loading, transosseous fixation at the meniscal horns provides superior load distribution at the involved knee compartment after meniscal transplantation compared with suture-only fixation. Particular attention should be directed to the ability of medial MAT to function during the early stance phase.

Clinical relevance: Transosseous fixation via bone plugs provides superior load distribution of a transplanted meniscal allograft compared with suture fixation alone at time zero.

Keywords: knee; mechanics; meniscus; simulated gait; sports trauma.

Figure 1

Inputs of the dynamic knee simulator. The simulator applies (A) flexion/extension rotation, (B) anterior/posterior force, (C) axial force, and (D) internal/external torque. The forces and torques were applied on the tibia, and flexion and extension were applied on the femur. The other degrees of freedom, varus/valgus rotation and medial/lateral translation, were not controlled.

Figure 2

Cadaveric model. (A) Photograph of a specimen on the Stanmore knee simulator. The simulator was driven by gait loads as described in Figure 1. (B) A Kirschner wire was pinned through the geometric epicondylar axis with the guidance of radiography and was used to align the knee position on the simulator. (C) The knee was augmented with a pressure sensor (Tekscan), while the soft tissues were carefully preserved (photograph was taken after dissection of the knee). (D) Real-time contact stresses on the tibial plateaus were collected at 100 Hz.

Figure 3

Schematic diagram of the fixation procedures. (A) Transosseous suture fixation via bone plugs. (B) Bone tunnel suture fixation.

Figure 4

Stress maps on the medial plateau for a typical knee under different meniscal conditions at 14% and 45% of the gait cycle. (A) The intact knee. A reduction in the contact area was observed after medial meniscectomy (B) at 14% of gait, while minimal changes were found at 45% of gait. Compared with suture-only fixation (C), bone plug fixation (D) exhibited better restoration in the contact area.

Figure 5

(A) Reduction in the contact area and (B) increase in peak contact stress across the medial tibial plateau throughout the stance phase of gait. The plots on the top show the mean curves for each condition; the shaded area of the intact condition indicates the standard error (shaded areas on the other curves were removed for better readability). The plots on the bottom show the values (mean ± standard deviation) of each condition at 14% and 45% of gait. *Statistically significant difference (P < .05).

Figure 6

Peripheral shift (relative to the intact condition) of the weighted center of contact stress within the central cartilage region throughout the stance phase of gait. The plot on the top shows the mean curve for each condition; the shaded area of the intact condition indicates the standard error. The plot on the bottom shows the peripheral shift (mean ± standard deviation) of each condition at 14% and 45% of gait. *Statistically significant difference (P < .05) compared with the baseline intact condition.