"" Lower Lumbar Facet Joint Complex Anatomy

Research Article

Austin J Anat. 2015;2(1): 1032.

Lower Lumbar Facet Joint Complex Anatomy

Gorniak G and Conrad W*

Department of Physical Therapy, University of St Augustine for Health Sciences, USA

*Corresponding author: Conrad W, Department of Physical Therapy, University of St Augustine for Health Sciences, 1 University Blvd, St Augustine, Fl. 32086-5783,USA.

Received: December 16, 2014; Accepted:March 16, 2015 Published: March 17, 2015

Abstract

Low back pain is often associated with osteoarthritis of the lower lumbar facet joints. Each facet joint has several structural components that interact to form a spinal segmental movement complex. The components of this complex are usually studied independently. In this descriptive cadaver study, the anatomy of the joint capsule and its relationship with the multifidus are described and compared to other studies. The sizes of the boney facets and the ligamentum flava of L3 – S1are compared for gender, sidedness and to other studies. Finally, the interaction of these components of the joint complex, relative to joint motion and wear, are discussed.

Keywords: Lumbar facet joints; Joint capsule; Ligamentum flava

Introduction

Osteoarthritis of the lumbar facet joints is a common source of low back pain and its prevalence increases with age [1-9]. It has been reported that as many as 89% -95% of individuals 65 and older have varying degrees of Facet Joint Arthritis (FJAO) and the L4-5 and L5-S1 are the most commonly seen [4,5,8,10]. From 2000 -2011, facet joint interventions in the Medicare population have increased by 308% per 100,000 beneficiaries and lumbosacral interventions by 544% per 100,000 [10]. As the population in the United States continues to age, further studies relating to lumbar facet joint degeneration and ageing changes are needed.

The anatomy of the lumbar facet joint has been studied macroscopically, microscopically and radiologically. L3/L4, L4/ L5, and L5/S1 have received the most attention. An overview of these studies indicates that the facet joint is an interacting complex of structures, working as a unit to produce functional segmental movements. The components of the lumbar facet complex are the articulating facets, the facet joint capsule, the ligamentum flavum and the multifidus muscle. Most studies tend to focus on one individual component of this facet complex, although, osteoarthritis of lumbar facet joints and other facet joint disorders may result from a disruption in the interactions of all these components of the joint complex. In this study, the roles of the joint capsule, ligamentum flavum and multifidus in regards to facet motion and wear are discussed.

The size, shape, and orientation of the lumbar facets have been described, as well as several have examined differences in these descriptors with age, gender and side [4,11-17]. The anatomy of the lumbar facet joint capsule has also been studied by many [1,18-26]. These studies describe different layers of the joint capsule, different collagen fiber directions, varying capsular thickness, menisci, subcapsular pockets and type I and type II capsular attachment patterns. Because most of these studies are microscopic and concentrate mainly on the fibrous capsule, the macroscopic relationships between the overlying ligamantum flavum and multifidus muscle needs clarification. Anatomical studies on the elastic ligamentum flavum describe its fiber composition, attachment sites, size, mechanical features and function [1,2,14,27-33]. The anatomy of the lumbar multifidus has also been described, and debated, but its actions on the spine are somewhat controversial [1,34-40].

The collagen arrangement of lumbar joint capsules and the configuration of the matching facets are associated with joint motion and joint dysfunctions [1,19,20,41-44]. The collagen fiber arrangement of a capsule may permit motion in one direction, but limit motion in another. Dysfunctional joint movements can result in excessive joint articular cartilage wear. Tightness of the capsule will limit motion and increase forces on the joint surfaces. This condition may result in joint pain and excessive articular surface wear. Stretched or torn capsules will increase motion, and may also produce articular damage because of abnormal motion and joint stress. Several studies describe lumbar facet movements, stresses on the joint surfaces and capsule, and the role of the joint capsule in limiting movement [1,6,18-21,43,45,46]. While these studies provide a good basic understanding of lumbar joint mechanics, the role of the facet complex on joint movement, and articular surface wear and damage need further investigation.

In this study, the sizes of the lumbar facets from L3 – S1 are described and compared with age, gender, side and spinal level. Attachments and fiber directions of the posterior and anterior aspect of the facet joint capsule are also described,as well as how these fiber directions may relate to joint movements is discussed. The relationship of the tendons of the lumbar multifidus relative to the posterior joint capsule is described and its role in joint motion discussed. In addition, the attachments of the ligamentum flavum are described relative to the anterior aspect of the facet joint. Their role during joint motion and the sizes of the ligament are compared relative to gender, side and spinal level.

Materials and Methods

This descriptive anatomical study of bilateral lumbar joints L3-L4, L4- L5 and L5-S1 involved 13 male (78.6 + 11.3 y.o.) and 12 female (80.9 + 11.2 y.o.) cadavers. Male and female mean ages are not significantly different. Table 1 shows the number of facets studied at each level, along with the number and reason facets were not included. Cadavers were randomly obtained from the Anatomical Board of the State of Florida. Exclusion criteria were lumbar spine surgery, and scoliosis. The age and gender were recorded. A number was assigned to each study specimen, coinciding with the cadaver number and right or left side. This numbering system allowed specimen data to be matched directly to cadaver data for comparison and analysis. This study was approved and monitored by the Institutional Review Board of the University of St. Augustine for Health Sciences.