Restoration of Normal Stifle Joint Function

A) Restoration of Natural and Authentic Evolved Stifle Biomechanics

Anatomically, the cranial cruciate ligament (CrCL) is comprised of two bands: The craniomedial band and the caudolateral band. The load (weight and force) coming to bear on the stifle joint is divided and distributed between these two bands, each band providing its own separate and distinct loading pathway that works together in combined unison to biomechanically provide constant and consistent isometric tension throughout the entire range of motion of the stifle joint.

NAHAH’s MFLS surgical services closely replicate the role and function of the cranial cruciate ligament by providing a stable and functional articulation that moves maintaining constant and consistent isometric tension throughout the range of motion of the stifle joint, as was previously provided by the cranial cruciate ligament. This is accomplished by surgically implanting two prostheses comprised of two distinct sets of nylon filaments. Each set of nylon prosthetic filaments comprises a prosthesis and each prosthesis carries approximately half the load on the stifle joint.

The divided load carried by each prosthesis is distributed along two separate load distribution pathways that correspond to and simulate the load distribution pathways provided by the original CrCL—a craniomedial pathway and a caudolateral pathway—and each prosthesis is strategically anchored to both the femur (the lateral fabella, attached to and behind the femur) and the tibia at the most ideal isometric points surgically accessible. This re-establishes a stable and functional articulation that has natural and authentic evolved stifle biomechanics, closely approximating the function and mirroring the load distribution of the original cranial cruciate ligament.

B) Duplication of Natural Stifle Joint Load Distribution

NAHAH’s MFLS surgical services closely approximate the function and load distribution of the two bands (craniomedial band and caudolateral band) of the original cranial cruciate ligament (CrCL) by employing two separate prostheses implanted along two separate load distribution pathways (a craniomedial pathway and a caudolateral pathway), which are strategically anchored close to and approximating anatomic isometric points in the canine stifle joint. These two separate and strategic load distribution pathways are essential for dividing and distributing the load on the stifle joint in the same manner as the CrCL originally divided and distributed the load, thereby duplicating natural load distribution and aiding to restore authentic evolved stifle biomechanics.

The CrCL has three main functions:

1. Prevent cranial displacement of the tibia in relation to the femur

2. Prevent hyperextension of the stifle joint

3. Prevent internal rotation of the tibia

The cranial cruciate ligament is important for neutralizing cranial tibial subluxation, internal rotation, and hyperextension of the stifle. The cranial cruciate ligament consists of two bands (craniomedial and caudolateral) that biomechanically provide constant and consistent isometric tension throughout the entire range of motion of the stifle joint. The craniomedial band is taut in both flexion and extension while the caudolateral band is only taut in extension. For this reason, the craniomedial band is often the first portion of the ligament to fail. These patients are considered to have a partial tear, which will typically develop into a full tear over time.

1. Craniomedial Pathway – Upper (Multi-planar) Pathway
   Also designated as PHV Pathway (proximal horizontal pathway)
   Approximately half of the load is distributed in a multi-planar manner along this pathway. This loading pathway distributes the load more proximally and along both horizontal (medial to lateral) and vertical planes.
2. Caudolateral Pathway – Lower Pathway
   Also designated as DLV Pathway (distal lateral vertical pathway)
   Approximately the other half of the load is distributed more distally along this loading pathway that carries its share of the load exclusively on the lateral aspect of the stifle joint and in the vertical plane.

In order for these two primary prostheses—each comprised of multiple secondary nylon prosthetic filaments of high combined material strength—to provide constant and consistent isometric tension throughout the entire range of motion of the stifle joint, the secondary nylon prosthetic filaments comprising each primary prosthesis must be tied/secured in a very specific order. First, the secondary prosthetic filaments comprising the Craniomedial Prosthesis and Pathway (Upper Multi-planar Prosthesis and Pathway) must be tied/secured, starting with the center-most filament, and proceeding sequentially and peripherally (dorsally) away from the center of the stifle joint. Then second, the secondary prosthetic filaments comprising the Caudolateral Prosthesis and Pathway (Lower Prosthesis and Pathway) are tied/secured, starting with the center-most filament, and proceeding sequentially and peripherally (ventrally).

If the secondary prosthetic filaments are tied/secured in this exact and specific order, all secondary prosthetic filaments will be taut and will remain taut and maintain constant and consistent isometric tension on the stifle joint throughout the entire range of motion of the stifle joint. If the secondary prosthetic filaments are not tied/secured in this exact and specific order, the secondary prosthetic filaments will not remain taut and will not maintain constant and consistent isometric tension on the stifle joint throughout the entire range of motion of the stifle joint.

Rather than carry one hundred percent of the entire load along a single prosthesis and loading pathway as other extracapsular procedures do, by planned redundancy and design, NAHAH’s MFLS surgical services effectively duplicate the load distribution and division originally provided by the two bands of the cranial cruciate ligament. NAHAH’s MFLS surgical services implant multiple monofilament nylon prosthetic filaments of high combined material strength along two separate multidimensional load distribution pathways. These two load distribution pathways effectively divide and distribute the load along both a craniomedial pathway and a caudolateral pathway in much the same manner and directions as the two bands comprising the original healthy CrCL once distributed the load on the stifle joint, thus restoring more natural or normal stifle biomechanics.

This research article published in July 2023 corroborates and justifies the science behind NAHAH’s MFLS surgical services, arriving at the same conclusion from which NAHAH’s MFLS surgical services were developed, designed, and implemented: “it is possible that two prostheses are required to restore normal stifle biomechanics”. In implementing the fundamental principles behind the MFLS surgical procedure, the objective and goal is to duplicate or closely approximate the biomechanics and load distribution originally provided by the two bands of the cranial cruciate ligament. As was separately concluded by the authors of the article, two prostheses would therefore be necessary to restore normal stifle biomechanics originally provided by the two bands of the CrCL. NAHAH’s MFLS surgical services strategically employ two prostheses surgically implanted along craniomedial and caudolateral pathways. It is evident that two prostheses are essential for restoring normal canine stifle biomechanics and for allowing the stifle joint to move normally once again and with natural and authentic, evolved stifle biomechanics, providing constant and consistent isometric tension throughout its entire range of motion.

The additional key advantage that dividing the load along two separate load distribution pathways also provides is that utilizing two primary prostheses deployed along two load distribution pathways allows for building in planned redundant components to the surgical procedure. If one component (one prosthesis and loading pathway) fails, the other component (prosthesis and loading pathway) can take over and carry the load. This incorporated redundancy provides a safety net that both minimizes the load on each of the two load distribution pathways and removes a potential SPOF, thereby making the surgical repair more resilient and reliable—and this is possibly the reason the CrCL evolved as having two bands in the first place. Resiliency and reliability are further improved by adding redundancy to the procedure because multiple points of failure must occur before the structural integrity of the surgical repair as a whole can be compromised or disrupted and risk a catastrophic failure of the surgical procedure.

NAHAH’s MFLS surgical services view the CrCL as the evolved ideal role model and template. Just as the original two bands (craniomedial and caudolateral) comprising the cranial cruciate ligament (CrCL) effectively bifurcate, separate, and distribute the load on the stifle joint, the surgical procedures utilize two separate prostheses implanted along two separate loading pathways (a craniomedial pathway and a caudolateral pathway) to divide and distribute the load (weight and force) coming to bear on the stifle joint. Each of the two primary prostheses or implants consists of multiple filaments that share the load within each of the loading pathways, their combined material strength maximizing the overall strength and endurance of each prosthesis in each pathway. Dividing and distributing the stifle joint load along both a craniomedial pathway and a caudolateral pathway, the NAHAH’s MFLS surgical services effectively duplicate or closely replicate the original articulation and function provided by the cranial cruciate ligament and restores more natural and normal stifle biomechanics.

The aforementioned 2023 article, ‘Determination of Isometric Points in the Stifle of a Dog Using a 3D Model’ (07-24-2023 – study conducted at the Koret School of Veterinary Medicine, Hebrew University of Jerusalem, CYVETS Veterinary Center, Cyprus, Department of Mechanical Engineering, Ben Gurion University of the Negev, Israel) provided two key conclusive findings: (1) “(it is possible that) two prostheses are required to restore normal stifle biomechanics” and (2) “the optimal configuration of an extracapsular prosthesis, based on suture tension, was shown to be between the lateral fabella and a pair of bone tunnels located in the proximal tibial crest”.

These authors’ independently derived and key conclusive findings independently conceived the basis and fundamental principles for NAHAH’s MFLS surgical services, and the authors’ findings that led them to these conclusive statements further validate the theory and science behind the surgery.  The study’s authors actually describe in theory what is documented in the patent as the essential elements of the surgical procedure. This article’s independent findings and conclusions directly correlate with and advocate the most crucial and essential aspects of the surgical procedure.

The authors also gave their opinion regarding what the objective of surgical management of CrCL tears should be, stating “The objective of surgical management of ruptured cranial cruciate ligament (CCL) is to reestablish a biomechanically normal joint with the resultant return to full function”, which is precisely the objective and goal of MFLS surgery.

As stated by the authors in the above-referenced conclusive findings, “…[it is possible that] two prostheses are required to restore normal stifle biomechanics”. Taking the original anatomy into consideration, this makes sense. The CrCL is comprised of two bands connecting the tibia to the femur that divide and distribute the load (weight and force) coming to bear on the stifle joint along two separate loading pathways. MFLS surgery not only utilizes two prostheses to restore normal stifle biomechanics, but NAHAH’s MFLS surgical services also call for these two extracapsular prostheses to be implanted in the precise locations where this study concludes “the optimal configuration of an extracapsular prosthesis” should be: “Between the lateral fabella and a pair of bone tunnels located in the proximal tibial crest”. As stated in the patent, the surgical procedure utilizes two separate extracapsular prostheses (implanted along craniomedial and caudolateral pathways) that divide and distribute the load on the stifle joint and reestablish a biomechanically normal joint; by providing stability of the stifle joint while restoring normal canine stifle joint function that maintains optimal isometric tension of the stifle joint throughout its entire range of motion.

Other extracapsular surgical procedures utilize a single prosthesis (one piece of material implanted along a single loading pathway) that carries one hundred percent of the load coming to bear on the stifle joint. Surgical procedures that distribute the entire load on the stifle joint along a single loading pathway not only do not duplicate the natural load distribution and function of the original CrCL, but they inherently create a single point of failure (SPOF) in the surgical procedure. The most straightforward way to remove a SPOF is by adding redundant components to the system – or to the surgery. When the surgical procedure has built-in redundancy, if one component fails then the other one can take over. Generally, the more redundant components the system or surgery has, the more resilient and reliable it will ultimately be. NAHAH’s MFLS surgical services have been developed to effectively duplicate and functionally replace the two separate CrCL bands and their loading pathways originally provided by the healthy intact cranial cruciate ligament (CrCL).

The authors stated in their hypothesis that “in order to improve the functional outcome of extracapsular suture techniques, the isometric principle has been extrapolated to the lateral aspect of the joint where it is thought that placing a prosthesis close to isometric points will result in improved outcome. Several studies have identified isometric points on the lateral aspects of the femur and tibia using a variety of techniques. However, it has been shown that although a good functional outcome can be expected using isometric points, the techniques do not restore normal stifle biomechanics, and the occurrence of implant failure remains high.” The authors further stated that “significant instability also persists in dogs treated with tibial osteotomies and although these dogs often do not show clinical lameness, failure to restore normal stifle biomechanics results in late meniscal damage and progressive osteoarthritis.”

NAHAH’s MFLS surgical services incorporate planned redundancy on a number of levels that divide and distribute the load on the implants (the two primary prostheses) implanted along two separate loading pathways. Adding these redundant components (at strategic anatomical points of attachment) not only duplicates (or closely replicates) the means by which the cranial cruciate ligament originally provided both stability and constant isometric function to the stifle joint, but also minimizes potential overloading of the implanted materials.

This minimization of potential overloading of the implanted materials is planned and effectuated on both a primary level—by dividing and distributing the load between the two primary prostheses—and again on a secondary level—by minimizing potential overloading of multiple secondary prosthetic filaments sharing the load within and comprising the two primary prostheses. This planned redundancy avoids any SPOF on multiple levels and means that multiple points of failure would be required before the structural integrity of the surgery is compromised and before the surgical repair itself could possibly fail.