|Title of Invention||
PROXIMAL TIBIAL PROSTHESIS WITH WEIGHT BEARING POLYMER PAD MECHANISM
|Abstract||ABSTRACT PROXIMAL TIBIAL PROSTHESIS WITH WEIGHT BEARING POLYMER PAD MECHANISM Proximal tibial prosthesis with pivotal hinge mechanism comprises of a femoral component, a median component, weight-bearing pads, tibial head, stem sub assembly, a pivot pin with lock screw and two collared bushes. When assembled and implanted the femoral components seat in the distal femur and the tibial system replaces the salvaged proximal tibia and the whole apparatus acts as a pivot hinge and allows 0° to 120° of movement dorsally. The weight-bearing polymer pad acts as a cushioning device that reduces the load transmitted to the proximal tibial head and the components below. This also reduces the friction that is generated on direct metal-to-metal contact, thereby reducing wear.|
Field of Invention:
This invention in general relates to the field of medical technology. Further, this invention relates to a novel custom-built endo-prosthesis namely the Proximal Tibial prosthesis. More particularly this invention relates to custom-built Proximal Tibial Prosthesis with WEIGHT BEARING POLYMER PAD Mechanism sans Rotating Hinge Mechanism.
Management of patients with muscloskeletal neoplasm's has always been one of the most challenging areas in oncology. Prior to 1970, almost every patient with a primary malignant tumor of musculoskeletal system would not have adjuvant chemotherapy or irradiation. Surgical treatment was almost always an amputation with a five year survival rate of 20%. For benign lesions such as Giant Cell Tumors, the treatment of curettage had a 40-60% recurrence rate. Patients with painful metastatic lesions were managed palliatively until they were mercifully relieved by death.
Prior Art Technique and Practice:
The following description explains in detail the various prior art practice, convention, method and technology known in the art. The following description give in detail the various shortcom¬ings known in the existing state of art. This invention offers a unique solution to surmount the problem associated with the prior art.
Era of Amputations:
Amputations were considered to be absolutely necessary for durable local control of the tumor. It was even believed that this kind of ablation should include the entire totality of the effected bone, i.e., for a lesion of the Proximal Tibia, disarticulation through the knee joint was advocated to include the skip lesions also. These radical mutilating cancer clearance surgeries led to marked disability and disfigurement. Amputations is the most merciful of surgeries when it is the only resort but the meanest of surgeries when better alternatives are available. Amputations not only remove a physical part of the human body but also a part of the personality of the patient. In order to overcome functional, physiological and social problems associated with amputations, the concept of Limb Salvage was evolved.
The aim of Limb Salvage in bone tumour management is to eradicate the di sease, retain the integrity of the skeletal system and preserve the limb with useful functions using metallic prosthesis.
Megaprostheses are defined as special segmental bone and joint prosthesis, which bridge large defects of the bone. The term Megaprosthesis was first used in The International Work¬shop on Design and Application of Tumour Prosthesis, held in Mayo Clinic in 1981. Nowadays, megaprosthesis are available for all major anatomic regions of the body i.e, scapula, shoulder joint. Proximal Humerus, elbow, portions of the pelvis, hip joint and proximal femur and also proximal tibia. In addition, total replacements of the femur as well as of the humerus including that of the adjacent joints are feasible.
Megaprosthesis are available as CUSTOM-MADE prosthesis and as modular systems. Custom made prosthesis are individually manufactured for each patient and therefore give an accurate fit. The Proximal Tibial Prosthesis discussed here is basically a Cemented Fixation Device. It permits a maximum flexion of 120 degrees before implantation with a normal valgus position of 4-6 degrees in the femoral component. The Prosthesis is so designed so as to have the pivotal axis of the prosthesis in the physiological axis of the bone.
Objects of Invention:
The Objects of the invention was to invent, design and construct a novel Proximal tibial prosthesis.
Which should be unique with Knee Joint
Which would Mimic the Physiological function of the proximal tibial bone Which Retains the functional aspects of the proximal tibial bone along with the knee joint
Which Takes care of the structural loading of proximal tibia after resection
Which would avoid disfigurement of knee and proximal tibial bone
Which would preserve the distal part of tibia
Which matches the anatomic region of the proximal tibia
Which is economical
Which is safe in usage
Which with a hinge mechanisam should aid free range of motion at the knee joint
Which should have the femoral stem tilt sideways by an angle ranging upto 2 to 6 degrees to the left when viewed from the frontal side for a RIGHT tibial configuration.
• Which should have the femoral stem tilt sideways by an angle ranging upto 2 to 6 degrees to the right when viewed from the frontal side for a LEFT tibial configuration.
• Which will have added advantages over earlier versions.
Further the objects of the invention will be clear from the following description Preferred
embodiment of new inventions:
The new design has 5 main components
1 - FEMORAL COMPONENT (Fig 2 = 1)
2 - MEDIAN COMPONENT (Fig 2 = 2)
3 - Weight bearing Polymer Pad (Fig 2 = 4, Fig 7=4, Fig 8=4)
4 - TIBIAL HEAD & STEAM ASSEMBLY (Fig 2 = 5&7)
5 - PIVOT PIN (Fig 2 = 6)
1. FEMORAL COMPONENT :
The long intramedullary stem portion of the femoral component (Fig 7 = 1) mates with median component (Fig 7=2) on one end with a threaded shank through the mating hole.
2. MEDIAN COMPONENT :
Median (Fig 7=2) links femoral component (Fig7=1) on one end to the tibial head (Fig 2=5_) on the other and forms the pivot mechanism.
The upper part of the median (Fig 7=2) has a threaded hole (Fig 2=f) whose axis (Fig 1=A-1) tilts sideways depending on whether the configuration whether its left or right when viewed from the lateral frontal side.
For the Right tibial configuration the femoral component tilts to the left side (Fig.3) and for the Left tibial configuration the femoral component tilts to the Right Side (Fig.4)
3. WEIGHT BEARING POLYMER BAD
The lower part of the Median (Fig 2=2a) has a flat surface to hold the polygonal weight bearing pad (Fig2=4)
This weight bearing Polymer pad (Fig2=4) is fixed the medians anterior surface using a bear¬ing fixing screw (Fig 2.10) throught the threaded screw hole (Fig 2 = j). The under surface of the weight bearing pad has two semicircular contoured concavity to accommodate the moving tibial head.
The central median projection (Fig 2 = h1) has a central tunnel (Fig 7 = 3). for the pivot pin (Fig 2 = 6) to pass through. It also has on its posterior surface a threaded hole (Fig 7=11) for the screw (Fig 7=11) to Secure the Pivot pin.
4. TIBIAL HEAD ASSEMBLY
Has two parts.
A Tibial Condylar Part (Fig 2 = 5)
This has two tunnelled hubs (Fig 5 = y&z) that engage the collared bushes (Fig 2=3) from within to out and allows the pivot pin to guide along the engage the femoral median component. The distal extension (Fig 2 = 5) has two anterior threaded holes (Fig 2 = n&o) for locking with the intramedullary stem (Fig 2=7)
B. Tibial Intramedullary stem ( Fig 2 = 7)
The proximal end of this has hollow cavity (Fig 2 = B) to acccommodate the distal tibial condylar part with two screws and washer (Fig 2 = 8 & 9) to secure on both. The distal end is the intramedullary stem with longitudinal grooves running along the entire length. Fig 2.i^
5. PIVQTPIN : (FIG 2 = 6)
it is the connection rod of the tibial and femoral componet. it has central threaded hole (Fig 2 = k) throught which screw (Fig 2 = 11) is fixed and the whole assembly is made into one structual unit.
PIVOT HINGE :
Following form the components of the Pivot hinge Mechanism
a) Tibial component (Fig 2 = 5)
b) Collared bushes (Fig 2 = 3
c) Median component (Fig 2=2)
d) Pivot Pint (Fig 2 = 6)
e) Locking screws (Fig 2 = 11)
All these when assembled resemble a hinge joint. The axis to the tibial component and the femoral component in its unflexed (unfolded) position is 180 deg to each other (Fig 3 & 4). This is taken as the zero flexion position. At this position S1 face of the median component butts with the S of the tibial component and acts as a stopper limiting further extension. From this zero position the hinge can flex (fold) dorsally (backward) upt to 180 deg. (Fig.2-)
It is to be noted that the complete specification disclose salient features of the invention. Within the scope of the invention various modifications are possible. The scope and ambit of the invention is defined in the following statement of claims.
1. Proximal tibial prosthesis with pivotal hinge mechanism comprises of the femoral compo¬nent, a median component, weight bearing pads, tibial head, stem sub assembly, a pivot pin with lock screw and two collared bushes. When assembled and imnplanted the femo¬ral component seats in the distal femur and the tibial system replaces the salvaged proxi¬mal tibia and the whole acts as a pivot hinge and allows 0 to 120° of movement dorsally.
2. Proximal tibial prosthesis with pivotal hinge mechanism as in claim I, where in the femo¬ral component has a solid stem with longitudinal surface scraping to increase bonding with bone cement and grooved undersurface of platform for adequate seating of the im¬plant.
3. Proximal tibial prosthesis with pivotal hinge mechanism as in claim I, where in the pivot joint mechanism of the median component being fitted to the proximal part of the tibial component with collared bushes, pivot pin and lock screw.
4. Proximal tibial prosthesis with pivotal hinge mechanism as in claim 3, where in the col¬lared bushes are wide and spcaed wide inside out which increases weight bearing area.
5. Proximal tibial prosthesis with pivotal hinge mechanism as in claim 3, where in the pivot pin is a straight pin without threads, with a central screw lock mechanism to enable smooth movements.
6. Proximal tibial prosthesis with pivotal hinge mechanism as in claim 3, where in the lock screw of the pivot pin controls both tibial and femoral component.
7. Proximal tibial prosthesis with pivotal hinge mechanism as in claim 1, where in has a new
thrust weight bearing polymer pad with concavity for tibial condylar part articulation aaids
even weight distribution all through the range of movement.
8. Proximal tibial prosthesis with pivotal hinge mechanism as in claim 1, where in the weight
bearing pad is screwed on to median component for stability
9. Proximal tibial prosthesis with pivotal hinge mechanism as in claim 1, where in tibial
condylar part has wide diameter hubs for the bush and pivot pin.
10. Proximal tibial prosthesis with pivotal hinge mechanism as in claim 1, where in the ante¬
rior contact surface of the tibial condylar unit is radially cut which prevents soft tissue
entrapment by automatically pushing tissues out during movement at knee joint.
11. Proximal tibial prosthesis with pivotal hinge mechanism as in claim 1, where in tibial
condylar part is fixed to the stem part through two anterior screws with spring washer
preventing screw backing and also for any delayed surgery long stem can be interchanged
retaing the rest of the implant.
12. Proximal tibial prosthesis with pivotal hinge mechanism as in claim 1, where in tibial stem
has surface scrapings to increase bone cement bonding.
13. Proximal tibial prosthesis with pivotal hinge mechanism as in claim 1, where in both tibial
and femoral component has a centre of alignment groove cut in to enable perfect place¬
ment of implant.
1. Figure 1 shows isometric view of proximal tibial prosthesis
2. Figure 2 shows exploded view of proximal tibial prosthesis
3. Figure 3 shows elevation and side view of proximal tibial prosthesis - Right configuration
4. Figure 4 shows elevation and side view of proximal tibiaki prosthesis - Left configuration
5. Figure 5 shows detail view of condylar region of tibial head
6. Figure 6 shows sectional view of tibial head
7. Figure 7 shows isometric view of the subassembly of the femoral side #
8. Figure 8 shows elevation of the prosthesis in fully flexed position.
9. Figure 9 shows sectional elevation front view of the prosthesis
10. Figure 10 shows sectional lateral view of the prosthesis.
|Indian Patent Application Number||1002/MAS/2002|
|PG Journal Number||23/2006|
|Date of Filing||30-Dec-2002|
|Name of Patentee||PROF. MAYIL VAHANAN NATARAJAN|
|Applicant Address||NO.4, LAKSHMI STREET, KILPAUK, CHENNAI 600 010|
|PCT International Classification Number||A61F2/00|
|PCT International Application Number||N/A|
|PCT International Filing date|