Title of Invention

A HEMI PROSTHESIS DEVICE SUITABLE FOR REPLACEMENT OF PROXIMAL HUMERUS OF INDIAN PATIENTS.

Abstract

A hemiprosthesis device, which is meant for treatment at a relatively low cost of persons of South-Asian and more particularly, Indian origin, having two-part, three-part and four-part displaced fracture with or without dislocations of shoulder joints in osteoporotic bones and fractures of the articular surface of the humeral head involving more than 40 % splitting fractures, and for pathologies of (pre-malignant as well as malignant) proximal humerus, comprising a head component (1), a stem component (2), a medial off-set component (3), and a lateral off-set component (4), the said components (1, 2, 3, 4) being arranged to operate in an inter-connected manner, characterized in that the axes of the head (1) and stem (2) components are held at angle (A) of 125° with a range varied from 120° to 130°, that the cross section of stem component (2) is substantially triangular, that the medial off-set component (3) has a flat base and that the lateral off-set component (4) tapers from the proximal end to the distal end thereof at an angle of 15°.

Full Text

The present invention relates to a hemjprosthesls device suitable for replacement of proximal humerus of Indian Patients. The invention is concerned with a shoulder joint hemiprosthesis for Indian scenario for the treatment of the patients of South Asian origin, more particularly of Indian of origin, having two-part, three-part and four-part displaced fractures with or without dislocations especially in elderly with osteoporotic bones,, and splitting fractures of the humeral head involving the articular surface of the shoulder affecting more than 40% split of humeral head and pathologies of (pre-malignant as well as malignant) proximal humers. Shoulder joint prostheses of different designs and constructions are known in the prior art. Reference is available in this regard to the monograph entitled 'Total Shoulder Athroplasty" edited by Lynn A crossley, published in India by Jaypee brothers Medical Publishers Ltd., New Delhi. Certain constraints have, however, been observed in the application of the prior art shoulder joint prosthesis to patients of South Asian, more particularly of Indian origin. The constraints are mainly as follows :- (a) The average head shaft angle of shoulder joint of people of Indian origin is found to be 125°.The head shaft angle of prior art prosthesis of unitary construction, which are designed primarily for treatment of patients having origin in Western Countries, is around 135° ± 3° and hence such prostheses are not quite compatible for use in the treatment of patients of Indian origin. 2 (b) The distal end of the stem portion of the prior art prosthesis is substantially of cylindrical cross-section and has a tendency to rotate inside the medullary canal of humerus, causing stress risers to the patients. (c) The prior art prostheses are too expensive for the patients in India, and are also not readily available in India. The objects of the invention are: (a) to design and construct shoulder joint hemiprosthesis which will match with the head shaft angle of the shoulder joints of patients of South-Asian, particularly Indian origin, (b) to have stem portions of the prosthesis having cross section which is triangular with flat comers leading to be substantially hexangular to prevent rotation thereof inside the medullary canal of humerus, (c) to reduce the cost of producing the prosthesis appreciately. A cadaveric study of proximal humerus was performed to assess the structural particulars of shoulder joints of people of Indian origin. Templates were drawn of proximal humerus using cadaveric bones. Radiological evaluation of cadaveric bones was done by taking plane X-ray photographs. The version of humeral head was evaluated by goniometric study. Geometric and numerical analysis of sixty humeri revealed the following features: (a) humeral head size i.e. diameter in coronal and sagittal plane, (b) diameter of surgical neck of humerus, (c) head-shaft inclination angle, (d) configuration and diameter of 3 medullary canal of proximal humeral shaft and (e) anatomical version of humeral head. From the above mentioned study it has been found that:- (a) Average head size is 41 mm with a range of variation from 37 mm to 50 mm; (b) Average head-shaft angle is 125° with a variation of about 5%. (c) Average diameter of proximal humeral medullary canal is 9 mm with variation from 8 mm to 12 mm. (d) Average anatomical version of humeral head is 30° with variation from 25° to 40°. (e) Bulk of humeral head is on the medial aspect of humeral shaft. The design and construction of the shoulder joint hemiprosthesis according to the invention are carried out on the basis of the above mentioned findings of the cadaveric study. The invented shoulder joint hemiprosthesis is made of the following four main components; namely, (i) Head, (ii) Stem, (iii) Medial offset and (iv) Lateral offset. 4 These components are made preferably of type 315L AISI (American Iron & Steel Institute) steel. Metals of other types such as stainless steel, and polymers, which are biocompatible, may be also used for constructing the said components. The Head component is substantially of hemispherical shape, and a hollow space is maintained between its hemispherical outer sheath and a cover plate for covering the hollow space in between. A central thread is kept for attachment of the Head component to the stem component. The cross section of the Stem is substantially hexangular with flat base corners of a triangle and is designed for insertion within the medullary canal of a resected humerus. The Medial offset component is provided with a flat base for its better sitting over the calcar region between the Head and Stem and contains at feast one hole for attachment of soft tissues and bones (lesser tuberosity). The Lateral offset component has a base tapering from its proximal to its distal end for mediallization of the Head component, is provided with multiple holes for myosseous anchorage of rotator cuff, and controlling the version of the hemiprosthesis, and is fitted between the Head and Stem components. 5 The invention is described fully without restricting the scope of the invention in any manner with reference to the drawings accompanying the provisional specification, in which Figure 1 shows one embodiment of the invented hemiprosthesis; Figure 2 shows another embodiment of the invented hemiprosthesis; and Figure 3 shows cross-section of the Stem component of the invented hemiprosthesis. Referring to Fig. 1, the hemiprosthesis comprises a Head component (1), a Stem component (2), a Medial off-set component (3), and a Lateral off-set component (4). As already stated herein before, all of the said four components are made preferably of metal type 315L AISI, steel. Head component (1) is substantially of hemispherical shape with outer diameter varying from 35 mm to 49 mm. A cover plate (5) is provided to cover the hollow space inside the Head component (1). A central thread (not shown) is kept for attaching the Head component to ttie proximal end of the Stem component (2). The Stem component (2) is an elongate body of preferred length 100mm and substantially of hexangutar (i.e. flat-comer triangular cross-section). tapering from the proximal end to the distal end at the tip and is provided with a threaded proximal end of a shaft angle (A). 6 The preferred head shaft angle (A) between the axis of Head component (1) and that of stem component (2) is 125°, which may be varied from 120° to 130°. Medial off-set (3) has a flat base with a hole (6) for attachment of soft tissues. Lateral off-set (4) has substantially straight medial and lateral sides tapering from the proximal to the distal ends thereof at a preferred angle of 15° and is fixed with the head component (1). It provides myosseous anchorage with the Stem component (2), and controls also the version and medialisation of the prosthesis. A plurality of holes (7), preferably numbering 3 or 4, are provided in the Lateral off-set (4) for allowing attachment of myosseous anchorage. Both the Medial and Lateral off-sets are attached to the junction of the Head and Stem components. The overall weight of the prosthesis is around 150g, which is compatible with patients of Indian origin. Referring to Fig. 2, the embodiment of the prosthesis is otherwise similar to the embodiment shown in Fig. 1 with the differences that the distal end of Stem (2) is rounded instead of being flattened as m Fig. 1, and that the upper 7 portion of the anterior side of the Lateral off-set is curved instead of being straight as in Fig. 1. Referring to Fig. 3, the height of the tip of the apex from base (b) of the substantially hexangular (i.e. fiat-corner equilateral triangular) cross-section of the Stem component (2), shown in Figs. 1 and 2, is preferably 7.5mm. The invented hemiprosthesis was inserted in the cadaveric humerus with or without cement fixation and the anatomical matching thereof was done. The radiological matching of the prosthesis was also done and compared with the normal humerus. A biomechanical study was conducted on the invented prosthesis before undertaking the clinical trial. A shoulder joint was fabricated using the cadaveric scapula with the upper end of the humerus being replaced by the invented prosthesis. The shoulder joint was prepared using a fine transparent polythene sheet anchored with glenoid and proximal numerous excluding the region, meant for insertion of rotator cuff. A rope was introduced through the region of bony insertion of rotator cuff and through the notes of the Lateral off-set (4) (Figs. 1 and 2) for exerting a tension of 15 kg in a direction making an angle of 20° with scapula humeral plane, for simulating the force normally applied on the rotator cuff. A weight of 2.75 kg was suspended from the middle of humerus shaft using Steinman's pin and Bower's stirrup to simulate the average weight of the arm of a person of Indian origin. The said study was done with a view to checking if the reconstructed rotator cuff is capable of bearing the average 8 weight of the upper arm. The biomechanical study showed that up to 90° of abduction at fabricated joint was possible with application of a force equivalent to 15 kg of spring balance working at 20° inclination to the shaft simulating the power of rotator cuff exerted via myoosseous anchorage at fateral offset when a load of 2.75 kgs was suspended from center of mass of a functional arm (20cm from shoulder), which is an avg. weight of the Indian arm. The clinical application of the invented prosthesis was performed on eleven patients of Indian origin, among which one had GCT of the upper end of the humerus, and nine had 3 or 4 - part fracture dislocations of the shoulder joints and one patient had head split fracture with apparently normal glenoid. The patients treated were both mate and female and of age varying from 28 to 74 years. The clinical outcome was evaluated dinicoradiologically. Clinical evaluation was done on the basis of pain, stability of shoulder, range of motion and functional outcome of the replaced shoulder and patient's satisfaction. Static and dynamic radiofogicaf evafuation was also performed. Patients were placed in supine position, with a small sandbag undertime scapula on the side undergoing surgery, to keep the shoulder and arm extended for easy dislocation or delivery of proximal humerus through the operating wound. A deltopectoral approach was used. The cephalic vein was identified and used as the landmark for the deltopectoral interval Any adhesions or bursa on the undersurface of the deltoid were freed from the proximal humerus and subacromial space. The rotator cuff was inspected for any tears that needed to be repaired before finaf closure. The capsuler refease was done subperiostealy to minimize the risk of injury to the axillary nerve. The humeral head was then delivered anteriorly. For the cases having 3 or 4 part fracture with or without dislocation, the head was delivered through the operating wound often with the help of a schanz screw inserted wfthin it. Proximaf end of fractured shaft was trimmed. The bony portions of greater tuberosity containing rotator cuff are carefully preserved for their achorage with the lateral offset of the prosthesis. The humera/ shaft was reamed and broached with the help of special instrument. The prosthetic humeral head size was selected based on the resected head and checked by trial reduction. The selected prosthesis was inserted with or without the hefp of bone cement Myosseous anchorge was done on the multiple lateral holes of lateral offset and bone grafts were given to bridge the bony component of greater and fesser tuberosies (if detached) and the proximal shaft from humeral head for osseous integration. After adequate soft tissue tensionfng, closure was done, with application of drain. The iimb was immobilized by arm to chest strapping. Suction drain was removed within 48 hours. Dressing was changed on sixth or seventh post-operative day. After the removal of the stiches on the 12th day if the wound was found healthy, the rehabilitation was started. Active motion was allowed in plane of flexion, except external rotation and extension. 10 External rotation may be allowed later on within limit, to the amount determined intra-operatively, that will not jeopardize the repair of subscapufaris. Supervised assisted and passive range of motion exercises were also initiated later on after expected osseous integration ofmyoosseous anchorage with main humeral shaft. Post operative range of motion was checked every 2 weeks for the first 6 weeks and the progress was monitored. After 8 weeks patients were allowed to perform internal rotation, stretching and gentle resisted exercises. At 12 weeks, all restrictions were lifted, but patients were cautioned not to participate in contact activities or do any aggressive weight training. Annual follow-up visits were made with serial radiographs to ensure no sign of component failure. The cases were assessed for 2 - 2.9 years clinically, subjectively and objectively on the basis of pain around the shoukfer, (Table II), stability of shoulder (Table-Ill), range of motion, (Table-IV) ability to perform daily activities (Tabfe-V) and functional outcome of the replaced shoulder. Static and dynamic radiological evaluation was also performed for component loosening, stem failure etc. Among the complications only one had stem extrusion. Nine patients regained painless satisfactory abduction av. 95° (90° - 135°), Internal rotation av. 55°, (55° - 80°), External rotation av. 63.5° (40° - 70°) and flexion av. 25.50 (20° -45°). The case who regained only 80* abduction, demonstrated maximum active forward flexion of 45° and was capable of performing his daily activities with satisfaction. Overall, ten cases became satisfied with painless stable shoulder 11 motion with satisfactory functional outcome of their shoulder following hemiarthroplasty. One case developed unsatisfactory function due to muscle weakness following improper repair of myosseous anchorage in the case of G.C.T. whether the whole proximal humerus was excised. So far patients satisfaction was concerned, 91% patients shows their satisfaction after this replacement operation. 12 13 Table-II 14 Post-operative results considering pain in replaced shoulder Table-III 15 Post-operative results considering stability of replaced shoulder 16 Table0 - V Post-operative results regarding the capabilities of daily activities after hemiarthroplasty of shoulder 17 Activities of Daily living - ADL I Claim: - 1. A hemiprosthesis device suitable for replacement of proximal humerus of Indian patients, which is meant for treatment at a relatively low cost of persons of South Asian and more particularly Indian origin, having two-part, three-part and four-part displaced fracture with or without dislocations of shoulder joints in osteoporotic bones and fractures of the articular surface of the humeral head involving more than 40% splitting fractures, and for pathologies of (pre-malignant as well as malignant) proximal humerus, comprising a head component (1), a stem component (2), a medial off-set component (3), and a lateral off-set component (4), the said components (1, 2, 3, 4) being arranged to operate in an inter-connected manner, characterized in that the axes of the head (1) and stem (2) components are held at angle (A) of 125° with a range varied from 120° to 130°, that the cross section of stem component (2) is substantially triangular, that the medial off-set component (3) has a flat base and that the lateral off set component (4) tapers from the proximal end to the distal end thereof at an angle of 15°. 2. The hemiprosthesis device as claimed in claim 1, wherein the head component (1) is of hollow hemispherical shape of outer diameter varying from 35 mm to 49 mm. 3. The hemiprosthesis device as claimed in claim 1 or 2 , wherein the head component (1) is provided with a cover plate (5) having a central thread to cover the hollow space thereof. 4. The hemiprosthesis device as claimed in claim 1, wherein the stem component (2) is an elongate body of length 100 mm tapering from the proximal end to the distal end thereof to a tip which is round or flattened, and has a cross section which is substantially hexagonal (i.e. flat-corner equilateral triangular) with height of the tip of the apex from the base of 7.5mm. /18/ 5. The hemiprosthesis device as claimed in claim 1, wherein the medial off-set component (3) is provided with a hole (6) for attachment of soft tissues and bones (lesser tuberosity). 6. The hemiprosthesis device as claimed in claim 1, wherein the lateral off-set component (4) comprises 3 or 4 holes (7) for allowing attachment of myosseous anchorage, medialisation of head and to provide proper version (30° retroversion) of the prosthesis. 7. The hemiprosthesis device as claimed in any proceeding claim, having a weight of 150g, compatible for Indian patients. A hemiprosthesis device, which is meant for treatment at a relatively low cost of persons of South-Asian and more particularly, Indian origin, having two-part, three-part and four-part displaced fracture with or without dislocations of shoulder joints in osteoporotic bones and fractures of the articular surface of the humeral head involving more than 40 % splitting fractures, and for pathologies of (pre-malignant as well as malignant) proximal humerus, comprising a head component (1), a stem component (2), a medial off-set component (3), and a lateral off-set component (4), the said components (1, 2, 3, 4) being arranged to operate in an inter-connected manner, characterized in that the axes of the head (1) and stem (2) components are held at angle (A) of 125° with a range varied from 120° to 130°, that the cross section of stem component (2) is substantially triangular, that the medial off-set component (3) has a flat base and that the lateral off-set component (4) tapers from the proximal end to the distal end thereof at an angle of 15°.

Documents:

00113-kol-2005 abstract.pdf

00113-kol-2005 claims.pdf

00113-kol-2005 correspondence.pdf

00113-kol-2005 description(complete).pdf

00113-kol-2005 description(provisional).pdf

00113-kol-2005 drawings.pdf

00113-kol-2005 form-1.pdf

00113-kol-2005 form-18.pdf

00113-kol-2005 form-2.pdf

00113-kol-2005 form-3.pdf

00113-kol-2005 form-5.pdf

00113-kol-2005 latters patent.pdf

00113-kol-2005 p.a.pdf

00113-kol-2005 reply f.e.r.pdf

113-kol-2005-description (provisional).pdf

113-kol-2005-granted-abstract.pdf

113-kol-2005-granted-drawings.pdf

113-kol-2005-granted-form 2.pdf

113-kol-2005-granted-specification.pdf