shoulder arthroplasty

shoulder arthroplasty

1. ClASSICAL SHOULDER ARTHROPLASTY vs reverse shoulder arthropalsty

2. IN BRIEF History. Anatomy & Biomechanics. Prosthesis deigns. Prosthesis & its features. Degenerative shoulder & its pathology. Types of arthroplasty . Surgical approach. Complications. Advantages & disadvanatages .

3. HISTORY The earliest known report of shoulder arthroplasty dates back to 1893, when a French surgeon, Jules Emil Péan , substituted a platinum and rubber implant for a glenohumeral joint destroyed by tuberculosis. In the early 1950s, Neer introduced a humeral head prosthesis for complex shoulder fractures . In 1951, he reported his initial results of replacement of the humeral head with an unconstrained cobalt-chromium alloy ( Vitallium ) prosthesis . In 1974, the Neer II humeral prosthesis, which was modified to conform to a glenoid component, was introduced . Total shoulder arthroplasty using a constrained articulated unit in patients with loss of the rotator cuff but with a functional deltoid muscle was popular in the early 1970s but had limited success.

4. In 1893, he attempted the first known total joint arthroplasty , implanting in the shoulder of a French waiter in 1893. He popularized the hemostat .

5. ANATOMY AND BIOMECHANICS The anatomy of the shoulder joint permits more mobility than any other joint in the body . The glenohumeral joint depends on the static and dynamic stabilizers for movement and stability, especially the rotator cuff . The articular surface of the humeral head is essentially spherical, with an arc of approximately 160 degrees covered by articular cartilage. The glenoid articular surface radius of curvature is 2 to 3 mm larger than that of the humeral head. The average neck-shaft angle is 45 degrees .

6. N ormal position of the glenoid surface in relation to the axis of the scapular body ranged from 2 degrees of anteversion to 7 degrees of retroversion. The superior margin of the humeral head articular surface normally is superior to the top of the greater tuberosity by 8 to 10 mm . The distance from the lateral base of the coracoid process to the lateral margin of the greater tuberosity is called the lateral humeral offset . The humeral offset defines the position of the proximal humeral articular surface relative to the humeral shaft .

7. Proximal humeral retroversion is highly variable, ranging from 0 to 55 degrees .

8. Increasing the humeral head thickness by 5 mm has been shown to reduce the range of motion at the glenohumeral joint by 20 to 30 degrees, whereas decreasing the thickness by 5 mm can diminish motion. Replacement of the anatomical humeral head size and position aims to restore normal shoulder biomechanics.

9. PROSTHESIS DESIGN Based on the clinical success of the Neer II implant, numerous modular designs were developed to improve implant fixation and durability . Modularity allows a better fit for individual patients because various stem and head sizes can be “mixed and matched” to an individual’s anatomy. Most stems are made of cobalt-chrome alloy, have proximal porous ingrowth coating, and have proximal fins( A fin is a thin component or appendage attached to a larger body or structure) for rotational stability.

10. C enter of the humeral head was 2.6 mm posterior and 6.9 mm medial to the center of the humeral shaft . Anatomical positioning of the humeral head prosthesis is best done with an eccentric locking position of the Morse taper, which allows adjustments to the variable medial offset and any posterior offset. P ostoperative kinematics after total shoulder arthroplasty do not mimic those of the native shoulder .

11. P rosthetic head should be within 4 mm of the original humeral head thickness. Most stems can be inserted with a press-fit or cemented technique. Cemented all-polyethylene components remain the most frequently used glenoid components, but most now have an increased radius of curvature compared with the humeral head (2 to 6 mm larger) to allow translation during movement and to decrease edge loading .

12. ROCKING HORSE EFFECT Such translation in a perfectly congruent joint may have a potential for localized wear and loosening (rocking-horse effect); however, increased loosening and polyethylene have not been reported to occur when the radii of curvature of the glenoid component and the humeral head are matched within 2 mm

13. N oted fewer radiolucencies with mismatches between the glenoid and humeral head diameters of more than 5.5 mm (6 to 10 mm ). I mproved stability with increasing sizes of glenoid components . B one quality was important in achieving solid glenoid component fixation . Polyethylene glenoid components generally have a single central or offset keel or multiple pegs for fixation into the glenoid vault .

14. B one stresses were not much affected by prosthesis design except at the tip of the central peg or keel. They did conclude, however, that pegged prostheses were better for normal bone, whereas keeled components were better for bone in rheumatoid patients.

15. GLENOHUMERAL ARTHRITIS Patients typically present with global pain about the shoulder with difficulty performing overhead activities. Joint space narrowing is not commonly seen in the shoulder owing to the non–weight-bearing position of the shoulder. Symmetrical joint space narrowing in RA .

16. Shoulder OA shows subchondral sclerosis and a large osteophyte on the inferior aspect of the humeral head This so-called “goat’s beard” is pathognomonic of advanced glenohumeral degeneration.

17. CAPSULORRHAPHY ARTHROPATHY Capsular distension. Posterior glenoid wear. Loose bodies. Osteophytes .

18. PREOPERATIVE PALNNING Routine Blood Investigations .(CBC,ESR,CRP) X-rays. MRI. CT(3D). Rule out sp.bacteria .( Aspiration and culture of glenohumeral joint fluid, holding the culture for at least 14 days to isolate Propionibacterium acnes )

19. RADIOGRAPHY Anteroposterior views . A 40-degree posterior oblique view in neutral internal and external rotation . S upine lateral scapula view (anterior oblique AP ). A xillary lateral view. Radiographs of the opposite, uninvolved shoulder.

20. AXILLARY LATERAL VIEW

21. AXILLARY RADIOGHRAPHY POSTERIOR OBLIQUE VIEW

22. MRI often shows- -Thinning of the subscapularis and degenerative changes in the joint. -Rotator cuff status. -Increased capsular volume posteriorly & capsular contraction anteriorly. - P recollapse osteonecrosis, MRI is useful for visualizing the area of dead bone and is often the best tool to make the diagnosis.

23. PRECOLLAPSE OSTEONECROSIS

24. CT E xcellent picture of the patient’s glenoid bone stock and the pattern of glenoid wear. Loose bodies may be seen in the axillary or subscapularis recess. M alunions or nonunions , three-dimensional reconstruction helps to precisely show the bony deformities and defects before surgery. Accurate glenoid component placement with either conventional or patient-specific implants. The role of preoperative planning based on three-dimensional CT scans to optimize implant position, size, and range of motion is an evolving area of investigation.

25. CT SHOWING DEGENERATIVE ARTHRITIS

26. PREOPERATIVE CHECKLIST Check for-Rotator cuff tears( Mc in RA than OA). Biceps tendinitis. Acromioclavicular joint involvement . Passive and active shoulder movements. Palpable crepitus feeling . Adhesive capsulitis.

27. OBSTACLES TO ARHTOPALSTY Malunited proximal humerus #( osteotomy usually is unnecessary as newer short-stem and stemless designs allow accommodation of these deformities). Major infective foci.

28. HEMIARTHROPLASTY INDICATIONS The predominant indication is end-stage joint degeneration in a patient with glenoid resurfacing.(CI for hemiarthroplasty ). Osteonecrosis,Glenoid dysplasia. C uff tear arthropathy .(With retained forward shoulder elevation) Y oung laborers, patients with glenoid bone stock insufficiency, and patients with high activity levels may benefit more from hemiarthroplasty . Rotator cuff tears remain a contraindication to prosthetic glenoid ( excellent pain relief and moderate improvements in function and motion after TSA acc. t o some)

29. MATSEN INDICATIONS OF HEMIRTHROPLASTY (1) The humeral joint surface is rough , but the cartilaginous surface of the glenoid is intact, and there is sufficient glenoid arc to stabilize the humeral head ; ( 2) There is insufficient bone to support a glenoid component; (3) There is fixed upward displacement of the humeral head relative to the glenoid (as in cuff tear arthropathy or severe rheumatoid arthritis ); (4) There is a history of remote joint infection; and ( 5)Heavy demands would be placed on the joint (anticipated heavy loading from occupation, sport, or lower extremity paresis).

30. CONTRAINDICATIONS Recent sepsis . Neuropathic joint . A Paralytic disorder of the joint. Deficiencies in shoulder cuff and deltoid muscle function. L ack of patient cooperation.

31. HEMIARTHROPLASTY

32. Biceps tenodesis before incising the subscapularis .

33. POSTOPERATIVE CARE Gentle home exercise program with passive forward elevation to 90 degrees and passive external rotation to neutral . E ncouraged to use a pillow behind the elbow while recumbent in the sling to support the extremity. Full-time sling immobilization continues for 6 weeks, followed by 6 weeks of sling use only in unprotected environments . Therapy progresses to full passive range of motion by 6 to 12 weeks and to isometric strengthening at 10 weeks.

34. OUTCOMES Hemiarthroplasty has been reported to initially relieve pain in 75% to 95% of patients with glenohumeral arthritis and severe rotator cuff deficiency, with modest improvements in range of motion and strength.Results have been compromised by persistent pain from glenoid arthrosis , anterosuperior instability, and progressive bone loss. The best results of shoulder hemiarthroplasty are in patients with osteonecrosis, good pain relief in 90 %, with an almost normal range of motion .Results are not quite as good in patients with rheumatoid arthritis, osteoarthritis , glenoid dysplasia, or posttraumatic glenohumeral arthrosis .

35. PEARLS Good deltoid function and an adequate coracoacromial arch are key to successful hemiarthroplasty in patients with severe rotator cuff arthropathy . If it is found to be torn, as much of the rotator cuff as possible should be repaired, emphasizing anterior and posterior reconstruction to provide stability to the implant.

36. Care should be taken to avoid a “big head” humeral prosthesis that can “overstuff” the joint

37. “Rocking-horse effect” Eccentric loading of the glenoid caused by superior migration of the humeral component has been cited as a cause of glenoid loosening. A ssociation between glenoid component loosening and irreparable rotator cuff tears.

38. TOTAL SHOULDER ARTHROPLASTY The primary indication for total shoulder arthroplasty is endstage glenohumeral joint degeneration with an intact rotator cuff.(OA,RA, osteonecrosis , posttraumatic arthritis , and capsulorrhaphy arthropathy )

39. CONTRAINDICATIONS Active or recent infection. I rreparable rotator cuff tears. Paralysis with complete loss of function of the deltoid. Debilitating medical status and uncorrectable glenohumeral i nstability .

40. SURGICAL TECHNIQUE Approach the glenohumeral joint as described . Fukuda retractor on the posterior aspect of the glenoid and subluxing the humerus posteriorly. Débride the glenoid vault . Typically, there is posterior erosion of the glenoid and the anterior rim of the glenoid needs to be lowered to reestablish correct version .This can be done by eccentric reaming. Once the glenoid vault is débrided , make a centering hole, typically with a guide . If posterior rim wear is significant and the anterior rim has not been lowered, the component sits excessively retroverted , and anterior glenoid neck perforation is likely .

41. Once reaming is complete, prepare the glenoid for either the pegged or keeled implant . Once the appropriate head is selected, dry the Morse taper and tap the head into position. Reduce the glenohumeral joint, and close the wound. The durability of total shoulder replacement is as good as or better than that of hip and knee replacements. Results at long-term follow-up in several series have reported 85% component retention at 20 years of follow-up and revision rates for all causes averaging less than 10%.

42. Problem of and solution for uneven wear and erosion of glenoid. A, Area of wear. B, If glenoid component is inserted without correction of slope, anchoring device passes out of medullary canal; tilt and loss of height also make implant unstable. C and D, Severe erosion is corrected by bone grafting. Piece of humeral head is secured to scapula with 4-mm AO navicular screw. Lesser erosion can be offset by building up low side with acrylic cement or lowering high side. Building up with cement is not recommended because of feared cement loosening. Lowering high side often requires shortening holding device of glenoid component and creates laxity between components, which can make implant temporarily unstable and requires special postoperative care. Glenoid component with thick side is available for moderate uneven erosion.

43. A lthough hemiarthroplasty can provide pain relief and increased range of motion in patients with osteoarthritis and a concentric glenoid , total shoulder arthroplasty generally provides superior results in terms of patient satisfaction, function, and strength , especially at longer-term follow-up . Cochrane Database systemic review of seven studies found that total shoulder arthroplasty is associated with better shoulder function than hemiarthroplasty .

44. In 1987, Grammont et al. [14, 15] introduced two major innovations in the reverse prosthesis: notably a large glenoid hemisphere with no neck and a small almost horizontally inclined (155 degrees) humeral component covering less than half of the hemisphere.

45. REVERSE SHOULDER ARTHROPALSTY The primary indication for reverse total shoulder arthroplasty is a nonfunctional rotator cuff. Until the introduction of reverse total shoulder arthroplasty , patients with cuff tear arthropathy were generally treated with hemiarthroplasty . Contraindications include loss or inactivity of the deltoid and excessive glenoid bone loss that would not allow secure implantation of the glenoid component.

46. CUFF TEAR ARTHROPATHY SOURCIL SIGN DECREASED JOINT SPACE PROXIMAL HUMERUS MIGARATION PSEUDOHUMERAL ARTICULATION OSTEOPHYTES

47. COMPLICATIONS OF SHOULDER ARTHROPLASTY O verall complication is approximately 15 %. Glenoid loosening is most common. G lenohumeral instability, R otator cuff tear, P eriprosthetic fracture, infection. Implant failure including dissociation of modular prostheses, and D eltoid weakness or dysfunction.

48. Complications after total shoulder arthroplasty tend to occur late in the postoperative course (5 to 10 years after surgery). C omponent loosening has been reported to occur approximately 8 years after surgery, infection at 12 years, and periprosthetic fractures at 6 years. Reverse total shoulder arthroplasty initially resulted in relatively high complication rates (50%) and some unique complications. The most common complications after reverse total shoulder arthroplasty are scapular notching, hematoma formation, glenoid dissociation such as baseplate failure or aseptic loosening, glenohumeral dislocation , acromial and scapular spine fractures, infection , loosening or dissociation of the humeral component and nerve injury.

49. INTRAOPERATIVE COMPLICATIONS The most common intraoperative complications in shoulder arthroplasty are fracture, usually of the humeral shaft in the mid to distal diaphysis nerve injury, most often to the axillary nerve.

50. POSTOPERATIVE COMPLICATIONS G lenoid loosening, G lenohumeral instability , R otator cuff tears , Periprosthetic fracture , Infection, D eltoid rupture , T uberosity nonunion or malunion , humeral loosening, impingement, heterotopic bone formation, mechanical failure of components, and loss of motion.

51. GLENOID LOOSENING Symptomatic loosening of glenoid or humeral components is the most common problem encountered in total shoulder arthroplasty . Radiographic lucent lines at the cement-bone interface of the glenoid component have been observed in varying degrees in up to 96% of patients. Injection of the cement under pressurization provided by a syringe and application of cement on the back side of the glenoid component has been reported to improve glenoid component fixation by providing more complete cementation. Radiolucencies tend to evolve late (after 5 years), indicating the need for further technical and prosthetic innovation to improve long-term component durability . Radiolucent lines also were significantly associated with osteolysis.

52. Keeled or peg glenoid. Glenoid lucencies develop over time, most likely as a result of the stresses placed across the bone-cement-polyethylene interface.

53. Instability is the second leading cause of complications associated with shoulder arthroplasty . 80% of instability complications after total shoulder arthroplasty involve anterior or superior instability Anterior instability most commonly is associated with subscapularis failure , glenoid anteversion , malrotation of the humeral component, or anterior deltoid dysfunction. Progressive superior migration of the humeral head has been reported in association with dynamic muscle dysfunction, attenuation of the supraspinatus, failed rotator cuff repairs , and frank rupture of the rotator cuff. INSTABILITY

54. PERIPROSTHETIC FRACTURE The reported prevalence of postoperative periprosthetic humeral shaft fractures ranges from 0.5% to 2%,most frequent in women & rheumatoid arthritis.

55. ROTATOR CUFF FAILURE Rotator cuff failure is the fourth most common complication after shoulder arthroplasty . Factors reported to be associated with postoperative tears of the subscapularis tendon include multiple operations , overstuffing of the joint, overly aggressive therapy involving external rotation and tendon compromise by lengthening techniques. Preoperative fatty infiltration of the infraspinatus and a glenoid component placed in superior tilt are risk factors for subsequent rotator cuff failure. Repair of large or massive tears may be impossible. One treatment for this difficult problem involves removing the glenoid component, bone grafting of the glenoid cavity defect, and allowing the humeral prosthesis to migrate superiorly.

56. INFECTION Infection is rare after both primary anatomic and reverse total shoulder arthroplasty (approximately 2%); male sex and younger age at the time of arthroplasty are risk factors . Propionibacterium acnes is the most commonly isolated organism after shoulder arthroplasty but has a protean presentation and is very difficult to diagnose. The most common symptom is unexplained pain. Intraoperative findings of humeral loosening, turbid fluid , and membrane formation all correlate with the likelihood of a positive culture for P. acnes .

57. If the infection is identified early (3 to 6 weeks after surgery ) and the organism is gram positive, retention of the components can be considered. One-stage irrigation and debridement with replacement of the humeral head, along with appropriate parenteral antibiotic therapy, has been shown to be effective treatment . If the organism is gram negative or the infection occurs late, removal of the implants and all cement generally is recommended

58. Deltoid muscle dysfunction caused by axillary nerve injury or detachment of the deltoid muscle can result in a catastrophic loss of shoulder function . Heterotopic ossification has been noted to occur after shoulder arthroplasty in 10% to 45% of patients. Male gender and osteoarthritis are risk factors.

59. Neer published a large rate of satisfactory results in his initial study. Most studies published later have reported a higher rate of failure. In the absence of complications, most patients experience little pain, but their motion and strength varies depending on the quality of the reconstruction and tuberosity healing. Average elevation is approximately 90 to 100 degrees, although it may range less than 30 to more than 150 degrees .

60. The main biomechanical advantages of reverse prosthesis according to Grammont’s concept are as follows: the large ball offers a greater potential arc of motion and more stability than a small ball , the small lateral offset (absence of neck) places the center of rotation directly in contact with the glenoid surface and reduces the torque at the point of fixation of the glenoid component, medializing the center of rotation recruits more of the deltoid fibers for elevation or abduction, and lowering the humerus increases tension on the deltoid. These biomechanical properties may lead to better functioning of the deltoid by an increase of its lever arm and moment of action, compensating for the lack of a functional rotator cuff .

61. An important limitation of this nonanatomical prosthesis is its inability to restore active internal and external rotation. This is caused mainly by design limitations of the prosthesis producing mechanical impingement and malfunctioning of the rotator cuff remnants. It can also be explained by the slackening of the remaining external rotators due to the medialization of the center of rotation.

62. A second prosthetic limitation of this reversed principle rises from its hinged rotation (the humeral component rotates around the glenosphere ) instead of a spinning rotation (the humeral head rotates on the spot) as seen in an anatomical setting. This type of rotation requires more room, because without it, a conflict between the humeral and glenoid parts can occur . Best known is the scapular notching in which the humerus is in conflict with the infraglenoid tubercle . This mechanical impingement also exists in the transverse plane of the body, thereby limiting the range of external and internal rotation and possibly leading to mechanical prosthetic failure when the tuberosities bump against the glenoid.

63. In 2005, these authors reported a minimum two-year follow-up study of sixty shoulders with cuff-tear arthropathy [ 40 ]. Reverse arthroplasty was associated with statistically significant improvements in pain and function, with a mean active elevation of approximately 105 degrees. However, there was a 17 % complication rate and a 12% rate of revision for implant failure.