Constrained arthroplasty of the shoulder

Constrained replacement, like all prosthetic replacements, is constantly undergoing change and will improve as the current state of the art changes. It is not a standard, usual operation like unconstrained arthroplasty, and it should be reserved for the patient who requires arthroplasty and does not have a functional rotator cuff mechanism. If, in addition, the acromial fulcrum and loss of deltoid is present, then there is a greater reason for constrained replacement; it is a salvage procedure that is not as durable as the unconstrained device. Constrained arthroplasty has much merit if the risks and possible complications are well understood; however, pain relief and improved function will be lost if the device fails. The dislocation feature of the MRTS is desirable in order to minimize the risk of scapular fracture. Its disadvantage is that, with this complication, open operation is needed to reduce the assembly and insert new polyethylene components. The method of surface mounting of the metal glenoid component without removing the glenoid subchondral plate or cancellous bone of the vault is believed to lessen the risk of glenoid component loosening or pull-out. Finally, active function always depends upon residual deltoid muscle power. Thus, a poor or absent deltoid will only permit passive motion.     

Lucent lines and glenoid components: What do they portend?

Glenoid component radiolucent lines following total shoulder arthroplasty are not uncommon postoperative radiographic findings and their incidence varies. With time, a certain percentage of radiolucent lines progress and potentially compromise component stability. The incidence of radiographic lucency progresses from 9% to 27% and then 73% at 2, 5, and 15 years, respectively. Radiolucent lines can be caused by posterior glenoid wear, inflammatory arthritis, design factors such as a metal-backed glenoid implant, and improper implantation techniques where the prosthesis is not fully seated or cement is used to fill a defect. Intraoperative techniques to prevent lucent lines include removing minimal bone from the glenoid vault and pressurizing cement into the cancellous bone at time of glenoid component implantation. Furthermore, a pegged glenoid component rather than a keel type is preferred, as this has been associated with a lower incidence of radiolucent lines.     

Trabecular metal fixation: A new chemical concoction

Secure fixation of metal prosthesis to bone has always been a challenge. Bone cement has been a great help in achieving this goal, but there can be complications, such as cement loosening and breakage. Therefore, it is reasonable to consider types of coating on a metal surface that will allow bone ongrowth or a type of metal (tantalum) that will allow bone ingrowth as it is a porous scaffold. Furthermore the stiffness of tantalum is between subchondral bone and cortical bone, which also promotes ingrowth. This metal can be overlayed on other metal or used by itself as an implant. In primary osteoarthritis of the glenohumeral joint, it can be used for both the humeral and glenoid components allowing for a cementless prosthesis. Thus the complications from the use of bone cement can be avoided. Tantalum can also be used with a reverse prosthesis. It is especially important for the glenoid baseplate component as it will take away stress from the screws that are used for early fixation. Tantalum is also useful in the revision setting where there is bone loss and secure fixation is needed to the remaining bone. Tantalum has been used in the shoulder for more than 5 years successfully and longer in the hip and knee.     

The cemented humerus and non-cemented glenoid: The optimal hybrid solution for total shoulder arthroplasty

Hybrid fixation of total joint arthroplasty has been recognized as an accepted form of surgical approach in multiple joints. Principles of implant fixation should focus on durability and on providing secure long-term function. To date, there is no conclusive evidence that pressed-fit humeral stem fixation has an advantage over well-secured cemented humeral fixation. Although revision may require cement removal, a well-fixed bone—ingrowth implant may require slatting and osteotomy of the humerus. On the contrary, need for revision in arthroplasty due to inadequate implant fixation has almost universally revolved around the failure of cement fixation and loosening of the glenoid component. A case will be made based on 30 years of experience of a surgeon performing total shoulder arthroplasty using secure modern cement-fixation techniques of humeral components. More recently, over the past 10 years an extremely high rate of durable secure glenoid implant fixation has been achieved using press-fit tantalum porous anchorage of polyethylene glenoid components. This has resulted in no cases of loosening of glenoid fixation and only one case of glenoid component fracture with greater than 95% survivorship over a 10-year period. A combination of well-cemented humeral stem and trabecular metal anchorage of the glenoid has provided durable and long-lasting function in primary total shoulder arthroplasty.     

Principles of shoulder prosthesis implantation

Patients with an intact rotator cuff and a humeral head that is centered in the glenoid fossa will benefit from both: a hemiarthroplasty and a total shoulder arthroplasty. However, the functional outcome following total shoulder arthroplasty is superior to that of hemiarthroplasty. Superior migration or mal-positioning of the humeral head in the anterior or posterior direction are generally associated with a maximum active flexion of 90 degrees and a high rate of loosening of the glenoid component. Total shoulder arthroplasty leads to superior results in patients with osteoarthritis and mal-positioning of the humeral head in the posterior direction. However, if the head can not be centralized in the glenoid fossa a significant risk of glenoid loosening remains. A superior functional outcome of total shoulder arthroplasty in patients with rheumatoid arthritis can be observed. On the other hand inferior bone quality and a rotator cuff might lead to loosening of the glenoid component. Radiographic signs of glenoid loosening are frequently observed. However, these hardly require operative revisions. If a glenoid component can not be inserted, a bipolar or inverse prosthesis might be considered an alternative.     

Current status and perspectives of shoulder replacement

Basis of the modern shoulder implants is the Neer II-system, a non constrained total shoulder prosthesis with conforming radii of curvature and improved protection against dislocation. The second generation of shoulder prosthesis is based on the geometric shaft design of the Neer II prosthesis and offers not only a variety of modular head- and shaft-sizes but also through different radii a physiologic rotation-translation-mechanism. The third generation of humeral head prosthesis carries the concept of an anatomic reconstruction one step further and enables the surgeon to adjust the inclination and the eccentric offset of the humeral head to restore the centre of rotation. The latest development in shoulder arthroplasty are humeral head prosthesis with a fully variable 3-dimensional modularity to independently adjust the prosthestic head position regardless of the individual shaft geometry. This achieves a 3-dimensional adaptability of the prosthetic head about the stem axis in the coronary and in the sagittal plane. Besides of the humeral shaft prosthesis an alternative concept of shoulder joint replacement is established – the replacement of the humeral head articular surface. A hemispheric surface prosthesis – cup arthroplasty – is cemented onto the residual humeral head, which eliminates the obligatory humeral head resection and the reaming of the medullary canal. Bipolar shoulder prosthesis are humeral shaft prosthesis with a bi-rotational head system. Their indication is limited to pre-existing lesions of the rotator cuff and/or the glenoid surface. The inverse total shoulder prosthesis reverses the articular surface morphology of the humeral head and the glenoid. The hemispheric glenoid component serves as the centre of rotation for the concave epiphyseal proximal humerus component. This implant is especially used in cases of massive rotator cuff deficiences. The role of shoulder prosthesis in treating acute humeral head fractures needs special consideration. A fracture prosthesis has to restore the exact length of the humerus, the centre of rotation, and the anatomical retroversion. Positioning of the tubercula and their adequate osteosynthesis is most critical and fundamental to ensure a correct healing process. A failed consolidation of the tubercula does not lead to a satisfying result. The shoulder joint replacement can be sufficiently fixated in cemented, cementless or hybrid techniques. Today several component design variations of cemented glenoid implants exist. Their main distinction is the fixation system which can be divided into two main groups – the keel – and the peg-shaped glenoid components. The peg-shaped anchorage system shall guarantee a greater stability against shear-forces. Cementless glenoid components consist of a polyethylen inlay and a surface treated metal-back with an integrated fixation system. These fixation systems are object of intensive biomechanical research and range from conventional screw fixation to specialised cone systems and self-cutting cage-screw-systems. The critical area of cementless glenoid components is the transition zone of the PE-inlay and the metal-back because of high force development. The question of implanting a hemi- or total shoulder prosthesis is answered by the morphologic changes of the glenoid articular surface, which includes the size of the subchondral defect and the underlying etiology of the shoulder joint disease, and the age of the patient. Preoperative planning must consist of an adequate radiologic work-up – X-ray, CT or MRI – to accurately assess the glenoid morphology. G. Walch categorised the different glenoid lesions and developed a very important classification of possible glenoid deformations. To compare and evaluate the operative results one must consider the different shoulder prosthesis and the discrepancies between a hemi- and a total shoulder prosthetic replacement. Looking at the loosening and survival rate of the implant the results are related to the type of prosthesis and the preoperative diagnosis. The Neer total shoulder prosthesis has a 15 year survival rate of 87 %, compared to 74 % of the hemi-prosthesis. The objective for the future has to be to further advance the development of prosthetic components, especially for primary joint replacement in acute humeral head fractures. Another point of interest is how to reduce the still existing high loosening rates of the glenoid components. A fairly new research-field is the computer-assisted surgery, e. g. navigation systems and robotics. The computer-assisted navigation could be of great advantage to accurately find the individual resection plane (inclination and restroversion) of the humeral head. The use of a surgery-robot could be very helpful to reproducibly achieve the desired conformity of the articular surface when preparing the glenoid.     

Current status and perspectives of shoulder replacement

Summary Basis of the modern shoulder implants is the Neer II-system, a non constrained total shoulder prosthesis with conforming radii of curvature and improved protection against dislocation. The second generation of shoulder prosthesis is based on the geometric shaft design of the Neer II prosthesis and offers not only a variety of modular head- and shaft-sizes but also through different radii a physiologic rotation-translation-mechanism. The third generation of humeral head prosthesis carries the concept of an anatomic reconstruction one step further and enables the surgeon to adjust the inclination and the eccentric offset of the humeral head to restore the centre of rotation. The latest development in shoulder arthroplasty are humeral head prosthesis with a fully variable 3-dimensional modularity to independently adjust the prosthestic head position regardless of the individual shaft geometry. This achieves a 3-dimensional adaptability of the prosthetic head about the stem axis in the coronary and in the sagittal plane. Besides of the humeral shaft prosthesis an alternative concept of shoulder joint replacement is established – the replacement of the humeral head articular surface. A hemispheric surface prosthesis – cup arthroplasty – is cemented onto the residual humeral head, which eliminates the obligatory humeral head resection and the reaming of the medullary canal. Bipolar shoulder prosthesis are humeral shaft prosthesis with a bi-rotational head system. Their indication is limited to pre-existing lesions of the rotator cuff and/or the glenoid surface. The inverse total shoulder prosthesis reverses the articular surface morphology of the humeral head and the glenoid. The hemispheric glenoid component serves as the centre of rotation for the concave epiphyseal proximal humerus component. This implant is especially used in cases of massive rotator cuff deficiences. The role of shoulder prosthesis in treating acute humeral head fractures needs special consideration. A fracture prosthesis has to restore the exact length of the humerus, the centre of rotation, and the anatomical retroversion. Positioning of the tubercula and their adequate osteosynthesis is most critical and fundamental to ensure a correct healing process. A failed consolidation of the tubercula does not lead to a satisfying result. The shoulder joint replacement can be sufficiently fixated in cemented, cementless or hybrid techniques. Today several component design variations of cemented glenoid implants exist. Their main distinction is the fixation system which can be divided into two main groups – the keel – and the peg-shaped glenoid components. The peg-shaped anchorage system shall guarantee a greater stability against shear-forces. Cementless glenoid components consist of a polyethylen inlay and a surface treated metal-back with an integrated fixation system. These fixation systems are object of intensive biomechanical research and range from conventional screw fixation to specialised cone systems and self-cutting cage-screw-systems. The critical area of cementless glenoid components is the transition zone of the PE-inlay and the metal-back because of high force development. The question of implanting a hemi- or total shoulder prosthesis is answered by the morphologic changes of the glenoid articular surface, which includes the size of the subchondral defect and the underlying etiology of the shoulder joint disease, and the age of the patient. Preoperative planning must consist of an adequate radiologic work-up – X-ray, CT or MRI – to accurately assess the glenoid morphology. G. Walch categorised the different glenoid lesions and developed a very important classification of possible glenoid deformations. To compare and evaluate the operative results one must consider the different shoulder prosthesis and the discrepancies between a hemi- and a total shoulder prosthetic replacement. Looking at the loosening and survival rate of the implant the results are related to the type of prosthesis and the preoperative diagnosis. The Neer total shoulder prosthesis has a 15 year survival rate of 87 %, compared to 74 % of the hemi-prosthesis. The objective for the future has to be to further advance the development of prosthetic components, especially for primary joint replacement in acute humeral head fractures. Another point of interest is how to reduce the still existing high loosening rates of the glenoid components. A fairly new research-field is the computer-assisted surgery, e. g. navigation systems and robotics. The computer-assisted navigation could be of great advantage to accurately find the individual resection plane (inclination and restroversion) of the humeral head. The use of a surgery-robot could be very helpful to reproducibly achieve the desired conformity of the articular surface when preparing the glenoid.      

Bone Grafting Severe Glenoid Defects in Revision Shoulder Arthroplasty

During revision total shoulder arthroplasty, bone grafting severe glenoid defects without concomitant reinsertion of a glenoid prosthesis may be the only viable reconstructive option. However, the fate of these grafts is unknown. We questioned the durability and subsidence of the graft and the associated clinical outcomes in patients who have this procedure. We retrospectively reviewed 11 patients with severe glenoid deficiencies from aseptic loosening of a glenoid component who underwent conversion of a total shoulder arthroplasty to a humeral head replacement and glenoid bone grafting. Large cavitary defects were grafted with either allograft cancellous chips or bulk structural allograft, depending on the presence or absence of glenoid vault wall defects, without prosthetic glenoid resurfacing. Clinical outcomes (Penn Shoulder Score, maximum 100 points) improved from 23 to 57 at a minimum 2-year followup (mean, 38 months; range, 24-73 months). However, we observed substantial graft subsidence in all patients, with eight of 11 patients having subsidence greater than 5 mm; the magnitude of graft resorption did not correlate with clinical outcome scores. Greater subsidence was seen with structural than cancellous chip allografts. Bone grafting large glenoid defects during revision shoulder arthroplasty can improve clinical outcome scores, but the substantial resorption of the graft material remains a concern. LEVEL OF EVIDENCE: Level III Prognostic study.     

Long-term results of total shoulder arthroplasty following bone-grafting of the glenoid.

BACKGROUND: The marked loss of glenoid bone volume or alteration of glenoid version can affect glenoid component fixation in patients undergoing total shoulder arthroplasty. The purpose of this study was to evaluate the long-term results associated with the use of bone-grafting for restoration of glenoid volume and version at the time of total shoulder arthroplasty. METHODS: Twenty-one shoulders received an internally fixed, corticocancellous bone graft for the restoration of peripheral glenoid bone stock at the time of total shoulder arthroplasty between 1980 and 1989. Grafting was indicated when glenoid bone stock was insufficient to maintain adequate version or fixation of the prosthesis. Seventeen shoulders were available for follow-up; the average duration of follow-up for the thirteen shoulders that did not have prosthetic failure within the first two years was seventy months. Total shoulder arthroplasty was performed because of osteoarthritis in five shoulders, chronic anterior fracture-dislocation in five, capsulorrhaphy arthropathy in three, inflammatory arthritis in two, recurrent dislocation in one, and failure of a previous arthroplasty in one. All patients had some form of anterior or posterior instability preoperatively. There were five anterior and twelve posterior glenoid defects. Bone from the resected humeral head was used for grafting in fifteen shoulders, and bicortical iliac-crest bone was used in two. RESULTS: The average glenoid version after grafting was 4 degrees of retroversion, with an average correction of 33 degrees. The graft failed to maintain the original correction in three shoulders due to nonunion, dissolution, or shift. Five total shoulder replacements failed, necessitating glenoid revision at two to ninety-one months postoperatively. The failures were associated with recurrent massive cuff tears (one shoulder), persistent instability (two shoulders), improper component placement (one shoulder), and loss of graft fixation (one shoulder). There were no humeral component failures. According to the criteria of Neer et al., the functional result was rated as excellent in three shoulders, satisfactory in six, and unsatisfactory in eight. CONCLUSIONS: Despite the finding that eight shoulders had an unsatisfactory functional result at the time of longterm follow-up, corticocancellous grafting of the glenoid successfully restored glenoid version and volume in fourteen of the seventeen shoulders in the present study. Patients with glenoid deficiency often have associated glenohumeral instability, which may affect the results of total shoulder arthroplasty. Bone-grafting of the glenoid is a technically demanding procedure that can restore bone stock in patients with structural defects.     

Periprothetische Humerusfraktur

The primary aims when performing revision arthroplasty of periprosthetic humeral fractures (PHF) are preservation of bone stock, achieving fracture healing and preserving a stable prosthesis with the focus on regaining the preoperative shoulder-arm function. The indications for revision arthroplasty are given in PHF in combination with loosening of the stem. In addition, further factors must be independently clarified in the case of an anatomical arthroplasty. In this context secondary glenoid erosion as well as rotator cuff insufficiency are potential factors for an extended revision procedure. For the performance of revision surgery modular revision sets including long stems, revision glenoid and metaglene components as well as plate and cerclage systems are obligatory besides the explantation instrumentation. Despite a loosened prosthesis, a transhumeral removal of the stem along with a subpectoral fenestration are often required. Length as well as bracing of revision stems need to bridge the fracture by at least twice the humeral diameter. Moreover, in many cases a combined procedure using an additional distal open reduction and internal fixation (ORIF) plus cable cerclages as well as biological augmentation might be needed. Assuming an adequate preparation, the experienced surgeon is able to achieve a high fracture union rate along with an acceptable or even good shoulder function and to avoid further complications.     

Die luxierte Schulterprothese – eine vermeidbare Katastrophe?

Instability after shoulder arthroplasty is a common problem, even though complete dislocations are rare. A distinction can be made between vertical and horizontal instabilities. The most common type of vertical instability is superior migration of the humeral head caused by rotator cuff insufficiency; the shoulder prosthesis should be changed for an inverse prosthesis if the patient is symptomatic. Horizontal instabilities can certainly lead to acute dislocation, but it is far more common for them to result in eccentric loading of the glenoid and in turn to increased wear and loosening. When a prosthesis is first implanted it is essential to reproduce the original bony situation before the deformity caused by arthrosis, arthritis or fracture, as this is the only way to prevent instability. This requires careful preoperative planning including evaluation of CT or MRI scans so that during the operation it will be possible, for example, to reorientate an eccentrically torn glenoid using a bone graft or by eccentric reaming and restore the original torsion. At least as much importance attaches to the treatment of the soft tissue, meaning careful release and later closure of the rotator cuff and capsule complex, as to the bony situation. In the authors' own institution 190 prostheses were implanted between 2000 and 2006 and there were three dislocations (1.6%).     

Radiographic assessment of ingrowth total shoulder arthroplasty

Sixty-two primary ingrowth total shoulder arthroplasties, performed between 1989 and 1992 and with a minimum radiographic and clinical follow-up of 2 years or until the time of revision surgery (mean, 4.6 years), were reviewed. To combine data on both the distribution and the thickness of periprosthetic lucency and change in component position, criteria were used to determine whether a component was radiographically "at risk" for clinical component loosening. A glenoid component was "at risk" when a complete lucent line was present, some part of it being 1.5 mm or greater in width, or when 2 of 3 or 3 of 3 independent observers identified migration or tilt of the component. A humeral component was "at risk" when a lucent line 2 mm or greater in width was present in 3 or more of 8 zones or when at least 2 of 3 independent observers identified tilt or subsidence of the component. Four (6.5%) of the 62 glenoid components and 6 (9.7%) of the 62 humeral components were judged to be "at risk." There were no identifiable patient, disease, or surgical characteristics associated with the development of an "at risk" glenoid or humeral component. Currently, despite this very favorable radiographic assessment, we reserve the use of a tissue ingrowth glenoid component for those patients with bone loss precluding bone cement fixation with a keel type of implant. Because advantages exist for use of a tissue ingrowth humeral component, a press-fitted component with ingrowth surfaces is currently used unless bone deficiencies prevent secure fixation without cement.     

The effect of cementing technique on structural fixation of pegged glenoid components in total shoulder arthroplasty

Although loosening of cemented glenoid components is one of the major complications of total shoulder arthroplasty, there is little information about factors affecting initial fixation of these components in the scapular neck. This study was performed to assess the characteristics of structural fixation of pegged glenoid components, if inserted with two different recommended cementing techniques. Six fresh-frozen shoulder specimens and two types of glenoid components were used. The glenoids were prepared according to the instructions and with the instrumentation of the manufacturer. In 3 specimens, the bone cement was inserted into the peg receiving holes (n = 12) and applied to the back surface of the glenoid component with a syringe. In the other 3 specimens, the cement was inserted into the holes (n = 15) by use of pure finger pressure: no cement was applied on the backside of the component. Micro-computed tomography scans with a resolution of 36 microm showed an intact cement mantle around all 12 pegs (100%) when a syringe was used. An incomplete cement plug was found in 7 of 15 pegs (47%) when the finger-pressure technique was used. Cement penetration into the cancellous bone was deeper in osteopenic bone. Application of bone cement on the backside of the glenoid prosthesis improved seating by filling out small spaces between bone and polyethylene resulting from irregularities after reaming or local cement extrusion from a drill hole. The fixation of a pegged glenoid component is better if the holes are filled with cement under pressure by use of a syringe and if cement is applied to the back of the glenoid component than if cement is inserted with pure finger pressure and no cement is applied to the back surface of the component.     

Total shoulder arthroplasty: Some considerations related to glenoid surface contact

The area of prosthetic surface contact is an important surgeon-controlled variable in total shoulder arthroplasty and is related to the geometry of the glenoid and humeral articular surfaces and their relative positions. This study explores some of the factors that affect joint surface contact area. We measured the humeral and the glenoid articular surface angles in the superior-inferior and anteroposterior planes for two prosthesis systems representative of those in common clinical use. On the basis of these data we determined the range of glenohumeral positions providing full glenoid surface contact, a condition in which all of the articular surface of the glenoid component is in contact with the articular surface of the humeral component. We found a wide variability in the range of glenohumeral positions providing full glenoid contact with different prosthetic combinations. Some combinations do not even offer full glenoid surface contact with the joint in the centered position, for example, when the center of the humeral head articular surface is opposed to the center of the glenoid articular surface. The maximal range of glenohumeral positions providing full glenoid surface contact was 117° for a combination with a small radius of head curvature and a large articular surface angle. The relative positions of the humeral and glenoid articular surfaces also have a major influence on the joint contact area. Some combinations offer full glenoid surface contact only in a position of humeral abduction with respect to the scapula. Loss of full glenoid surface contact between the glenoid and humerus may allow for unwanted translations of the humeral head on the glenoid in the direction where contact is lacking. Furthermore, in positions where full surface contact is lacking, humeral bone or soft tissue may make unwanted contact with the glenoid. These results suggest that the design of the humeral articular surface and the surgical procedure should maximize full glenoid surface contact in functionally important positions.     

Treatment of periprosthetic humerus fractures associated with shoulder arthroplasty

The incidence of periprosthetic humerus fracture associated with shoulder arthroplasty is approximately 0.6% to 3%. Fractures of the humerus occur most often intraoperatively and are more common during total shoulder arthroplasty than hemiarthroplasty because of difficulties in gaining access to the glenoid. Osteopenia, advanced age, female sex, and rheumatoid arthritis are medical comorbid factors that may contribute to humerus fractures and associated delayed healing and poorer function. When the humeral prosthetic component is loose or the fracture line overlaps the majority of the length of the prosthesis, revision with a long-stem implant should be considered. When the fracture overlaps the tip of the prosthesis and extends distally, open reduction and internal fixation is recommended. When the fracture is completely distal to the prosthesis and satisfactory alignment at the fracture site can be maintained with a fracture brace, then a trial of nonsurgical treatment is recommended. The primary goals of treatment are fracture union and pain relief. Loss of glenohumeral motion has limited the successful treatment of this challenging problem.     

Baseplate placement in failed total shoulder replacement: Builder’s choice

Glenoid component loosening has been recognized as one of the common indications for revision surgery after total shoulder arthroplasty. Replacement with a standard glenoid component is sometimes possible when bone loss is minimal and contained within the glenoid vault. If glenoid bone stock is poor, more complex revision strategies include bone graft reconstruction, custom implants, and the use of augmented components. Reverse total shoulder arthroplasty has also developed into a platform for revision surgery. However, surgeons must be aware that when used for revision, complication rates are higher and survival times are shorter. Glenoid revision is technically demanding even for an experienced shoulder surgeon and may lead to early revision failures if done improperly. Shoulder surgeons must have a detailed understanding of expected outcomes, proper indications and current bone grafting techniques when attempting glenoid reconstruction.     

The effect of humeral component anteversion on shoulder stability with glenoid component retroversion

BACKGROUND: Posterior glenoid bone loss is often seen in association with glenohumeral osteoarthritis. This posterior asymmetric wear can lead to retroversion of the glenoid component and posterior instability after total shoulder arthroplasty. Options for the treatment of this asymmetric wear include eccentric reaming of the so-called high side, bone-grafting, and/or anteverting the humeral component. Although anteverting the humeral component has been advocated by many, it has not been substantiated on the basis of biomechanical data. The purpose of the present study was to determine whether anteverting the humeral component increases the stability of a total shoulder replacement with a retroverted glenoid component. METHODS: A total shoulder arthroplasty was performed in eight human cadaveric shoulders. The glenoid component was placed in 15 degrees of retroversion. Two humeral versions were tested for each specimen: anatomic version and 15 degrees of anteversion relative to anatomic version. The specimens were mounted supine in a custom fixture on a servohydraulic testing system. The humerus was translated posteriorly by one-half of the width of the glenoid. Three positions of humeral rotation were tested for each position of humeral version. Both the energy and the peak load were analyzed as measures of joint stability. RESULTS: There was no significant difference in either energy or peak load between the tests performed with the humeral component in 15 degrees of anteversion and those performed with the component in anatomic version in any of the three rotational positions (p > 0.05). CONCLUSIONS: Although anteverting the humeral component during total shoulder arthroplasty to compensate for glenoid retroversion has been advocated, these data suggest that compensatory anteversion of the humeral component does not increase the stability of a shoulder replacement with a retroverted glenoid component.     

The superolateral approach for shoulder prosthesis

We describe a superolateral approach to the shoulder for implantation of total shoulder prostheses or humeral prostheses. The advantages of this approach include preservation of the supraspinatus tendon and an excellent exposure of the posterior part of the glenoid cavity. We illustrate this approach with three clinical examples: total shoulder arthroplasty with reconstruction of the posterior part of the glenoid using a screwed autograft for central degeneration with posterior wear of the glenoid, intermediate arthroplasty for excentric degeneration with irreparable rotator cuff tears, and simple humeral arthroplasty with bone suture of the tuberosities for cephalotuberosity fracture.     

Traumatische Schultergelenkluxation (akut und chronisch)

It is essential to differentiate primary dislocation, ventral instability and chronic neglected dislocation. Open procedures are indicated only rarely and in specific cases after primary dislocation of the shoulder: with fracture of the ventral glenoid rim, huge humeral head impression fracture (reversed Hill-Sachs lesion) and rupture of the rotator cuff. Early reconstruction of rotator cuff rupture is very important for the outcome of treatment. Bony lesions of the glenoid rim are fixed with lag screws, while impression fractures of the humeral head are elevated and buttressed with cancellous bone grafts. The standard procedure for ventral shoulder instability is open reconstruction of the labrum–capsule complex according to Bankart, if necessary combined with a capsular shift and / or closure of any defect in the rotator cuff interval. The indications for rotation osteotomy according to Weber and ¶J-span plasty according to Resch are highly specific and must be strictly observed. Other procedures should be avoided. For neglected chronic dislocations, which are dorsal dislocations, no standard procedure can be defined. We prefer to perform internal rotation osteotomy of the upper arm in such cases.     

Glenoid bone-grafting in total shoulder arthroplasty

Abnormal glenoid architecture resulting from loss of bone usually is listed among the contraindications to total shoulder arthroplasty using an unconstrained prosthesis. However, in a series of 463 consecutive replacement procedures that were performed between 1973 and 1985, in only two patients did the lack of bone make the implantation of a glenoid component impossible. Of the remaining sixty-five shoulders that had an abnormal glenoid, twenty were successfully treated with a large, internally fixed bone graft or grafts and forty-five, with smaller bone grafts that were not internally fixed. Nineteen of the twenty shoulders that had a large graft or grafts were followed for two years or more (average, 4.4 years). The clinical results were judged to be excellent in sixteen and satisfactory in one, and the desired limited goals were obtained in two. Two fixation screws broke and one screw was worn by contact with the humeral component. None of the glenoid components clinically loosened or migrated, and no patient has needed further surgical treatment. Although bone-grafting was necessary in only twenty (4.3 per cent) of the 463 replacement procedures, this procedure provided sufficient osseous support to allow implantation of a component in a severely damaged glenoid.