Introduction

Little guidance exists regarding the minimum screw length and number necessary to achieve fixation with reverse shoulder arthroplasty (rTSA). The goal of this study is to quantify the pre- and post-cyclic baseplate displacements associated with two baseplate designs of different sizes using multiple screw lengths and numbers in a low density polyurethane bone substitute model.

The results of revision TSA do not historically match the results of primary TSA. This is especially true if the diagnosis is a soft tissue related problem that leads to the revision. When a revision TSA is considered in this setting, instability is the major problem to overcome and a reverse TSA is most often needed. In the past this would require that the glenoid and humeral components be removed. Some manufacturers have produced shoulder prosthetic systems that can be converted to a reverse TSA without removing the humeral stem making the revision surgery potentially easier for both the patient and the surgeon.

The data bank from two academic shoulder services were utilised to compare outcomes of revision TSA with and without removing the humeral stem at the time of revision surgery. Sixty-seven patients were identified in which 22 did not have the stem removed and 45 required the stem to be revised. The pre-operative and post-operative data for 1 and 2 years were available. Codman's scores, range of motion, estimated blood loss, time in the operating room, complications and cost of the implants were evaluated.

The average blood loss was 280 cc vs. 500 cc, 145 minutes vs. 211 minutes, constant scores were 32 pre-op and 75 post-op vs. 32 pre-op and 70 post-op, complications 0 vs. 9 and the cost of the implants were 23% more in the stem removal group.

The results of revision TSA do not match the results of primary arthroplasty. The results of not having to remove the humeral stem when doing a revision arthroplasty vs. using a system that has to remove both components has certain advantages. The overall outcome score are similar, however, the complication rate, blood loss, time in the operating room and cost of the implants are significantly less.

Scapular spine fracture is a serious complication of reverse total shoulder arthroplasty (RTSA) often caused by a fall on an outstretched arm or a forced movement to the shoulder. The incidence of scapular fractures occurring after RTSA is reported between 5.8% and 10.2%. These fractures have been classified into 3 discrete fracture patterns. Avulsion of the anterior acromion (Type I), Acromion fractures (Type II) and Scapular spine fractures (Type III). This discussion will review the incidence of these post-operative peri-prosthetic fractures of the scapula after reverse TSA and describe potential treatment options and prevention methods to avoid this complication.

We know little regarding the long head of the biceps tendon's function but it is generally felt that it serves as a humeral head stabiliser by resisting superior migration during shoulder elevation. In total shoulder arthroplasty (TSA) the long head tendon is most commonly tenodesed as some have reported post-operative pain generated from an intact long head tendon.

How does tenotomy or tenodesis of the long head tendon after TSA effect superior translation of the humeral head? We do not know the answer to this or if this increased tension causes any increase in subscapularis tendon failure. This will be presented as a possible reason to not remove the long head tendon of the biceps during TSA.

Introduction

The clinical impact of scapular notching is controversial. Some reports suggest it has no impact while others have demonstrated it does negatively impact clinical outcomes. The goal of this clinical study is to analyze the pre- and post-operative outcomes of 415 patients who received rTSA with one specific prosthesis (Equinoxe; Exactech, Inc).

Before reverse shoulder replacement was an option for rotator cuff tear arthropathy the treatment modalities were limited to injections and physical therapy for pain control, arthroscopic debridement with or without biceps tenodesis/tenotomy and hemiarthroplasty. Functional improvement was limited with these treatment options and success for pain control was moderate at best. The destructive nature of the rotator cuff deficient shoulder continued with medialization of the glenoid and erosion of the acromion seen even after replacement with hemiarthroplasty. The end result usually left the patient with a pseudo paralysis of the shoulder region functionally and uncontrolled pain that made later revision with a reverse implant difficult or impossible.

Reverse arthroplasty was released for use in United States in 2004 for rotator cuff tear arthropathy. This initial procedure had a number of related complications that have been improved on over time with changes in implant design and better operative techniques. The long term results with reverse total shoulder arthroplasty have made this the procedure of choice for contained cuff tear arthropathy.

Reverse total shoulder arthroplasty has become popular for primary replacement in complex proximal humerus fractures. Hemiarthroplasty and open reduction and internal fixation (ORIF) with locked plating were the treatment of choice but with variable functional outcomes and concerns of glenohumeral arthritis, rotator cuff problems, and tuberosity healing difficulties. This is especially concerning in the older population that has a higher incidence of rotator cuff problems and poor bone quality. Reverse total shoulder arthroplasty has resulted in excellent pain relief and seems to have a more consistent functional outcome in early reports when compared to hemiarthroplasty.

Complication rate after total shoulder arthroplasty ranges around 10%. These can be divided into intra-operative and post-operative complications. Intra-operative complications are periprosthetic fracture, nerve injury and malpositioning of components. Post-operative complications are instability, infection, rotator cuff tear, periprosthetic fracture, aseptic loosening, stiffness, heterotopic ossification and implant dissociation. The most effective means of preventing a complication are meticulous pre-operative planning, experience of the surgeon, adherence to sound surgical technique and intelligent patient selection and education.

Revision shoulder arthroplasty for failure secondary to soft tissue problems has improved with the availability of the reverse total shoulder system. The initial concept of a platform (convertible) stem was introduced in 2006. Removal of a well-fixed humeral stem can be a significant challenge and may require the surgeon to use osteotomy windows to successfully remove the implant. The increased time in the operating room, potential for complications and the cost of replacing the humeral component are all factors that make platform stem use a important consideration. The first report on total shoulder arthroplasty revision utilizing the platform stem concept confirmed improvements in patient morbidity and decreased costs. However, the overall functional improvement did not reveal a statistically significant improvement in pain relief or range of motion compared to those patients that had the humeral stem revised. Almost all major companies have adopted this concept of a convertible stem system for shoulder arthroplasty.

Contracture of the anterior musculature causes posterior humeral head subluxation and results in a posterior load concentration on the glenoid. This reduced contact area causes glenoid wear, humeral medialisation and eventually posterior instability. After arthroplasty that does not correct for this, posterior wear stress increases in the implant, across the cement mantle and bone thus increasing the risk of aseptic loosening over time.

Correction of the posterior wear pattern at the time of arthroplasty of the shoulder is recommended. Asymmetric reaming of the glenoid has been recommended as a means to correct this deformity but leads to producing a smaller glenoid which is medialised. This shortening of the glenoid causes the stabilising muscle envelope to shorten and the glenoid vault to become much smaller in volume. These potential changes may have a destabilising effect on the implant leading to early loosening and secondary failure of the prosthetic implant.

Other options include using an implant to make the correction of the deformity such as augmented glenoid components. Early uses of these implants were not successful mainly due to the design flaws of the early implants. Newer implants have made design changes to overcome these early failures. CT scan evaluation is important to determine the degree of correction that is needed to balance the glenohumeral joint. Correcting the deformity and keeping the muscle envelope at the appropriate tension may lead to better long term outcomes. These implants are currently in use but long term outcome studies are not yet available to determine their ultimate values to the patients.

Indications for total shoulder arthroplasty (TSA) require that the patient have a functioning rotator cuff to stabilise the glenohumeral joint. Without rotator cuff integrity the prosthesis will be unstable and the functional result will be less than expected. Physical exam can be difficult in the arthritic shoulder as contractures will limit the range of motion needed to adequately exam the rotator cuff status. The diagnosis can help as osteoarthritis has a 5% incidence of rotator cuff tear while rheumatoid arthritis has an incidence of greater than 40%. MRI can be obtained to determine the rotator cuff status before arthroplasty is performed but may not be necessary. Most total shoulder implant companies have both reverse and anatomic implants available. More recently the uses of platform stems that can be used with either RSA or TSA have been available. With this development in prosthetic design it is no longer necessary to determine the status of the rotator cuff before surgery. The surgeon can make the decision at the time of surgery which implants RSA or TSA will be necessary based on the status of the rotator cuff. There have been recent reports of longer follow up of TSA patients that had fatty atrophy of the infraspinatus muscle that had rotator cuff tears at 10–15 years. MRI may still be warranted in the older individual that is being considered for TSA to determine the quality of the rotator cuff musculature.

Reverse shoulder arthroplasty (RSA) was released into the United States market in 2004 for the indication of Rotator Cuff Tear Arthropathy. Since that time the indications have widened and now include massive rotator cuff tears that are not deemed to be surgically repairable. This diagnosis includes patients that are considered young in terms of shoulder replacement surgery. These patients do not have the radiographic changes of arthropathy, but most have undergone multiple surgical procedures in the past to attempt to repair the rotator cuff deficiency. These younger patients have a different post-op expectation than the patient with advanced arthropathy over the age of 70.

The complication rate seen in this younger patient population is higher than seen in the older population undergoing RSA. The post-operative survey for satisfaction is also considerably lower in the younger population group.

RSA for massive rotator cuff tears in a younger population under the age of 65 years gives a lower patient satisfaction result and a higher complication rate than age-matched patients older than 65 years. Although this is still the best procedure available for this difficult diagnosis, patients younger than 65 years should be consulted as to what their expectations are post-operatively. Pain relief is still the main reason to undergo an RSA.