Lateralization in reverse total shoulder

Lateralized Reverse Shoulder Arthroplasty Maintains Rotational Function of the Remaining Rotator Cuff

In this paper the authors sought to determine the rotational moment arms, the origin-to-insertion distances of the teres minor and subscapularis, and the flexion and abduction moment arms. In seven cadaveric shoulder specimens. Three-dimensional shoulder surface models were created from CT scans before and after implantation. The implant investigated is shown below.

                      

Inspection of this illustration in relation to the scaplar anatomy makes us wonder how contact between the medial humeral component and the lateral scapula (notching) is avoided with this implant. 

While the authors did not examine the effects of non-lateralized glenospheres in this study, a prior study, Reverse shoulder arthroplasty leads to significant biomechanical changes in the remaining rotator cuff., found that moment arms for humeral rotation were significantly smaller for the cranial segments of the subscapularis and the teres minor in abduction angles of 30 degrees and above. Origin to insertion distances were significantly smaller for all muscles. These findings may  be a possible explanation for the clinically observed impaired external and internal rotation when the center of rotation

In their study, the authors achieved lateralization using an 8 mm thick block implanted between the baseplate of the glenosphere and the glenoid. Not only does this lateralization reduce the risk of notching but the authors found that after lateralized reversed total shoulder arthroplasty, the subscapularis and teres minor maintained their length and rotational moment arms, their flexion forces were increased, and abduction capability decreased. They suggested that these finding might  explain clinically improved rotation in lateralized RSA in comparison to nonlateralized reverse total shoulders. 

It is of interest that different designs of reverse total shoulder result in different locations of the center of rotation, these differences result in differences in stability and as this recent article shows, differences in the moment arms for the residual external rotators. Thus it is important to understand these effects and to know the reverse system you are using. Some designs of reverse total shoulder have the lateralization built into the design of the glenoid component, so that a bone graft (with possible risk of resorption or collapse) is not needed.

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A complication-based learning curve from 200 reverse shoulder arthroplasties. CORR

A complication-based learning curve from 200 reverse shoulder arthroplasties.

This is a very important article. It details the odyssey of an experienced shoulder surgeon to learn to do the reverse total shoulder. The concept of a learning curve is critical to every surgical procedure - how can individual surgeons achieve mastery? It is important to recognize that the learning curve is not only about surgical technique, but also about patient selection, in-hospital management, and rehabilitation.

As shown in the figure below from this article, experience is a great teacher. The rate of local complications was over 20% for the first 40 shoulders and less than 7% for the last 160 shoulders.

The most common complications were transient neuropathy, intraoperative fracture, postoperative dislocation, incompletely seated glenosphere, intraoperatively broken screw head, broken drill bit, chronic subluxation, acromion fatigue fracture, and painful cerclage wires.  Perioperative systemic complications occurred in 5% of the cases.

Part of the learning curve may be reflected in changes in the prosthesis selected. In this study all patients received a Grammont-style RTSA prosthesis, but between shoulders 16 and 25 the surgeon gradually transitioned from one manufacturer to another and between shoulders 73 and 160 there was another transition. Each prosthesis has its own learning curve.

This study brings to the fore the topic of surgeon experience and case volume. It has been shown that the quality of outcome is related to surgeon case volume. The explanation may like in the fact that low volume surgeons remain at the left hand side of the learning curve shown above.

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Subscapularis Release in Shoulder Replacement Determines Structural Muscular Changes CORR

Subscapularis Release in Shoulder Replacement Determines Structural Muscular Changes CORR

This is an interesting paper in that it considers the effect of detachment and reattachment of the subscapularis via bone block on the structure and function of the muscle in 37 shoulders having total shoulder arthroplasty by a highly experienced surgeon. The authors remarked that the bone block detachment method allowed excellent access to the glenoid for reaming and all lesser osteotomies healed. One patient had a greater tuberosity fracture and one a large hematoma - these did not appear to affect the outcome.

Preoperatively, 60% of the shoulders had fatty atrophy (47% grade 1 fatty atrophy and 13% grade 2). At a minimum of 13 months (mean 18 mo) after shoulder arthroplasty 56% of the muscles showed fatty degeneration (39% grade 1, 14% grade 2 and 3% grade 3).  The cross sectional area of the muscle was reduced by 13%. These findings appeared to be of clinical significance: the post operative Constant-Murley score correlated with the fatty degeneration of the subscapularis muscle (r = -0.496; p = 0.002)  and the ratio of the anterior (subscapularis) to posterior (intraspinatus-teres minor) cross sectional area (r = -0.600; p<0.001).

Many approaches have been described for the takedown and repair of the subscapularis for shoulder arthroplasty, including tendon detachment from bone, tenotomy and lesser tuberosity osteotomy. Each method requires attention to the technique of the procedure; each has its own set of risks; and each has an effect on access to the glenoid. These authors report favorable results with what they refer to as a "C-block osteotomy" of the lesser tuberosity. They have provided some benchmarks against which other methods can be compared with respect to complications, technical difficulty, healing rates, muscle structure, and clinical function.

Perhaps the most important message from this paper is that the health of the subscapularis does matter in terms of the quality of the result. In our efforts to optimize the post-surgical health of this muscle-tendon-bone construct, we must consider its preoperative status, the technique of detachment and reattachment, the degree and method of soft tissue release, early protection/mobilization and the subsequent rehabilitation.

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Are Shoulders with A Reverse Shoulder Prosthesis Strong Enough? A Pilot Study CORR

Are Shoulders with A Reverse Shoulder Prosthesis Strong Enough? A Pilot Study CORR

This is an important study that attempts to correlate function with strength after a Reverse total shoulder arthroplasty. The study population was 37 shoulders in 33 patients having 21 primary and 16 revision Tornier reverse total shoulders. The shoulders were evaluated a 4 - 63 months after surgery. The postoperative SST for primary reverse total shoulders was 8 ± 4 in contrast to 4 ± 3. 

While the average shoulder could generate 15 Nm of abduction/adduction torque, only 14 shoulders could be tested for internal and external rotation torque; for those the average external rotation torque was 9.3 Nm. Interestingly the authors correlated measured maximum torque at 60 degrees/second with the Dutch version of the Simple Shoulder Test. Their results are shown below, showing that the strongest correlation of the SST was with external rotation torque:

By design, the reverse total shoulder displaces the center of rotation medially and distally to optimize the deltoid moment arm for elevation. However, this medial displacement puts the anterior and posterior deltoid and any residual rotator cuff at a mechanical disadvantage for rotation.

In reverse total shoulder arthroplasty, design does matter. As we pointed out in a recent post and here,  different component designs have different effects on the position of the center of rotation - both superiorinferiorly (which affects deltoid tension) and mediolaterally (which affects stability, the proximity of the medial aspect of the humeral component to the glenoid, and the moment arms for rotation).

This study suggest that strategies be developed for optimizing the abduction and rotator strength of shoulders with reverse total shoulders. Such strategies may include prosthesis design and placement, muscle transfers and special rehabilitation protocols.

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Does Augmentation with a Reinforced Fascia Patch Improve Rotator Cuff Repair Outcomes? CORR

Does Augmentation with a Reinforced Fascia Patch Improve Rotator Cuff Repair Outcomes? CORR

This is a study of the surgical repair of surgical incomplete (2/3 rds) release and acute repair of the infraspinatus tendon in young dogs. Thus it is not a study of 'rotator cuff repair outcomes' and the model is quite different than the clinical situation we encounter where the issue is usually a chronic defect with tendon tissue loss in individuals older than 60 years. The authors acknowledged support of the Musculoskeletal Transplant Foundation, which makes the patches used in this series of experiments.

Identical lesions were created on each side of the dogs' shoulders, one one side, the repair was reinforced with a "novel poly-L-lactic acid-reinforced (human) fascia patch" and the other without. It is of note that this patch was applied over a robust tendon to bone repair and was not used to bridge a defect in the rotator cuff or to reinforce a tenuous repair.  At 12 weeks, the ultimate load of augmented  repairs was 16% less than nonaugmented repairs.

Curiously, the authors conclude that "... these findings support the possibility that reinforced fascia patches would incorporate and provide (at least early) mechanical augmentation to rotator cuff repair in human patients." However, the value (benefit to the patient/cost) of the patches now commercially in rotator cuff surgery remains to be demonstrated in the clinical situation.

The most interesting aspect of this paper was the retraction of the tendon stump from the osseous repair site - even in this ideal rotator cuff repair model.  As early as three months after the repairs, 4 of 11 non augmented repairs and 6 of 11 augmented repairs had retracted by a centimeter or more! These results again emphasize how difficult it is to achieve durable reconstruction of the anatomy of the tendon insertion - even under idealized circumstances.

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Rotator Cuff Integrity Correlates With Clinical and Functional Results at a Minimum 16 Years After Open Repair. CORR

Rotator Cuff Integrity Correlates With Clinical and Functional Results at a Minimum 16 Years After Open Repair. CORR

This article reports on 67 patients average age 52 years having rotator cuff repairs. Tears involved the supraspinatus only (53%), the supraspinatus and infraspinatus (36%), the supraspinatus, infraspinatus, and subscapularis (6%), and the supraspinatus and subscapularis (4%). These were chronic tears with an average time from onset of symptoms to repair of 2.4 year. Tear size at surgery was measured in two directions in 43 patients: 23 tears measured 9 square centimeters or less and 20 tears measured greater than 9 square centimeters. Free tendon grafts were used in 52 of the 67 shoulders.

At a minimum followup of 16 years, the full thickness re tear rate was 94%; the remainder had partial thickness re tears. None of the repairs were fully intact at followup. Simple shoulder test results at followup were 9.1 for re tears with an area of 4 square centimeters or less and 7.6 for re tears with an area over 4 square centimeters (p .069). Preoperative SST data were not available.

These repairs were performed between 1980 to 1989, so it could be argued that the repair methods were below the standard of those used today. On the other hand, it can be pointed out that we do not have anywhere close to this duration of followup on current attempts to repair cuff defects of this magnitude. 

We must continue to try to define when it is worth trying to repair a rotator cuff defect and when a smooth and move would be preferable.

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Does Open Repair of Anterosuperior Rotator Cuff Tear Prevent Muscular Atrophy and Fatty Infiltration? CORR

Does Open Repair of Anterosuperior Rotator Cuff Tear Prevent Muscular Atrophy and Fatty Infiltration? CORR

This article reports results of 23 shoulders with combined tears of the supraspinatus and upper subscapularis repaired with open surgery. The supraspinatus was repaired to a trough, the biceps was usually tenodesed, and the subscapularis was repaired to the lesser tuberosity. At a minimum of 36 months, two of the supraspinatus repairs had failed. Successful repair did not prevent the progression of fatty infiltration. Post operative Constant scores were not related to the degree of fatty infiltration.

These are important lesions to distinguish from isolated supraspinatus tears for two reasons: (1) repair of the subscapularis seems important to prevent propagation of the tear and (2) biceps instability is always a concern because of the likely disruption of the the transverse humeral ligament. Two of our former colleagues prepared a masterful treatise on the anatomy of this area: Tendons, ligaments, and capsule of the rotator cuff. Gross and microscopic anatomy. Read it!

Once again we see a that, in spite of the technique of repair, failure of cuff repairs is not uncommon. See our previous posts on this topic.

Finally, since we're talking recently about the value equation (benefit/cost), it is time that we question the value of MRI's and ultrasound examinations to assess fatty infiltration/fatty atrophy. We are having difficulty understanding how these findings inform clinical decision-making in the management of cuff pathology. Is this assessment valuable?

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How Much Are Upper or Lower Extremity Disabilities Associated with General Health Status in the Elderly? CORR

How Much Are Upper or Lower Extremity Disabilities Associated with General Health Status in the Elderly? CORR

This paper uses a population of 272 individuals without a history of surgery for musculoskeletal disease or trauma to test the hypothesis that the DASH score (Disabilities of the Arm Shoulder and Hand - a self-reported measure of upper extremity comfort and function) is correlated with the SF 36 (a self-reported measure of overall well-being. Not surprisingly, the results of the two are correlated, the DASH is particularly associated with the physical component summary scale of the SF 36.

In that there was no documentation of the presence of upper extremity disability in these individuals, one might expect that the observed effect would have been even stronger in those with known rotator cuff tears, arthritis, carpal tunnel syndrome and the like. We have previously reported on the correlation of comorbidity with function of the shoulder and health status of patients who have glenohumeral degenerative joint disease and on the relationship of the SF 36 and shoulder function in degenerative disease and rheumatoid arthritis.

What was particularly interesting was the effect of gender and age on the DASH. Recalling that a score of 0 is no disability and 100 is total disability, males averaged a score of 15.67 ± 13.34 while women average 27.07 ± 20.00 (p<0.001). Individuals aged 65 to 75 averaged 19.60 ± 17.20 while those over 75 averaged  24.68 ± 18.80 (p<0.029).  This indicates that, in contrast to the usual practice, DASH scores need to be normalized by age and gender and that combining ages and genders in reporting results may lead to erroneous conclusions.

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Immediate Postoperative Radiographs After Shoulder Arthroplasty Are Often Poor Quality and Do Not Alter Care CORR

Our ability to continue to provide the best care to our patients requires that we focus on every aspect of the value equation: benefit/cost. The authors of this paper do just that – they ask are recovery room x-rays worth the money? In their experience a single underpenetrated internal rotation view of the shoulder taken in the recovery room did not change their postoperative care or serve as a useful baseline for follow-up studies. The average cost of these films was $228/patient. An example might be something like this

 We agree that such a film is of limited value. By contrast, they found films in multiple projections (internal rotation and external rotation AP, scapular Y, and axillary views) taken 2-7 weeks after surgery to be of greater use, although neither the cost nor the value of these films was documented.

Our experience is a bit different. First of all many of our patients leave town on discharge, so that the opportunity to obtain a film in the weeks after surgery is limited. Secondly we carefully position the patient for an AP in the plane of the scapula and an axillary view, obtaining high quality films that not only confirm the desired position and relationship of the components, but also serve as a baseline for followup studies.

Below is an example of PACU radiographs on a patient from the Southeastern United States who came to Seattle this week for a ream and run procedure.

These views enabled us to verify the excellence of the reshaping of the glenoid, the position of the implant in the humeral shaft, the relation of the humeral head to the glenoid, and the absence of fractures. We were able to provide copies of these films to the patient and to review them with him and his wife before they left the medical center several days after surgery. They will hand carry them to show his referring physician back home.

So the title of this paper is a bit of an over generalization. The data apply to the specific practice of the authors.

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To What Degree do Shoulder Outcome Instruments Reflect Patients’ Psychologic Distress? CORR

To What Degree do Shoulder Outcome Instruments Reflect Patients’ Psychologic Distress? CORR

This is an important question – if we are using an instrument to measure the status of our patients, we need to understand what all is being measured by the measurement.

The authors correlated measures of psychological distress, depression and anxiety with commonly used measures of shoulder function in 119 patients with chronic shoulder problems. The authors found that the Constant-Murley score (which includes assessments of pain, function, range of motion and strength) correlated highly with range of motion, pain and strength and less with psychological factors – not surprising. The Simple Shoulder Test and DASH (which are patient self-assessments of comfort and function without measurements of range of motion or strength) were more heavily influenced by psychological factors. The tempting conclusion is that the differences observed are related to the inclusion of range of motion and strength measurements in the Constant score which overwhelm the effect of the psychologic factors. The authors could have examined this possibility by repeating the analysis of the Constant score without the strength and range of motion components.

Shoulder conditions and psychological conditions are each common, so it is expected that many individuals will have both, even in the absence of a cause-effect relationship. Furthermore, it is expected that an individual with a chronic shoulder issue will experience distress as a result. Finally, psychological distress (for example about job related issues) would be expected to intensify the impact of a shoulder condition on an individual’s assessment of his/her shoulder function.

Patients often ask, “how much of my problem is in my head and how much is in my shoulder?”. Our answer is “we can’t know, but our task is to consider you as a whole person – shoulder and head included”. As the authors of this study might suggest, individuals with substantial psychological distress may benefit from management of this component along with or even before management of the shoulder issue.

As for the relative value (benefit/cost) of different ‘outcome instruments’, we favor the SST because it provides a quick and inexpensive patient self-evaluation of shoulder comfort and function. Since our goal is to improve self-assessed comfort and function, we can measure our success (whether by non-operative or non-operative means) in terms of the change in SST score. The Constant score and the DASH are more expensive to administer and to record; this study does not provide evidence that either of these generates data that is more useful than the SST.

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