Friday, February 5, 2016

Revision shoulder arthroplasty

Revision shoulder arthroplasty: does the stem really matter?

These authors retrospectively reviewed 40 revision shoulder arthroplasties. They did not find significant differences in blood loss, drop in hemoglobin level, need for blood transfusion, or hospitalization time between stemmed and surface replacements.  Reoperation were performed in 3 patients in the surface replacement group.

Comment: Revision arthroplasty is a challenge and the results depend on many factors. These authors point out the difficulties in removing well fixed humeral stems. Our approach to stem removal is shown in this link, including the use of the bodice repair:
In performing our own arthroplasties, we use impaction grafting to preserve bone and facilitate revision (should it become necessary) as shown in this link


Does the literature support surgery for shoulder arthritis?

Is there sufficient evidence to support intervention to manage shoulder arthritis?



The authors searched the literature published between 2002 and 2012 for Level 1 and 2  research studies concerning the management of shoulder arthritis to identify whether current management recommendations are adequate. As an indication of the lack of standardization in shoulder arthroplasty management, the authors point out that in the UK, the rates of TSA and hemiarthroplasty are approximately one-tenth and one-fifth the respective rates in the USA.

Sixteen studies met the inclusion criteria but they did not provide a clear indication of best intervention for shoulder arthritis.

The inclusion of a range of shoulder pathologies in some studies and the diversity in outcome measures used made it difficult for systematic reviews to effectively pool data. The outcome scales used in the studies varied widely, confounding comparisons between studies.

While better outcomes were reported with total shoulder replacement over hemiarthroplasty for shoulder osteoarthritis, the studies were often of limited quality. The type of glenoid component used in total shoulders employed had impact on revision rates, with 6.8% of TSAs with metal backed glenoids requiring revision compared to 1.7% of TSAs with polyethylene glenoids. For 'biological resurfacing' the overall complication rate was 13.3% and the re-operation rate was 26%, which was higher than the reported values for other treatment options.Sparse evidence was available for all other interventions, regardless of whether operative or non-operative.

The authors point to the need for standardization of outcome assessment following treatment of shoulder arthritis and find that more rigorous and robust primary studies are needed to guide clinical practice on the best interventions for arthritis of the shoulder.

Comment: The results of management for the patient with shoulder arthritis are influenced by the characteristics of the shoulder problem, the patient, the procedure and the physician performing the
procedure (the 4Ps). While the authors state that "determining the effectiveness of nonsurgical treatments, the optimal timing of surgical intervention and the effectiveness of surgical interventions would be best achieved by conducting large, multicentre randomized clinical trials," we suggest that such a process is unlikely to be put in place for many logistical, ethical and fiscal reasons. Instead we propose an approach that would increase the value of the commonly performed level III and Level IV studies: if each study provided in online appendix data for each case (including the characteristics of the shoulder problem, the patient, the procedure and the physician) as well as the outcome scale results before and after surgery, then the patients could be included as individuals in a combined analysis that would avoid the limitations of 'between study' comparisons.

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Thursday, February 4, 2016

Does acromioplasty adversely affect glenohumeral mechanics?

The effect of coracoacromial ligament excision and acromioplasty on the amount of rotator cuff force production necessary to restore intact glenohumeral biomechanics.

These authors noted that coracoacromial ligament (CAL) excision and acromioplasty increase superior and anterosuperior glenohumeral translation. In 9 cadaver shoulders they found that at 150 to 200 N of anterosuperior loading, CAL excision and acromioplasty increased the rotator cuff force required to maintain normal glenohumeral biomechanics by 25% to 30%.


Comment: We always like to recall the quote from the father of shoulder surgery:


In a series of our own experiments (including one in which loads were measured in vivo) we were able to show that superiorly directed loads applied to the humerus were proportionally resisted by loading of the acromion 



In another experiment we showed that acromioplasty was followed by 8 mm of superior translation and increased contact pressure (decreased contact area) with the residual acromion.


The combination of acromioplasty and cuff deficiency can lead to anterosuperior escape.

More on the importance of the coracoacromial arch can be seen on this link.

The bottom line is that the CA arch provides important superior stability to the shoulder.



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Shoulder fusion - conversion to reverse?

Once an arthrodesis, always an arthrodesis?

These authors present four patients (2 men, 2 women; age 46-66 years) with a longstanding shoulder arthrodesis (5-11 years) and periscapular pain. The shoulders were fused in 60 to 80 degrees of abduction, 20 to 40 degrees of flexion, and 40 to 50 degrees of internal rotation. Preoperative EMG showed activity in at least the posterior or middle parts of the deltoid, or both.

The patients were satisfied; the Constant-Murley scores were modestly improved from 15-21 to 30-60; rotation was somewhat increase. Pain did not disappear but decreased considerably, from visual analog scale 8-10 to 0-4. No dislocations were noted.

Comment: It is interesting that these shoulders had been fused in extreme positions of abduction and moderate flexion so that substantial winging of the scapula would have been necessary  for the patient to adduct the arm to a rest position by the side. Because such positions of fusion are usually productive of periscapular pain and difficulties lying flat or sitting in a firm-backed chair, our preferred position of fusion is 0-15 degrees of flexion, 0-15 degrees of abduction and sufficient internal rotation so that the hand can easily reach the mouth and zipper.

While shoulder arthrodesis is not commonly performed these days, it remains an alternative. The position of arthrodesis needs to be carefully considered in light of the discussion above, which is in contrast to the ‘conventionally recommended’ position. In performing an arthrodesis, our current technique seeks to preserve the deltoid by avoiding an acromiohumeral plate (in the event that subsequent conversion to an arthroplasty may be considered down the line). 



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Total shoulder arthroplasty: glenoid component wear and rim failure


Analysis of severely fractured glenoid components: clinical consequences of biomechanics, design, and materials selection on implant performance

These authors studied 16 retrieved glenoid components that had failed because of severe fracture. The fractures primarily occurred along the exterior rim. Fourier transform infrared analysis and fractography revealed significant oxidative embrittlement for all gamma-sterilized glenoids (gamma-sterilized Hylamer; gamma-sterilized UHMWPE) leading to crack inception and subsequent fracture. By contrast, fatigue striations and internal flaws with little oxidation detected were evident on the fracture surfaces of the gas plasma-sterilized, remelted, highly cross-linked UHMWPE [HXL]), suggesting that brittle fracture resulted from a combination of elevated contact stress due to nonconforming surfaces, internal flaws, and reduced resistance to fatigue crack growth.

Comment: This article demonstrates the frailty of the glenoid component under rim loading. This frailty can manifest in terms of (1) rocking horse loosening, (2) cold flow deformity of the rim or (3) fracture. Avoiding rim loading requires careful attention to optimizing the relationships between the humeral and glenoid surfaces as well as the stability of the articulation.

Three prior articles are among those of interest in this regard. Their abstracts are reproduced here

Intrinsic stability of unused and retrieved polyethylene glenoid components.
The surface geometry of polyethylene components can be altered by in vivo use. The purpose of this investigation is to document the effects of these changes on the intrinsic stability provided by the glenoid component. We validated a method of measuring the intrinsic stability of glenoid components as indicated by the balance stability angle (the maximal angle between the glenoid centerline and the resultant humeral force before dislocation of the humeral head occurs). We compared observed values with those predicted for unused glenoid components for which the geometry was known. We then applied this method to retrieved glenoid components in which the surface geometry had been altered by in vivo use. The balance stability angles measured in retrieved glenoids were often substantially reduced: 11 of 24 glenoids had diminished balance stability angles of at least 30% in at least one direction. We concluded that the surface geometry of polyethylene glenoid components can be altered by in vivo use in a manner that may compromise their contribution to glenohumeral stability.

Observations on retrieved polyethylene glenoid components.
It is recognized that retrieved polyethylene hip and knee components may undergo substantial changes from their preimplantation form. Little information is available, however, regarding retrieved polyethylene glenoid components. We report on 39 glenoid components removed at an average of 2.5 years after implantation. Of components for which clinical data were available, the commonest reason for the revision arthroplasty was loosening of the glenoid component; many components also showed glenohumeral instability. The articular surface contours of most of the components were altered. Of components, 28 had obvious erosion of the rim, 27 had surface irregularities, 11 were fractured, and 9 had central wear. These observations in retrieved glenoid components point to the potential of polyethylene for deformation in vivo, especially when the mechanics of the arthroplasty are compromised.

Alterations in surface geometry in retrieved polyethylene glenoid component.
This study characterized and quantified the changes found in retrieved glenoid polyethylene components found at revision total shoulder arthroplasty (TSA). Twenty components obtained at revision TSA were evaluated, all from a system (Global, DePuy, Warsaw, IN) with a glenoid radius of curvature 3 mm greater than that of the humeral head. Laser surface scanning provided three-dimensional analysis of the surface of the glenoid component. Scans of unused components of similar sizes enabled determination of the changes occurring after implantation. Alterations in radius of curvature were noted in every glenoid. All showed loss of the balance stability angle (BSA, the maximal angle that the net humeral joint reaction force can make with the glenoid center line before the humeral head would dislocate) of at least 5 degrees in one or more directions. Increase in BSA in one direction was seen in 11 of the components. In five of these, the increase was associated with a reduction of the local radius to match that of the humeral component. Glenoid surface morphology and stability can be changed by in vivo use. While correlation with clinical instability in the patients from whom the implants were obtained was not possible, many of the observed changes in surface morphology are of sufficient magnitude to compromise the contribution of the glenoid surface to shoulder stability. Three patterns of wear were identified: "humeral" that showed loss of the mismatch between the humeral and glenoid radii of curvature (5 of 20 components), "diffuse" that showed broad surface irregularity (18 of 20), and "rim" wear with loss of the polyethylene rim of the component (14 of 20). More than one type of wear was possible within a single glenoid.

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Rotator cuff tears - does inflammation account for the pain?

Association of synovial inflammation and inflammatory mediators with glenohumeral rotator cuff pathology

These authors point out that chronic inflammation has recently been recognized as a source of joint pain and dysfunction in those with pathologies previously considered purely degenerative. They hypothesized that patients with full-thickness rotator cuff tears would have greater synovial inflammation compared with those without rotator cuff tear pathology, with gene expression relating to histologic findings.

Synovial sampling was obtained from a common site within the rotator interval after anterior portal establishment in 19 patients with full thickness rotator cuff tears (RTC group) and in 11 patients without rotator cuff pathology (control group).

The synovitis score was significantly increased in the RTC group compared with controls. Immunofluorescence demonstrated significantly increased staining for CD31, CD45, and CD68 in the RTC vs control group. CD45+/68– cells were found perivascularly, with CD45+/68+ cells toward the joint lining edge of the synovium. Levels of matrix metalloproteinase-3 (MMP-3) and interleukin-6 were significantly increased in the RTC group, with a positive correlation between the synovitis score and MMP-3 expression. No correlation was found between the synovitis score and tear size or Goutallier classification nor between MMP-3 levels and AP tear size, amount of retraction, or Goutallier classification for those with cuff tears.

The authors concluded that shoulders with full-thickness rotator cuff tears had greater levels of synovial inflammation, angiogenesis, and MMP-3 upregulation compared with controls. Gene expression of MMP-3 correlated with the degree of synovitis.

Comment: These results indicate an association between synovial inflammation and cuff tears; they do not indicate whether synovial inflammation contributes to the development of cuff tears or vice versa. Nevertheless, this association may help understand the effectiveness of anti-inflammatory medications in the management of symptoms from rotator cuff pathology. It may also help explain the mechanism by which the smooth and move procedure (which includes the excision of inflammatory tissue in the humeroscapular motion interface) leads to improved comfort and function of shoulders with cuff tears, even though the tear itself is irreparable.

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"Expert' rotator cuff surgeons, what do they say about rotator cuff surgery?

A Survey of Expert Opinion Regarding Rotator Cuff Repair.

Rotator cuff tears are a common shoulder problem among people older than sixty years of age. The American Academy of Orthopaedic Surgeons published clinical practice guidelines for optimizing the treatment of rotator cuff problems based on a systematic review of the current literature (see this link). However, many of those recommendations were inconclusive because of the lack of high-level evidence. The purpose of this study was to determine common clinical practices among 372 members of the American Shoulder and Elbow Surgeons and the Association of Clinical Elbow and Shoulder Surgeons  regarding rotator cuff repair. 111 surgeons (29.8%) completed all or part of the survey.

Comment: 

There are some interesting aspects of the results of the survey. Among them:

(1)  91% of the respondents report operating on patients who are smoking in spite of the evidence that smoking is associated with an increase rate of cuff tear and repair failure.

(2) 87% of the shoulder surgeons did not routinely use an imaging modality to assess healing of their rotator cuff repairs, yet the respondents felt comfortable quoting healing rates of 80-90% for tears < 2 cm, 70-80% for tears 2-4 cm, and 50-60% for tears >5 cm; this is in spite of the fact that these healing rates are higher than those reported by high quality studies in which post operative imaging was carried out.

(3) the majority of respondents allow their patients on Worker’s compensation to return to work at 6 months after rotator cuff surgery, a delay substantially longer that that used in a recent study (see this link) that assumed that workers lost an average of only twenty-eight additional days as a result of rotator cuff repair compared with those undergoing nonoperative treatments.

(4) A consensus response (>50% agreement) was achieved on only 24 of 49  (49%) of the questions. 

As pointed out recently (see this link), better evidence on the factors affecting the outcomes of the treatment of rotator cuff tears will require that we do a better job of collecting the data that are available.
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