Shoulder & Elbow

Glenoid fracture still an issue in shoulder arthroplasty

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The longevity of total shoulder arthroplasty is usually considered to be limited by the glenoid component. The large forces placed across a small surface area (in traditional arthroplasty) and large lever arm (in reverse arthroplasty), both resisted by the relatively slight bone seen in the glenoid, are more often than not the cause of wear, loosening and failure. The advent of more modern materials, in particular polyethylene bearings which can form carbon-carbon cross-links between polyethylene molecules during irradiation, changes to glenoid designs and different joint kinematics have potentially improved the longevity of these components and their functional outcomes. There is, however, a wide array of component designs, and material scientists in Berkeley (USA) have set out to establish which of these design variations are associated with mechanical failure and fracture.¹ This interesting and insightful study is based on the retrieval of 16 glenoid components, all presenting with fracture. The implants consisted of a range of materials, including gamma-sterilised Hylamer and ultra-high-molecular-weight polyethylene (UHMWPE), and gas plasma-sterilised, remelted, highly cross-linked (HXL) UHMWPE, and a range of conformities between a 0 mm and 10 mm radial mismatch. The explanted components were subjected to highly detailed analysis including scanning electron microscopy (SEM) and oxidative analysis. There was a common pattern of failure with fracture at the rim of the component for all 16 explanted components, and significant oxidative change was seen in the components subjected to gamma sterilisation. However, this was not seen in the HXL glenoid component. Fracture at the rim of the glenoid component in traditional total shoulder arthroplasty is still clearly a problem, despite evolution in component design. Whilst this paper cannot quantify the problem, it is interesting and important to note that the failure mechanisms remain the same, with the exception that heat annealing does appear to reduce the rates of oxidative degradation in the glenoid component.

Glenoid retroversion and pathology

Little is known about posterior instability, other than the associations with fits and electrocution. The reasons why some patients suffer from unidirectional posterior instability are far from clear. Given that there is a natural range of glenoid versions, it would be reasonable to expect that if the glenoid version varies, this is likely to impact on shoulder stability. Researchers in Boston (USA) have investigated the impact of glenoid version relative to the scapula body and the effect that this has on stability of the shoulder.² The authors report three groups of patients: those with anterior pathology (33 patients), those with posterior instability or glenoid labral tears (34 patients) and a number of normal controls (30 patients). Version was established with plain films using a variety of methods. Despite the potential for inaccuracy in this methodology, there was a 5° greater posterior version (-9° vs -4°) in the control group. This patient group is essentially a retrospective cohort study that establishes an association between posterior version and unidirectional instability. Although there is no clear take home message from a clinical standpoint, the observation of association alone is enough to raise some extremely interesting questions.

How long is long enough? Stemmed shoulder arthroplasties

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The effects on bone loading of implant design have become the province of computer scientists and engineers. Gone are the days of following plain films for years to establish what the long-term effects are. Despite the significant advances in computer modelling, this has rarely translated into generic design feature evaluations – the technology is more often used to design or prove the design benefits of one particular implant. We were delighted to see this paper from London, Ontario (Canada) which was devised to evaluate the benefits or otherwise of longer-stemmed humeral components.³ The authors used digital imaging and communications in medicine (DICOM) standard CT images to construct finite element analysis models of five patients with short, standard and stemless humeral components, and then simulated loading in various degrees of shoulder abduction. The aim was to establish the level of stress transfer to the humerus. Results were reported as average with bone stresses at eight transverse slices as a percentage of intact values. As perhaps would be expected, the shorter stems matched the normal humeral loading better than the longer stems. This paper very capably and succinctly summarises the effects on biomechanical loading although it doesn’t tell us anything about other design constraints such as fixation. However, it has brought the issue back into orthopaedic discussion. This kind of comparative generic biomechanical computer-modelled study provides an insight into specific design features that would not be investigated with industry-run studies.

Steroids apparently not great in bursitis

Some of the most common conditions in orthopaedics are those with the poorest evidence for treatment and the most debated best treatment choice. We were delighted to see this randomised controlled trial from Goyang-si (South Korea) which asks the question, do steroid injections have any benefit over compression bandaging in the non-operative management of olecranon bursitis?⁴ The authors recruited 90 patients from two centres, all of whom had confirmed non-infected olecranon bursitis and were allocated to receive one or other treatment on a 1:1 basis for the three interventions tested: compression bandage and NSAIDs, aspiration alone, or aspiration with steroid injection. There was some attrition with seven patients lost to follow-up, making some of the groups rather small. Outcomes were assessed using the VAS pain scale and signs of symptom resolution. Broadly speaking, the authors didn’t see any difference with either group in their study. However, three-way studies are always notoriously difficult to power adequately, and the authors here appear to have performed a retrospective power calculation, concluding that they were only adequately powered to detect a 30% difference in the primary outcome measure, suggesting that this study is hugely underpowered. Although we would commend the authors for selecting an interesting and relevant topic for their study, it is somewhat surprising that they have then sadly chosen not to adequately power the study.

When surgery of the olecranon fails

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The olecranon is a fracture that is not very tolerant of failure. The fracture itself can be difficult to stabilise, and with large eccentric forces crossing the joint, the metalwork failure rate is not insignificant. To top it all, the thin and mobile soft-tissue envelope is prone to irritation and infection and, as such, the re-intervention rate is also quite high. Surgeons in Boston, Massachusetts (USA) utilised their large in-hospital registry to identify 392 patients, all with operative treatment of an isolated olecranon fracture, with the intention of identifying factors that are associated with both implant removal and re-operation.⁵ The patients had a combination of plate fixation (n = 138; 35%) and tension band wiring (n = 254; 65%). Outcomes were assessed at a minimum of four months, and in that time one quarter of patients had required further intervention. The predictors of the need for further surgery were well explored by the authors, and re-operation was more common in women than men (64% vs 36%) and younger patients, and the same was true for patients requesting metalwork removal.

Designing the best total elbow arthroplasty

Total elbow arthroplasty (TEA) can sometimes be a poisoned chalice. Done well, it can provide reliable and satisfactory performance for a range of diagnoses including degenerate and traumatic indications. However, the excellent pain control and range of motion achievable in modern devices belies the short lifespan and restrictions in upper limb weight-bearing imposed by most surgeons to improve outcomes. The survival of TEAs is inextricably linked to the inherent design of most modern arthroplasties, with large torsional and tension forces dissipated across a small bearing surface. In what is an excellent review article from the Hospital for Special Surgery, New York (USA), the authors walk through current implant designs and review the limitations, expanding indications and challenges faced by surgeons, patients and device manufacturers in the coming years.⁶ This is an excellent read from a world-leading centre and we would thoroughly commend the article to the 360 readership.

Can septic arthritis of the shoulder be treated with closed suction drainage?

Septic arthritis of the shoulder can be a challenging diagnosis, particularly when the infection includes the other spaces around the shoulder such as the subacromial space. Effective debridement and lavage can be difficult to achieve, leaving the patient at risk of recurrence. These surgeons in Seoul (South Korea) report their experience of treating septic arthritis using a predominantly closed suction drainage method.⁷ The surgical team performed a fairly aggressive debridement on 68 patients, combined with arthrotomy and irrigation. A suction drain was placed in the glenohumeral joint and left in place for an average of 24 days at a constant negative pressure of 15 cm H2O. This strategy appeared to be rather successful with a reported cure rate (in combination with around five weeks of antibiotics) of 98%. The authors conclude that their approach provides reliable eradication of the infected joint with little in the way of recurrence. Nonetheless, we would inject a note of caution; nearly four weeks of closed suction drainage isn’t without its morbidity, and the presence of a drain in the joint for that period may well accelerate any future arthritic change. Slightly less enthusiastically than the authors, we would perhaps recommend this as a reasonable option for patients in whom traditional methods have failed as it certainly does appear to have an excellent outcome here in terms of clearance of the primary septic arthritis.

Depression hinders outcomes in total shoulder arthroplasty

There doesn’t seem to be much in the way of positive news for the depressed with regard to their health outcomes. Surgeons at NYU Hospital for Joint Diseases, New York (USA) conducted a study to explore the link between depression and outcomes in total shoulder arthroplasty (TSA).⁸ The study team used the US National Inpatient Sample to identify 224 060 patients undergoing elective TSA. There was a pre-existing incidence of depression of 12.4% in those patients, which was associated with significant independent risks for post-operative complications, including delirium (OR 2.29), anaemia (OR 1.65), infection (OR 2.09) and discharge to an alternate location (OR 1.65). Due to the large sample size, all of these observations were of course highly significant. It is interesting that this incidence of pre-operative depression is associated with poorer post-operative results in the selected outcome measures that were used in this study. Whilst the study of course only establishes an associative link, rather than a causation, there is a clear message here: patients with depression are at higher risk of complications, and perhaps this should be taken into consideration when making treatment decisions.

Link to article