Hip & Pelvis

Hip arthroplasty more complicated in the mentally unwell

A small piece in the hemiarthroplasty puzzle

A second look at cement in trauma

A fresh look at resurfacing?

It is easy to confuse the concerns surrounding metal-on-metal arthroplasty and the concept of hip resurfacing. The complication profile is different, and although the two often go hand in hand, given the tribological restrictions on larger bearing surfaces it is important perhaps to remember that resurfacing as a concept does not necessarily require a metal-on-metal bearing, and that difficulties with many resurfacings are due to the tribology of the bearing surface and not necessarily the concept itself. At a time when hip resurfacing has largely fallen from favour due to concerns over adverse reactions to metal debris, it is interesting to read this series describing the seven- to ten-year results of a metal-on-polyethylene (MoP) hip resurfacing arthroplasty system. Running the risk of high wear rates due to adhesive wear, large sliding distances and restrictions on the thickness of the polyethylene, ‘hard-on-soft’ resurfacing was largely abandoned in the 1990s due to the high wear rates associated with the larger head size. However, things have moved on in surface technologies and hence surgeons from Washington (USA) have reported their results of a prospective series of 190 patients (all of whom were self-selecting) who underwent hip resurfacing rather than total hip arthroplasty.⁴ The series reports hip resurfacing using highly cross-linked polyethylene, with the rationale that the perceived improvement in wear properties of the highly cross-linked polyethylene may allow for the potential benefits of hip resurfacing without the drawback of a metal-on-metal bearing surface. Although some previous authors and surgeons have expressed serious concerns over the possibility for delamination and catastrophic failure within the weight-bearing portion of the acetabular liner when manufactured from polyethylene, this particular series certainly makes a reasonable case for such a system. Survivorship at between seven and ten years was 97%, and perhaps more importantly there were substantial improvements in patient satisfaction scores following the procedure. A subgroup of 51 patients also underwent metal artefact reduction CT scanning post-implantation as part of osteolysis surveillance, and CT visible osteolysis rates were found to be only in the region of 2%. While further evaluation and longer-term follow-up are clearly required for wider interest to develop in the use of such a system, these early results are certainly promising, suggesting that with a few design tweaks, resurfacing as a concept may not be consigned to the scrapheap just yet.

Tranexamic acid in hip arthroplasty surgery

Reducing complications in anterior hips

The overwhelming success of total hip arthroplasty is one of the medical miracles of the 20th century. However, despite the great benefits that can be achieved, surgeons continue to innovate in attempts to improve what is one of the most successful medical treatments. Use of the direct anterior approach to the hip (DAA) is gaining popularity, mainly due to perceived benefits of earlier post-operative recovery and the lower dislocation rate associated with a technique that is muscle sparing. The steep learning curve and reported complications in the hands of an inexperienced surgeon have discouraged experienced surgeons from trying ‘something new’. The common complications associated with the DAA include femoral shaft fracture, component misalignment, anterior dislocation and wound complications, with some series reporting an incidence as high as 9% for major complications and a 6.5% early re-operation rate. Using what the authors from Juntendo University (Tokyo, Japan) rather hopefully term ‘countermeasures’⁶ may, however, reduce these complications and help keep the unwary out of trouble. The measures evaluated in this study include: exclusion criteria for DAA; no positioning table; use of fluoroscopy; and experienced assistant having performed over 100 procedures. The authors also excluded the procedure for surgeons new to the DAA in patients with a previous history of osteotomy, or femoral abnormality (Perthes, or developmental dysplasia) and soft-tissue contractures. The modified technique described utilised fluoroscopy to aid in the osteotomy level of the neck, reaming of the acetabulum and position of the components during both trial and implant insertion. The authors applied this technique to three surgeons starting to undertake DAA, and reported the results of the first 40 procedures performed by each using their ‘countermeasures’. As perhaps would be expected, there was a fairly long operating time of 117+/- 27 minutes, and over one minute of fluoroscopy was used. Amazingly, however, the authors report no intra-operative complications and no re-operations. There was one late anterior dislocation which was treated by a closed reduction and had no further dislocation. Having compared their early results with those in the published literature, the authors concluded that they had demonstrated a lower complication rate by employing these four measures.

Having your cake and eating it? The outcomes of ERAS

Hip dislocation due to ‘silent’ trunnion corrosion

It is always tempting when things don’t quite work out, and the patient suffers a complication, to find a reason or excuse as to why this might have happened. We can admit to being slightly cynical here at 360 on encountering this report on ‘silent’ trunnion corrosion being responsible for late hip dislocation. However, in what is a short paper describing ten cases of hips revised in Vancouver (Canada), the authors make a fairly compelling argument that pseudotumour formation can be seen in metal-on-polyethylene hips, and that this can present as a late dislocation.⁸ The authors present a case series of ten MoP THAs with delayed dislocation, and demonstrated that pseudotumour is an infrequent (and often unsuspected) but important contributor to delayed instability following MoP THA. In their series, the patients presented at around five years following primary hip replacement, and in all cases there was histological confirmation of adverse local tissue metal reaction. The authors make the valid point that pseudotumour formation, due to its rare incidence in MoP hips, is often not on the list of differential diagnoses, however, malaligned components can result in increased trunnion forces and fretting corrosion, just as they can at an articulating surface. It is clearly better to establish this diagnosis prior to revision, as the rates of complications are high and a revision of this nature would ideally be undertaken by a surgical team experienced in the management of adverse metal reactions.