In metal-on-metal (MoM) hip arthroplasties and resurfacings, mechanically induced corrosion can lead to elevated serum metal ions, a local inflammatory response, and formation of pseudotumours, ultimately requiring revision. The size and diametral clearance of anatomical (ADM) and modular (MDM) dual-mobility polyethylene bearings match those of Birmingham hip MoM components. If the acetabular component is satisfactorily positioned, well integrated into the bone, and has no surface damage, this presents the opportunity for revision with exchange of the metal head for ADM/MDM polyethylene bearings without removal of the acetabular component. Between 2012 and 2020, across two centres, 94 patients underwent revision of Birmingham MoM hip arthroplasties or resurfacings. Mean age was 65.5 years (33 to 87). In 53 patients (56.4%), the acetabular component was retained and dual-mobility bearings were used (DM); in 41 (43.6%) the acetabulum was revised (AR). Patients underwent follow-up of minimum two-years (mean 4.6 (2.1 to 8.5) years).Aims
Methods
In metal-on-metal (MoM) hip replacements or resurfacings, mechanical induced corrosion can lead to a local inflammatory response, pseudo tumours and elevated serum metal ions, requiring revision surgery. The size and diametral clearance of Anatomic (ADM) and Modular (MDM) Dual Mobility bearings matches that of certain MOM components. Presenting the opportunity for revision with exchange of the metal head for ADM/MDM bearings without removal of the acetabular component if it is well-fixed and appropriately positioned. Between 2012 and 2020, across two centres, 94 patients underwent revision of a MoM hip replacement or resurfacing. The mean age was 65.5 (33–87) years. In 53 patients (56.4%), the acetabular component was retained, and dual mobility bearings were used (DM); in 41 (43.6%) the acetabulum was revised (AR). DM was only considered where the acetabular component was satisfactorily positioned and well-integrated into bone, with no surface damage. Patients underwent clinical and radiographic follow-up to at least one-year (mean 42.4 (12–96) months). One (1.1%) patient died before one-year, for reasons unrelated to the surgery. In the DM group, two (3.8%) patients underwent further surgery; one (1.9%) for dislocation and one (1.9%) for infection. In the AR group, four (12.2%) underwent further procedures; two (4.9%) for loosening of the acetabular component and two (4.9%) following dislocations. There were no other dislocations in either group. In the DM group, operative time (68.4 v 101.5 mins, p<0.001), postoperative drop in haemoglobin (16.6 v 27.8 g/L, p<0.001), and length of stay (1.8 v 2.4 days, p<0.001) were significantly lower. There was a significant reduction in serum metal ions postoperatively in both groups (p<0.001 both Cobalt and Chromium) although there was no difference between groups for this reduction (p=0.674 Cobalt; p=0.186 Chromium). In selected patients with MoM hip arthroplasty, where the acetabular component is well-fixed, in a satisfactory position and there is no surface damage, the metal head can be exchanged for ADM/MDM bearings with retention of the acetabular prosthesis. Presenting significant benefits through a less invasive procedure, and a low risk of complications, including dislocation.
Many worldwide regulatory authorities recommend regular surveillance of metal-on-metal hip arthroplasty patients given high failure rates. However concerns have been raised about whether such regular surveillance, which includes asymptomatic patients, is evidence-based and cost-effective. We determined: (1) the cost of implementing the 2015 MHRA surveillance in “at-risk” Birmingham Hip Resurfacing (BHR) patients, and (2) how many asymptomatic hips with adverse reactions to metal debris (ARMD) would have been missed if patients were not recalled. All BHR patients subject to the 2015 MHRA recall (all females, and males with head sizes 46mm or below, regardless of symptoms) at one specialist centre were invited for review (707 hips). All patients were investigated (Oxford Hip Score, radiographs, blood metal ions, and targeted cross-sectional imaging) and managed accordingly. Surveillance costs were calculated using finance department data, as was the number needed to treat (NNT) to avoid missing one case of asymptomatic ARMD.Introduction
Methods
In August 2007 NICE issued its guidance for the treatment of patients with knee osteoarthritis (OA) with arthroscopic lavage. The recommendations stated that referral for arthroscopic lavage and debridement should not be offered as part of treatment for osteoarthritis, unless the person has osteoarthritis with a clear history of ‘mechanical locking’ (not gelling, giving way, or x-ray evidence of loose bodies). The aim of this study was to assess both the application of these guidelines over a four month period and whether this procedure had improved symptoms at first follow-up. This was a retrospective review from August-December 2011. The total number of arthroscopies performed during this period was obtained from theatre records. Further data was obtained through the hospital's electronic database. The diagnosis of OA was made through the analysis of referral and clinic letters, plain radiographs, MRI reports and operation notes. Only those patients with persisting OA symptoms were included, those with OA and recent history of injury or trauma were excluded. During this time period, 222 knee arthroscopies were performed in total, 99 were identified with persistent OA symptoms. Having identified these patients, referral letters were further analysed to identify the initial presenting symptom. Of the 99, 50 presented with pain, 28 presented with pain plus another symptom other than locking e.g. stiffness/swelling/giving-way, 21 presented with pain plus mechanical locking. According to current guidelines only these 21 patients should have been offered arthroscopic lavage as a form of treatment. In addition to these findings we identified what procedures had been carried out during arthroscopy for each symptom. Of those presenting with pain, 82% had a washout and debridement, 8% had washout, 4% had partial medial meniscectomy, 4% had lateral patellar release and 2% had partial lateral meniscectomy. Those with pain plus other symptoms not including locking, 82% had washout and debridement, 11% had partial medial meniscectomy, and 7% had a washout. Of those presenting with pain plus mechanical locking, 81% had washout and debridement and 19% had partial medial meniscectomy. Following the procedure, we analysed the outcome of symptoms at first-follow up. The mean follow-up time was 8 weeks. Of those presenting with just pain, 44% showed improvement, 52% had no change/on-going symptoms, 2% were unknown. Of those with pain plus other symptoms other than locking, 57% showed improvement, 35% had no change/on-going symptoms, 8% unknown. Of those with pain plus mechanical locking, 80% showed improvement, 10% had no change/on-going symptoms, 10% unknown. The results of this study support the current evidence that unless there are clear mechanical symptoms of locking, the use of arthroscopy in arthritic knee joints should be judicious and the reasons should be clearly documented.
