David J. Dunlop

Patient Satisfaction and Functional Status After Treatment of Infection at the Site of a Total Knee Arthroplasty with Use of the PROSTALAC Articulating Spacer

BACKGROUND Two-stage exchange arthroplasty remains the standard treatment of infection at the site of a total knee arthroplasty. The clinical and functional outcomes associated with the use of an articulating antibiotic spacer for two-stage revision for infection are not well established. We conducted a retrospective study to evaluate the outcomes associated with the use of the PROSTALAC articulating spacer between the first and second stages. METHODS Fifty-eight patients underwent two-stage revision total knee arthroplasty for infection between January 1997 and December 1999. Of these, fifty-four were alive at the time of follow-up and forty-seven were available for inclusion in the present retrospective study. In all patients, a prosthesis of antibiotic-loaded acrylic cement (the PROSTALAC system) was implanted during the first stage after débridement. The amount of osteolysis that occurred between the stages and the range of motion of the knee joint were measured. After two years of follow-up, outcomes were assessed with use of the WOMAC, Oxford-12, and SF-12 instruments as well as a satisfaction questionnaire. RESULTS At a minimum of two years (average, forty-one months) after revision arthroplasty, two patients (4%) had had a recurrence of infection. The amount of bone loss was unchanged between stages, and the range of movement of the knee improved from 78.2 degrees before the first stage to 87.1 degrees at two years. The average normalized WOMAC function and pain scores were 68.9 and 77.1, respectively; the average Oxford-12 score was 67.3; the average SF-12 mental and physical scores were 53.7 and 41.2, respectively; and the average satisfaction score was 71.7. CONCLUSION A revision operation for infection at the site of a total knee replacement with use of an articulating spacer was associated with reasonable function and satisfaction scores. These findings may be related to the articulating features of the PROSTALAC system, which permits full active movement of the knee in the early postoperative period.

Revision of Metal-on-Metal Hip Replacements and Resurfacings for Adverse Reaction to Metal Debris: A Systematic Review of Outcomes:

Purpose This systematic review assessed evidence on outcomes following revision of MoM hip resurfacings (HRs) and total hip replacements (THRs) for adverse reaction to metal debris (ARMD). Methods Four electronic databases were searched between January 2009 and July 2013 to identify studies reporting clinical outcomes following revision of MoM HRs and THRs for ARMD. Only studies reporting cohorts with more than 10 metal-on-metal (MoM) hips revised for ARMD were included. Outcomes of interest following ARMD revision were: 1) complication rates; 2) re-revision rates; 3) surgical intervention other than re-revision; 4) functional outcome. Results Of 148 unique studies identified, six studies were eligible for inclusion containing 216 MoM hips (197 HRs and 19 THRs) revised for ARMD. Mean follow-up time from ARMD revision ranged between 21-61 months. Complication rates were 4%-50% for HR and 68% for THR. Re-revision rates were 3%-38% for HR and 21% for THR. Dislocation (n = 14), ARMD recurrence (n = 11), and acetabular loosening (n = 9) were the three commonest complications and indications for re-revision. All six studies reported between one and three cases of ARMD recurrence during follow-up. One study specifically reported on performing procedures other than re-revision with 26% requiring closed reductions for dislocated THRs. Functional outcomes following ARMD revision were good or satisfactory in all but two studies. Conclusions Limited evidence exists regarding outcomes following revision of MoM hips for ARMD, especially for THRs. This should be addressed in future studies and may be important when counselling asymptomatic individuals in whom revision is considered for raised blood metal ions.

What is the significance of a positive Propionibacterium acnes culture around a joint replacement

The purpose of this study was to show the significance of a positive Propionibacterium acnes sample around a joint replacement. Records from the microbiology laboratory data over a 3-year period were reviewed to identify patients with prosthetic joints from whom Propionibacterium acnes was isolated at least once. The medical records of all those patients were retrieved and the demographic, clinical, microbiological and haematological data were collected and examined. The preoperative values of erythrocyte sedimentation rate (ESR) and C-reactive protein (CRP) were recorded. Fifty patients underwent a routine revision of a joint arthroplasty; six patients had a joint aspiration. Only one patient had further revision surgery for infection. The preoperative values of ESR and CRP were very variable. The presence of a positive sample around a joint arthroplasty is of uncertain significance. Further studies are needed in order to establish uniform criteria for the diagnosis of infection caused by Propionibacterium acnes.RésuméLe propos de cette étude était de montrer l’importance de la présence autour d’une prothèse articulaire de propionibactério acnes. L’étude des données d’un laboratoire de microbiologie sur une période de trois ans a permis d’identifier les patients porteurs de prothèses articulaires et pour lesquels la propionibactério acnes a été isolée au moins une fois. Les données médicales de ces patients mais aussi les données cliniques, microbiologiques, hématologiques ont été collectées et examinées de même que les valeurs pré-opératoires de la CRP et de l’ESR. 50 patients ont été revus, six avaient nécessité une aspiration articulaire et un une révision chirurgicale pour infection. Les valeurs préopératoires de l’ESR et de la CRP sont variables. La présence autour d’une articulation de propionibactério acnes a une signification très incertaine. Il sera nécessaire de pratiquer des études ultérieures de façon à établir les critères du diagnostic d’une infection secondaire à propionibactério acnes.

Predictors of time to revision and clinical outcomes following revision of metal-on-metal hip replacements for adverse reaction to metal debris

We undertook a retrospective cohort study to determine clinical outcomes following the revision of metal-on-metal (MoM) hip replacements for adverse reaction to metal debris (ARMD), and to identify predictors of time to revision and outcomes following revision. Between 1998 and 2012 a total of 64 MoM hips (mean age at revision of 57.8 years; 46 (72%) female; 46 (72%) hip resurfacings and 18 (28%) total hip replacements) were revised for ARMD at one specialist centre. At a mean follow-up of 4.5 years (1.0 to 14.6) from revision for ARMD there were 13 hips (20.3%) with post-operative complications and eight (12.5%) requiring re-revision. The Kaplan-Meier five-year survival rate for ARMD revision was 87.9% (95% confidence interval 78.9 to 98.0; 19 hips at risk). Excluding re-revisions, the median absolute Oxford hip score (OHS) following ARMD revision using the percentage method (0% best outcome and 100% worst outcome) was 18.8% (interquartile range (IQR) 7.8% to 48.3%), which is equivalent to 39/48 (IQR 24.8/48 to 44.3/48) when using the modified OHS. Histopathological response did not affect time to revision for ARMD (p = 0.334) or the subsequent risk of re-revision (p = 0.879). Similarly, the presence or absence of a contralateral MoM hip bearing did not affect time to revision for ARMD (p = 0.066) or the subsequent risk of re-revision (p = 0.178). Patients revised to MoM bearings had higher rates of re-revision (five of 16 MoM hips re-revised; p = 0.046), but those not requiring re-revision had good functional results (median absolute OHS 14.6% or 41.0/48). Short-term morbidity following revision for ARMD was comparable with previous reports. Caution should be exercised when choosing bearing surfaces for ARMD revisions.

The Effectiveness of Blood Metal Ions in Identifying Patients with Unilateral Birmingham Hip Resurfacing and Corail-Pinnacle Metal-on-Metal Hip Implants at Risk of Adverse Reactions to Metal Debris.

BACKGROUND We investigated whether blood metal ions could effectively identify patients with metal-on-metal hip implants with two common designs (Birmingham Hip Resurfacing [BHR] and Corail-Pinnacle) who were at risk of adverse reactions to metal debris. METHODS This single-center, prospective study involved 598 patients with unilateral hip implants (309 patients with the BHR implant and 289 patients with the Corail-Pinnacle implant) undergoing whole blood metal ion sampling at a mean time of 6.9 years. Patients were classified into two groups, one that had adverse reactions to metal debris (those who had to undergo revision for adverse reactions to metal debris or those with adverse reactions to metal debris on imaging; n = 46) and one that did not (n = 552). Three metal ion parameters (cobalt, chromium, and cobalt-chromium ratio) were compared between groups. Optimal metal ion thresholds for identifying patients with adverse reactions to metal debris were determined using receiver operating characteristic analysis. RESULTS All ion parameters were significantly higher (p < 0.0001) in the patients who had adverse reactions to metal debris compared with those who did not. Cobalt maximized the area under the curve for patients with the BHR implant (90.5%) and those with the Corail-Pinnacle implant (79.6%). For patients with the BHR implant, the area under the curve for cobalt was significantly greater than that for the cobalt-chromium ratio (p = 0.0005), but it was not significantly greater than that for chromium (p = 0.8483). For the patients with the Corail-Pinnacle implant, the area under the curve for cobalt was significantly greater than that for chromium (p = 0.0004), but it was similar to that for the cobalt-chromium ratio (p = 0.8139). Optimal blood metal ion thresholds for identifying adverse reactions to metal debris varied between the two different implants. When using cobalt, the optimal threshold for identifying adverse reactions to metal debris was 2.15 μg/L for the BHR group and 3.57 μg/L for the Corail-Pinnacle group. These thresholds had good sensitivities (88.5% for the BHR group and 80.0% for the Corail-Pinnacle group) and specificities (84.5% for the BHR group and 76.2% for the Corail-Pinnacle group), high negative predictive values (98.8% for the BHR group and 98.1% for the Corail-Pinnacle group), and low positive predictive values (34.3% for the BHR group and 20.0% for the Corail-Pinnacle group). The authority thresholds proposed by the United States (3 μg/L and 10 μg/L) and the United Kingdom (7 μg/L) missed more patients with adverse reactions to metal debris at 2.0% to 4.7% (twelve to twenty-eight patients) compared with our implant-specific thresholds at 1.2% (seven patients missed). CONCLUSIONS Patients who underwent metal-on-metal hip arthroplasty performed with unilateral BHR or Corail-Pinnacle implants and who had blood metal ions below our implant-specific thresholds were at low risk of adverse reactions to metal debris. These thresholds could be used to rationalize follow-up resources in asymptomatic patients. Analysis of cobalt alone is acceptable. Implant-specific thresholds were more effective than currently recommended fixed authority thresholds for identifying patients at risk of adverse reactions to metal debris requiring further investigation. LEVEL OF EVIDENCE Diagnostic Level II. See Instructions for Authors for a complete description of levels of evidence.

Predicting high blood metal ion concentrations following hip resurfacing.

Purpose To determine whether gender, femoral head size, acetabular inclination, and time since surgery predicted high blood metal ion concentrations following Birmingham Hip Resurfacing (BHR). Methods BHR patients with unilateral bearings at one specialist centre with blood cobalt and chromium concentrations measured up to May 2013 were included. This comprised a mixed (at-risk) group including symptomatic patients and asymptomatic individuals with specific clinical and/or radiological findings. Blood sampling was at a mean of 7.5 years (range 1-15.4 years) postoperatively. Results Of 319 patients (mean age 49.3 years; 53% male), blood metal ions greater than 7 µg/l were observed in 9% (n = 28). Blood metal ions were significantly higher in females (p<0.001), femoral head sizes ≤48 mm (p<0.01), and cup inclinations >55° (p<0.001). Linear regression demonstrated femoral head size was responsible for the highest proportion of variance in blood metal ions (cobalt p<0.001, R2 = 8%; chromium p<0.001, R2 = 11%). Analysis of femoral head size and inclination together demonstrated 36% of BHRs with head sizes of 38-44 mm and inclination >55° had blood metal ions >7 µg/l. BHR 10-year survival for this at-risk group was 91% (95% confidence intervals 86.0%-95.0%) with 30 hips revised. Conclusions If blood metal ions are used to screen hip resurfacing patients for adverse reactions to metal debris it is recommended those with small femoral head sizes (38-44 mm) and high acetabular inclinations (>55°) are targeted. These findings require validation in other cohorts as they may not be applicable to all hip resurfacing devices given the differences in radial clearance, coverage arc, and metallurgy.

Clinical outcome following surgical intervention for periprosthetic hip fractures at a tertiary referral centre

Complications following surgical intervention for periprosthetic hip fractures are not uncommon. We report the clinical outcome following definitive surgical intervention for this indication at a single tertiary referral centre. All patients admitted between 2003 and 2009 undergoing such treatment were included. Patient demographics, all surgical interventions, complications following definitive fracture treatment, and postoperative mortality were recorded. Radiographs were reviewed to determine the Vancouver classification for each fracture. There were 67 patients (mean age at revision 76.7 years; 61% female). Fractures occurred around primary total hip arthroplasties (43%), revision arthroplasties (34%), and hip hemiarthroplasties (23%). Mean time to fracture from the most recent arthroplasty performed was 7.0 years. Most fractures were Vancouver type B2 (49%). The majority of patients underwent revision total hip arthroplasty (96%), using long-stemmed prostheses or proximal femoral endoprostheses, with cables for fracture fixation. Wound infection and systemic complications were seen in 16% and 13% respectively. One or more further surgical interventions were performed in 12%. There were no deaths in-hospital or at 30-days, with 10 fatalities (15%) at a mean 2-year follow-up. Lower rates of re-intervention and mortality were observed when surgery for acute periprosthetic hip fractures was performed at a tertiary centre. Revision hip arthroplasty with or without fracture fixation proved an effective and safe treatment of periprosthetic hip fractures in a high-risk patient population.

The utility of repeat ultrasound imaging in the follow-up of metal-on-metal hip arthroplasty patients.

INTRODUCTION We assessed changes in metal-on-metal hip arthroplasties (MoMHAs) after repeat ultrasound examination. METHODS This retrospective, single-centre cohort study involved all patients undergoing two ultrasound examinations of the same MoMHA. Between 2010 and 2014, 96 ultrasound examinations were performed in 48 MoMHAs (mean time between scans = 1.1 years). A radiologist assigned each scan to one of four grades and measured volumes of any solid/cystic masses. Changes in grade and lesion volume between scans were analysed. RESULTS Change in grade between scans was significant (p=0.012); 27% (n=13) of MoMHAs increased in grade, 67% (n=32) had no grade change, and 6% (n=3) decreased in grade. The mean increase in lesion volume was 24.2cm(3) by the second scan, and was significant (p=0.023). Evidence of progression in findings was observed in 54% (26/48) of MoMHAs. Of patients with normal scans initially, 44% (8/18) developed abnormalities. No factors (including blood metal ion concentrations and cup position) were associated significantly with progression of ultrasound findings. CONCLUSIONS Repeat ultrasound in MoMHA patients demonstrated that findings frequently progress in the short-term. Therefore, regular surveillance of MoMHA patients is important, with ultrasound representing an effective investigation for identifying the development and progression of lesions.

High rates of postoperative urinary retention following primary total hip replacement performed under combined general and spinal anaesthesia with intrathecal opiate.

BACKGROUND Postoperative urinary retention (POUR) occurs frequently following hip replacement. METHODS 94 consecutive primary hip arthroplasty patients were assessed prospectively for POUR. 80 patients followed our anaesthesia protocol with combined general and spinal anaesthesia using bupivacaine and intrathecal diamorphine. RESULTS 29 instances of POUR with higher rates in men and younger patients (under-50s), independent of either pre-existing renal impairment or opiate strength. POUR was observed to increase length of stay by 1.6 days. CONCLUSIONS We report a 36% overall rate of POUR. Males demonstrated a 3-fold increased risk. Patients should be counselled pre-operatively on the risk of urinary retention.

Treatment of the Infected Total Hip Arthroplasty

: Based on our present experience, excisional arthroplasty is the most reliable option. Infections caused by organisms of significant virulence are best treated with excisional arthroplasty or Girdlestone resection followed by delayed reinsertion after adequate antibiotic treatment has controlled the sepsis, as determined by clinical and laboratory criteria. In patients with infections caused by organisms of relatively low virulence, for example, Staphylococcus epidermidis or anaerobic diphtheroids, the surgeon should seriously consider either incision and drainage, debridement, and local and systemic antibiotics if there is no component loosening, or direct exchange (removing both components and reinserting them with antibiotic cement) if there is loosening of one or both components. However, if incision and debridement or direct exchange fails, then excisional arthroplasty as a definitive procedure or as a first stage of a removal and reinsertion should be carried out. While we have not been successful in treating even early infections caused by Staphylococcus aureus with incision, drainage, and antibiotics, the morbidity associated with this procedure is extremely low compared with that of the other procedures; therefore it seems reasonable to use this modality as an emergency treatment for acute infections, with the full realization that it probably will not succeed as the definitive procedure, and the surgeon should prepare for early, more definitive surgical intervention.