Objectives

Unicompartmental knee replacement (UKR) is a conservative option for degenerative disease, with mobile (Oxford UKR) and fixed bearing (Physica ZUK) the most commonly used devices. The primary reasons for revising UKRs include disease progression (36.9%), loosening (31.7%), and pain (7.5%). Loosening typically occurs due to osteolysis caused by wear particles from the polyethylene (PE) inserts. There is limited published literature which has quantified volumetric material loss from the PE inserts of cemented fixed-bearing UKRs. This study aimed to quantify bearing wear and backside deformation of these PE components.

Objectives

Several studies have reported elevated blood cobalt (Co) and chromium (Cr) concentrations in patients with total knee replacements (TKRs). Up to 44% of tissue samples taken from patients with failed TKRs exhibit histological evidence of metal sensitivity/ALVAL. In simulated conditions, metal particles contribute approximately 12% of total wear debris in TKR. We carried out this investigation to determine the source and quantity of metal release in TKRs.

Objectives

We identified an unusual pattern of backside deformation on polyethylene (PE) inserts of contemporary total knee replacements (TKRs). The PE backside's margins were inferiorly deformed in TKRs with NexGen central-locking trays. This backside deformation was significantly associated with tray debonding. Furthermore, recent studies have shown high rate of tray debonding in PS NexGen TKRs. Subsequently, a field safety notice was issued regarding the performance of this particular device combination and the Option tray has been withdrawn from use. Therefore, we hypothesised that the backside deformation of PS inserts may be greater than that of CR inserts.

The introduction of robotics for total knee arthroplasty (TKA) into the operating theatre is often associated with a learning curve and is potentially associated with additional complications. The purpose of this study was to determine the learning curve of robotic-assisted (RA) TKA within a multi-surgeon team.

This prospective cohort study included 83 consecutive conventional jig-based TKAs compared with 53 RA TKAs using the Robotic Surgical Assistant (ROSA) system (Zimmer Biomet, Warsaw, Indiana, USA) for knee osteoarthritis performed by three high-volume (> 100 TKA per year) orthopaedic surgeons. Baseline characteristics including age, BMI, sex and pre-operative Kellgren-Lawrence grade were well-matched between the conventional and RA TKA groups. Cumulative summation (CUSUM) analysis was used to assess learning curves for operative times for each surgeon. Peri-operative and delayed complications were reviewed.

The CUSUM analysis for operative time demonstrated an inflexion point after 5, 6 and 15 cases for each of the three surgeons, or 8.7 cases on average. There were no significant differences (p = 0.53) in operative times between the RA TKA learning (before inflexion point) and proficiency (after inflexion point) phases. Similarly, the operative times of the RA TKA group did not differ significantly (p = 0.92) from the conventional TKA group. There was no discernible learning curve for the accuracy of component planning using the RA TKA system. The average length of post-operative follow-up was 21.3 ± 9.0 months. There was no significant difference (p > 0.99) in post-operative complication rates between the groups.

The introduction of the RA TKA system was associated with a learning curve for operative time of 8.7 cases. Operative times between the RA TKA and conventional TKA group were similar. The short learning curve implies this RA TKA system can be adopted relatively quickly into a surgical team with minimal risks to patients.

Introduction

We aimed to identify genes associated with the development of ALVAL at relatively low levels of wear.

Background

Some reports have suggested that debris generated from the head neck taper junction is more destructive than equivalent doses from metal bearing surfaces.

Introduction

In this study, we aimed to investigate the effect of the topography of the female taper surface on taper wear.

Background

Previous studies have suggested that the modular junction of metal on metal (MoM) total hip replacements (THR) is an important source of metallic debris.

Background

We have previously described the relationship between wear rates of MOM components and soft tissue necrosis. In this study we investigated the link between wear rates, metal ion concentrations and osteolysis.

Background

The failure and subsequent withdrawal of the ASR device in both its resurfacing and THR form has been well documented. The National Joint Registry report of 2010 quoted figures of 12–13% failure at five years. Adverse reaction to metal debris (ARMD) is a poorly understood condition and patients developing severe metal reactions may go unrecognised for sometime.

Introduction

Adverse reaction to metal debris (ARMD) is an increasingly recognised complication of metal-on-metal hip arthroplasty. A previous study described poor results following revision and recommended early intervention¹. We determined the outcome of revision for ARMD and present the largest case series to date.

Introduction

We conducted independent wear analysis of retrieved metal on metal (MoM) hip components from around the world. All patients with resurfaced hips who developed adverse reactions to metal debris (ARMD) were found to have increased wear of the bearing surfaces. This was untrue in patients with large diameter (?36mm) MoM total hip replacements. This led us to search for other factors leading to ARMD.

Objectives

An ongoing prospective study to investigate failing metal-on-metal hip prostheses was commenced at our centre in 2008. We report on the results of the analysis of the first consecutive 126 failed mated total hip prostheses from a single manufacturer.

There is widespread concern regarding the incidence of adverse soft-tissue reactions after metal-on-metal (MoM) hip replacement. Recent National Joint Registry data have shown clear differences in the rates of failure of different designs of hip resurfacing. Our aim was to update the failure rates related to metal debris for the Articular Surface Replacement (ASR). A total of 505 of these were implanted.

Kaplan-Meier analysis showed a failure rate of 25% at six years for the ASR resurfacing and of 48.8% for the ASR total hip replacement (THR). Of 257 patients with a minimum follow-up of two years, 67 (26.1%) had a serum cobalt concentration which was greater than 7 μg/l. Co-ordinate measuring machine analysis of revised components showed that all patients suffering adverse tissue reactions in the resurfacing group had abnormal wear of the bearing surfaces. Six THR patients had relatively low rates of articular wear, but were found to have considerable damage at the trunion-taper interface. Our results suggest that wear at the modular junction is an important factor in the development of adverse tissue reactions after implantation of a large-diameter MoM THR.

Introduction: The senior author undertakes single stage revision hip arthroplasty for cases with no preoperative evidence of infection based on history and examination, ESR and CRP results and negative results from selective aspirations. Despite this a large proportion of intra-operative samples are positive for infection. The purpose of our study is to look at the results of intra-operative histology and microbiology samples in these cases and to assess the subsequent incidence of infection.

Methods: Retrospective case study comprising of 230 single stage revision total hip arthroplasties carried out by a single surgeon over 5 year period (2003–2008). Intra-operatively tissue samples were taken from multiple sites and sent for both histology and microbiology. Microbiology results were reported at 24hrs, 48hrs, 7 days and 21 days and correlated with histology reports.

Results: From a total number of 230 patients, we had 98 left and 132 right hip revision arthroplasties. There were 95 men and 135 women with a mean age of 73 years (range 40–93). Intra-operative microbiology was negative in 108 patients (46.95%), of which 3 patients’ histology samples were consistent with infection. Of the 122 microbiology positive patients (53.04%), there were 8 histology samples consistent with infection. The most frequent growths were of Coagulase negative Staphylococcus (64 cases) and Propionibacterium (18 cases). 3 cases subsequently developed deep infection.

Discussion: This study highlights a significant discrepancy between intra-operative microbiology and intra-operative histology results. There is also a very high discrepancy between pre-operative assessment and intra-operative microbiological findings although the majority of cases subsequently did not show any clinical evidence of infection.

Introduction: The Corail stem is a well proven femoral implant used for the past 22 years. It is the most common uncemented femoral stem used for total hip replacements in the UK. The stem was modified in 2004 with an increased neck taper to allow for an increased range of bearings and modular heads. This study reviews a series of primary total hip replacements using this recently modified Corail stem to assess if this implant is still performing to acceptable standards.

Method: A prospective patient database collated by 2 arthroplasty surgeons recorded data at the time of operation and subsequent follow up. All intra-operative and post-operative complications were recorded. Pre and postoperative oxford hip scores were analysed.

Results: 751 cases were reviewed. The average age was 63 with females accounting for 69%. The pinnacle cup was used in 83% of cases, with a polyethylene bearing in 48%. Survival of the stem at 3 years was 99.9% (1 periprosthetic fracture following a fall), the cup 99.6%, with overall survival of 99.5%. The most common intra operative complication was calcar fracture occurring in 0.9%. Dislocation occurred in 0.5%, subsidence in 0.3%, deep infection in 0.1% and leg length discrepancy requiring shoe raise in 0.1%. Average 3 year oxford hip score was 12.

Discussion: 3 year survival of both the femoral stem and the total hip replacement are above the quoted rates in the National Joint Registry’s 4th annual report for corail and uncemented stems (98.8% and 98.1% respectively), and also exceeds that of cemented stems (99.1%). The same report quotes similar rates of calcar fractures (0.8%), although we recorded no other perioperative complications. We conclude the new generation of Corail stem has excellent 3 year performance.

Nerve blocks are a common form of peri-operative analgesia that is administered for patients undergoing joint Replacement surgeries. The long term sequel following these peripheral nerve blocks used in total knee replacement not reported in the literature. Nerve blocks given under the guidance of nerve stimulators are in practice in most of the hospitals and are considered safe.

We report a series of two cases with residual neurological deficit following these peripheral nerve blocks in total knee replacements. In both these cases the femoral, sciatic, obturator and lateral cutaneous nerve of thigh were blocked with 0.25% of Bupivacaine with the help of a nerve stimulator.

First patient post operatively had residual numbness in the right lower leg after 4 weeks of surgery. Nerve conduction studies confirmed absent response in right Saphenous and superficial peroneal nerves. Patient has no improvement in her neurological deficit even after 16 months post operatively. Further to this she developed complex regional pain syndrome on the affected side.

Second patient post operatively developed knee extensor weakness of grade II/V and loss of sensation in femoral nerve distribution. Nerve conduction studies confirmed severe femoral nerve damage around groin. She went through a turbulent phase, knee stiffness range of movements 0–20 degrees requiring Manipulation Under Anaesthesia, later Exploration and Release of adhesions which improved her range of movements to 0–95 degrees. At 12 months post operative the neurological status improved to grade 3/5 in knee extensors.

Conclusion: Long term Complications of Peripheral nerve blocks in total knee replacements are not reported in the literature. These complications though uncommon, unfortunately for patients affect the surgical outcomes. The purpose of this case series is not only to report complications but also to share our experience of managing these complications, their outcomes and relevant literature review.