Abstract

Over 8000 total hip arthroplasties (THA) in the UK were revised in 2019, half for aseptic loosening. It is believed that Artificial Intelligence (AI) could identify or predict failing THA and result in early recognition of poorly performing implants and reduce patient suffering.

The aim of this study is to investigate whether Artificial Intelligence based machine learning (ML) / Deep Learning (DL) techniques can train an algorithm to identify and/or predict failing uncemented THA.

Consent was sought from patients followed up in a single design, uncemented THA implant surveillance study (2010–2021). Oxford hip scores and radiographs were collected at yearly intervals. Radiographs were analysed by 3 observers for presence of markers of implant loosening/failure: periprosthetic lucency, cortical hypertrophy, and pedestal formation.

DL using the RGB ResNet 18 model, with images entered chronologically, was trained according to revision status and radiographic features. Data augmentation and cross validation were used to increase the available training data, reduce bias, and improve verification of results.

184 patients consented to inclusion. 6 (3.2%) patients were revised for aseptic loosening. 2097 radiographs were analysed: 21 (11.4%) patients had three radiographic features of failure.

166 patients were used for ML algorithm testing of 3 scenarios to detect those who were revised. 1) The use of revision as an end point was associated with increased variability in accuracy. The area under the curve (AUC) was 23–97%. 2) Using 2/3 radiographic features associated with failure was associated with improved results, AUC: 75–100%. 3) Using 3/3 radiographic features, had less variability, reduced AUC of 73%, but 5/6 patients who had been revised were identified (total 66 identified).

The best algorithm identified the greatest number of revised hips (5/6), predicting failure 2–8 years before revision, before all radiographic features were visible and before a significant fall in the Oxford Hip score. True-Positive: 0.77, False Positive: 0.29.

ML algorithms can identify failing THA before visible features on radiographs or before PROM scores deteriorate. This is an important finding that could identify failing THA early.

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Aims

There is little published on the outcomes after restarting elective orthopaedic procedures following cessation of surgery due to the COVID-19 pandemic. During the pandemic, the reported perioperative mortality in patients who acquired SARS-CoV-2 infection while undergoing elective orthopaedic surgery was 18% to 20%. The aim of this study is to report the surgical outcomes, complications, and risk of developing COVID-19 in 2,316 consecutive patients who underwent elective orthopaedic surgery in the latter part of 2020 and comparing it to the same, pre-pandemic, period in 2019.

Introduction

The Opera acetabular component (Smith & Nephew Ltd) shares many same design features with the Ogee (Depuy Int.). Differences are a malleable flange, instrumentation designed to improve cement pressurisation and the specifics of the UHMW-poly used.

Litigation costs are significant and increasing annually within the National Health Service (NHS) in England.

The aim of this work was to evaluate the burden of successful litigation relating to hip surgery in England. Secondary measures looked at identifying the commonest causes of successful legal action.

A retrospective review was conducted on the National Health Service Litigation Authority (NHSLA) database. All successful claims related to hip surgery over a 10 year period from 2003–2013 were identified. A total of 798 claims were retrieved and analysed.

The total cost of successful claims to the NHS was £66.3 million. This compromised £59 million in damages and £7.3 million in NHS defence-related legal costs. The mean damages for settling a claim were £74,026 (range £197-£1.6million). The commonest cause of claim was post-operative pain with average damages paid in relation to this injury being £99,543. Nerve damage and intra-operative fractures were the next commonest cause of claim with average damages settled at £103,465.

Legal action in relation to hip surgery is a considerable source of cost to the NHS. The complexity of resolving these cases is reflected in the associated legal costs which represent a significant proportion of payouts. With improved understanding of factors instigating successful legal proceedings, physicians can recognise areas where practice and training need to be improved and steps can be taken to minimise complications leading to claims.

Introduction

Traditionally it has been thought that the use of a small diameter femoral head in conjunction with a posterior surgical approach would result in a high rate of dislocation. We present the results of a consecutive series of 350 total hip replacements performed using a 22mm femoral head and a standard posterior approach, with prospective data collection.

Introduction

Varus malpositioning of femoral stems has been recognised as a poor prognostic feature with regard to loosening and failure of cemented composite beam implants, but there have been no published results of the long-term effect on taper-slip designs.

Introduction

Negative remodelling of the femoral cortex in the form of calcar resorption due to stress shielding and cortical hypertrophy at the level of the tip of the implant, due to distal load transfer, is frequently noted following cemented total hip replacement, most commonly with composite beam implants, but also with polished double tapers. The C-stem polished femoral component was designed with a third taper running from lateral to medial across and along the entire length of the implant, with the aim of achieving more proximal and therefore more natural loading of the femur. The hoop stresses generated in the cement mantle are transferred to the proximal bone starting at the calcar, which should theoretically minimise stress-shielding and calcar resorption, as well as reducing distal load transfer, as signified by the development of distal femoral cortical hypertrophy.

Introduction

Traditionally the use of small diameter femoral head (22mm) with the posterior approach has been perceived as an increased risk of dislocation. We present this prospective study of 400 consecutive total hip replacements performed using a 22mm femoral head and the posterior approach.

Negative remodelling of the femoral cortex in the form of calcar resorption due to stress-shielding, and femoral cortical hypertrophy at the level of the tip of the implant due to distal load transfer, is frequenly noted following cemented total hip replacement, most commonly with composite beam implants, but also with polished double tapered components.

The C-stem polished femoral component was designed with a third taper running from lateral to medial across and along the entire length of the implant, with the aim of achieving more proximal and therefore more natural loading of the femur. The implant is designed to subside within the femoral cement mantle utilising the cement property of creep, generating hoop stresses, which are transferred more proximally to the femoral bone, starting at the level of the medial calcar. The intention is to load the proximal femur minimising stress-shielding and calcar resorption, as well as reducing distal load transfer as signified by the lack of distal femoral cortical hypertrophy.

We present the results of a consecutive series of 500 total hip replacements using C-stem femoral components, performed between March 2000 and December 2005 at a single institution. Data was collected prospectively and all patients remain under annual follow-up by a Specialist Arthroplasty Practitioner. The operations were performed using a standard surgical technique with third generation cementing using Palacos-R antibiotic loaded cement.

500 arthroplasties were performed on 455 patients with an average age at the time of surgery of 68.3 years (23-92). There were 282 (62%) female and 173 (38%) male patients with osteoarthritis being the predominant diagnosis. 77 patients have died (73 hips) and the average duration of follow-up for the entire series is 81 months (52-124).

Only 2 femoral implants have been revised - one for deep sepsis and the other as part of a revision procedure for a loose acetabulum, although the femoral component itself was not loose. One implant is currently loose following a periprosthetic fracture treated by internal fixation, but none of the remaining implants demonstrates any progressive radiolucencies in any Gruen zones or any features suggestive of current or future loosening. Calcar rounding has been observed, but there have been no cases with obvious loss of calcar height and no cases of distal femoral cortical hypertrophy.

The C-stem femoral component has therefore performed well in clinical practice and the objective of eradicating negative bone remodelling has been achieved. The study is ongoing.

Cemented acetabular components continue to be used in more than half of the total hip replacements performed in the United Kingdom. The implants are relatively inexpensive but the results rely heavily on precise surgical technique, with restoration of the centre of rotation of the hip and the creation of an equal cement mantle with good pressurisation and penetration of the cement into the bone.

The Opera all polyethylene acetabular component was designed with a malleable flange, which could be independently pressurised, a long posterior wall to promote stability and instrumentation which ensured that pressurisation could be maintained throughout the curing process.

We present for the first time, the medium-term results of 409 consecutive cemented flanged Opera acetabular components performed in 374 patients.

247 operations were performed via a trochanteric osteotomy and 162 via a posterior approach, using multiple key holes, cement pressurisation and Palacos-R cement. Autograft was used in 32 cases.

Cemented femoral components were used in all cases. There were 241 Charnley stems with 22mm heads and 168 polished triple tapered C-stems (146 with 22mm heads and 22 with 26mm heads).

The average age at the time of surgery was 68.2 years (32–87) and the average duration of follow-up was 89 months (60–130). 54 patients (56 hips) died during the follow-up period.

The acetabulum was assessed using the zones of DeLee and Charnley, and the Hodgkinson classification.

There was one temporary femoral nerve palsy, two dislocations and 3 non-fatal pulmonary emboli.

Both components were revised in two hips for deep sepsis, and in two hips only the femoral implant was revised, one for a fractured stem and one for aseptic loosening, with the original acetabular components remaining in situ.

Of the remaining original acetabular components 6% have shown progressive radiological demarcation, none have migrated, but in two hips there is evidence of rapid wear and the development of osteolysis.

The use of polished femoral implants employing the taper-slip philosophy now dominates the cemented portion of the hip arthroplasty market in the United Kingdom. Despite this fact, there have been very few published or presented series reporting the medium to long-term results of double tapered implants and only one previously reported series looking at the results of the triple tapered stem.

We present the results of 500 consecutive polished triple tapered C-stem femoral components performed in 455 patients.

All operations were performed using a posterior appproach, with cemented all polyethylene acetabular components and the use of third generation femoral cementing techniques, restrictors, centralisers and Pala-cos-R cement.

There were 282 female patients (62%) and 173 males (38%). The average age at the time of surgery was 68.3 years (23 to 92), with an average duration of follow-up of 71 months (36 to 112). 47 patients (51 hips) died during the follow-up period at an average of 54 months (1–87).

There were 3 dislocations, 2 on one occasion and one twice, at an average of 4 years. There were 2 deep infections, one of which required revision, and 4 non-fatal pulmonary emboli. There were 3 undisplaced trochanteric cracks treated by cerclage wiring and 3 nerve palsies: 2 femoral (temporary) and one sciatic (permanent). There was only one case of significant heterotopic ossification (Brooker Class 4).

The stem was neutral in 89% of cases, varus in 7% and valgus in 4%. Subsidence within the cement mantle occurred in 79% of cases, with an average of 0.87mm. 9 stems subsided 2 to 4mm but all stopped at 2 years and there was no further subsidence thereafter.

One hip was revised for deep infection but none of the remaining implants demonstrated any progressive radiolucencies in any Gruen zones and none demonstrated any features suggestive of current or future loosening. There was no evidence of negative bone remodelling.

The data was collected prospectively and the study is ongoing.

We present the results of the polished triple tapered C-stem femoral component.

Prospective data was collected on a consecutive single surgeon series of 326 hip replacements in 293 patients performed between 2000 and 2005. All operations were performed via the posterior approach with a cemented all polyethylene acetabular component and third generation cementing of the femoral component.

There were 169 (58%) female patients and 124 (42%) males. There were 111 (34%) left sided procedures, 149 (46%) right sided and 33 bilateral (10%). Average age at time of surgery was 66.3yrs (25 – 89), with an average duration of follow-up of 50 months (12 – 78). The majority of the replacements were for osteoarthritis (271 hips 83%).

Nine patients (10 hips) died during the follow-up period at an average of 36 months (18 – 52), but outcome data was available on all patients and none were lost to follow-up. There was 1 temporary femoral nerve palsy, 2 non-fatal pulmonary emboli and 3 undisplaced trochanteric fractures. There were no dislocations, fatal pulmonary emboli, deep infections or revisions for any reason.

The stem was neutral in 90%, varus in 8% and valgus in 2%. There were no progressive radiolucencies in any Gruen zones and no distal femoral cortical hypertrophy. The average subsidence was 0.83mm, with none in 21%, < 0.5mm in 28%, 0.5 – 1mm in 41%, 1 – 2mm in 8% and 2 – 4mm in 2%.

There were no revisions and no stems demonstrated any features suggestive of current or future loosening. The study and prospective data collection is ongoing.

Many studies exist that assess intramedullary and extra-medullary fixation of these fractures, but few exist that compare the two. We performed a retrospective cohort study to compare the above implants in the management of subtrochanteric femoral fractures. 100 fractures in 95 patients were studied, with 47 in the recon nail group and 53 in the DCS group, with 33 male and 62 females, average age 68 years (16–98 years). Data was obtained by review of case notes and x-rays of all cases. The following information was obtained :- age, sex, energy/mechanism of injury, fracture classification (AO & Russell-Taylor, single observer), grade of surgeon, duration of surgery, ASA grading, co-morbidity (using Covinsky score), pre-operative mobility, postoperative mobility (using D’Aubigne & Postel score), mortality, intra-operative complications, post-operative complications, revision surgery/implant failure, follow-up and radiological assessment of reduction/implant position(single observer). Statistical analysis of the data was performed using chi-squared, Fisher’s, Mann-Whitney U and unpaired t-tests. Results showed no significant differences in co-morbidity, complications, mortality, duration of surgery, hospital stay, sex, surgical grade or pre-operative mobility. There were significant differences in age, fracture classification, radiological assessment of reduction/implant position, mechanism of injury and post-operative mobility. Overall 28-day mortality was 8%, post-op complications were seen in 54% and 19 cases required further surgery (detailed breakdown to be presented). Certain areas of bias were identified, in that the DCS had a higher number of complex fracture patterns, thus affecting post-op mobility, whereas the recon nail group had a higher proportion of pathological fractues.

Introduction: Fractures of the femoral stem component in total hip Arthroplasty have been a well documented complication. The incidence over recent years has decreased due to improvements in surgical technique and implant design and manufacture.

Methods/Results: We report two cases of femoral stem fracture. Both occurred in CDH stems from the C-stem system (Depuy International, Leeds, UK). These are the first reported fractures in this stem. Both patients were women weighing 83kgs and 98kgs at the time of fracture giving them BMI’s of 31 and 41 respectively. In both cases the BMI had increased since the time of operation.

Discussion: The design of the CDH stem is fundamentally different from the rest of the standard stems with absence of the medial strut. In addition to this factor, both stems fractured through the insertion hole which acted as a stress raiser. Finally both patients BMI’s were above 25. At the time of operation no weight limit was imposed on this prosthesis.

We conclude that if possible, a standard C-stem should be inserted but if a CDH stem is used attention to patients’ weight is paramount.

Introduction: The Opera Acetabular cup (Smith and nephew) was designed in North Manchester General and has been in use since 1997. The initial results were with multiple surgeons, different approaches and 2 different stems. We report the early results of the opera cup in primary hip replacements using the C-Stem.

Methods: This is a prospective radiological follow up of patients operated on between June 2000 and November 2004. 202 consecutive primary hip replacements were carried out using the Opera cup and a standard C-stem. All operations were performed by a single surgeon using the posterior approach. Initial and annual x-rays were studied and the following measurements taken: cup angle; radiolucent lines in the bone-cement interface of the acetabulum; heterotopic ossification; radiolucent lines or osteolysis in the femoral component and stem orientation.

Results: Full data is available in 166 hips performed on 149 patients. Average follow up is 37 months (12–65). 84 patients were female and 65 male. There were 56 left hip replacements, 76 right hip replacements and 17 were bilateral. 162 hips had an elite head whereas 4 had a ceramic head. Average cup angle was 44.6 degrees. 20 Cups had 0.5mm lucency in zone 1 of the acetabulum and 1 cup had 1mm lucency in zone 1. None were progressive. 14 patients had grade 1 heterotopic ossification 3 patients had grade 2. 1 stem was in valgus and 13 stems were in varus.

Complications were 1 calcar fracture and 1 greater trochanter fracture (both of which required circlage wires). There was also 1 temporary femoral nerve palsy which resolved in 3 months. There were no fatal PE’s, deep infections or dislocations. No hips have required revision.

Discussion: We conclude that in the short term the Opera cup is performing to the standard required by NICE.