The association between pre-operative pain sensitisation and chronic pain after knee replacement: an exploratory study.

OBJECTIVE: Chronic pain after total knee replacement (TKR) is a prevalent condition, affecting about 20% of patients. The aim of this study was to explore the relationship between pre-operative pain thresholds and chronic pain after TKR. DESIGN: Patients listed for a TKR because of osteoarthritis participated in a Quantitative Sensory Testing (QST) session prior to surgery. Pressure pain thresholds (PPTs) and hot pain thresholds were assessed at the osteoarthritic knee and the forearm. Patients were followed-up at 1-year after TKR, and the severity of pain in the replaced knee was assessed using the WOMAC Pain score. Pre-operative median QST thresholds were compared to thresholds from a normative database collected from 50 people with no knee pain. The relationship between pre-operative pain thresholds and pain severity post TKR were tested using correlations. RESULTS: Fifty-one patients participated in a pre-operative QST session and completed a 1-year WOMAC Pain score. Pre-operatively, patients demonstrated evidence of localised (knee) and widespread (forearm) pain sensitisation in response to pressure stimuli compared to healthy participants. Pre-operative PPTs at the forearm were found to be significantly correlated with 1-year WOMAC Pain scores (r = 0.37, P = 0.008). CONCLUSIONS: This study provides preliminary evidence that pre-operative widespread pain sensitisation, measured using pressure algometry, may be associated with chronic pain after TKR. Further research is needed to explore the predictive value of an assessment of pre-operative widespread pain sensitisation in identifying who is likely to develop chronic pain after TKR.

Test-retest reliability of Quantitative Sensory Testing in knee osteoarthritis and healthy participants.

Quantitative Sensory Testing (QST), which assesses somatosensory function by recording participant's responses to external stimuli of controlled intensity, is a useful tool to provide insight into the complex pathophysiology of osteoarthritis (OA) pain. However, QST is not commonly used in rheumatology because the test-retest reliability properties of QST in OA patients have not yet been established. This brief report presents the finding of a study which assessed the test-retest reliability of light touch thresholds, pressure pain thresholds, thermal sensation thresholds and thermal pain thresholds in 50 knee OA patients and 50 healthy participants. Pressure pain thresholds were found to be the least variable measurement, as median thresholds did not differ significantly over the 1 week period and the results were highly correlated. This provides support for the inclusion of pressure algometry in studies assessing pain perception abnormalities in OA.

Metal-on-metal bearings total hip arthroplasty: the cobalt and chromium ions release concern.

With certain concerns recently reported on metal-on-metal bearing couples in total hip arthroplasty, this study's objective is to review the current knowledge concerning release of metal ions and its potential consequences. Each metal-on-metal implant presents different tribological properties. The analytical techniques for metals are accurate and the Co ion rates seem acceptable up to 2 µg/L. A delayed type IV hypersensitivity reaction (atypical lymphocytic vasculitis-associated lesion [ALVAL]) may be the source of arthroplasty failure. Idiosyncratic, it remains unpredictable even using cutaneous tests and apparently is rare (0.3%). Today, there are no scientific or epidemiologic data supporting a risk of carcinogenesis or teratogenesis related to the use of a metal-on-metal bearings couple. Solid pseudotumors nearly exclusively are observed with resurfacing procedures, carrying a high annual revision rate in women under 40 years of age, occurring particularly in cases of acetabular malposition and with use of cast molded Cr-Co alloys. Osteolysis manifests through complete and progressive radiolucent lines or through cavitary lesions stemming from ALVAL-type alterations or impingement problems or implant incompatibility. The formation of wear debris exceeding the biological tolerance is possible with implant malposition, subluxation, and jamming of the femoral head in cases of cup deformity. Moreover, each implant presents different metal ion production; assessment of their performance and safety is required before their clinical use. With the knowledge available today, metal-on-metal bearing couples are contraindicated in cases of metal allergies or end stage renal dysfunction and small size resurfacing should cautiously be used.

Skin closure after total hip replacement: a randomised controlled trial of skin adhesive versus surgical staples.

We undertook a randomised controlled trial to compare the outcomes of skin adhesive and staples for skin closure in total hip replacement. The primary outcome was the cosmetic appearance of the scar at three months using a surgeon-rated visual analogue scale. In all, 90 patients were randomised to skin closure using either skin adhesive (n = 45) or staples (n = 45). Data on demographics, surgical details, infection and oozing were collected during the in-patient stay. Further data on complications, patient satisfaction and evaluation of cosmesis were collected at three-month follow-up, and a photograph of the scar was taken. An orthopaedic and a plastic surgeon independently evaluated the cosmetic appearance of the scars from the photographs. No significant difference was found between groups in the cosmetic appearance of scars at three months (p = 0.172), the occurrence of complications (p = 0.3), or patient satisfaction (p = 0.42). Staples were quicker and easier to use than skin adhesive and also less expensive. Skin adhesive and surgical staples are both effective skin closure methods in total hip replacement.

Subsidence of the stem after impaction bone grafting for revision hip replacement using irradiated bone.

Loss of bone stock is a major problem in revision surgery of the hip. Impaction bone grafting of the femur is frequently used when dealing with deficient bone stock. In this retrospective study a consecutive series of 68 patients (69 hips) who had revision of a hip replacement with femoral impaction grafting were reviewed. Irradiated bone allograft was used in all hips. Radiological measurement of subsidence of the stem, incorporation of the graft and remodelling was carried out and showed incorporation of the graft in 26 of 69 hips (38%). However, there was no evidence of trabecular remodelling. Moderate subsidence of 5 mm to 10 mm occurred in ten hips (14.5%), and massive subsidence of > 10 mm in five (7.2%). The results of this study are less favourable than those of others describing studies of revision of the femoral stem using impaction bone grafting. The absence of the characteristic changes of graft remodelling noted in other series raises the question as to whether irradiated bone graft may be a significant factor influencing the post-operative outcome.

The Harris-Galante porous-coated, hemispherical, polyethylene-lined acetabular component in patients under 50 years of age: a 12- to 16-year review.

We have reviewed 70 Harris-Galante uncemented acetabular components implanted as hybrid hip replacements with cemented stems between 1991 and 1995 in 53 patients whose mean age was 40 years (19 to 49). The mean follow-up was for 13.6 years (12 to 16) with no loss to follow-up. We assessed the patients both clinically and radiologically. The mean Oxford hip score was 20 (12 to 46) and the mean Harris hip score 81 (37 to 100) at the final review. Radiologically, 27 hips (39%) had femoral osteolysis, 13 (19%) acetabular osteolysis, and 31 (44%) radiolucent lines around the acetabular component. Kaplan-Meier survival curves were constructed for the outcomes of revision of the acetabular component, revision of the component and polyethylene liner, and impending revision for progressive osteolysis. The cumulative survival for revision of the acetabular component was 94% (95% confidence interval 88.4 to 99.7), for the component and liner 84% (95% confidence interval 74.5 to 93.5) and for impending revision 55.3% (95% confidence interval 40.6 to 70) at 16 years. Uncemented acetabular components with polyethylene liners undergo silent lysis and merit regular long-term radiological review.

Ten-year results of a bone-preserving low-modulus composite total hip replacement stem.

A cementless composite femoral stem was developed with the aim of reducing bone loss secondary to stress shielding. Thirty-one stems were implanted in 27 patients, combined with a cementless acetabular component with polyethylene bearing surface in 30 cases and a bipolar head in 1 case. Patients were followed-up annually with clinical and radiographic evaluation. Fourteen hips underwent dual X-ray absorptiometry (DEXA) scans to monitor postoperative bone mineral density around the stem. The mean follow-up was 10.1 years. The mean Harris hip score improved from 57 to 92. To date, no stem has required revision. All stems are radiographically stable. Acetabular component revision has been required in 8 cases; 3 for liner dissociation and 5 for polyethylene wear. Radiographs and DEXA scans have shown some improvement in bone mineral density (BMD) between the 2 and 5-year follow-up. A cohort of patients displayed improvement in radiographic appearance and BMD in Gruen zone 7. This stem shows evidence of proximal bone preservation and has excellent results at medium to long-term follow-up. The limiting factor in our cohort of patients has been the polyethylene bearing surface.

Validation for the reduced Western Ontario and McMaster Universities Osteoarthritis Index function scale.

PURPOSE: To assess the criterion validity, repeatability, and the missing value protocol of the reduced Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC) function scale ('reduced scale'). METHODS: Three separate studies were performed: a cross-over study to compare the full- and reduced-scale scores in 66 UK patients for validity, a test-retest study for repeatability in 103 Australian patients, and a study for the missing value protocol of the reduced-scale questionnaire. RESULTS: There was no significant difference between scores for the full- and reduced-scale questionnaires in both cross-over and test-retest studies. For the missing value protocol of the reduced-scale questionnaire, when 3 or more of the 7 items were missing, the patient's response was regarded as invalid and the sub-scale score was eliminated from further analysis; when 2 or fewer items were missing, the mean value of the sub-scale was substituted for the missing values. CONCLUSIONS: The reduced-scale questionnaire retains excellent validity and repeatability. Its use is recommended along with the original pain dimension in studies of total joint replacement.

Precision of wear measurement using the shadowgraph technique.

The shadowgraph technique is a relatively easy-to-use and inexpensive method of wear measurement from explanted acetabular cups. In this technique, from a mould of the internal surface of the cup, measurements of linear wear and wear angle can be obtained, from which volumetric wear can be calculated. In this study the measurement precision of this technique was assessed and the influence of different observers and multiple moulds was also determined. It was found that linear wear (coefficient of variation (CV) = 1.49 per cent) can be more precisely determined than wear angle (CV = 8.18 per cent) and that both the observer and the mould can significantly influence the results obtained, although the influence of the mould is considerably less than that of the observer.

The development of a model for in vitro testing of femoral stems in impaction bone grafting.

Comprehension of the biomechanical behaviour of orthopaedic implants is essential. This paper describes the development of an in vitro model to investigate the behaviour of femoral implants in the revision setting. The development of a femoral model and a bone graft substitute is described. The properties of human, bovine, ovine morselized bone graft, and a graft substitute were compared. On measuring hoop strain after impaction bone grafting there was no significant difference between the ovine bone graft and graft substitute with the size 1 Exeter stem. The results suggest that this bone graft substitute is a viable alternative for in vitro testing. The authors recommend the use of the graft substitute and the femoral model to predict femoral stem biomechanics.

Total knee replacement: is it really an effective procedure for all?

Total knee replacement (TKR) is considered an effective intervention for the treatment of chronic knee pain and disability. Yet there is increasing evidence, based on research using patient-based outcome measures, that a significant proportion of patients experience chronic knee pain, functional disability, a poor quality of life and dissatisfaction after TKR. Although some poor outcomes after TKR are due to surgical technique and implant factors, much of the pain and disability after surgery is medically unexplained. A range of possible patient factors could contribute to a poor outcome after TKR. Socio-demographic factors that have been found to correlate with a poor outcome after TKR include female gender, older age and low socio-economical status. Medical factors that are highly predictive of pain and disability after TKR are a greater number of co-morbidities and a worse pre-operative status. A range of psychological factors could be predictive of a poor outcome after surgery including depression, low self-efficacy, poor pain coping strategies, somatization, low social support and patient expectations. It is also proposed that a biological explanation for continuing pain after TKR could involve central sensitisation, a dysfunction of pain modulation by the central nervous system. To improve patient selection for TKR, future research needs to focus on developing a pre-operative screening protocol to identify those patients at risk of medically unexplained pain and disability after TKR.

Orthopaedic metals and their potential toxicity in the arthroplasty patient: A review of current knowledge and future strategies.

The long-term effects of metal-on-metal arthroplasty are currently under scrutiny because of the potential biological effects of metal wear debris. This review summarises data describing the release, dissemination, uptake, biological activity, and potential toxicity of metal wear debris released from alloys currently used in modern orthopaedics. The introduction of risk assessment for the evaluation of metal alloys and their use in arthroplasty patients is discussed and this should include potential harmful effects on immunity, reproduction, the kidney, developmental toxicity, the nervous system and carcinogenesis.

Zirconia heads in perspective: a survey of zirconia outcomes in total hip replacement.

Zirconia ball heads have been implanted successfully from the late 1980s, but reports of wear and fractures have raised concerns about this ceramic biomaterial. This paper reviews the literature on clinical wear of zirconia-polyethylene bearings, zirconia head degradation and fractures, analysing the different factors that have led to clinical failure, such as material source, manufacturing process and type of polyethylene. The results underline the need for more homogeneous clinical series. Careful follow-up of patients with zirconia-polyethylene bearings is recommended.

Numerical predictions of the thermal behaviour and resultant effects of grouting cements while setting prosthetic components in bone.

Acrylic cements are commonly used to attach prosthetic components in joint replacement surgery. The cements set in short periods of time by a complex polymerization of initially liquid monomer compounds into solid structures with accompanying significant heat release. Two main problems arise from this form of fixation: the first is the potential damage caused by the temperature excursion, and the second is incomplete reaction leaving active monomer compounds, which can potentially be slowly released into the patient. This paper presents a numerical model predicting the temperature-time history in an idealized prosthetic-cement-bone system. Using polymerization kinetics equations from the literature, the degree of polymerization is predicted, which is found to be very dependent on the thermal history of the setting process. Using medical literature, predictions for the degree of thermal bone necrosis are also made. The model is used to identify the critical parameters controlling thermal and unreacted monomer distributions.

The entrapment of corrosion products from CoCr implant alloys in the deposits of calcium phosphate: a comparison of serum, synovial fluid, albumin, EDTA, and water.

Physical wear of orthopedic implants is inevitable. CoCr alloy samples, typically used in joint reconstruction, corrode rapidly after removal of the protective oxide layer. The behavior of CoCr pellets immersed in human serum, foetal bovine serum (FBS), synovial fluid, albumin in phosphate-buffered saline (PBS), EDTA in PBS, and water were studied using X-ray Photoelectron Spectroscopy (XPS) and Time-of-Flight Secondary Ion Mass Spectroscopy (ToF-SIMS). The difference in the corrosive nature of human serum, water, albumin in PBS and synovial fluid after 5 days of immersion was highlighted by the oxide layer, which was respectively 15, 3.5, 1.5, and 1.5 nm thick. The thickness of an additional calcium phosphate deposit from human serum and synovial fluid was 40 and 2 nm, respectively. Co and Cr ions migrated from the bulk metal surface and were trapped in this deposit by the phosphate anion. This may account for the composition of wear debris from CoCr orthopedic implants, which is known to consist predominantly of hydroxy-phosphate compounds. Known components of synovial fluid including proteoglycans, pyrophosphates, phospholipids, lubricin, and superficial zone protein (SZP), have been identified as possible causes for the lack of significant calcium phosphate deposition in this environment. Circulation of these compounds around the whole implant may inhibit calcium phosphate deposition.

Clinical experience with metal-on-metal total joint replacements: indications and results.

Survivorship of total joint arthroplasty depends on the durability of fixation and durability of articulation. The metal-on-polyethylene articular couple has been the most widely used. Polyethylene wear (and the associated cytochemical events that culminate in osteolysis) has been identified as a major factor adversely influencing the durability of joint replacement. This stimulated the orthopaedic community to explore the possibility of using alternative bearings with lower wear rates. Hard-on-hard bearings have been shown to be associated with reduced wear. Metal-on-metal bearings have wear rates that are 20-100 times lower than metal on conventional polyethylene. However, patients with metal-on-metal articulations have increased levels of cobalt and chromium in the serum and urine, and this has raised concerns about toxicity, mutagenesis, and hypersensitivity. At this stage there is no epidemiological evidence to suggest that the risk of carcinogenesis is anything more than theoretical. Successful long-term results have been reported with the cast cobalt-chromium metal-on-metal couples of the mid-1960s. Tissues retrieved at revision of these implants did not show the giant-cell inflammatory response associated with polyethylene particles. Several researchers have reported excellent mid-term results with the current generation of high-precision metal-on-metal bearings.

Femoral cementing techniques: current trends in the UK.

INTRODUCTION: The results of a survey conducted amongst hip surgeons in Great Britain on the use of bone cement and femoral cementing techniques are reported. MATERIALS AND METHODS: A postal questionnaire was sent out to the members of the British Orthopaedic Association for their opinion on cement usage and femoral cementing techniques in primary hip arthroplasty. RESULTS: A majority of surgeons use high viscosity cement (82%) and cement containing antibiotics (77%). Almost a fifth of the respondents were unaware of the place of storage of the cement and of the ambient theatre temperature. Over two-thirds experienced inconsistencies in the handling of cement and attributed this to inconsistent theatre temperature (40%) and storage temperature (14%). A majority of the surgeons followed the 'modern' femoral cementing technique of vacuum mixing (94%), plugging the femoral canal (98%), pulsed lavage (87%), retrograde cement introduction (95%), use of stem centralisers (62%) and cement pressurisation. Four-fifths of the surgeons used time as a guide for cement and stem insertion rather than consistency of the cement. CONCLUSIONS: Though most of the surgeons follow contemporary cementing techniques, it appears that inconsistency of the working properties of the cement is a major impediment. Many surgeons are also unaware of the variables that can influence polymerisation and working time of the cement.

The practical limitations of resurfacing hip arthroplasty.

Resurfacing hip arthroplasty has recently experienced a resurgence in popularity, associated with an unprecedented amount of coverage in the media. This article assesses what proportion of a consecutive series of young adults presenting for total hip arthroplasty would have been suitable for resurfacing arthroplasty. Retrospective review of the preoperative radiographs was performed, with templating for the resurfacing prostheses. The hips were divided into those appropriate and those inappropriate for the procedure, and those in whom the procedure would be technically challenging. Sixty-one hips in 57 patients were reviewed, with ages ranging from 17 to 49 years. Twenty-eight hips were assessed as suitable, 26 as unsuitable, and 7 as technically challenging. Reasons for unsuitability included collapse and/or cystic degeneration of the femoral head.

Distal femoral cortical hypertrophy: predisposing factors and their effect on clinical outcome.

The clinical and radiographic features of 109 hybrid total hip replacements performed between 1986 and 1992 in 96 consecutive patients were retrospectively reviewed. A cementless Harris-Galante (HGP1) cup and a 32 mm monobloc straight Muller stem were used in all cases. The overall prevalence of distal femoral cortical hypertrophy (DCH) was 43.1%. Male sex, underlying diagnosis of avascular necrosis and Charnley grade A were among the factors that predisposed to the development of DCH. The prevalence of stem radiolucencies was lower in the group of patients who developed DCH compared with those without hypertrophy. The Harris Hip Score ranged between 5 and 54 preoperatively and the average HHS was more than 80 postoperatively. No association was found between DCH and thigh pain.

A radiological and laboratory assessment of polyethylene wear in failed total hip replacement.

This study assessed the reliability of radiological assessment of polyethylene wear in loose total hip replacements (THRs) by comparing it with a laboratory assessment using the shadowgraph technique. It was performed in Avon Orthopaedic Centre, Southmead Hospital, from September 1997 to June 1998. True linear wear depth measured using the shadowgraph technique was 42% greater than that determined from the radiological femoral head eccentricity in standard non-weightbearing plain x-rays. There was an inverse statistically significant correlation between cup inclination angle and the volumetric wear rate. The linear wear rate, as determined with the shadowgraph technique, was greater in retrieved cups during the first six years postoperatively, but reduced to a lower level in cups retrieved after that time of service.