The aim of this study was to perform a cost–utility analysis of total hip (THR) and knee replacement (TKR). Arthritis is a disabling condition that leads to long-term deterioration in quality of life. Total joint replacement, despite being one of the greatest advances in medicine of the modern era, has recently come under scrutiny. The National Health Service (NHS) has competing demands, and resource allocation is challenging in times of economic restraint. Patients who underwent THR (n = 348) or TKR (n = 323) between January and July 2010 in one Scottish region were entered into a prospective arthroplasty database. A health–utility score was derived from the EuroQol (EQ-5D) score pre-operatively and at one year, and was combined with individual life expectancy to derive the quality-adjusted life years (QALYs) gained. Two-way analysis of variance was used to compare QALYs gained between procedures, while controlling for baseline differences. The number of QALYs gained was higher after THR than after TKR (6.5 vs 4.0 years, p < 0.001). The cost per QALY for THR was £1372 compared with £2101 for TKR. The predictors of an increase in QALYs gained were poorer health before surgery (p < 0.001) and younger age (p < 0.001). General health (EQ-5D VAS) showed greater improvement after THR than after TKR (p < 0.001). This study provides up-to-date cost-effectiveness data for total joint replacement. THR and TKR are extremely effective both clinically and in terms of cost effectiveness, with costs that compare favourably to those of other medical interventions.

Cite this article: Bone Joint J 2013;95-B:115–21.

The aim of this study was to determine the association between the Oxford knee score (OKS) and direct assessment of outcome, and to examine how this relationship varied at different time-points following total knee replacement (TKR). Prospective data consisting of the OKS, numerical rating scales for ‘worst pain’ and ‘perceived mean daily pain’, timed functional assessments (chair rising, stairs and walking ability), goniometry and lower limb power were recorded for 183 patients pre-operatively and at six, 26 and 52 weeks post-operatively. The OKS was influenced primarily by the patient’s level of pain rather than objective functional assessments. The relationship between report of outcome and direct assessment changed over time: R² = 35% pre-operatively, 44% at six weeks, 57% at 26 weeks and 62% at 52 weeks.

The relationship between assessment of performance and report of performance improved as the patient’s report of pain diminished, suggesting that patients’ reporting of functional outcome after TKR is influenced more by their pain level than their ability to accomplish tasks.

End-stage osteoarthritis is characterised by pain and reduced physical function, for which total knee arthroplasty (TKA) is recognised to be a highly effective treatment. Most implants are multi radius in design, though modern kinematic theory suggests a single flexion/extension axis is located in the femur. A recently launched TKA implant (Triathlon, Stryker US), is based on this theory, adopting a single radius of curvature femoral component. It is hypothesised that this design allows better function, and specifically, that it results in enhanced efficiency of the quadriceps group through a longer patello-femoral moment arm.

Change in power output was compared between single and multi radius implants as part of a larger ongoing randomised controlled trial to benchmark the new implant. Power output was assessed using a Leg Extensor Power Rig, well validated for use with this population, pre-operatively and at 6, 26 and 52 weeks post-operatively in 101 Triathlon and 82 Kinemax implants. All patients were diagnosed with osteoarthritis, and drawn from a single centre. Output was reported as maximal wattage (W) generated in a single leg extension, and expressed as a proportion of the contralateral limb power output to act as an internal control.

The results are shown in the table below. Two-way repeated measures ANOVA demonstrated a significant effect of TKA on the quadriceps power output, F = 249.09, p = <0.001 and also a significant interaction of the implant group on the output F = 11.33, p = 0.001. Independent samples t-tests of between group differences at the four assessment periods highlighted greater improvement in the single radius TKA group at all post-operative assessments (p <0.03), see table.

The theoretical enhanced quadriceps efficiency conferred by single radius design was found in this study. Power output was significantly greater at all post-operative assessments in the single radius compared to the multi radius group. This difference was particularly relevant at early 6 week and 1 year assessment. Lower limb power output is known to link positively to functional ability. The results support the hypothesis that TKAs with a single radius design have enhanced recovery and better function.

Introduction

Recovery of muscle strength following Total Knee Replacement (TKR) is variable, and can affect the resultant function of the patient. Satellite cells are undifferentiated myogenic precursors considered to be muscle stem cells that lie quiescently around the muscle fibre. These cells repair damaged fibres and have the potential to generate new muscle fibres. Therefore, theoretically, they could be associated with the variation in muscle recovery following surgery. We hypothesised that the recovery of muscle strength following knee replacement in a given patient would be influenced by the underlying number of satellite cells in that patient.

Aim

To investigate the incidence, types and trends in diagnosis of venous thromboembolic events (VTE) in patients undergoing total knee arthroplasty (TKA) over a ten-year period.

Introduction: Patient-reported outcome and satisfaction scores have become increasingly important in evaluating successful surgery. There is continued enthusiasm for metal-on-metal resurfacing of the hip, particularly as an alternative to total hip replacement (THR) in young, active patients with osteoarthritis. However, although mid-term survivorship data is promising, it remains unclear whether patient-reported outcomes following resurfacing match those following THR.

Patients and Methods: This case-matched control study compared patient-reported outcome and satisfaction data following hip resurfacing and total hip arthroplasty. Thirty-three consecutive patients selected for hip resurfacing were compared with 99 patients undergoing cemented total hip replacement (THR), matched for age, sex and pathology. Participants completed a Short-Form 12 Health Survey (SF-12) and Oxford Hip Score (OHS) questionnaire pre-operatively and 6 months post operatively, with an additional patient satisfaction questionnaire.

Results: There was no difference in length of hospital stay. Both groups reported improved outcome scores, with mean OHS improvements of 19.5 (95% CI: 17.0–22.1), and 20.6 (95% CI: 18.6–22.5) following resurfacing and THR respectively. There were similar improvements in SF-12 PCS of 14.2 (95% CI: 9.5 to 14.2) and 15.2 (95% CI: 13.2 to 18.2) for the resurfacing and THR groups respectively. The improvement in outcome scores did not differ between the two groups on multivariate regression analysis (P=0.509 for OHS, P=0.629 for SF-12 PCS). Both groups reported high levels of satisfaction, which tended to be better in patients undergoing hip resurfacing (97.0% vs 92.9%), with resurfacing patients reporting better pain relief (P=0.022) and better heavy lifting (P=0.038) at 6 months.

Discussion: This study shows that the short-term patient-centred outcome scores for hip resurfacing are at least as good as for conventional hip replacement, with slightly higher levels of satisfaction.

We welcome letters to the Editor concerning articles which have recently been published. Such letters will be subject to the usual stages of selection and editing; where appropriate the authors of the original article will be offered the opportunity to reply.

Study Purpose: To investigate whether the use of reinfusion drains and post-operative autogenous blood transfusion reduces the rate of allogeneic blood transfusion after primary total knee replacement in our unit.

Methods: A prospective audit was carried out over a 14-week period. Patients received either a reinfusion drain, a suction drain or no drain according to surgeon preference. Post-operative allogeneic blood transfusion criteria were based on clinical indication rather than an absolute haemoglobin level.

Results:127 consecutive patients underwent total knee replacement during the study period. Patients were matched between the three groups for age, medical co-morbidity, DVT prophylaxis, and implant used.

Conclusion: The use of reinfusion drains did not significantly reduce the requirement for post-operative allogeneic blood transfusion. This directly contrasts much of the published literature.

Aim: To investigate the incidence and type of venous thromboembolic event (VTE) diagnosed in patients undergoing total knee arthroplasty (TKA) and the trends over time following the introduction of a rigorously enforced thromboprophylaxis protocol.

Methods: Data from all 3260 TKAs performed in our unit between April 1996 and March 2003 were prospectively collected by the Scottish Arthroplasty Project (SAP). The SAP data identified 84 of these patients as having being admitted with or died from a VTE episode. A unified thromboprophylaxis protocol was introduced in 1999, from 2001 it was included as part of the integrated care pathway. We retrospectively reviewed all available casenotes of these patients to identify the assessment and thromboprophylaxis given, the precise diagnosis of VTE, the treatment and adverse outcomes.

Results: Of the 84 VTEs identified, 29 had pulmonary emboli (PE), 12 had above knee deep vein thrombosis (DVT), 24 had calf DVT and 10 had no evidence of VTE though were coded as such (but not treated) by physicians elsewhere. Data were unavailable for the remaining 9 but these were assumed to have had VTE for the purposes of this study. Of the 24 patients with calf only DVT, 16 were given therapeutic anticoagulation of whom five developed haemorrhagic complications. From 2001 the thromboprophylaxis protocol was followed in 100% of patients. The rate of VTE in our unit has fallen steadily from 2.26% in 1996–7 to 1.05% in 2002–3.

Conclusions: There has been a steady decline in the rate of venous thromboembolism in our unit over the seven years of the study. A thromboprophylaxis protocol has been successfully introduced in our unit and consistently applied since 2001. There is considerable overdiagnosis and treatment of calf DVT with significant resultant morbidity.

Purpose: This study aims to explore the role of pain, fear of movement and learned helplessness on functional knee range of motion and daily functioning in a patients awaiting total knee arthroplasty (TKA)

Methods and results: Sixty-five patients (mean age 69 years old) with osteoarthritis were assessed an average of 37 days prior to TKA. Dynamic knee angle was measured during 11 functional activities including getting up from a chair and walking up and down a slope and stairs using flexible electrogoniometry. Function was assessed using the function components of the Knee Society Score (KSS) and the Western Ontario & McMaster University Osteoarthritis Index (WOMAC). Other self-report measures included the 8 item Tampa scale for kinesiophobia to assess ‘activity avoidance’ (TSK-AA), and the 5 item Helplessness subscale of the rheumatology attitudes index.

The pain component of the WOMAC was negatively associated with the knee angle during sitting down and getting up from a low chair and stepping in and out of a bath (r=0.40–0.45), but not with the peak knee angle during ascending and descending a slope or walking speed. Higher scores of the activity avoidance and the helplessness scales however, were associated with reduced knee angles during descending a slope and a slower walking speed (r=0.31–0.38). Both psychosocial scales were also associated with function (r=0.39–0.45). Another important finding was that activity avoidance was not associated with pain.

Conclusions: Not only pain but also fear of movement and learned helplessness play a role on specific components of knee function in patients with final stage osteoarthritis of the knee. Further research into the impact of pain and psychosocial variables on functional outcome in ostearthritis is indicated.

Modifications in the design of knee replacements have been proposed in order to maximise flexion. We performed a prospective double-blind randomised controlled trial to compare the functional outcome, including maximum knee flexion, in patients receiving either a standard or a high flexion version of the NexGen legacy posterior stabilised total knee replacement. A total of 56 patients, half of whom received each design, were assessed pre-operatively and at one year after operation using knee scores and analysis of range of movement using electrogoniometry. For both implant designs there was a significant improvement in the function component of the knee scores (p < 0.001) and the maximum range of flexion when walking on the level, ascending and descending a slope or stairs (all p < 0.001), squatting (p = 0.020) and stepping into a bath (p = 0.024). There was no significant difference in outcome, including the maximum knee flexion, between patients receiving the standard and high flexion designs of this implant.

If an arthroplasty patient presents with wound breakdown, sinus formation or a hot, red joint the diagnosis of infection is straightforward. However, most total joint replacement (TJR) infections are difficult to distinguish from aseptic loosening. It is imperative to know if a painful TJR is infected to plan appropriate management.

In this prospective study of 204 patients we analysed the diagnostic accuracy of various tests for infection: Inflammatory Markers (CRP/ESR); Aspiration Microbiology; and the Polymerase Chain Reaction (PCR) – a novel technique in this situation. We used international criteria as the gold standard for infection, applied at the time of revision surgery. Any of – a sinus; frank pus in the wound; positive intra-operative microbiology; positive histology – classified the patient as infected. The sensitivity (Sens), specificity (Spec), positive predictive value (PPV) and negative predictive value (NPV) of each test were calculated.

52 patients with an original diagnosis of inflammatory arthritis were excluded, as histology may be inaccurate. The results for the remaining 152 patients are: CRP > 20mg/l: Sens 77%; Spec 76%; PPV 49%; NPV 92%. ESR > 30 mm/hr: Sens 61%; Spec 86%; PPV 57%; NPV 87%. Aspiration Microbiology: Sens 80%; Spec 83%; PPV 71%; NPV 88%. PCR: Sens 71%; Spec 78%; PPV 43%; NPV 89%.

Few patients with negative CRP/ESR were found to be infected; if positive, there was a 50/50 chance that the joint was infected. Positive aspiration microbiology was associated with underlying infection 3 times out of every 4, and negative results were correct 9 times out of 10. PCR was no more accurate than existing tests.

All patients with painful TJR’s should have inflammatory markers checked – if negative the clinician can be relatively reassured that the implant is not infected. If positive or suspicion remains, further investigation should be undertaken. Joint aspiration for microbiology is currently the best available second line investigation.

The aim of this randomised, controlled in vivo study in an ovine model was to investigate the effect of cylic pneumatic pressure on fracture healing. We performed a transverse osteotomy of the right radius in 37 sheep. They were randomised to a control group or a treatment group where they received cyclic loading of the osteotomy by the application of a pressure cuff around the muscles of the proximal forelimb. Sheep from both groups were killed at four or six weeks. Radiography, ultrasonography, biomechanical testing and histomorphometry were used to assess the differences between the groups. The area of periosteal callus, peak torsional strength, fracture stiffness, energy absorbed over the first 10° of torsion and histomorphometric analysis all showed that the osteotomies treated with the cyclic pneumatic pressure at four weeks were not significantly different from the control osteotomies at six weeks.

Introduction If an arthroplasty patient presents with wound breakdown, sinus formation or a hot, red, painful joint replacement the diagnosis of infection is relatively straightforward. However, most total joint replacement (TJR) infections present in an indolent fashion and are impossible to distinguish from aseptic loosening. It is imperative to know if pain in a TJR is due to infection to plan appropriate further management.

Methods In this prospective study of 204 patients we analysed the diagnostic accuracy of various tests for infection in the setting of TJR: Inflammatory Markers (CRP/ESR); Aspiration Microbiology; and the Polymerase Chain Reaction (PCR) – a novel technique in this situation. We used internationally agreed criteria as the gold standard for infection. The patient was deemed to be infected if any of the following were found at the time of revision surgery: a sinus; frank pus in the wound; positive microbiology or positive histology on intra-operative specimens. The sensitivity (Sens), specificity (Spec), positive predictive value (PPV) and negative predictive value (NPV) of each test were calculated.

Results 52 patients with an original diagnosis of inflammatory arthritis were excluded, as histology may be inaccurate. Their results have been presented elsewhere. The results for the remaining 152 patients are: CRP > 20mg/l: Sens 77%; Spec 76%; PPV 49%; NPV 92%. ESR > 30 mm/hr: Sens 61%; Spec 86%; PPV 57%; NPV 87%. Aspiration Microbiology: Sens 80%; Spec 83%; PPV 71%; NPV 88%. PCR: Sens 71%; Spec 78%; PPV 43%; NPV 89%.

Findings and Conclusions Only a few of the patients with negative inflammatory markers later turned out to be infected. If the inflammatory markers were positive, there was roughly a 50/50 chance that the joint was infected. Positive aspiration microbiology was associated with underlying infection approximately 3 times out of every 4, and negative results were correct 9 times out of 10. PCR was no more accurate than existing tests.

We recommend that all patients with painful TJRs have inflammatory markers checked as a screening test – if negative then the clinician can be relatively reassured that the implant is not infected. If positive, further investigation should be undertaken. Joint aspiration for microbiology is currently the best available second line investigation.

Introduction and Aims: Cyclic pneumatic pressure applied to the musculature proximal to a fracture of the distal radius has been shown to produce compressive loading of the fracture. The aim of this randomised controlled in vivo study in an ovine model was to investigate the effect of the pneumatic pressure on fracture healing.

Method: Thirty-seven sheep underwent a transverse osteotomy of the right radius. All sheep were managed in a plaster cast and splint to ensure non-weight bearing during rehabilitation. Nineteen of the sheep were randomised to receive cyclic loading by the application of a pressure cuff around the muscles of the proximal forearm deep to the cast. The other 18 sheep acted as controls. The sheep in the experimental group received 120 cyclic loads over two 10-minute sessions each day starting one week post-osteotomy. Sheep from both groups were sacrificed at either four or six weeks. X-rays, ultrasonography, biomechanical testing and histomorphometry were used to assess differences between the groups.

Results: The area of periosteal callus on lateral and antero-posterior x-ray, the peak torsional strength, the fracture stiffness, the energy absorbed over the first 10 degrees of torsion and histomorphometric analysis all showed that the fractures in the group treated with the cyclic pneumatic pressure achieved the same level of union at four weeks as the control group fractures at six weeks (not significantly different p> 0.05). The density of the woven bone in the periosteal callus of the treated sheep was significantly greater than the controls (p< 0.01). Ultrasonography showed no significant difference (p> 0.05) in the amount of muscle wasting between the treated group and the control group.

Conclusion: This study has shown that the rate of healing is enhanced when cyclic pneumatic pressure is applied to the musculature proximal to a transverse fracture of the distal radius in an adult sheep model. There is potential for this treatment to be used in a human population.

We assessed the functional outcome following fracture of the tibial plateau in 63 consecutive patients. Fifty-one patients were treated by internal fixation, five by combined internal and external fixation and seven non-operatively. Measurements of joint movement and muscle function were made using a muscle dynamometer at three, six and 12 months following injury. Thirteen patients (21%) had a residual flexion contracture at one year. Only nine (14%) patients achieved normal quadriceps muscle strength at 12 months, while 19 (30%) achieved normal hamstring muscle strength. Recovery was significantly slower in patients older than 40 years of age. We conclude that there is significant impairment of movement and muscle function after fracture of the tibial plateau and that the majority of patients have not fully recovered one year after injury.

Introduction Following any intraarticular fracture, joint range of movement and muscle strength recovery are vital factors in patient’s return to activities. Quadriceps weakness is a known complication of any injury affecting the knee. The purpose of this study was to investigate the recovery of knee ROM and quadriceps and hamstrings muscle strength in the first year after tibial plateau fracture and to assess factors that affect the recovery.

Method 63 patients were recruited over a 5-year period. Data regarding the age and sex of the patient, the mechanism of injury, the grade of the fracture according to Shatzker’s classification and the treatment received were recorded. All patients underwent a standard rehabilitation regime. At 3, 6 and 12 months after injury the patients were seen by a research physiotherapist. The range of movement was recorded. Thigh muscle peak torque was measured using isokinetic dynanmometry. The uninjured limb was used as the control – the peak torque in the injured limb was expressed as a percentage of the value in the uninjured limb to give the percentage recovery in the injured limb.

Results There was an initial extension deficit of 7° at 3 months, which improved to 3° at 12 months. Quadriceps strength recovery lagged behind that in the hamstrings at all times and only achieved only 77% at 12 months, compared to 90% in the hamstrings (p< 0.001). Patients under 40 outperformed those over 40 at each time point. At 12 months under 40s had achieved 85% recovery in their quadriceps, while over 40s only reached 74% (p< 0.01). Patient sex, mechanism of injury and grade of fracture had no effect on the level of recovery in this study.

Conclusion Patients who sustain a tibial plateau fracture have a residual small extension deficit and objective quadriceps weakness at 1 year post injury. Patient age has a significant effect on the level of quadriceps recovery. This information is useful when counselling patients who sustain these injuries.

Studies on recurrent disc herniation quote rates of recurrence without regard to the times of recurrence and the influence of longer follow-up. Our objective was to assess the use of survival analysis to measure the rate of revision after lumbar microdiscectomy. We undertook a retrospective analysis of the hospital records of 993 patients who underwent lumbar microdiscectomy over a period of ten years. After calculating the overall rate of revision for the mean length of follow-up, we carried out a survival analysis using the life-table method. During the study period 49 patients had a revision microdiscectomy. This gave an overall rate of revision of 4.9% at a mean follow-up of 5.25 years. Using survival analysis, the rate of revision was 7.9% at a follow-up of ten years when the number at risk was 84. Survival analysis gives a more accurate estimation of the true rate of recurrence for patients undergoing lumbar microdiscectomy. The method allows better comparison between different interventions for disc herniation.

We investigated the use of PCR (the Polymerase Chain Reaction) to detect the presence of infection in a group of patients undergoing revision arthroplasty for loose TJR (total joint replacement), compared to internationally agreed criteria used as the ‘gold standard’ for infection.

We prospectively tested samples taken from 108 patients undergoing revision arthroplasty (76 hips, 32 knees). Antibiotics were omitted prior to obtaining samples. DNA was extracted by 2 methods – a previously published technique (reference) and a commercial extraction kit (Qiagen^®). PCR involved amplification of an 882 base pair segment of the universal bacterial 16S RNA gene. During revision arthroplasty multiple specimens were taken from around the joint for microbiological and histological examination and the presence or absence of pus was noted. The patient was deemed to be infected if one of the following criteria was found: presence of a sinus pre-operatively; 2 or more intra-operative cultures positive for the same organism; an acute inflammatory response on histology; pus in the joint at revision.

Using the published DNA extraction technique PCR had a sensitivity of 50%, specificity of 93%, positive predictive value of 67% and negative predictive value of 88%. Using commercial extraction the sensitivity improved to 60%, specificity to 98%, positive predictive value to 90% and negative predictive value to 90%.

The previous report stated that PCR had a high sensitivity but a low specificity for detecting low grade infection. However, when using the published technique we found the opposite results – a moderate sensitivity and a high specificity. Introduction of a new DNA extraction technique improved the sensitivity. The refined PCR technique had a high accuracy, but further work is needed to improve sensitivity before we would recommend this method for routine clinical use.

A knowledge of bacteriological profiles in previously treated cases is helpful as a guide to management of infected joint replacements, especially in those cases where bacteriology results are not available. The object of this study was to assess the changing trends of the bacteriology of infected total knee replacements (TKR) over 2 decades.

The records of 79 patients undergoing revision for infected TKR between 1979 and 1999 were reviewed. There were 30 males and 49 females, average age 63 years, range 36 – 82 years. The types and sensitivities of bacteria identified, and the use of prophylactic systematic and cement antibiotics, was recorded. The Chi-squared test was used to test statistical significance.

70 organisms were identified in 62 patients: 29 Staphylococcus aureus; 27 Coagulase Negative Staphylococci (CNS); 8 Streptococci; 6 Coliforms. In the 1980s S. aureus accounted for 55% of infections, CNS 25%. In the 1990s S. aureus 38%, CNS 41%. Following the use of systematic antibiotics (3 x cefuroxime) or antibiotic cement (bacitracin/erythromycin/colistin – BEC) at primary TKR, fewer CNS infections were seen (p< 0. 05). There was only 1 case of methicillin resistant S. aureus. Coagulase negative staphylococci had a 36% resistance to flucloxacillin. With BEC cement there was a tendency to increased erythromycin resistance in CNS, but this did not achieve statistical significance.

At revision for infected TKR, different bacterial profiles were observed depending on prophylactic antibiotic usage. As CNS now causes > 40% of infections, patients undergoing revision TKR should have antibiotics effective against CNS until definitive results are available.