In severe destructive spinal infections, with neurological deficit, progressive deformity or uncontrolled sepsis, the mainstay of treatment is surgical debridement with anterior and posterior stabilisation. We retrospectively reviewed 14 patients (11 Male 3 female) with a mean age of 63 (range 38 to 85) who underwent anterior only surgery consisting of an expandable vertebral body cage and a ventrolateral locking plate (Synthes). Organisms included Tuberculosis (7), Staphylococcus (5), E-Coli (1) and Pseudomonas (1). Radiological and functional outcomes were assessed upto 18 months post surgery. Cobb angles were used to measure angular deformity.

Good early results in terms of safety, resolution of pain, control of deformity and improvement of neurological deficits was observed. Average blood loss was 633mls (range 300mls to 1500mls) with a mean deformity correction of 23 degrees. Post operative radiological assessment showed the cages to be relatively stable in the under 80 yrs groups (mean loss of correction 15 %). In elderly patients (> 80 yrs) there was significant subsidence leading to a loss of correction (mean 52%) which required stabilisation using vertebral body cement augmentation. In one case, there was implant displacement requiring revision and additional posterior stabilisation. 11 patients showed significant improvement in neurology and 3 patients remained neurologically normal ie Frankel E.

We propose assessing severe spinal infections using the spinal trilogy of neurological deficit, deformity and sepsis. Anterior stabilisation using an expandable cage and locking plate alone or with additional vertebral body cement augmentation in elderly patients provides a satisfactory solution for severe destructive spinal infections. It preserves the posterior column and reduces the need for further posterior surgery.

Injuries to the spinal cord are rarely isolated problems. Multiple trauma patients with spinal injuries can face significant long-term disability. In this retrospective, descriptive study we investigated the relationship between the level of spinal trauma and the injuries associated with this. We aimed to define the populations at risk and highlight trends identified.

METHODS: Analysis of 1500 trauma patients admitted to the Royal London Hospital by the Helicopter Emergency Medical Service (HEMS) over 6 years was undertaken. 265 patients of these patients had spinal cord injuries (SCI). Data was obtained from the HEMS trauma registry, patient records and interviews with patients.

RESULTS: 265 patients sustained SCI (mean age: 38 25% female). The most common mechanisms of injury were motor vehicle accidents (46%) and falls (29%) Attempted suicide was a common cause of SCI in our study group (mean age 32. M:F ratio 2:1) The most common associated injuries were limb and head trauma. C-spine injuries were the most common spinal injury and were associated with the highest mortality rates (37%). C-injuries presented with a bimodal age distribution, 84% had head trauma and 30% had significant chest injuries. In patients who sustained thoracic spinal injuries 71% had severe chest injuries and 34% had head injuries. The most common associated injury in lumbar spine trauma was injuries to the limbs or pelvis (68%). Injuries to the lumbar spine occurred more frequently in the 20–40 year old age groups.

Discussion: Mortality rate in our study was 26%. Mortality rates were highest in patients with cervical spine injuries (37%). The causes of mortality were from suicide attempts, falls and RTA. The mortality rates in these groups were 20%, 22% and 32% respectfully. Our review highlights significantly higher mortality in the over 60-age group. Our population had high numbers of suicide attempts. We highlight suicide attempts as a significant aetiology for SCI. All the deaths in the suicide group were as a result of jumping from high buildings. In patients over 60, c-spine injuries are by far the common level of SCI. Subdural haematomas occurred in almost 10% of patients with c- spine injuries. Any injury to the cervical spine should therefore prompt investigation for intracranial trauma. The GCS should be closely monitored and a low threshold for performing a CT scan is advisable. Thoracic spine injuries are strongly associated with severe chest injuries. Lumbar spine and sacral injuries are strongly associated with severe pelvic and lower limb injuries. Understanding the demographics and etiology is essential to allow effective planning for spinal services. Appreciating the injuries associated with SCI should ensure better care for patients, by recognizing problems earlier and using a multidisciplinary approach to optimize treatment and reduce morbidity and mortality.

Background: The cause of intervertebral disc degeneration (IVDD) is multifactorial. One proposed mechanism is that IVDD originates in the nucleus pulposus (NP) and progresses radially to the annulus fibrosis (AF). Failure of current treatment modalities in preventing and treating IVDD and thereby low back pain have led to a growing interest in tissue-engineered solutions where a biological repair is induced. By preventing the abnormality at the NP it may be possible to halt further progression of IVDD. Injection of NP cells into an early degenerative IVD, where the AF is still intact, may retard the degenerative process and is presently under investigation. Using a 3-dimensional scaffold that could be successfully introduced into the NP cavity through minimally invasive techniques would prevent the loss of chondrocytic phenotype of the cells and be an improvement over the existing technique by which cells are directly injected into the NP cavity.

Methods:

CaSO4 and CaCO3 3% alginate hydrogels were injected into the NP cavity of a bovine tail. After 90 minutes the tail was dissected to reveal the gel.

Results:

Injectable alginate suspensions formed solid viscoelastic gels, filling the exact shape of the NP cavity.

Discussion: This study demonstrates that slowly polymerising CaCO3 and CaSO4 alginate gels are injectable and capable of sustaining NP cells in-vitro. Cells remain viable, maintain their phenotype, proliferate and produce ECM during the culture period. CaCO3 alginate gel provides a 3-dimensional matrix more favourable to NP cellular activity than the CaSO4 alginate gel. Synvisc® has a chondro-stimulatory effect on NP cells in-vitro. These effects are similar to those observed previously with hyaluronic acid, in that it binds to cell surface CD44 receptors, thereby affecting essential cellular functions and cytoskeleton structure. Synvisc® however has an advantage in that it is highly viscous and can reside longer within an alginate construct thereby having a sustained long-term stimulatory effect. This study demonstrates a successful tissue-engineered approach for replacing the NP and, subject to further studies, may be used for retarding mild-to-moderate IVDD, alleviating lower back pain and restoring a functional NP through a minimally invasive technique.

Scoliosis and hip subluxation/dislocation are common and often coexistent problems encountered in patients with cerebral palsy (CP). The underlying mechanism may be related to muscle imbalance. Surgical correction may become necessary in severe symptomatic cases. The effect of surgical correction of one deformity on the other is not well understood.

We retrospectively reviewed a series of 17 patients with total body cerebral palsy with diagnoses of both scoliosis and hip subluxation who had undergone either surgical correction of their scoliosis (9 patients) or a hip reconstruction to correct hip deformity (8 patients). In all patients, the degree of progression of both deformities was measured, radiographically, using the Cobb angle for the spine and the percentage migration index for hip centre of rotation at intervals before and at least 18 months post surgery.

All patients who underwent scoliosis correction had a progressive increase in the percentage of hip migration at a rate greater than that prior to scoliosis surgery. Similarly, patients who underwent a hip reconstruction procedure demonstrated a more rapid increase in their spine Cobb angles post surgery.

There may be a relationship between hip subluxation/dislocation and scoliosis in CP patients. Surgery for either scoliosis or hip dysplasia may in the presence of both conditions lead to a significant and rapid worsening of the other. The possible negative implications on the overall functional outcome of the surgical procedure warrants careful consideration to both hip and the spine before and after surgical correction of either deformity. In selected cases there may be an indication for one procedure to follow soon after the other.

Objective: The purpose of this study was to assess whether the use of high dose methylprednisolone (MPS) given to trauma patients with acute spinal cord injury improves neurological and long term functional outcomes.

Summary of Background Data: The National Acute Spinal Cord Injury Studies (NASCIS II and III) recommend the early administration of high dose MPS in the context of acute spinal cord injury. However, controversy exists surrounding its long term benefits.

Methods: A retrospective data analysis was performed using the Helicopter Emergency Medical Service (HEMS) trauma registry, medical records, and rehabilitation notes of 263 trauma patients with acute spinal injury admitted over a 6-year period. All survivors over 16 years of age with documented spinal cord injuries were selected. Frankel grade, Injury Severity Score (ISS), and Functional Independence Measure (FIM) scores (minimum FIM of 18 implies total dependence, and a maximum of 126 implies no disability) as indicators of neurological and functional morbidity were recorded at initial presentation, hospital discharge, and intervals up to 12 months post injury. Details of the age, gender, mechanism of injury, nature of injury and associated injuries were also recorded.

Results: There were 139 patients (107 males and 32 women) with documented acute spinal cord injuries, of which 74 patients had neurological deficits (Frankel A–D) at presentation. 49 patients were given high dose MPS within 8 hours of injury according to a standard protocol. The remaining 25 patients with documented neurological injury did not meet criteria or failed to receive the agent within the recommended time. The mean ISS scores were shown to be comparable in both groups. 59% (29/49) of patients who were given MPS showed an improvement of one or greater Frankel grade at the time of discharge whereas 52% (13/25) of patients who did not receive MPS showed a similar improvement in Frankel grades. We had long term functional outcome data (FIM scores) on 48% (67/139) of the total number of patients. At the time of discharge, the mean FIM scores for the MPS treated group and non MPS treated group were 68 and 90, respectively. Whereas at 12 months, there was no significant difference in the mean FIM scores between the two groups (both of which were > 100).

Conclusions: The Frankel grade assesses the degree of neurological impairment while FIM scores are a basic measure of the severity of disability regardless of the underlying impairment. In our study, patients given high dose MPS in the context of acute spinal cord injury showed some early improvement in Frankel grades. However, we have shown, there is no short term or long term benefit in terms of functional outcome by using MPS in trauma patients with acute spinal cord injury.

Study Purpose: The cause of intervertebral disc degeneration (IVDD) is multifactorial. One proposed mechanism is that IVDD originates in the nucleus pulposus (NP) and progresses radially to the annulus fibrosis (AF). Failure of current treatment modalities in preventing and treating IVDD and thereby low back pain have led to a growing interest in tissue-engineered solutions where a biological repair is induced. By preventing the abnormality at the NP it may be possible to halt further progression of IVDD. Injection of NP cells into an early degenerative IVD, where the AF is still intact, may retard the degenerative process and is presently under investigation. Using a three-dimensional scaffold that could be successfully introduced into the NP cavity through minimally invasive techniques would prevent the loss of chondrocytic phenotype of the cells and be an improvement over the existing technique by which cells are directly injected into the NP cavity.

Methods: (1) CaSO4 and CaCO3 alginates were injected into the NP cavity of a bovine tail. After 90 minutes the tail was dissected to reveal the gel. (2) NP cells released from pooled bovine NP tissue were dispersed into the CaSO4 and CaCO3 alginate gels (10x106 cells.mL-1) with and without Synvisc® and cultured for 21 days.

Results: (1) Injectable alginate suspensions formed solid viscoelastic gels, filling the exact shape of the NP cavity. (2) NP DNA and ECM synthesis was significantly greater in the CaCO3 alginate gel than in the CaSO4 alginate gel (p< 0.05). (3) Synvisc® significantly increased sulphated GAG (p< 0.01) and collagen (p< 0.05) production. These effects were supported histologically and immunohistologically where cells in the CaCO3 and Synvisc® gels stained more intensely for proteoglycan and collagen type II.

Conclusions: Both CaCO3 alginate gel and CaSO4 alginate gel are injectable and are capable of sustaining NP cells in-vitro. Cells remain viable, maintain their phenotype, proliferate and produce ECM during the culture period. The CaCO3 alginate gel provides a three-dimensional matrix more favourable to NP cellular activity than the CaSO4 alginate gel. Synvisc® behaves as a chondro-stimulant significantly enhancing NP cell metabolic activity. This study demonstrates a successful tissue-engineered approach for replacing the NP and, subject to further studies, may be used for retarding mild-to-moderate IVDD, alleviating lower back pain and restoring a functional NP through a minimally invasive technique.

Study Design: Experimental study to assess tissue engineered solutions to disc degeneration.

Objectives: To investigate the use of a novel biodegradable hydrogel which is capable of minimally invasive introduction into an intervertebral disc (IVD) and support of cultured nucleus pulposus (NP) cells for the purpose of developing a tissue-engineered solution to retard progression of IVD degeneration. There were 3 objectives: (1) To introduce a slowly polymerising alginate hydrogel into the NP cavity of a bovine vertebral disc model. (2) To demonstrate the viability and metabolic activity of cultured NP cells in the hydrogel in vitro. (3) To determine the effect of Synvisc (hylan G-F 20) on NP cell proliferation and extracellular matrix (ECM) production.

Summary of Background Data: The cause of intervertebral disc degeneration (IVDD) is multifactorial. One proposed mechanism is that IVDD originates in the NP and progresses radially to the annulus fibrosis (AF). There is a growing interest in tissue-engineered solutions where a biological repair is induced. By preventing the abnormality at the NP it may be possible to halt progression of IVDD. Injection of NP cells into an early degenerative IVD, where the AF is still intact, may retard the degenerative process.

Subjects/Methods: CaSO₄ and CaCO₃ alginates were injected into the NP cavity of a bovine tail. After 90 minutes the tail was dissected to reveal the gel. NP cells released from pooled bovine NP tissue were dispersed into the CaSO₄ and CaCO₃ alginate gels (10x10⁶ cells.mL⁻¹) with and without Synvisc and cultured for 21 days.

Results: Injectable alginate suspensions formed solid viscoelastic gels, filling the exact shape of the NP cavity. NP DNA and ECM synthesis was significantly greater in the CaCO₃ alginate gel than in the CaSO₄ alginate gel (p< 0.05). Synvisc significantly increased sulphated GAG (p< 0.01) and collagen (p< 0.05) production. These effects were supported histologically and immunohistologically where cells in the CaCO₃ and Synvisc gels stained more intensely for proteoglycan and collagen type II.

Conclusions: Both CaCO₃ alginate gel and CaSO₄ alginate gel are injectable and are capable of sustaining NP cells in-vitro. Cells remain viable, maintain their phenotype, proliferate and produce ECM during the culture period. The CaCO₃ alginate gel provides a three-dimensional matrix more favourable to NP cellular activity than the CaSO₄ alginate gel. Synvisc behaves as a chondro-stimulant significantly enhancing NP cell metabolic activity.

Mosaicplasty¹ and Autologous Chondrocyte Implantation² (ACI) are both modern cartilage repair techniques used to repair symptomatic articular cartilage defects in the knee, based on small osteochondral grafts and cultured chondrocytes respectively. The aim is the restoration of articular cartilage, but until now there is no data comparing the two methods.

100 consecutive patients aged 15–45 with a symptomatic articular cartilage lesion in the knee suitable for cartilage repair were randomised at arthroscopic assessment to undergo either mosaicplasty or ACI. 42 patients underwent mosaicplasty, 58 had ACI. Mean age at time of surgery was 31 years and the average defect size 4. 66 cm².

46% of the defects were post-traumatic, 19% had osteochondritis dissecans, 14% had chondromalacia patella and 16% had lesions of unknown aetiology. 53% had a medial femoral condyle lesion, 25% patella, 18% lateral femoral condyle, 3% trochlea and there was one defect of the lateral tibial plateau.

The mean duration of symptoms was 7. 2 years and the average number of previous operations (excluding arthroscopies) was 1. 5. Only 6 patients had no prior surgical interventions to the affected knee. The mean follow-up was 1. 7 years.

Patients were evaluated using Modified Cincinnati and Stanmore Functional rating systems, visual analogue scores and clinical assessment. Arthroscopy and biopsy was performed at one year and repair assessed with the International Cartilage Repair Society grading system.

Clinical results at one year showed 70% of mosaic-plasty patients and 87% of ACI patients had a good or excellent result. Arthroscopy at one year demonstrated more complete healing in ACI patients. Eleven (26%) of the mosaicplasty group subsequently failed clinically and arthroscopically, with peak failure at 2 years.

At one year follow-up, both techniques of articular cartilage repair can be useful in selected patients. ACI is preferred for lesions of the patella. Long-term follow-up is needed to assess the durability of articular cartilage repair using these methods, in particular mosaicplasty which showed signs of progressive failure over 2 years.

Autologous Chondrocyte Implantation’ (ACI) is a cartilage repair technique that involves implantation of cultured chondrocytes beneath a membrane of autologous periosteum. In this study a porcine biodegradable membrane was also used to assess its effectiveness. The aim is to restore articular cartilage to symptomatic defects, rather than initiating a fibrocartilagenous repair.

We undertook a prospective study of 125 consecutive patients who underwent ACI. Average age at the time of surgery was 30. 9 years (range 14 – 49), 55% of patients were male. The average size of the defect was 4. 35 cm².

44% of defects were attributable to known traumatic incidents, 2 1 % had osteochondritis dessicans, 18% chondromalacia patella, 12% had defects of unknown aetiology and 5% other.

The average duration of symptoms prior to this surgery was 7. 16 years. The mean number of previous operations (excluding arthroscopies) was 1. 6. Only 9 patients had no previous major surgery to the affected knee. 44% had defects of the medial femoral condyle, 31% patella, 20% lateral femoral condyle and 5% had a trochlea lesion. 26% of the defects were covered with periosteum and 74% with a porcine collagen membrane (chondrogide)

Minimum follow-up was six months, 70 patients had minimum follow-up of one year. Mean follow-up 18 months.

Patients were assessed using Modified Cincinnati and Stanmore Functional rating systems, visual analogue scores and clinical evaluation.

Arthroscopy and biopsy was performed at one year and the repair assessed using the International Cartilage Research Society grading system.

At one year follow-up overall 41 % patients had an excellent result, 48% good, 8% fair and 3% poor. For defects of the medial femoral condyle, 88% had a good or excellent result, 85% for the lateral femoral condyle and 80% for the patella.

61 patients were arthroscopically assessed at one year. 50/61 (82%) demonstrated ICRS grade 1 or 2 repair. Healing of the defect occurred with either a periosteum or chondrogide defect cover.

Results at one year suggest that ACI is a successful articular cartilage repair technique in selected patients. Long-term follow-up is required to assess the durability of the repair.

The use of intra-articular hyaluronic acid injections for the treatment of early osteoarthritis is in widespread clinical use. Hyaluronate (HA) is a major component of connective tissue¹ and is available commercially for the intra-articular injective treatment of osteoarthritis of the knee and periarthritis of the shoulder. Although it is known to improve intra-articular lubrication it is also thought to promote articular cartilage structure and prevent catabolism of matrix proteoglycans in osteoarthritis. Clinical studies have shown beneficial effects lasting for many months after cessation of therapy unlike anti-inflammatory drugs that have relatively short term relieving effects^2,3 . Documentation of the true chondroprotective effects of hyaluronic acid (HA) at the cellular level is lacking and therefore this study aimed to identify the effects of HA on chondrocytes cultured in vitro.

Bovine articular chondrocytes were isolated by sequential digestion with pronase and collagenase and seeded in 2% alginate at 1x10⁷ cells/ml. The constructs were cultured for up to 14 days in standard culture medium (DMEM + 20% Fetal calf serum) containing varying concentrations of HA (Sigma), including doses equivalent to those found in vivo. The medium was replaced every 3 days and representative constructs were removed from culture, digested and assayed for DNA, glycosaminoglycans and Collagen. Further constructs were fixed in 4% paraformaldehyde for standard histology and immunolocalisation of collagen types I, II and chondroitin-6-sulphate.

Chondrocytes cultured in the HA system proliferated (increase in DNA) at a faster rate than the controls. There was a 2.2 fold increase in cell concentration at 14 days compared to a 1.2 fold increase in the controls. Total GAG levels at each time point were significantly greater for cells cultured in HA than in controls. Histologically, constructs were characterised by extensive cell cluster formation and intense Safranin-O staining. The newly synthesised matrix also stained positive for type II collagen. By contrast, control constructs exhibited minimal cluster formation, Safranin-O and type II collagen staining.

Cells maintained with HA exhibited a significantly greater rate of proliferation and matrix production. The presence of matrix rich in type II collagen indicates maintenance of chondrocytic phenotype. By contrast, cells cultured without HA did not show these features. These results support the use of intra-articular injections for the treatment of osteoarthritis. The benefits of HA injections may be due to cellular mechanisms as well as mechanical.

The use of intra-articular corticosteroid injections for their anti-inflammatory effects is widespread amongst clinicians. Despite their use in both rheumatoid arthritis and osteoarthritis, the effect of these agents on articular chondrocytes is not fully established. Previous reports suggest a detrimental effect on cartilage explants resulting from inhibition of matrix synthesis¹. However it has also been suggested that the beneficial effects in vivo may be due to prevention of inflamed synovium causing cartilage degradation². Our aim was to assess the effect of a commercially available preparation of methylprednisolone (MP), at clinical doses, on articular chondrocytes cultured in vitro.

Bovine articular chondrocytes were isolated by sequential digestion with pronase and collagenase and seeded in 2% alginate at 1x10⁷ cells/ml. The constructs were cultured for up to 15 days in standard culture medium (DMEM + 20% Fetal calf serum) containing varying concentrations of MP, including doses equivalent to those found in vivo. The medium was replaced every 3 days and representative constructs were removed from culture, digested and assayed for DNA and glycosaminoglycans. Further constructs were fixed in 4% paraformaldehyde for standard histology and immunolocalisation of collagen types I, II and chondroitin-6-sulphate.

Chondrocytes cultured in MP containing medium showed a significant abnormality in cell morphology compared to controls at the day 15 time point. Histologically there was evidence of cell necrosis, reduced amounts of extracellular matrix and loss of collagen type II staining. The effects were dose dependant, with significant damage occurring even at clinical doses. Biochemical analysis revealed a reduction in DNA content and an inhibition of glycosaminoglycan and collagen type II synthesis. In contrast, in the controls, there was cell proliferation with a cell doubling time of 14 days, collagen type II containing extracellular matrix synthesis occurred and the chondrocytes maintained their phenotype throughout the culture period.

Methylprednisolone has a significant detrimental effect on cultured articular chondrocytes in vitro. There was significant cell necrosis associated with inhibition of extracellular matrix synthesis. Based on these results, intra-articular corticosteroid injections should be used with extreme caution.

Nicotine is a constituent of tobacco smoke and is present in the body fluids of smokers^1,2. Numerous studies have confirmed that smoking is a strong risk factor for back pain³. The most widely accepted explanation for the association is that smoking leads to malnutrition of spinal discs due to carboxyhaemoglobin formation. However, other constituents of smoke, such as nicotine, may also be responsible for intervertebral disc (IVD) degeneration by leading to cell necrosis in both the nucleus pulposus and annulus fibrosis. Despite evidence suggesting the detrimental effect on a variety of tissues, the effect of nicotine on IVD cells has not previously been investigated. This study investigated the influence of nicotine on the metabolism and viability of IVD cells cultured in vitro.

Bovine nucleus pulposus (NP) intervertebral disc cells were isolated by sequential digestion of caudal spinal disc nuclei with pronase and collagenase and seeded in 2% alginate at 5x10⁶ cells/ml. The constructs were cultured for 21 days in standard culture medium (DMEM + 20% Fetal calf serum) containing free base nicotine (Sigma) at concentrations ranging from 25nM and 300nM, which reflected the normal physiological concentrations found in the serum of smokers. The medium was replaced every 3 days and representative constructs were removed from culture, digested and assayed for DNA, glycosaminoglycan (GAG) and hydroxyproline content at time points 3, 7, 14 and 21 days. Further constructs were processed for standard histology and immunolocalisation of collagen types I, II and chondroitin-6-sulphate.

The results were analysed statistically using an ANOVA test followed by a non-parametric Dunnit’s test. NP cells demonstrated a dose dependent response. At 25nM dose of nicotine there was a significant increase (p< 0.05) in DNA content, GAG and collagen synthesis in the constructs. At 100nM, 200nM and 300nM doses, there was a significant dose dependent decrease (p< 0.05) in all of these parameters compared to controls cultured under nicotine free conditions. In addition, adverse morphological changes were observed on histology, which included reduced cell proliferation, disrupted cell architecture, disintegration of cells and extracellular matrix. Immunohistochemistry showed the production of type I collagen rather than type II collagen as in the controls.

Nicotine has an overall detrimental effect on cultured nucleus pulposus disc cells in vitro. There was significant inhibition of cell proliferation and extracellular matrix synthesis. Nicotine in tobacco smoke may therefore play a role in the aetiology of disc degeneration that leads to back pain in smokers.

Deep infection is a devastating complication of total joint arthroplasty. In a significant proportion of cases it remains a diagnostic challenge. Haematological tests are not specific, particularly in chronic cases, and radiological investigations such as bone scan and radiographs are of only limited value. The most common infective organisms are staphylococcus and some streptococcus species. Acidity is a well established occurrence in infective processes and is caused by the direct production of acid by the organism or by enzymatic degradation of tissues ^1,2. In wound infections, peritonitis and some other conditions pH is used as an indicator of infection in clinical practice³. The aim was to assess whether fluid biochemistry (pH, pCO2, pO2, Lactate and Glucose) is altered in infected total knee replacements and whether it could be used as a diagnostic test.

Nineteen consecutive patients undergoing either revision total knee replacement (TKR) or arthroscopic synovial biopsy were included in the study. All had had their primary joint replacement within the previous 3 years. All had a painful total knee replacement and some had evidence of loosening of the prosthesis on radiological investigations. The following investigations were performed on each patient, White cell count (WCC), Erythrocyte Sedimentation Rate (ESR), C-Reactive Protein (CRP), interface synovial biopsy for histology and microbiology and a synovial fluid aspiration from the affected joint prior to application of a tourniquet. A blood gas analyser was used to measure pH, pCO2, pO2, Lactate and Glucose in all synovial fluid specimens.

Seven patients were diagnosed as having an infected TKR on clinical and laboratory investigations. The mean synovial fluid biochemistry results were pH = 7.09, pO2= 5.08kPa, pCO2=10.40kPa, Lactate = 5.33 mmol/l, Glucose = 2.30 mmol/l. In the non-infected group the results were pH = 7.23, pO2 = 7.72kPa, pCO2 = 8.41kPa, Lactate = 4.03 mmol/l, Glucose = 3.42 mmol/l. The differences in pH, pCO2/pO2 ratio, and glucose levels were statistically significant (t-Test p < 0.05) between the two groups. Lactate levels were not significantly different. There was no correlation between high WCC’s and synovial fluid biochemistry or laboratory results for infected cases. Using laboratory results as a gold standard and a synovial fluid pH of less than 7.20, the sensitivity was 85% and specificity 77% for diagnosing an infection. Using a combination of the synovial fluid biochemistry results these values were greater.

Synovial fluid biochemistry is significantly altered in infected total knee replacements. pH levels below 7.2, pCO2/pO2 ratio above 2.5 and Glucose levels below 2.5 mmol/l are strong indicators of an infected TKR. Synovial pH assessment may prove to be a quick, cheap and effective method of diagnosing an infected TKR and may also apply to other joints. Further studies using non-problematic TKR’s as controls are required.