Primary lymphomas of bone are uncommon malignancies with involvement of spine, long bones, pelvis, ribs and skull in decreasing order of frequency. We describe an unusual case who presented with recurrent knee effusions turned out to be a high grade B-cell non-Hodgkin lymphoma.

A 34-year-old man is presented with painful recurrent knee effusions without any systemic aberration. Multiple aspirations were carried out to help knee pain and swelling with immediate response, but had negative cytology. Hematological and biochemical parameters were normal. Plain radiographic examination of the knee failed to show any bony abnormalities. An MRI scan of the knee showed extensive marrow oedema of the distal femur with breach in the anterior cortex. Subsequently, open biopsy of the lesion was carried out which confirmed the diagnosis of a high grade B-cell Non-Hodgkin lymphoma. Staging CT-scan of the chest, abdomen and pelvis failed to show any other lesions elsewhere. He was subsequently treated with the help of multi-drug chemotherapy and radiotherapy. At 7 months post treatment, the patient had no relapse and a repeat MRI at 7 months showed reduction in the size of lesion.

This case illustrates the limitations of plain radiograph and the usefulness of MRI in the diagnosis of bony lymphoma. The diagnostic dilemmas while investigating recurrent knee effusions due to primary skeletal Non Hodgkin lymphoma should be resolved by timely MRI scan and histological diagnosis.

Background: Metaphyseal fracture healing presents special biomechanical challenges in orthopaedic surgery. The void typically created by damage to the metaphyseal cancellous bone must usually be filled in order to recover the biomechanical integrity of the bone. While autologous bone grafting is a standard treatment for these fractures, bone graft substitutes delivered with or without pharmacologic agents may augment healing.

Hypothesis: Tricalcium phosphate (TCP) is a known osteoconductive bone filler and OP-1 an osteoinductive bone morphogenetic protein; both have been used in the past in diaphyseal fractures with success. PTH (parathyroid hormone) has been recently shown to enhance osteoblastic activity, to have a net anabolic effect on bone mass, and to enhance healing of diaphyseal fractures. Each of these agents may also enhance healing of metaphyseal fractures.

Objective: The potential of all above factors to accelerate metaphyseal fracture healing has been evaluated in a new metaphyseal fracture model developed in our laboratory in a rabbit model.

Material and Methods: A metaphyseal wedge osteotomy was created in the distal tibia of 16-week-old female New Zealand White rabbits (n=20). The osteotomy was bridged with a custom-made external fixator. The osteotomy gap was filled with TCP containing OP-1 (n=4), TCP alone with daily subcutaneous injections of 10μg/Kgr BW PTH (n=4), or TCP alone with daily subcutaneous administration of 40μg/Krg BW PTH (n=4). Two control groups, TCP alone (n=4) and normal healing (n=4), were also included. Assessment methods included biomechanical testing in both compression and torsion, radiographic examination, and QCT scans.

Results: Healing was observed in both PTH treated groups as well as in the OP-1 group at 4 weeks post-surgery. PTH appeared to have a systemic effect on bone formation, whereas the effect of OP-1 was local to the osteotomy site. In comparison, healing was delayed in the normal healing and TCP alone groups.

Conclusion: PTH and OP-1 both enhance metaphyseal fracture healing. The different systemic vs. local effects of these two agents, suggest that PTH and OP-1 may have potential synergism in accelerating healing of metaphyseal fractures.

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.