A Radiologists' Guide to En Bloc Resection of Primary Tumors in the Spine: What Does the Surgeon Want to Know?

En bloc resection in the spine is performed for both primary and metastatic bone lesions and has been proven to lengthen disease-free survival and decrease the likelihood of local recurrence. It is a complex procedure, which requires a thorough multi-disciplinary approach. This article will discuss the role of the radiologist in characterizing the underlying tumor pathology, staging the tumor and helping to predict possible intraoperative challenges for en bloc resection of primary bone lesions. The postoperative appearances and complications following en bloc resection in the spine will be considered in subsequent articles.

A guide to assessing post-operative complications following en bloc spinal resection.

En-bloc resection of spinal tumours is a complex procedure with significant morbidity and mortality. The extensive resection leaves a large soft tissue and osseous defect requiring reconstruction. Following en-bloc resection, there may be complications relating to both the removal of the tumour and the subsequent reconstruction. This paper outlines the imaging appearances of the frequently encountered complications in our experience. The primary aim is to improve the confidence of the radiologist when reporting imaging following spinal en-bloc resection, however we believe this is also useful for the spinal and orthopaedic surgeons in assessing the patients following en block resection.

A rare case of Paget's disease affecting the cervical spine.

We present the case of a 75-year-old man with a rapidly progressive cervical myelopathy on a background of a 3-year history of neck pain and a severely degenerative cervical spine. The patient developed progressive myelopathy over a six-month period and suffered from worsening kyphosis. Suspicion of an underlying oncological process prompted transfer to our tertiary referral unit. Biopsy was consistent for Paget's disease, an extremely rare diagnosis of the cervical spine. Magnetic resonance imaging revealed cord compression between C4 and C6 with associated cord signal change indicative of myelopathy. A three-level corpectomy and posterior instrumented fusion was performed. There was significant blood loss (3.5l) intraoperatively, consistent with a diagnosis of Paget's disease of the bone. Cell salvage was used, as was neuromonitoring for both the anterior and posterior part of the procedure. Postoperatively, neurological function improved slightly and the patient required community neurorehabilitation to allow independent living.

Acute symptomatic calcific discitis in adults: a case report and review of literature.

Symptomatic calcific discitis has been reported in the paediatric population but is a rare entity in adults with only eight cases reported in the English literature. We present a case of adult calcific discitis presenting with acute onset back pain. Radiographs and CT demonstrated central T11-T12 disc calcification with diffuse marrow oedema on subsequent MRI. The patient was referred to our spinal oncology unit due to the extensive marrow oedema as a possible underlying primary bone tumour. Review of the CT confirmed an end-plate defect with herniated calcific nucleus pulposus with no underlying bone lesion. Features were in keeping with acute calcific discitis. The patient was treated symptomatically and made an uneventful recovery. We discuss the characteristic imaging features seen on radiograph, CT and MRI and review the current literature. Calcific discitis is a self-limiting pathology requiring symptomatic management only. Radiologists need to be aware of this rare entity as it can occur in adults and may be mistaken for a more sinister pathology such as infective discitis or a bone tumour and lead to further unnecessary imaging or invasive procedures.

Imaging appearances and clinical outcome following sacrectomy and ilio-lumbar reconstruction for sacral neoplasia.

OBJECTIVE: Sacrectomy and ilio-lumbar reconstruction is an uncommonly performed complex surgical procedure for the treatment of sacral neoplasia. There are many challenges in the post-operative period including the potential for tumor recurrence, infection, and construct failure. We present our experience of this patient cohort and describe the complications and imaging appearances that can be encountered during the follow-up period. MATERIALS AND METHODS: Retrospective review of our Orthopaedic Oncology database was undertaken which has been collected over a 30-year period to identify patients that had undergone sacrectomy and ilio-lumbar reconstruction. Pre and post-operative imaging including radiographs, CT, and MRI was reviewed. These were viewed by two experienced musculoskeletal radiologists with consensus opinion if there was disagreement over the imaging findings. Data regarding patient demographics, tumor type, and dimensions was collected. Serial review of radiographs, CT, and MRI was performed to assess implant position and integrity, strut graft position and union, and for the presence of recurrence within the surgical bed. RESULTS: Five male and two female patients (mean age 36 years, age range 15-54 years) were treated with this procedure. Histological diagnoses included chordoma, chondrosarcoma, osteosarcoma, and spindle cell sarcoma. Mean maximal tumor size on pre-operative imaging was 10.7 cm (range, 6-16 cm). Post-operative follow-up ranged from 10-46 months. A total of 76 imaging studies were reviewed. Commonly identified complications included vertical rod and cross-connector fracture and screw loosening. Fibula strut graft non-union and fracture was also evident on imaging review. Two patients demonstrated disease recurrence during the follow-up period. CONCLUSIONS: This study demonstrates the spectrum and frequency of complications that can occur following sacrectomy and ilio-lumbar reconstruction for sacral neoplasia.

Adaptation of skull clamp for use in image-guided surgery of children in the first 2 years of life.

INTRODUCTION: We describe a simple but effective modification of the skull clamp, aimed at stabilising the head of very young children, while avoiding the risk of creating a depressed skull fracture, in order to enable the utilisation of image-guidance in such young patients. METHODS: We machined three small perspex discs 3 cm in diameter. On the outer surface of these pads we drilled reception holes for the pins to prevent slippage. To avoid direct contact with the skin, we interfaced a thick pad of soft felt. During intraoperative positioning, the weight of the head was supported by a suction bean-bag placed on the operating table. Hence, the clamp apparatus was employed only to secure the head position, and not to support the weight of the head, thus requiring less clamp force. We employed this modification in three children (aged 9, 13 and 15 months) who required image-guided surgery for brain tumours. OUTCOME: In all cases the head remained immobile throughout the operation, making possible the accurate use of image guidance. At the end of the operation, some transient skin redness was noticed in the contact areas, which settled in a few days.

The effect of biological effective dose on time to symptom progression in metastatic renal cell carcinoma.

AIMS: Renal cell carcinoma is commonly thought to be a radioresistant malignancy. Retrospective studies report conflicting results on the effect of radiotherapy dose escalation on response and time to progression in symptomatic metastatic disease; studies using the linear quadratic model have used alpha/beta ratios that are inappropriate for slow growing tumours. We aim to describe our experience with palliative radiotherapy in this context, relating Biological Effective Dose to outcome. MATERIALS AND METHODS: From December 1995 to April 2001, 143 independent palliative radiotherapy treatments were delivered to 78 patients in a single institution. Retrospective data was obtained on the radiotherapy schedule used, symptom response and time to symptom progression. The biological effective dose (BED) was calculated using alpha/beta ratios of 3 and 7 Gy (BED3 and BED7). The Log-Rank test was used to assess any differences in time to progression, and the Cox Proportional Hazards analysis to determine prognostic factors of time to progression. RESULTS: Overall symptomatic response rate was 73%, with most responses being partial (67%). Forty-three (38%) patients had symptomatic progression after a median follow-up of 425 days. BED (BED3 or BED7) was not significantly different across response types (complete, partial or no response; P=0.90 and 0.88, respectively) and was not predictive for time to symptomatic progression (P=0.99 for BED3 and P=0.70 for BED7). Patients with bone metastases received less total dose (P=0.001), less BED (BED3, P=0.0013, and BED7, P=0.0005) and had a significantly longer time to progression than other sites of metastases (hazard ratio (HR) 0.4; 95% confidence interval (CI) 0.2-0.7; P=0.004). Initial treatment with interferon-alpha alone in patients presenting with metastatic disease, before palliative radiotherapy, was also associated with a shorter time to symptom progression (HR 4.6; 95% CI 1.5-14.1; P=0.007). On removal of these criteria, brain metastases became a significant predictor of progression time, with an HR of 2.5 (95% CI 1.0-5.9; P=0.05), showing an increased risk of progression with brain metastases compared with metastases elsewhere. Time from primary diagnosis to development of metastatic disease was not predictive of time to symptom progression (P=0.29). CONCLUSION: Despite the widespread assumption that renal cell carcinoma is radioresistant, retrospective assessment showed high response rates to palliative radiotherapy. On the basis of our data, higher BED does not seem to be a predictor of response or of duration of response in the palliative treatment of renal cell carcinoma. Palliation of bone pain seems to be particularly durable compared with the palliation of symptoms at other sites of metastases. A trend for shorter duration of palliative effect of whole-brain radiotherapy was noted.

The 22 kDa component of the protein complex on the surface of Plasmodium falciparum merozoites is derived from a larger precursor, merozoite surface protein 7.

The gene coding for merozoite surface protein 7 has been identified and sequenced in three lines of Plasmodium falciparum. The gene encodes a 351 amino acid polypeptide that is the precursor of a 22-kDa protein (MSP7(22)) on the merozoite surface and non-covalently associated with merozoite surface protein 1 (MSP1) complex shed from the surface at erythrocyte invasion. A second 19-kDa component of the complex (MSP7(19)) was shown to be derived from MSP7(22) and the complete primary structure of this polypeptide was confirmed by mass spectrometry. The protein sequence contains several predicted helical and two beta elements, but has no similarity with sequences outside the Plasmodium databases. Four sites of sequence variation were identified in MSP7, all within the MSP7(22) region. The MSP7 gene is expressed in mature schizonts, at the same time as other merozoite surface protein genes. It is proposed that MSP7(22) is the result of cleavage by a protease that may also cleave MSP1 and MSP6. A related gene was identified and cloned from the rodent malaria parasite, Plasmodium yoelii YM; at the amino acid level this sequence was 23% identical and 50% similar to that of P. falciparum MSP7.

The merozoite surface protein 6 gene codes for a 36 kDa protein associated with the Plasmodium falciparum merozoite surface protein-1 complex.

A complex of non-covalently bound polypeptides is located on the surface of the merozoite form of the human malaria parasite Plasmodium falciparum. Four of these polypeptides are derived by proteolytic processing of the merozoite surface protein 1 (MSP-1) precursor. Two components, a 22 and a 36 kDa polypeptide are not derived from MSP-1. The N-terminal sequence of the 36 kDa polypeptide has been determined, the corresponding gene cloned, and the protein characterised. The 36 kDa protein consists of 211 amino acids and is derived from a larger precursor of 371 amino acids. The precursor merozoite surface protein 6 (MSP-6) has been designated, and the 36 kDa protein, MSP-6(36). Mass spectrometric analysis of peptides released from the polypeptide by tryptic digestion confirmed that the gene identified codes for MSP-6(36). Antibodies were produced to a recombinant protein containing the C-terminal 45 amino acid residues of MSP-6(36). In immunofluorescence studies these antibodies bound to antigen at the parasite surface or in the parasitophorous vacuole within schizonts, with a pattern indistinguishable from that of antibodies to MSP-1. MSP-6(36) was present in the MSP-1 complex immunoprecipitated from the supernatant of in vitro parasite cultures, but was also immunoprecipitated from this supernatant in a form not bound to MSP-1. Examination of the MSP-6 gene in three parasite lines detected no sequence variation. The sequence of MSP-6(36) is related to that of the previously described merozoite surface protein 3 (MSP-3). The MSP-6(36) amino acid sequence has 50% identity and 85% similarity with the C-terminal region of MSP-3. The proteins share a specific sequence pattern (ILGWEFGGG-[AV]-P) and a glutamic acid-rich region. The remainder of MSP-6 and MSP-3 are unrelated, except at the N-terminus. Both MSP-6(36) and MSP-3 are partially associated with the parasite surface and partially released as soluble proteins on merozoite release. MSP-6(36) is a hydrophilic negatively charged polypeptide, but there are two clusters of hydrophobic amino acids at the C-terminus, located in two amphipathic helical structures identified from secondary structure predictions. It was suggested that this 35 residue C-terminal region may be involved in MSP-6(36) binding to MSP-1 or other molecules; alternatively, based on the secondary structure and coil formation predictions, the region may form an intramolecular anti-parallel coiled-coil structure.

Wound complications following resection of adductor compartment tumours.

Purpose Limb salvage surgery of soft tissue sarcomas is associated with both a risk of local recurrence and wound complications. Although the lower limb appears to be at greater risk of wound-related morbidity, few studies separate anatomical compartments. We believe that the adductor compartment of the thigh has a particularly high rate of complications and so performed a retrospective analysis of all soft tissue sarcomas arising in this region undergoing limb salvage.Patients Patients with intermediate and high grade adductor compartment tumours were identified from our database and the case notes were reviewed for patient, tumour, surgical and wound variables, identifying those with wound complications both before and after discharge.Results Of 49 patients who underwent limb salvage surgery, 22 (42.9%) developed complications. Twelve patients (24.5%) required further surgery prior to wound healing and 10 patients had delays in post-operative radiotherapy. There were significant differences in the rates of preceding surgery, open biopsy performed at other centres and previous radiotherapy to this region between the complicated and uncomplicated groups.Discussion The management of these difficult tumours carries a high rate of wound complications and requires careful planning prior to tissue biopsy. Open biopsies should be performed by the tumour surgeon to allow easy inclusion of this site in the definitive procedure. In previously irradiated or operated limbs, alternative strategies for wound management may need to be considered.

PCR-based gene synthesis as an efficient approach for expression of the A+T-rich malaria genome.

The A+T-rich genome of the human malaria parasite Plasmodium falciparum encodes genes of biological importance that cannot be expressed efficiently in heterologous eukaryotic systems, owing to an extremely biased codon usage and the presence of numerous cryptic polyadenylation sites. In this work we have optimized an assembly polymerase chain reaction (PCR) method for the fast and extremely accurate synthesis of a 2.1 kb Plasmodium falciparum gene (pfsub-1) encoding a subtilisin-like protease. A total of 104 oligonucleotides, designed with the aid of dedicated computer software, were assembled in a single-step PCR. The assembly was then further amplified by PCR to produce a synthetic gene which has been cloned and successfully expressed in both Pichia pastoris and recombinant baculovirus-infected High Five(TM) cells. We believe this strategy to be of special interest as it is simple, accessible and has no limitation with respect to the size of the gene to be synthesized. Used as a systematic approach for the malarial genome or any other A + T-rich organism, the method allows the rapid synthesis of a nucleotide sequence optimized for expression in the system of choice and production of sufficiently large amounts of biological material for complete molecular and structural characterization.

PfSUB-2: a second subtilisin-like protein in Plasmodium falciparum merozoites.

Erythrocyte invasion by the malaria merozoite requires the activity of merozoite proteases. We have previously identified a Plasmodium falciparum protein belonging to the superfamily of subtilisin-like serine proteases, which is expressed in a subset of secretory organelles in free merozoites. Here we describe the identification of a second P. falciparum subtilisin-like merozoite protein. Called PfSUB-2, it is encoded by a single copy gene and is expressed as a large putative type I integral membrane protein which undergoes extensive post-translational processing. The terminal processing product is expressed in an apical location in merozoites. PfSUB-2 may mediate one or more of the serine protease activities known to be associated with erythrocyte invasion.

A subtilisin-like protein in secretory organelles of Plasmodium falciparum merozoites.

In the vertebrate host, the malaria parasite invades and replicates asexually within circulating erythrocytes. Parasite proteolytic enzymes play an essential but poorly understood role in erythrocyte invasion. We have identified a Plasmodium falciparum gene, denoted pfsub-1, encoding a member of the subtilisin-like serine protease family (subtilases). The pfsub-1 gene is expressed in asexual blood stages of P. falciparum, and the primary gene product (PfSUB-1) undergoes post-translational processing during secretory transport in a manner consistent with its being converted to a mature, enzymatically active form, as documented for other subtilases. In the invasive merozoite, the putative mature protease (p47) is concentrated in dense granules, which are secretory organelles located toward the apical end of the merozoite. At some point following merozoite release and completion of erythrocyte invasion, p47 is secreted from the parasite in a truncated, soluble form. The subcellular location and timing of secretion of p47 suggest that it is likely to play a role in erythrocyte invasion. PfSUB-1 is a new potential target for antimalarial drug development.

Association between circulating antigen and parasite load in a model filarial system, Acanthocheilonema viteae in jirds.

Jirds (Meriones libycus) were infected with various numbers of Acanthocheilonema viteae L3 stage parasites. During the course of the ensuing 16 weeks, blood samples were collected at 2 weekly intervals and the amount of the major parasite excretory-secretory product (E-S 62) and antibodies directed against it measured. After 16 weeks, animals were sacrificed and the size of the mature worm burden established. In spite of interaction between E-S 62 and host antibody, a statistically significant relationship was found to exist between the amount of E-S 62 present in the bloodstream and the size of the parasite load. It is suggested that the detectable antigen level is more influenced by the size of the worm burden than the presence of antibody and that antibody is only likely to affect adversely antigen measurement in situations where the amount released is relatively low. Examples of this are early in infection and in low-level infections. These ideas are discussed in relation to the development and assessment of serological assays which attempt to predict parasite burden in human filarial infections.

Origin, kinetics of circulation and fate in vivo of the major excretory-secretory product of Acanthocheilonema viteae.

The excretions-secretions (E-S) of Acanthocheilonema viteae consist mainly of one product, molecular weight 62kDa. This molecule is synthesized during the vertebrate phase of the parasite life-cycle and is first detectable in the E-S of L4 parasites. It is cross-reactive with E-S of human filarial parasites as a consequence of possessing a phosphorylcholine (PC) moiety. The 62 kDa molecule has been employed as a model for the study of the origin and fate of filarial E-S. Immunohistological analysis has shown the molecule to be located predominantly in the parasite gut. Transplantation of adult female [35S] methionine pulsed worms into uninfected jirds resulted in the radio-labelled secreted 62 kDa antigen being detected in the bloodstream within 4 h by SDS-PAGE/immunoprecipitation analysis. The systemic half-life of the molecule as estimated by clearance of injected, purified 125I-labelled material was measured in naive and infected jird hosts. It was reduced from 2-7 h in naive animals to less than 30 min in 4-10 week infected rodents, a finding which correlated with clearance of antigen by antibody in the infected group. In animals infected for longer time periods the serum half-life returned to the values observed in naive jirds. The idea that this change in half-life may reflect differences in the nature of 62 kDa antigen containing circulating immune complexes as infection progresses is discussed. The 125I-labelled antigen is predominantly removed from the circulation via the liver and ultimately excreted in the urine in a non-antigenic form. This work provides the first description of the origin, kinetics of circulation and fate of a defined filarial E-S product and may aid in determining the function and assessing the diagnostic utility of PC-bearing E-S components.

Evaluation of the potential of excretions-secretions (E-S) of Litomosoides carinii to substitute for human filarial E-S.

The antigenic cross-reactivity of the excretions-secretions (E-S) of Litomosoides carinii was investigated. Immunoprecipitation using pooled sera from a number of human filarial infections in combination with sodium dodecyl sulphate-polyacrylamide gel electrophoresis (SDS-PAGE) analysis revealed variations in the cross-reactivity of individual molecules. Some were specific to L. carinii, the major examples in this category being two E-S components of 140 and 160 kDa released by day 40- to 42-day-old female worms. Another, a high-molecular-weight product of 26- to 28-day E-S, was broadly cross-reactive. A third group appeared to exhibit reactivity to antibody to some but not all human filarial parasites. The most striking examples of this were two distinct 14-kDa products that bound solely to antibodies in an onchocerciasis serum pool. These results are discussed in relation to the use of cross-reacting molecules in investigating the immunisation potential, defining the function, and evaluating the diagnostic utility of human filarial E-S.