Hangman's fracture: the relationship between asymmetry and instability

There is ambiguity concerning the nomenclature and classification of fractures of the ring of the second cervical vertebra (C2). Disruption of the pars interarticularis which defines true traumatic spondylolisthesis of C2, is often wrongly called a pedicle fracture. Our aim in this study was to assess the influence of asymmetry on the anatomical and functional outcome and to evaluate the criteria of instability established by Roy-Camille et al. We studied the plain radiographs and CT scans of 24 patients: 13 were judged to be asymmetrical, ten were considered unstable and 14 stable. Treatment was with a Minerva jacket in 15 fractures and by operation in nine. Surgery was undertaken in patients with severe C2 to C3 sprains. One patient with an unstable lesion refused operation and was treated conservatively with a poor radiological result. Our study showed that asymmetry of the fracture did not affect the outcomes of treatment and should not therefore influence decisions in treatment. The criteria of Roy-Camille seem to be reliable and useful. We prefer the posterior approach to the cervical spine, which allows both stabilisation of the fracture and correction of a local kyphosis.

Skeletal muscle regeneration and the mitotic clock

Regeneration of muscle fibers following damage requires activation of quiescent satellite cells, their proliferation and finally their differentiation and fusion into multinucleated myotubes, which after maturation will replace the damaged fiber. The regenerative potential of human skeletal muscle will be determined, at least partly, by the proliferative capacity of the satellite cells. In this study, we have measured the proliferative life span of human satellite cells until they reach senescence. These analyses were performed on cell populations isolated from old and young donors as well as from one child suffering from Duchenne muscular dystrophy, where extensive regeneration had occurred. In order to see if there are any age-related changes in the myogenic program we have also compared the program of myogenic differentiation expressed by satellite cells from these subjects at different stages of their proliferative lifespan.

[Comminuted fractures in multiple trauma patients: an analysis of 31 cases]

PURPOSE OF THE STUDY

We analyzed calcaneum burst fractures in multiple trauma patients and propose a management scheme.

MATERIAL AND METHODS

In a retrospective study, we isolated 23 patients with 31 calcaneum burst fractures. All were stage V in the Duparc classification. We call them "pied de mine" fractures as they resembled those described in military reports. Half of them (16 cases; 54%) were open fractures. All patients suffered multiple injuries and 12 had a psychiatric history. These fractures were associated with spinal fracture in 17 cases (73%) and half had neurologic deficit, limb fracture in 16 (73%), and pelvic fracture in 12 (52%). The most frequent associated foot injuries were a talus fracture in 9 cases (29%) and Chopart displacement in 10 cases (32%). Clinical evaluation used the Maryland foot score, foot print and radiologic evaluation with lateral retrotibial view.

RESULTS

Mean follow-up was 35 months. Mean Maryland foot score was 62.7 and 13 cases were pain free. Pain was due to conflict with the lateral malleolus, bony plantar thorns, medial malleolus and subtalar osteoarthritis. Orthopedic shoes were used 11 times. The other patients used sports shoes. Subtalar mobility was most frequently absent (23/29 cases, 2 amputations). Foot print showed 13/16 flat feet; 6 thorns were indirectly visible. Two patients had retraction toes and were initially treated by external fixation. Radiologic evaluation showed 23/29 complete subtalar arthrodeses, 23/29 migration of the great tuberosity, often(17/23 cases) associated with varus angulation. Eleven patients needed subsequent surgery: 5 for arthrodeses and 6 for resection of bony thorns. Rate of complication was high, especially for open fractures: 2 infections for 15 closed fractures, and 8 infections (50%) for 16 open fractures with 2 cases of chronic osteitis. Secondary amputation was required in 2/31 cases due to sepsis. TREATMENT PROPOSITIONS: For closed calcaneum burst fractures, it is better to wait one week before osteosynthesis. This delay is used to decrease edema with limb elevation and compressive bandaging. Skin tension due to trauma is increased by edema and osteosynthesis gives a high risk of wound disunion. We recommend reduction and Y-plate fixation even for burst fracture. Reduction must lower the tuberosity and correct the varus. After surgery, subtalar spontaneous arthrodesis is usually observed in a good position. Any bony plantar thorn must be resected. For open calcaneum burst fracture, the risk of sepsis is high. First treatment is debridement, stabilization and external fixation with antibiotic therapy. Stabilization should improve vascularization and facilitate internal fixation. The external fixation can be placed on the medial side to free the lateral approach to the calcaneum. Flap repair can be performed after one week when skin tension has subsided and areas of necrosis controlled.

Sagittal alignment in lumbosacral fusion: relations between radiological parameters and pain

The objective of this study was to conduct a radiological analysis of posture before and after lumbosacral fusion to evaluate the influence of spinal alignment on the occurrence and pattern of post surgical pain. The study included 81 patients, of whom 51 had a history of previous low back surgery. We excluded patients with suspected or confirmed nonunion. In the fusion group, the 27 patients who were pain free after the procedure were compared to the 54 patients with residual pain. Thirty patients had pain only or primarily when they were standing immobile, 18 when they were sitting immobile, and six in both positions. Measurements were done on full-length lateral radiographs of the spine, with the patient standing according to Duval Beaupère criteria. The subgroup with postfusion pain was characterized at baseline by a more vertical sacrum with less sacral tilt (ST) (P < 0.0062) and more pelvic tilt (PT) (P < 0.0160). PT at last follow-up (PT fu) correlated with the presence of postfusion pain (NP: P = 0.0003). In the patients with postfusion pain, PT was almost twice the normal value. ST at last follow-up (ST fu) in the standing position was also correlated with the presence of postfusion pain (P < 0.0001) indicating that the sacrum remained abnormally vertical in the subjects with postfusion pain. Using logistic regression, the only prognostic factor for residual pain at last follow-up was ST fu. Both at pre-operative evaluation and at last follow-up, patients with pain in the standing position or in both the standing and sitting positions were characterized at pre-operative status by a more vertical sacrum with less sacral tilt. The results of this study indicate that, achieving a strong fusion should not be the only goal. Appropriate position of the fused vertebrae is also of paramount importance to minimize muscle work during posture maintenance. The main risk is failing to correct or to causing excessive pelvic retroversion with a vertical sacrum leading to a sagittal alignment that replicates the sitting position. This situation is often accompanied by loss of lumbar lordosis and adversely affects stiff or degenerative hips.

[Direct cost assessment of wrist fractures]

PURPOSE OF THE STUDY

The cost effectiveness of wrist fractures in 1996 at Pitié-Salpétrière Hospital in Paris has been thoroughly analysed. The purpose of this retrospective study was to identify the factors responsible for the variation in the treatment cost of those fractures.

MATERIAL AND METHODS

Cost, hospital stay, functional status, ASA score and surgical treatment were analysed in 53 patients with a median age of 57 years.

RESULTS

The mean cost per patient was 6,120 FF divided as follows: 26.1% for pre-operative care, 36.4% for surgical procedures, 37.5% for post-operative care. The mean hospital stay was 4.3 days. The cost of personnel (43%) and medical investigations (35%) were the two main sources of hospital expenses beside medical materials (12.5%), hostelry (5.5%), and drugs (4%).

DISCUSSION

The duration of hospital stay, the age and the type of the fracture were the only factors that affected statistically the mean cost per patient. Furthermore, factors related to the patient as sex, place of residence prior to admission, functional status, ASA score, had no influence on cost variation.

CONCLUSION

Therefore, the best way to reduce the cost of wrist fractures management is to minimize the hospital stay before and after surgical procedure to avoid a lengthy and costly hospital stay and to minimize the abuse utilisation of systematic medical investigations.

Anatomic basis of minimal anterior extraperitoneal approach to the lumbar spine

Anterior lumbar spine approaches may be indicated for fusion in degenerative lumbar spine disorders or to fill discal and bone gaps after fracture reduction. We present an anterior extraperitoneal approach applicable to any discal and vertebral levels from T12 to S1. The anatomic study, based on 25 cadavers, highlights retroperitoneal dissection principles for easy kidney and duodenopancreatic mobilisation and direct left anterior access to the entire lumbar spine. We established a precise description of the lumbar veins and the anastomoses between the left renal vein and hemiazygos system, in order to define different topographic and anatomic factors related to safe and easily reproducible approaches for cage or graft implementation. Independent of the level and previous intraperitoneal surgery, lumbar spine access with this approach safeguards the kidney, ureter, spleen, hypogastric plexus and duodenopancreatic system. Regarding operating time, blood-loss and possibilities for freshening and grafting, this technique seems an effective counterbalance to the difficulties and complex technology of endoscopic approaches. The clinical study includes our first 42 cases in traumatic and degenerative lesions. Avoiding the neurologic or hemorrhagic risk inherent in classical posterior lumbar interbody fusion (PLIF) techniques, it can be considered as a reasonable and valid alternative. This technique could be used in the near future for mini invasive discal prosthesis insertion.

Severe hyperflexion sprains of the lower cervical spine in adults

Severe sprains of the cervical spine result from a traumatic rupture of the intervertebral disc and ligaments. Although rare, these lesions may lead to a significant kyphotic deformity if they are not surgically treated. The treatment of such a kyphotic deformity may consist of surgical fixation of the lesion through either an anterior or posterior approach. A retrospective study has been done examining 44 severe cervical sprains in 41 patients surgically treated through a posterior approach, using Roy-Camille plates. With an average followup of 29 months (range, 6-60 months), 73% of the patients recovered a normal range of spinal motion, with either moderate or no pain. No neurologic or vascular complications directly attributable to posterior plating and no secondary kyphosis were observed. A moderate sagittal displacement with kyphotic angulation occurred above the fusion in five patients. Posterior screw plate fixation appears to be a safe and effective treatment for severe hyperflexion sprain of the lower cervical spine in the adult.

[Value and limits of determining serum cobalt levels in patients with metal on metal articulating prostheses]

PURPOSE OF THE STUDY

The purpose of this study was to measure the serum cobalt levels and their correlation with clinical and radiological findings in patients with metal on metal hip articulating surfaces.

METHOD

Forty-one patients with metal on metal hip arthroplasty were reviewed retrospectively at mean follow-up of 12.9 months. Serum cobalt levels were determined for each patient by atomic absorption spectrometry at the maximal follow-up and were compared to a control group (19 patients). Two patients and one control subjects also performed exercise on a treadmill in order to appreciate the influence of physical activity on serum cobalt levels.

RESULTS

The metal on metal group presented higher serum cobalt levels than those of the control group (p < 0.0001). There was no correlation between serum cobalt and clinical and radiological findings at the exception of patient age (n = 40, r = 0.37). However, when the follow-up was greater than 18 months, mean serum cobalt was significantly higher compared to a follow-up less than 18 months. The physical exercise test led to a moderate elevation (around 10 p. 100) of cobalt in the two patients but not in the control subject.

DISCUSSION AND CONCLUSION

The interpretation of an elevated cobalt serum level is difficult. Cobalt-containing drugs, other implants, excess of activity and diseases (renal failure) may influence serum cobalt level. In this study, the high serum cobalt levels seem not linked to a failure of the implant, mainly because of the short follow-up. They could rather be attributed to an increase of the patient activity beginning 18 months after the surgery. Because potential long-term cobalt toxicity and carcinogenicity is not well known, careful medical follow-up should be emphasized specially in young patients.

Vertical atlantoaxial dislocation

An unusual case of vertical atlantoaxial dislocation without medulla oblongata or spinal cord injury is reported. The pathogenic process suggested occipito-axial dislocation. The case was treated surgically with excellent results on mobility and pain.

Acute spinal cord compression due to intraspinal bleeding from a vertebral hemangioma: two case-reports

Vertebral hemangiomas can cause acute spinal cord compression either after a minor trauma or during the last 3 months of pregnancy. Failure to recognize the lesion can lead to potentially serious treatment delays. An emergency MRI scan usually establishes the diagnosis of vertebral hemangioma responsible for spinal cord compression requiring laminectomy. We report two cases showing that posterior fixation should be considered: in our experience it prevents vertebral collapse during the interval preceding secondary vertebroplasty, which, if performed, provides highly significant pain relief.

[Mobility of a polyethylene tibial insert in a mobile total knee prosthesis]

PURPOSE

We have studied the mobility of a mobile tibial implant in total knee arthroplasty (TKA) by a radiographical evaluation.

MATERIAL AND METHODS

We analyzed mobility of the polyethylene tibial insert of 15 "G2S" TKA implanted for one year or more. We established a dynamic radiographical evaluation. We used 3 weight-bearing radiographs: AP in extension and two lateral (one in extension and one at 90 degrees of flexion), two AP with femoral internal and external rotation, 2 strict lateral X-rays in neutral rotation in antero-posterior replacement with a 25 kilograms strength Telos, and 2 AP in varus and valgus with Telos. Wilcoxon's test and Fisher's exact test were used for statistical evaluation.

RESULTS

Our study demonstrated preservation of the polyethylene mobility in tibial TKA implant in all movements: in rotation, in antero-posterior translation with Telos, and even in antero-posterior translation during physiological condition with flexion-extension weight-bearing radiographs. Statistical tests were very significant. We noticed that flexion induced anterior translation of tibial polyethylene when PCL was preserved.

CONCLUSION

This study answered to our question whether mobility of TKA tibial implant persists after implantation. This mobility should reduce loosening forces to the tibia and stress in the polyethylene component. Now we have to determine the amplitude of mobility required to reach this objective.

[Ipsilateral hip and femoral shaft fractures: components of therapeutic choice]

PURPOSE OF STUDY

Ten cases of ipsilateral hip and femoral shaft fractures were reviewed.

MATERIAL AND METHODS

All patients were treated operatively for both fractures between 1988 and 1997 in Pitié Hospital. Five were treated with antegrade reamed intramedullary nails and cancellous screw fixation of the femoral neck, and 5 by long Gamma nail. The shaft fractures were fixed prior to definitive neck stabilization.

RESULTS

Ipsilateral hip and femoral shaft fractures accounts for 5.6 p. 100 of the whole femoral shaft fractures registered in the same period. All cases occurred in young adults and resulted from high-energy impaction injuries. There were numerous associated injuries and all patients were polytrauma. The hip fracture was initially overlooked in 1 case without subsequent nonunion or avascular necrosis. At a mean follow-up examination of 22 months, two-thirds had a good result and one-third a fair or a poor result. Nonunion of the femoral neck occurred in one patient as a result of initial displacement and subsequent malreduction, while all shaft fractures united.

DISCUSSION

X-ray films of the hip should be done in all cases of femoral shaft fracture in order to decrease the high incidence of missed femoral neck fractures in ipsilateral injuries of the femur. The results indicate that patients with ipsilateral fractures of the femoral neck and shaft can obtain good results when rigid anatomic stabilization of the femoral neck is performed. The femoral shaft fracture is given first priority and is reduced and immobilized with antegrade closed intramedullary nailing. The femoral neck fracture is then treated with cancellous screw fixation or compression screw with long Gamma nail.

CONCLUSION

The authors recommend the use of a long Gamma nail to fix this dual fracture whenever possible.

Effects of propofol, propofol-nitrous oxide and midazolam on cortical somatosensory evoked potentials during sufentanil anaesthesia for major spinal surgery

Recording of cortical somatosensory evoked potentials (CSEP) enables monitoring of spinal cord function. We studied the effects of propofol, propofol-nitrous oxide or midazolam during sufentanil anaesthesia on CSEP monitoring during major spinal surgery. Thirty patients with normal preoperative CSEP were allocated randomly to one of the following anaesthesia regimens: propofol (2.5 mg kg-1 followed by 10-6 mg kg-1 h-1) with or without nitrous oxide, or midazolam (0.3 mg kg-1 followed by 0.15 mg kg-1 h-1) combined with sufentanil 0.5 microgram kg-1 h-1 in the propofol and midazolam groups, or 0.25 microgram kg-1 h-1 in the propofol-nitrous oxide group. CSEP were elicited by alternate right and left tibial posterior nerve stimulation and recorded before and after induction (15 min, 1, 2 and 3 h), and during skin closure. CSEP latencies were not significantly modified in the three groups. CSEP amplitude decreased significantly in the propofol-nitrous oxide group (from mean 2.0 (SEM 0.3) to 0.6 (0.1) microV; P < 0.05) but not in the propofol (from 1.8 (0.6) to 2.2 (0.3) microV) or midazolam (1.7 (0.5) to 1.6 (0.5) microV) groups. The time to the first postoperative voluntary motor response (recovery) delay was significantly greater in the midazolam group (115 (19) min) compared with the propofol and propofol-nitrous oxide groups (43 (8) and 41 (3) min, respectively). Consequently, the use of propofol without nitrous oxide can be recommended during spinal surgery when CSEP monitoring is required.

Intraoperative ultrasonography evaluation of posterior vertebral wall displacement in thoracolumbar fractures

Intraoperative ultrasonography (IOUS) was used to evaluate the location and compressive effects of intraspinal fragments in thoracolumbar fractures and the efficacy of reduction maneuvers in patients operated on for isolated or attached intraspinal fragments or for global posterior wall disruption. Dynamic IOUS was used to evaluate the effects of traction and lordosis. Fifty-eight patients were evaluated using a 7.5 MHz ultrasound probe, including 27 treated by impaction, 19 by removal of apparently isolated fragments, and 12 by traction followed by lordosis for global posterior wall disruption. IOUS had limitations and problems caused by split fragments and residual pedicular attachments that can compromise intraoperative maneuvers. The risk of secondary displacement of isolated fragments treated by impaction was very high. In particular, the pinching effect produced by T-shaped fractures was commonly responsible for secondary displacement. IOUS evaluation of canal clearance after fragment removal was satisfactory, but did not provide quantitative data. IOUS was easier to perform and apparently more reliable than intraoperative myelography. The dynamic IOUS data suggest that, except for severely tilted fragments that are completely free or remain attached to a pedicle, residual discal attachments significantly influence the likelihood of successful reduction.

Anatomic bases of a new technique of juxta-acetabular osteotomy. Technical principles and performance

Pelvic osteotomies were developed to increase or restructure the acetabular surface. Periacetabular osteotomies are considered the most difficult from the technical point of view and necessitate sufficient residual cartilaginous surface. Juxta-acetabular osteotomies avoid major disorganization of the pelvic framework and allow easier reorientation of the acetabulum. The authors present a technical variant that preserves the entire posterior column, as in the Ganz osteotomy. The effects on the vascularisation of the periacetabular region are strictly the same and there is no necrosis of the subchondral bone. This osteotomy is easier to perform, because of a single positioning associating two simultaneous approaches. The osteotomies are rectilinear and easy to check peroperatively by fluoroscopy thanks to this positioning. Another valuable aspect of this double approach consists of very easy correction of "automatic" unwanted retroversion due to the lowering of the acetabular roof. This unintended displacement is rarely reported in the literature, despite its anatomic evidence in 3-dimensional CT-scan reconstructions for pre- and peroperative evaluation.

[Possibilities of anterior approach to the lumbar spine by minimal retroperitoneal access. Anatomical bases. Technical principles and initial results]

Anterolateral approach to the lumbar spine using a retroperitoneal approach is a common technique. But conventional approaches are performed laterally, resulting in parietal muscular damage, which may alter functional results. The authors present their experience about a minimized pararectal retroperitoneal approach from T12 to S1. Some anatomical aspects are important for a safe and reproductive procedure. The authors used mainly this technique in association with posterior correction and fixation in traumatic and degenerative pathologies. They point out the simplicity of this technique which is performed without special equipment. It seems a real alternative to laparoscopic techniques and micro-surgical antero-lateral interbody fusion, especially because of minimal potential complications and low post operative morbidity.

[Orthopedic treatment of fractures of the lower extremity of the radius by the Judet technique. Anatomic results in function of the type of lesion: apropos of 280 cases]

PURPOSE OF THE STUDY

The authors evaluated the anatomical results and limits of the conservative treatment for displaced Colle's fracture.

MATERIAL AND METHODS

The anatomical results of 280 consecutive fractures were retrospectively analysed. Conservative treatment was performed according to Judet. Stability of the reduction was assessed for grade 0, 1, 2 of Kapandji's classification. Radiographical mean follow-up for all patient was three months (2 months to 8 years).

RESULTS

In 122 cases (64 per cent) mal-union was observed. Mal-union was due in 93.5 per cent of cases (114) to secondary displacement of the distal fragment and in 6.5 per cent (8 cases) to poor reduction. Secondary displacement was essentially posterior in the sagittal plane. The principal factors of instability were radial shortening superior to 3 mm (p = 0.005), patient age of 55 years of more (p = 0.004), metaphyseal comminution (p = 0.004) and degree of primary displacement in the frontal plane (p = 0.01). Stability after reduction was determined by crossing the distal fragment in relation to the anterior cortex of the proximal fragment. There were 10.5 per cent algodystrophies and 9 per cent median nerve paresthesiae which were avoided by 45 degrees of wrist flexion.

DISCUSSION

Judet's conservative treatment is indicated in extra-articular Colle's fractures (grade 0, 1, 2 of Kapandji's classification), after evaluation of factors of instability, secondary displacement and mal-union. Minor mal-unions may be well tolerated, and do not seem to affect wrist function with 3 mm of radial shortening and 10 degrees of radial glenoid posterior angulation on the sagittal plane.

[Evaluation of the direct cost of trochanteric fractures in the elderly]

PURPOSE OF THE STUDY

The cost effectiveness of trochanteric hip fractures in 1995 at Pitié-Salpétrière Hospital in Paris has been thoroughly analysed. The aim of this retrospective study was to identify the factors responsible for the variation in the treatment cost of those fractures.

MATERIAL AND METHODS

Cost, Hospital stay, functional status, ASA score, mental status and surgical treatment were analysed in 74 patients aged over 60 years old.

RESULTS

The mean cost per patient was 23,901 FF divided as follows: 8.5 per cent for preoperative care, 40.5 per cent for surgical procedures, 51 per cent for post-operative care. The mean hospital stay was 18 days. The cost of hospital personnel (44 per cent) and medical materiel (26 per cent) were the two main sources of hospital expenses beside medical investigations (11 per cent), hostelry (8 per cent), blood transfusion (6 per cent) and drugs (5 per cent).

DISCUSSION

The duration of hospital stay was the only factor that affected statistically the mean cost per patient. Furthermore, factors related to the patient as age, sex, place of residence prior to admission, functional status, ASA score, mental status, had no influence on cost variation.

CONCLUSION

Therefore, the best way to reduce the cost of trochanteric fractures treatment is to develop convalescence structures to avoid a lengthy and costly hospital stay and to minimize the abuse utilization of medical materials.

[Dislocation of the femoral component of an unicondylar knee prosthesis. Apropos of a case]

INTRODUCTION

Femoral component dislocation in unicondylar knee arthroplasty is rare. One case is reported.

MATERIAL AND METHODS

A 59 years old man required revision of his unicondylar knee arthroplasty for loosening and dislocation of the femoral component 3 years after its insertion. Revision was performed and we found a technical error: distal and posterior femoral cut was too thin, and with components in place, there was a tendancy for the components to "rock" as the knee was flexed. The implants were too tight in flexion. A new unicondylar knee arthroplasty was performed.

DISCUSSION

The posterior condylar bone resection should reach at least the thickness of the metal implant. It is better to resect slightly too much of the posterior condyle than too little in order to avoid tightening of the knee in flexion. The femoral component must accurately reproduces the anterior-posterior dimension of the femoral condyle.

CONCLUSION

With better selection of patients and surgeons who are more familiar to this type of procedure loosening and dislocation of an unicondylar knee arthroplasty should be avoided.

Vertebral metastases: a critical appreciation of the preoperative prognostic tokuhashi score in a series of 71 cases

STUDY DESIGN

The utility of the Tokuhashi score was assessed in a retrospective study in 71 patients with vertebral metastases.

OBJECTIVES

To study the importance of the site of the primary tumor as a parameter in the preoperative prognostic Tokuhashi score.

SUMMARY OF BACKGROUND DATA

A preoperative score composed of six parameters, each rated from zero to two, has been proposed by Tokuhashi for the prognostic assessment of patients with metastases to the spine.

METHODS

Seventy-one patients with vertebral metastases were studied. There were 34 cases of thyroid cancer metastases, 28 cases of renal cancer metastases, and nine cases of metastases of unknown origin. In each patient, a local and a systemic tumor search were performed. Patients were divided into groups based on the primary site of the tumor, and each group was analyzed separately.

RESULTS

In cases of vertebral metastases of thyroid cancers, surgery to excise single metastases was found to provide good results, as was palliative surgery of multiple metastases. Vertebral metastases of renal tumors were rarely single, and the results of palliative surgery were less satisfactory. Vertebral metastases of unknown primary tumors had a poor outcome, regardless of whether surgery was excisional or palliative. The median survival period in patients with metastases of unknown primary tumors was significantly shorter than that in patients with renal or thyroid cancer metastases.

CONCLUSION

The Tokuhashi preoperative score is successful as a prognostic tool. However, it attributes the same one-point rating to metastases of renal cancer and to those of unknown primary tumors. In the case of metastases of unknown primary tumors, this rating is too high and should be reduced to 0.

Comparison of the effects of ketamine-midazolam with those of fentanyl-midazolam on cortical somatosensory evoked potentials during major spine surgery

Cortical somatosensory evoked potentials (CSEP) allow monitoring of spinal cord function during surgery. Ketamine has been shown to enhance CSEP amplitude, but there is no previous study comparing its effects with those of other anaesthetic regimens. Therefore, we have compared the effects of ketamine with those of fentanyl, both combined with midazolam, on CSEP monitoring during major spine surgery. Twenty patients with normal preoperative CSEP were allocated randomly to a ketamine or fentanyl group. Anaesthesia was induced with ketamine 3 mg kg-1 or fentanyl 6 micrograms kg-1 i.v., and midazolam 0.3 mg kg-1 i.v in both groups, and maintained with continuous i.v infusion of ketamine 2 mg kg-1 h-1 or fentanyl 3 micrograms kg-1 h-1, combined in both groups with midazolam 0.15 mg kg-1 h-1 and 60% nitrous oxide in oxygen. CSEP were elicited by tibial posterior nerve stimulation and measured P1 and N1 latencies, and P1-N1 amplitude, CSEP were recorded before and after induction, at 15 min, 1 and 2 h after induction, during skin closure and after removal of nitrous oxide. Both groups were comparable in characteristics, duration of surgery, mean arterial pressure and temperature. CSEP latencies were not significantly affected in either group. CSEP amplitude decreased significantly over time in the fentanyl group (from mean 2.02 (SEM 0.41) to 0.95 (0.17) microV, P < 0.05), but not in the ketamine group (from 1.33 (0.36) to 1.05 (0.31) microV, ns). Nevertheless, we did not observe any significant differences in amplitudes or latencies between the two groups. The delay in obtaining the first voluntary postoperative motor response was significantly greater in the ketamine group (170 (54) vs 55 (17) min, P < 0.01). Both ketamine and fentanyl allowed us to obtain reliable CSEP during major spine surgery, and there were no significant difference between these two anaesthetic regimens for CSEP monitoring, but a longer delay for voluntary postoperative motor assessment was observed in the ketamine group.

Surgery of the deformities in ankylosing spondylitis: our experience of lumbar osteotomies in 31 patients

Corrective surgery for kyphotic deformities of the spine in ankylosing spondylitis is a major surgery for rare indications. The authors report 31 lumbar osteotomies. The goal is to correct the deformity through a posterior limited approach and to minimise the neurological risks. The modifications developed by the authors for monosegmental closing wedge osteotomies are explained. The posterior resection is rhomboid shaped with a bilateral lamina removal. An osteotomy is performed in a forwards direction on the lateral aspects of the vertebral body without bone resection. This osteoclasty allows progressive vertebral body compression. Pediclectomy is associated if the corresponding foramen at the osteotomy level becomes too narrow in the process of redressing the spine. The resection level is adjusted so that superior and inferior posterior arches come into contact with a good compression. The authors point out the risk of lateral translation. Before the osteotomy, the two adjacent vertebrae are implanted with 5-mm cylindrical pedicular screws, so that posterior fixation can be carried out at any time. Posterior monobloc fixation allows for very great compression of the osteoclasty. The authors compare the results of their experiences in opening and closing osteotomy. They progressively changed their technique for closing osteotomies, because of published vascular complications and mechanical risks (instability and pseudarthrosis in opening osteotomies). Closing osteotomy also minimises the risk of stenosis with radicular compression or traction if an important correction is performed. The level of the osteotomy varied in this series, which had a correction rate of up to 75 degrees. The choice of level depends on secondary effects on pelvic position and projection of the centre of gravity. The preferred procedure remains a monosegmental correction because it is faster and easier, with minimum bleeding. Short monobloc posterior fixation is sufficient to maintain reduction and to obtain stability from posterior compression.

Dynamic anatomy of the acetabulum: an experimental approach and surgical implications

The deformations and stresses acting on the acetabular rim have not been very precisely documented. The authors present a study based on an experimental simulation of hip loading with anatomic correlations. 122 dissections were performed in order to define the anatomic aspect of the roof (and especially of Byers's "area 17") and the intermediate area between the anterior and posterior acetabular cornua. Ten fresh cadavers were tested on the lines of previous studies on monopodal or bipodal loading. An extensometric study was performed with special attention to the transverse acetabular ligament, supra-acetabular area and obturator foramen. The area 17 of Byers is a transitional zone and the mobility of the posterior cornu is 3 times that of the anterior cornu. Resection of the acetabular ligament modifies the displacement of the posterior cornu under loading but has no influence on deformation of the oburator foramen. The biomechanical behavior of the acetabular roof in the standing position is influenced by the conditions of monopodal or bipodal loading and by femoral rotation, but a tendency to extrusion was constantly noted.