Claes Olerud

Odontoid fractures: high complication rate associated with anterior screw fixation in the elderly

Abstract This study is a retrospective analysis of patients older than ¶65 years with odontoid fractures. The series consisted of 29 consecutive patients with odontoid fractures (18 women, mean age 78, range 66–99 years). Twenty-six patients were neurologically intact, Frankel E, whereas three had neurological symptoms: two Frankel D and one Frankel C. Eleven patients were treated with anterior screw fixation according to Böhler, seven with a posterior C1–C2 fusion. Ten patients with either minimally displaced ¶fractures or with complicating medical conditions were treated conservatively. At follow-up, 7/7 patients with posterior fusion had healed without any problems, whereas ¶8/11 patients treated with anterior screw fixation, and 7/10 conservatively treated patients were either failures or had healed, but after a complicated course of events. We conclude that anterior screw fixation according to Böhler is associated with an unacceptably high rate of problems in the elderly. Probable causes may be osteoporosis with comminution at the fracture site, or stiffness of the cervical spine preventing ideal positioning of the screws. As non-operative treatment also often fails, the method of choice seems to be posterior C1–C2 fusion.

Biomechanical comparison of five different atlantoaxial posterior fixation techniques.

Study Design. Five different reconstructions of the atlantoaxial complex were biomechanically compared in vitro in a nondestructive test. Objectives. To determine whether non–bone graft–dependent one-point fixation affords stability levels equivalent to three-point reconstructions. Summary of Background Data. Previous investigations have demonstrated that three-point fixation, using bilateral transarticular screws in combination with posterior wiring, provide the most effective resistance to minimize motion around C1–C2. However, placement of transarticular screws is technically demanding. Posterior wiring techniques affording one-point fixation have failure rates of ∼15%, with failure considered to be secondary to structural bone graft failures. One-point, non–bone graft–dependent fixations have not been tested. Methods. Eight human cervical specimens, C0–C3 were loaded nondestructively. Unconstrained three-dimensional segmental motion was measured. The reconstructions tested were two one-point fixations, one two-point fixation, and two three-point fixations. Results. Under axial rotation two and three-point reconstructions provided better stiffness than the one-point reconstructions (P < 0.05). During flexion–extension, higher stiffness levels were observed in one- and three-point fixations when compared with the intact spine (P < 0.05). In lateral bending no significant differences were observed among the six groups, although the trend was that reconstructions including transarticular screws provided greater stability than one-point fixations. Conclusion. The current findings substantiate the use of three-point fixation as the treatment of choice for C1–C2 instability. [l: atlantoaxial fixation, biomechanics, cervical spine, instability, spinal instrumentation, transarticular screws]

Embolization of spinal metastases reduces peroperative blood loss : 21 patients operated on for renal cell carcinoma

We evaluated the peroperative blood loss in 21 patients who were treated with 29 operative procedures for thoracolumbar spinal renal cell carcinoma metastases. Embolization was undertaken prior to 11 operations. At posterior surgery the average blood loss was one third after embolization compared with when embolization had not been performed. The blood loss was also lower during anterior surgery, although this difference was smaller. We recommend that preoperative embolization should precede surgical treatment of spinal metastases of renal cell carcinoma where it can be anticipated that the operation will extend into the pathological tissue.

Spinal fractures in patients with ankylosing spondylitis

Thirty-one consecutive patients with ankylosing spondylitis and spinal fractures were reviewed. There were 6 women and 25 men with a mean age of 60±11 years; 19 had cervical and 12 had thoracolumbar injuries. Of the patients with cervical fracture, two had an additional cervical fracture and one had an additional thoracic fracture. Three trauma mechanisms were identified: high-energy trauma in 13 patients, low-energy trauma in 13 and insufficiency fracture in 5. One-third of the patients suffered immediate neurological impairment, a further one-third developed neurological impairment before coming for treatment and only one-third remained intact. Two patients with thoracolumbar fractures had deteriorated neurologically due to displacements during surgery at other hospitals. All patients were treated operatively except the two patients with two-level cervical fractures, who were managed in halo vests. In the cervical spine both anterior and posterior approaches were employed. In the thoracolumbar spine the majority of the patients were initially treated using a posterior approach only. Complications were common. Of the 27 patients with neurological compromise, 10 had remained unchanged; 12 had improved one Frankel grade; 4 had improved by two Frankel grades; 1 had improved by four Frankel grades. We conclude that even minor trauma can cause fracture in an ankylosed spine. A high proportion of patients with spinal fractures and ankylosing spondylitis have neurological damage. The risk of late neurological deterioration is substantial. As the condition is very rare and the treatment is demanding and associated with a very high risk of complications, the treatment of these patients should be centralised in special spinal trauma units. A combined approach that stabilises the spine from both sides is probably beneficial.

Hydroxyapatite coating improves fixation of pedicle screws: A CLINICAL STUDY

We investigated the effects of hydroxyapatite (HA) coating on the purchase of pedicle screws. A total of 23 consecutive patients undergoing lumbar fusion was randomly assigned to one of three treatment groups. The first received uncoated stainless-steel screws, the second screws which were partly coated with HA, and the third screws which were fully coated. The insertion torque was recorded. After 11 to 16 months, 21 screws had been extracted. The extraction torque was recorded. Radiographs were taken to assess fusion and to detect loosening of the screws. At removal, the extraction torques exceeded the upper limit of the torque wrench (600 Ncm) for many HA-coated screws. The calculated mean extraction torque was 29 +/- 36 Ncm for the uncoated group, 447 +/- 114 Ncm for the partly-coated group and 574 +/- 52 Ncm for the fully-coated group. There were significant differences between all three groups (p < 0.001). There were more radiolucent zones surrounding the uncoated screws than the HA-coated screws (p < 0.001). HA coating of pedicle screws resulted in improved fixation with reduced risk of loosening of the screws.

The significance of radiolucent zones surrounding pedicle screws DEFINITION OF SCREW LOOSENING IN SPINAL INSTRUMENTATION

We examined the radiographs from a prospective clinical study of fixation by pedicle screws and those from an experimental study in a sheep model. In the clinical study, instruments were removed from 21 patients after implantation for 11 to 16 months and the extraction torques of the screws were recorded. A structured protocol was used for the radiological examinations. In the experimental study, loaded pedicle screw instrumentations were implanted in the sheep for six or 12 weeks. After radiological examination the pull-out resistance and the histological characteristics were studied. In the clinical study, all screws with radiolucent zones had a significantly reduced mean extraction torque compared with screws without radiolucent zones (16 +/- 10 Ncm v 403 +/- 220 Ncm; p < 0.0001). In the experimental study the mean maximum pull-out resistance for the screws with radiolucent zones was significantly lower than for those with no radiolucency (243 +/- 156 N v2214 +/- 578 N; p = 0.0006) and the mean bone-to-screw contact was reduced for screws with zones compared with those without zones (8 +/- 9% v 55 +/- 29%; p = 0.0002). Our findings showed that all screws with radiolucent zones had low extraction torques or low pull-out resistance. A radiolucent zone is a good indicator of loosening of a pedicle screw.

Outcome After Limited Posterior Surgery for Thoracic and Lumbar Spine metastases

SummaryThe efficacy of ‘limited posterior surgery’ for metastases in the thoracic and lumbar spine was studied prospectively in 51 patients (32 men and 19 women, mean age 64 years). The most common primary tumors were prostate, breast, and renal carcinoma, 37 patients had metastases in the thoracic spine and 14 in the lumbar spine. Indications for surgery were severe pain or neurologic deficit. Of the 46 patients with neurologic symptoms, 25 were unable to walk. Surgery was confined to direct or indirect decompression and stabilization with a pedicle screw fixator over few segments as possible. Pain, as well as a variety of functional performance parameters and residential status were registered preoperatively and after surgery at 3, 6, 9, and 12 months, and at 6-monthly intervals thereafter. Pain was rated by the patient on a Visual Analog Scale, and functional performance was assessed with the Eastern Co-operative Oncology Group (ECOG) Performance Status Scale. We had no perioperative neurologic deterioration or death. Nineteen of the 25 nonambulatory patients regained their walking ability. Postoperative pain relief was significant and lasting over time. Nearly half of the patients attained improvement in functional performance. The median survival was 8 months. Older age and intact postoperative walking ability were positive factors for survival.

Hydroxyapatite coating enhances fixation of loaded pedicle screws: a mechanical in vivo study in sheep

Abstract. Loosening of the pedicle screws with subsequent non-union or loss of correction is a frequent problem in spinal instrumentation. In a clinical pilot study, coating of pedicle screws with plasma-sprayed hydroxyapatite (HA) resulted in a significant increase of removal torque. An experimental study was performed to investigate the effects of HA coating on the pull-out resistance. Thirteen sheep were operated on with destabilising laminectomies at two levels, L2-L3 and L4-L5. Two instrumentations with four pedicle screws in each were used for stabilisation. Uncoated screws (stainless steel) or the same type of screws coated with plasma-sprayed HA were used in either the upper or the lower instrumentation in a randomised fashion. Four sheep were examined immediately after the application of the screws, three sheep at 6 weeks and four sheep at 12 weeks. Two sheep were euthanised early due to complications. The pull-out resistance was recorded in two HA-coated and two standard screws in each animal. The maximum pull-out resistance was higher for the HA-coated screws at 0 weeks (P<0.02) and at 12 weeks (P<0.01) when compared to the uncoated screws, while there was no significant difference between the groups at 6 weeks. We believe that the higher pull-out resistance for HA-coated screws at 0 weeks was mainly caused by differences in surface roughness, while the difference at 12 weeks was due to a favourable bone reaction around the HA-coated screws. At 12 weeks, the average stiffness was significantly higher for the HA-coated screws, while there was no significant differences in stiffness between the two screw types at 0 and 6 weeks. Energy to failure was significantly higher for coated screws when compared to the uncoated screws at all three time points. HA coating improves fixation of loaded pedicle screws, with increased pull-out resistance and reduced risk of loosening.

Subchondral screw fixation for femoral neck fractures

We describe a method of internal fixation for femoral neck fractures which has been newly developed to reduce the frequency of early complications. Two cannulated screws are inserted in the axis of the femoral neck to reach into the subchondral bone of the femoral head. The screws are inserted over guide pins and the tip of the screw is self-tapping and designed to provide good anchorage in the femoral head. We used this method in 44 consecutive patients in a prospective study with no exclusions, followed for a minimum of 24 months. All fractures healed within 12 months, and there were no cases of early loosening or nonunion. In four cases, late segmental collapse had developed during the mean follow-up period of 30 months.

The significance of radiolucent zones surrounding pedicle screws : definition of screw loosening in spinal instrumentation

We examined the radiographs from a prospective clinical study of fixation by pedicle screws and those from an experimental study in a sheep model. In the clinical study, instruments were removed from 21 patients after implantation for 11 to 16 months and the extraction torques of the screws were recorded. A structured protocol was used for the radiological examinations. In the experimental study, loaded pedicle screw instrumentations were implanted in the sheep for six or 12 weeks. After radiological examination the pull-out resistance and the histological characteristics were studied. In the clinical study, all screws with radiolucent zones had a significantly reduced mean extraction torque compared with screws without radiolucent zones (16 +/- 10 Ncm v 403 +/- 220 Ncm; p < 0.0001). In the experimental study the mean maximum pull-out resistance for the screws with radiolucent zones was significantly lower than for those with no radiolucency (243 +/- 156 N v2214 +/- 578 N; p = 0.0006) and the mean bone-to-screw contact was reduced for screws with zones compared with those without zones (8 +/- 9% v 55 +/- 29%; p = 0.0002). Our findings showed that all screws with radiolucent zones had low extraction torques or low pull-out resistance. A radiolucent zone is a good indicator of loosening of a pedicle screw.