High failure rates with a large-diameter hybrid metal-on-metal total hip replacement: clinical, radiological and retrieval analysis.

This study reports the mid-term results of a large-bearing hybrid metal-on-metal total hip replacement in 199 hips (185 patients) with a mean follow-up of 62 months (32 to 83). Two patients died of unrelated causes and 13 were lost to follow-up. In all, 17 hips (8.5%) have undergone revision, and a further 14 are awaiting surgery. All revisions were symptomatic. Of the revision cases, 14 hips showed evidence of adverse reactions to metal debris. The patients revised or awaiting revision had significantly higher whole blood cobalt ion levels (p = 0.001), but no significant difference in acetabular component size or position compared with the unrevised patients. Wear analysis (n = 5) showed increased wear at the trunnion-head interface, normal levels of wear at the articulating surfaces and evidence of corrosion on the surface of the stem. The cumulative survival rate, with revision for any reason, was 92.4% (95% confidence interval 87.4 to 95.4) at five years. Including those awaiting surgery, the revision rate would be 15.1% with a cumulative survival at five years of 89.6% (95% confidence interval 83.9 to 93.4). This hybrid metal-on-metal total hip replacement series has shown an unacceptably high rate of failure, with evidence of high wear at the trunnion-head interface and passive corrosion of the stem surface. This raises concerns about the use of large heads on conventional 12/14 tapers.

The effect of hip and knee arthroplasty on oral anti-inflammatory use and the relationship to body mass index: results from the UK general practice research database.

OBJECTIVE: To determine the use of oral anti-inflammatory drugs in the year before and the 2 years after primary total hip (THR) or knee (TKR) replacement, and whether this varies according to Body mass Index (BMI). DESIGN: 28,068 THR's and 24,364 TKR's, with five matched controls per case were identified from the General Practitioner Research Database. Anti-inflammatory usage was categorized into "zero coverage" - no prescribed anti-inflammatory medication and ">80% coverage" - prescribed anti-inflammatory medication for greater than 80% of the days in the year. Secondary subset analysis was performed according to BMI. RESULTS: 1 year post-surgery the proportion of cases on >80% coverage reduced from 21% (95%confidence interval (CI): 20-22%) to 8% (95%CI: 7-10%) for THR and 21% (95%CI: 20-22%) to 13% (95%CI: 11-14%) for TKR, with no ongoing reduction at 2 years. Zero coverage increased at one and both time points. The proportion of THR's on >80% coverage increased with BMI pre-op. The magnitude in reduction post-op was similar across all BMI groups. The proportion of TKR's on >80% coverage pre-op was greatest in extreme BMI categories. The magnitude in reduction post-op was similar across all BMI groups. CONCLUSION: THR/TKR's reduce the need for anti-inflammatory medication with most benefit observed in the first post-operative year. Increasing BMI affects anti-inflammatory use both in the general population and those undergoing THR/TKR surgery but without strong evidence of a detrimental effect on the benefits of pain relief.

Hemiarthroplasty: To cement or not to cement? A preliminary report.

Two hundred hemiarthroplasties were studied to compare uncemented Austin Moore and cemented Thompsons prostheses. The following variables were compared: preoperative mobility, ASA grade, Abbreviated Mental test scores, surgeon grade, peri-operative mortality, infection rate, operation time, intra-operative fractures, dislocation rate, thigh pain and revision rate to total hip replacement. Both groups were comparable in all respects. The incidence of intra-operative fractures, infection, postoperative dislocation and conversion to Girdlestone arthroplasty was higher in the uncemented group. The mortality remained the same in both groups. The incidence of significant thigh pain was higher in the uncemented group (13%), of whom half (6%) had to undergo a conversion to a total hip replacement within the 24 months follow-up period. Our current study of changed practice concluded that cemented Thompsons prosthesis performs better than uncemented Austin Moore when the incidence of hip pain and subsequent conversion to a total hip replacement were considered. (Hip International 2004; 14: 189-92).

Chronic osteomyelitis. The effect of the extent of surgical resection on infection-free survival.

We studied prospectively a consecutive series of 50 patients with chronic osteomyelitis. Patients were allocated to the following treatment groups: 1) wide resection, with a clearance margin of 5 mm or more; 2) marginal resection, with a clearance margin of less than 5 mm; and 3) intralesional biopsy, with debulking of the infected area. All patients had a course of antibiotics, intravenously for six weeks followed by orally for a further six weeks. No patients in group 1 had recurrence. In patients treated by marginal resection (group 2), 8 of 29 (28%) had recurrence. All patients who had debulking had a recurrence within one year of surgery. We performed a survival analysis to determine the time of the recurrence of infection. In group 2 there was a higher rate of recurrence in type-B hosts (p < 0.05); no type-A hosts had recurrence. This information is of use in planning surgery for chronic osteomyelitis.

A high risk group for thoracolumbar fractures.

Unconscious patients with multiple injuries present a major diagnostic and therapeutic problem. The incidence of neurological deficit increases if diagnosis of a spinal injury is delayed or missed. Thoracolumbar fractures are commonly the result of high energy injuries and in an unconscious patient the risk of missing such fractures is increased considerably. There is little consensus on which blunt trauma patients warrant thoracolumbar spine films when no pain, tenderness, neurological deficit or cervical spine injuries are identified. We present a retrospective analysis of all patients who were admitted to the Major Injuries Unit at the Birmingham General Hospital and underwent radiological survey of the thoracolumbar spine. Of the 110 patients, all spinal fractures were detected in 94 patients with a Glasgow Coma Scale (GCS) > or = 11. Of the 16 with a GCS < or = 10, 9 patients had sustained injuries of their thoracolumbar spine 4 of which were not detected initially due to a decreased level of consciousness. The common features amongst the 4 patients with missed injuries were: (1) High velocity injury. (2) Decreased level of consciousness on admission. (3) Associated head injury. (4) Pelvis/lower extremity injury. We describe the four cases and identify a group of high risk patients for thoracolumbar fractures. Radiological examination of the thoracolumbar spine is essential in this group.

The pathologic effects of intrathecal betamethasone.

STUDY DESIGN: The histopathologic effects of the intrathecal injection of betamethasone (Celestone Chronodose; Schering Corporation, Kenilworth, New Jersey) were assessed after the injection of various volumes of the preparation in 20 sheep. OBJECTIVE: To assess the safety of Celestone Chronodose injected into the intrathecal space. SUMMARY OF BACKGROUND DATA: The safety and efficacy of epidural steroid have received considerable attention in the medical literature in recent years. In Australia, reports of possible adverse effects of Depo-Medrol (methylprednisolone), including the complication of arachnoiditis, have been followed by statements from the manufacturers of commonly used steroid preparations recommending they should not be administered epidurally. Previous evidence suggests that arachnoiditis does not result from epidural administration of steroids, but may develop from the intrathecal administration of Depo-Medrol. There are no reports concerning the safety of Celestone Chronodose (beta-methasone). METHODS: Twenty-three adult merino sheep had lumbar punctures performed at the L6-S1 level, and different volumes of Celestone Chronodose or normal saline were injected into the subarachnoid space. The animals were killed after 6 weeks, and the spinal cord, meninges, and nerve roots of the lumbar spine were examined for evidence of pathologic changes. RESULTS: There were no abnormalities demonstrated in three sheep injected with up to 18 ml of normal saline solution. Eleven sheep injected with 1 ml (5.7 mg) of Celestone Chronodose even when repeated at weekly intervals (five sheep, three injections) did not demonstrate pathologic changes. One of six sheep injected with 2 ml of Celestone Chronodose and all of three sheep injected with greater volumes showed histopathologic changes of arachnoiditis. CONCLUSIONS: Given that the volume of cerebrospinal fluid in the sheep is approximately one third of that in humans, this study suggests that small volumes (up to 2 ml) of Celestone Chronodose injected intrathecally in humans are unlikely to cause arachnoiditis, but that the risk of this complication increases substantially with higher doses.

Does plate fixation prevent disc degeneration after a lateral anulus tear?

STUDY DESIGN: The sheep model was used to investigate the development of disc degeneration after outer anular tearing. OBJECTIVES: The authors determined whether plate fixation promotes healing of peripheral anular tears and thereby minimizes disc degeneration. SUMMARY OF BACKGROUND DATA: A limited outer anular tear (similar to the rim lesion) in the sheep lumbar disc causes progressive and irreversible degeneration within 6 months. Incomplete healing of the tear may result from continued movement in the vicinity of the lesion. METHODS: In 15 sheep, a cut 4 x 10 mm was made in the lateral anulus of two nonadjacent lumbar discs, and a metal plate was fixed across one. Three sheep were killed immediately, and the remainder were killed after 6 months for histologic examination. RESULTS: There were no significant differences in propagation of the cut through the inner anulus, extent of healing, or extent of nuclear degeneration, between plated and nonplated motion segments after 6 months. Vascularization of the cartilage endplate was significantly increased on the operated side (P < 0.01), but remained unchanged on the nonoperated side. CONCLUSIONS: Disc degeneration was not prevented by this method of plate fixation, despite similar but limited healing of the outer anulus tear in both plated and nonplated levels.

Mechanical consequences of annular tears and subsequent intervertebral disc degeneration.

The relationship between degeneration of the intervertebral disc and changes to its mechanics is unclear. The aim of this study was to examine, in a sheep model, the effect of creating a lesion in the outer, anterior annulus on the mechanics of the intervertebral joint complex and the disc. Forty-one 2-year-old Merino wethers were allocated randomly into a control group or an annular lesion group and additionally to non-survivors which were sacrificed immediately or survivors sacrificed 6 months later. The annular lesion group had incisions made in two non-adjacent intervertebral discs and a plate was secured across the vertebrae at one level. Mechanical tests were performed on specimens consisting of the two vertebrae, the intervening disc and associated ligaments. Stiffness of the specimens was measured in flexion, extension, and in pure torsion. The tests were conducted first on the intact intervertebral joints and then after removal of the zygapophyseal joints and the interspinous and supraspinous ligaments. The results showed that the creation of an annular lesion caused immediate changes to the mechanics of the disc. In torsion, where no axis of rotation was imposed on the joints, there was a clear reduction in stiffness compared with controls. After 6 months the discs in the lesion groups approached the stiffness of the controls. The plates had a marked effect on the stiffness of the joints in flexion and extension, but after 6 months this difference was not apparent. The mechanics of the intact joints were not affected immediately by the lesion but after 6 months they were less stiff than the controls. There was clear evidence of a progressive degenerative response in the nucleus in all discs with a lesion. The addition of a plate to limit movement did not markedly affect this biological response to the injury but there was some evidence that after 6 months there were fewer degenerative changes to the zygapophyseal joints in the plated specimens. Recovery of the mechanical integrity of the disc was more marked in the joints that were plated, supporting the concept that limiting motion of an injured intervertebral disc facilitates a healing response in the annulus.

Cervical epidural haematoma following minor trauma.

Cervical epidural haematoma following minor trauma is unusual in normal adults. It is important that the condition is diagnosed and treated promptly in order to improve the prognosis. Surgery to evacuate the haematoma is the treatment of choice.