Aims

Our aim was to estimate the total costs of all hospitalizations for treating periprosthetic joint infection (PJI) by main management strategy within 24 months post-diagnosis using activity-based costing. Additionally, we investigated the influence of individual PJI treatment pathways on hospital costs within the first 24 months.

Staphylococcus aureus (SA), the predominant pathogen in human osteomyelitis, is known to persist by forming intracellular reservoirs, including in bone cells (Schwarz et al., 2019, Yang et al., 2018, Krauss et al., 2019, Gao et al., 2020, Bosse et al., 2005), promoting decreased antibiotic susceptibility. However, there are no evidence-based treatment guidelines for intracellular SA infections in osteomyelitis. We sought to address this by systematically reviewing the literature and, testing a selection of antibiotic treatments in a clinically relevant in vitro assay.

We conducted a systematic review of the literature to determine the current evidence for the efficacy of antibiotics against intracellular SA infections relevant to osteomyelitis. For the antibiotics identified as potentially useful, we determined their minimal inhibitory concentration (MIC) against 11 clinical osteomyelitis SA- isolates. We selected those for further testing reported able to reach a higher concentration in the bone than the identified MIC against the majority of strains. Thus, rifampicin, oxacillin, linezolid, levofloxacin, oritavancin and doxycycline were tested in human SaOS-2-osteocyte infection models (Gunn et al., 2021) of acute (1d) or chronic (14d) infection to clear intracellular SA. Antibiotics were tested at 1x/4x/10x the MIC for the duration of 1d or 7d in each model.

A systematic review found that osteoblasts and macrophages have mostly been used to test immediate short-term activity against intracellular SA, with a high variability in methodology. However, some extant evidence supports that rifampicin, oritravancin, linezolid, moxifloxacin and oxacillin may be effective intracellular treatments. While studies are ongoing, in vitro testing in a clinically relevant model suggests that rifampicin, oxacillin and doxycycline could be effectively used to treat osteomyelitic intracellular SA infections. Importantly, these have lower MICs against multiple clinical isolates than their respective clinically-achievable bone concentrations.

The combined approach of a systematic review and disease-relevant in vitro screening will potentially inform as to the best approach for treating osteomyelitis where intracellular SA infection is confirmed or suspected.

Metal on metal hip resurfacing is increasing in popularity for the young, active patient. We present the results of a consecutive series from a single surgeon over a ten year period; 295 hip resurfacings (McMinn and Cormet; Corin, Cirencester, UK) with a minimum follow up of 2 years and a mean follow up of 4 years. There were 173 males with a mean age of 53.4 years and 121 females with a mean age of 50.3 years. Forty-six patients underwent bilateral resurfacings. All resurfacings were performed through a posterior approach.

The aetiology in this group was primary OA in 75.9%, inflammatory arthritis in 6.1%, DDH in 6.1%, AVN in 4.7%, trauma in 4.7%, Perthes in 1.7% and SUFE in 0.7%. Patients were reviewed clinically and radiographically on an annual basis. Follow-up was available on 93% of patients. 94.2% of hips have survived and the mean Harris Hip Score is 87.5. Females had a higher failure rate (10.7%) than males (2.3%). There was no clear trend between patient age and failure rate. The highest failure rate (33.3%) was seen in patients with DDH whilst only 4.5% of patients with OA failed. One patient with AVN failed but no failures occurred in patients with inflammatory arthritis, trauma, Perthes or SUFE. Failures occurred due to cup loosening (2.0%), neck fractures (1.7%), head loosening (1.0%), head collapse (0.3%), infection (0.3%) and pain (0.3%). The five patients who suffered neck fractures were symptomatic within 3 months of surgery.

We remain cautiously optimistic about the medium term results of hip resurfacing. Careful patient selection is important and caution should be taken in females and patients with DDH

Introduction: Impaired muscle function due to pain or inactivity may contribute to poor outcome following disc surgery. This study investigated the effects of postoperative exercise on pain, disability and spinal function in patients undergoing microdiscectomy.

Methods: Volunteers who gave informed consent (65M/26F) were blindly randomised to Exercise and Control groups. All patients were assessed the week before surgery. Posture and range of motion were measured using the 3-Space Fastrak, and back muscle fatigue was evaluated during the Biering-Sorensen test from changes in median frequency of the electromyographic signal. In 42 patients, intra-operative muscle biopsies were obtained. Four weeks after surgery, patients underwent a second functional assessment, after which the Exercise group began a 4-week exercise programme. Further assessments were performed at 2, 6, 12, 18 and 24 months after surgery. Pain, disability and psychological status were evaluated throughout using appropriate questionnaires.

Results: Marked type II fibre atrophy was evident at surgery, and this was reflected in pre-operative measures of median frequency. At 4 weeks, both groups showed significant improvements in pain, disability and psychological status but limited improvements in function. At 2 months, the Exercise group showed further improvements in pain, disability and psychological status, increased ranges of motion, and improved fatigability. Increases in initial median frequency in the fatigue test suggested fibre hypertrophy. Further improvements in the Control group generally achieved significance 6–12 months after surgery.

Conclusions: Surgery is effective in improving pain, disability and psychological status. Recovery of muscle function after surgery is naturally slow but can be accelerated by post-operative exercise.

Introduction: Hip resurfacing has become re-established in recent years as a viable option in younger, active individuals. The results of a multi-centre evaluation of the Cormet resurfacing device are presented.

Materials and Methods: Data has been entered from 1997 onwards from 5 centres, patients being selected as suitable by 8 individual surgeons. Pre and intraoperative details recorded including indications, patient details, implant used, Harris Hip Score (HHS) and surgical approach.

Results: A total of 781 procedures in 676 patients have been recorded (54% posterior approach, 40% antero-lateral, 6% Ganz approach). The mean follow-up is 2.5 years (0.1–9.7 yrs) and the mean postoperative HHS is 85.9 (range 25–100). The mean age at surgery was 54.2 years. 60% of implantations were on male patients. The principal diagnosis was; OA 87%, RA 5%, AVN, post-traumatic OA and DDH 2% each, Perthes 1% and the remainder 1%. It is thought likely that many cases of OA had many of the above-named pathologies as a precursor. The mean maximum flexion postoperatively was 98.6 degrees. Uncemented heads (a recent innovation) were used in 7%. Kaplan-Meier survivorship is 93% at 9 years. In the OA subgroup 3.3% have been revised, approximately equal numbers for femoral head collapse, dislocation and cup loosening, but the vast majority due to femoral neck fracture, which in turn was generally associated with the posterior approach.

Conclusions: The results of this cohort (which includes the learning period of the contributing surgeons) indicate highly satisfactory outcomes in terms of HHS and implant longevity. Sub-classification of cases into those presenting abnormal anatomy and those with ‘ordinary’ OA indicates better survivorship still in the latter group. The surgical challenge varies more with hip resurfacing than with standard hip arthroplasty and this should be considered when results of surgery are reviewed. The revision options are generally much simpler than after standard THR.

Introduction: Hip resurfacing has become re-established in recent years as a viable option in younger, active individuals. The results of a multi-centre evaluation of the Cormet resurfacing device are presented.

Methods: Data has been entered from 1997 onwards from 5 centres, patients being selected as suitable by 8 individual surgeons. Pre and intraoperative details recorded including indications, patient details, implant used, Harris Hip Score (HHS) and surgical approach.

Results: A total of 905 procedures in 782 patients have been recorded (52% posterior approach, 39% anterolateral 9% Ganz approach). The mean follow-up is 2.8 years (0.1–9.5 yrs) and the mean postoperative HHS is 86.1 (range 25–100). The mean age at surgery was 54.4 years. 61% of patients were male. The principal diagnosis was; OA 88.3%, RA 4.3%, AVN 2.1%, posttraumatic OA 1.1%, DDH 2.1%, Perthes 0.7% and the remainder 1.4%. It is thought likely that many cases of OA had many of the above-named pathologies as a precursor. The mean maximum flexion postoperatively was 98.7 degrees. Uncemented heads (a recent innovation) were used in 10%. Kaplan-Meier survivorship is 93% at 9 to 10 years. Survivorship in the OA subgroup was 96.7% with approximately equal numbers for femoral head collapse, dislocation and cup loosening, but the vast majority due to femoral neck fracture, which in turn was generally associated with the posterior approach.

Discussion: The results of this cohort (including all contributors’ learning curves) indicate highly satisfactory outcomes in terms of HHS and implant longevity. Subclassification of cases into those presenting abnormal anatomy and those with ‘ordinary’ OA indicates better survivorship still in the latter group. The surgical challenge varies more with hip resurfacing than with standard hip arthroplasty and this should be considered when results of surgery are reviewed. The revision options are generally much simpler than after standard THR.

Introduction: The advent of metal on metal resurfacing in the United Kingdom has resulted in increasing interest in the procedure. The operation is more demanding than primary joint replacement and the complications involved are frequently peculiar to the technique. We present a single-surgeon series from a district hospital performed within the ambit of a larger multicentre study.

Method: Data on 83 cases in 80 patients (51 males, 29 females, age 34y–68y, mean age 50.6y) were collected. Patients were reviewed preoperatively and postoperatively at 6 months and annually (mean 21 months, range 1–60 months). At review Harris Hip scores were recorded with a radiological assessment to assess implant orientation. Technical difficulties with implant insertion were recorded. All cases were approached via an anterolateral exposure.

Results: Postoperative scores improved dramatically in nearly all cases. There was persistent pain in two cases, one of spinal origin, the other unexplained. 2 loose femoral components were revised at 2 and 3 years respectively years leaving the intact cup. 1 cup rotated slightly over 3 months and stopped, 4 cups were incompletely seated and 1 femoral component was inserted in slight varus. All remain asymptomatic to date. There was one unrelated death (mesenteric infarction) and no femoral neck fractures.

Discussion: Resurfacing arthroplasty is technically more demanding than total hip replacement and the exchange of experiences via a multicentre user group is important. The conservative nature of the device means that revision for fractured neck of femur (commonest cause of failure) to a stemmed implant retaining the cup is relatively easy. The results of this series are encouraging.

Metal on metal hip resurfacing is increasing in popularity for the young, active patient despite the fact that no long term results are available. The potential advantages of the conservative nature of the prosthesis coupled with the stability of the large diameter bearings and the much reduced wear compared to conventional metal-UHMWPE hips are clear. We present the results of a consecutive series from a single surgeon using a modern device from 1997 to date. All hips used cementless cups and cemented heads and were implanted using a posterior approach. All patients were reviewed annually from the time of operation.

Between September 1997 and March 2004, 345 primary Total Hip Resurfacings were performed by one surgeon. No cases were lost to follow-up. The average age of the patient group was 52 years, range (21–74 years), 190 were male (30 bilaterals) and 104 were female (21 bilaterals) & there were 11 reoperations. The follow-up ranged from 79 months to 3 months, mean follow-up was 29 months. With a Kaplan-Meier survivorship of 94% at 7 postoperative years.

Of the reoperations there were; 5 fractured necks of femur, 3 aseptic cup loosenings, 2 femoral head collapses and 1 joint infection. All 5 femoral neck fractures occurred within 3 months of the primary operation.

This series is one of the longest using a currently available device and the medium term results are encouraging with revision rates occuring within agreed national standards. It should be noted that the numbers of implantations increased as time went on which skews the follow-up slightly. We remain cautiously optimistic about the long term results of this type of device.

A painful osteoarthritic knee in a young patient presents a therapeutic dilemma. Non-operative modalities, such as physical therapy, modification of activities to limit those that involve impact, and anti-inflammatory medications often provide only limited and temporary benefit. Operative options include arthroscopic debridement, arthrodesis, proximal tibial osteotomy, and uni-compartmental or total knee replacement. Total knee replacement has generally been reserved for patients who are at least sixty years old because of the potential for numerous revision operations in the course of a lifetime.

Mobile bearing total knee arthroplasty systems is emerging as the next wave of development in knee joint prosthetic reconstruction. The mobile bearing allows very high conformity between articulating surfaces on both sides of the polyethylene insert. The forces involved in these highly conforming articulations are very low, well below the theoretical yield point of the polyethylene bearing surface. Because the bearing is mobile, the interface between components and bone is protected from excess shear stress, therefore protecting the fixation.

The main concern of this prospective study was to determine the clinical, radiographic and functional results of Rotaglide mobile-bearing total knee arthroplasty in young active patients who were fifty-nine years old or less at time of the arthroplasty. We evaluate medium-long term results and survivorship of 81 patients who have their total knee replacement implanted for at least 3 years in Birmingham Heartlands & Solihull Hospital (UK), using Rotaglide total knee replacement (Corin).

The average follow-up of 7.3 years was reported in this prospective study with range of 3 – 12 years. The average age at the primary operation was 50.7 years with range of 37 – 58 years. The knee scores are satisfactory with an average of 195.6 points using IKSS and 14.6 using OKS. The average postoperatively range of motion was 126.2 with range of 95 – 130 degree. The radiological assessment of the X-ray in AP and lateral views show that both the femoral and tibial components well aligned with no radiolucent lines.

We conclude from this prospective study that Rota-glide mobile-bearing total knee arthroplasty in patient 59 years or younger is a reliable procedure with excellent results at medium-long term follow-up, with an estimated survivorship of 98 percent at 12 years.

Metal ion release is a concern with all metal-on-metal (MOM) hip replacements. The Cormet Resurfacing Hip replacement, in use since 1997, has been validated in vivo and in vitro. In addition to clinical follow-up, extensive wear testing has been carried out under standard and severe conditions. A 6-year study on the serum metal ion levels in patients has also been done.

Between September 1997 and November 2003, 383 primary total hip resurfacings were performed in five centres. The mean age of the 196 men (23 bilateral procedures) and 146 women (18 bilateral procedures) was 55.4 years (24 to 73). Mean follow-up was 17 months (3 to 84). At the latest review the mean modified Harris hip score (truncated format) was 77.9 out of 91 (mean 86%), with a range of 49 to 91. The Kaplan Meier survivorship rate was 96% at 7 years.

Wear testing has shown that heat treatments do not affect the wear of cast high carbon cobalt chrome alloys and that larger bearings (56-mm and 40-mm diameter) have lower wear rates than conventional 28-mm bearings. Metal ion levels rose initially, then decreased over time.

Metal ion release does not appear to be a major long-term concern and medium-term clinical results are very encouraging.

Introduction A prospective, randomised, controlled study has been conducted to compare the clinical outcomes of patients treated with a Presige® artificial cervical disc (Medtronic Sofamor Danek, Memphis, TN) to patients who receive fusion after cervical discectomy for the treatment of primary cervical disc disease. It is hypothesized that maintenance of motion after anterior cervical discectomy will prevent the high rate of adjacent level premature degeneration. The primary purposes of the study are to (1) prove equivalence (non inferiority) of outcome of the disc prosthesis in the short term compared with fusion; and (2) to asses the ability of the prosthesis to maintain motion. Enrolment has closed and this is a report of the data with 50 cases with 6 month follow-up and 9 cases having reached 24 month final follow-up.

Methods In four centres, 52 patients with primary, single level cervical disc disease producing radiculopathy and/or myelopathy were randomised prospectively to receive anterior cervical discectomy with either fusion or artificial cervical disc replacement. The patients were evaluated with pre and postoperative serial flexion-extension cervical x-rays at 6 weeks, 3, 6, 12, and 24 months. At the same intervals, the patients had pre and postoperative neck disability indexes, visual pain analogue scales, European myelopathy scores, SF-36 general health scores, and neurological status examinations assessing the patient’s reflex, motor and sensory function.

Results At 6 weeks the neck disability index reduced by 34.1 for the investigational group compared to 35.2 for the fusion group. The improvement seen in the treatment groups was statistically equivalent (p < 0.05, non-inferiority margin = 10) up to the 24-month follow-up interval. The pain score had reduced by 7.7 for the investigational group and by 9.7 for the control group. Both groups improved statistically from preoperatively though statistical equivalence could not be shown. This improvement appeared to be maintained until the 12 month follow-up. Mean arm pain scores improved in both groups with statistical equivalence being demonstrated (p < 0.05, non-inferiority margin = 10). The adverse events in both groups were similar. Analysis of range motion showed a mean preoperative range of motion in the arthroplasty group of 5.9 degrees and 6.3 degrees in the fusion group. At twelve months the arthroplasty group had a mean range of motion of 5.9 degrees and the fusion group had a mean range of motion of 1.1 degrees

Discussion Anterior cervical discectomy and fusion has a good short term outcome though there is a high incidence of failure at adjacent levels over time. It is hypothesised that the maintenance of motion of a segment will prevent adjacent premature degeneration. It will take long term follow-up studies however to prove this. In the mean time, the justification to insert artificial cervical prostheses rests on being able to prove equivalence of outcome between fusion and prosthesis in the short term. This paper shows that, in the short to medium term, the clinical outcomes appear to be equivalent to fusion. And that range of motion is maintained.

Introduction: A prospective, randomized, controlled study has been conducted to compare the clinical outcomes of patients treated with an artificial cervical disc to patients who receive fusion after cervical discectomy for the treatment of primary cervical disc disease. It is hypothesized that maintenance of motion after anterior cervical discectomy will prevent the high rate of adjacent level premature degeneration. The primary purpose of the study is to prove equivalence (non inferiority) of outcome of the disc prosthesis in the short term compared with fusion. Enrolment has closed and this is a report of the data with 50 cases with 6 month follow-up and 9 cases having reached 24 month final follow-up.

Methods: In four centres, 52 patients with primary, single level cervical disc disease producing radiculopathy and/or myelopathy were randomised prospectively to receive anterior cervical discectomy with either fusion or artificial cervical disc replacement. The patients were evaluated with pre- and post-operative serial flexion-extension cervical x-rays at 6 weeks, 3, 6, 12, and 24 months. At the same intervals, the patients had pre and postoperative neck disability indexes, visual pain analogue scales, European myelopathy scores, SF-36 general health scores, and neurological status examinations assessing the patient’s reflex, motor and sensory function.

Results: At 6 weeks the neck disability index reduced by 34.1 for the investigational group compared to 35.2 for the fusion group. The pain score had reduced by 7.7 for the investigational group and by 9.7 for the control group. This improvement appeared to be maintained until the 12 month follow-up. The mean pain scores at 24 months were similar (4.3 and 5.6 respectively) In general there appeared to be a slightly better outcome for the investigational group, though the investigational group showed slightly less preoperative pain (p=0.091) and disability (p=0.055) than the fusion group. Both pain score and disability scores improved statistically significantly compared to the pre op scores (p< 0.001 all comparisons). Analysis of non-inferiority of outcome for the investigational group using ANCOVA with the preoperative score as the covariate and a non-inferiority margin of 5 points (5%) showed statistical significance at 12 weeks for Neck Disability Index.

Discussion: Anterior cervical discectomy and fusion has a good short-term outcome though there is a high incidence of failure at adjacent levels over time. It is hypothesized that the maintenance of motion of a segment will prevent adjacent premature degeneration. It will take long term follow-up studies however to prove this. In the mean time, the justification to insert artificial cervical prostheses rests on being able to prove equivalence of outcome between fusion and prosthesis in the short term. This paper shows that the outcomes appear to be equivalent. Though there is insufficient power to prove equivalence with a clinical margin of 5%.

Introduction: A prospective, randomized, controlled study has been conducted to compare the clinical outcomes of patients treated with an Artificial Cervical Disc to patients who receive fusion after cervical discectomy for the treatment of primary cervical disc disease. It is hypothesized that maintenance of motion after anterior cervical discectomy will prevent the high rate of adjacent level premature degeneration. The primary purpose of the study is to prove equivalence (non inferiority) of outcome of the disc prosthesis in the short term compared with fusion.

Methods: In four centers, 60 patients with primary, single level cervical disc disease producing radiculopathy and/or myelopathy are randomized prospectively to receive anterior cervical discectomy with either fusion or artificial cervical disc placement. The patients are evaluated with pre and postoperative serial flexion-extension cervical x-rays at 6 weeks, 3, 6, 12, and 24 months. At the same intervals, the patients have pre and postoperative neck disability indexes, visual pain analogue scales, European myelopathy scores, SF-36 general health scores, and neurological status examinations assessing the patient’s reflex, motor and sensory function.

Results: Data is presented for the first 47 patients. At 6 weeks the neck disability index reduced by 36.1 for the investigational group compared to 34.8 for the fusion group. The pain score had reduced by 8.2 for the investigational group and by 9.9 for the control group. This improvement appeared to be maintained until the 12 month followup. In general there appeared to be a slightly better outcome for the investigational group. Both pain score and disability scores improved statistically significantly compared to the pre op scores (p< 0.001 all comparisons). Analysis of non inferiority of outcome for the investigational group using ANCOVA with the preoperative score as the covariate and a non inferiority margin of 5 points showed statistical significance at 6 and 12 weeks for Neck disability index. Operative time appeared slightly less (2.3 hrs) for the investigational group compared to the fusion group(2.5hrs). Blood loss also appeared higher in the fusion group (165 mls compared to 91 mls). Hospital stay was equivalent (2.8 days and 2.9 days).

Discussion: Anterior cervical discectomy and fusion has a good short term outcome though there is a high incidence of failure at adjacent levels over time. It is hypothesized that the maintenance of motion of a segment will prevent adjacent premature degeneration. It will take long term followup studies however to prove this. In the mean time, the justification to insert artificial cervical prostheses rests on being able to prove equivalence of outcome between fusion and prosthesis in the short term. This paper shows that the outcomes appear to be equivalent. Early statistical evidence is available for some of the outcome measures at early post op followup. Further statistical power will be available when the full 60 cases are available for study and this may give further weight to the hypothesis of equivalence of outcome.

INTRODUCTION: A prospective, randomised, controlled study has been conducted to compare the clinical outcomes of patients treated with an Artificial Cervical Disc to patients who receive fusion after cervical discectomy for the treatment of primary cervical disc disease. It is hypothesised that maintenance of motion after anterior cervical discectomy will prevent the high rate of adjacent level premature degeneration. The primary purpose of the study is to prove equivalence (non inferiority) of outcome of the disc prosthesis in the short term compared with fusion.

METHODS: In four centres, 60 patients with primary, single level cervical disc disease producing radiculopathy and/or myelopathy are randomised prospectively to receive anterior cervical discectomy with either fusion or artificial cervical disc placement. The patients are evaluated with pre- and post-operative serial flexion-extension cervical X-rays at six weeks, three, six, 12, and 24 months. At the same intervals, the patients have pre- and post-operative neck disability indexes, visual pain analogue scales, European myelopathy scores, SF-36 general health scores, and neurological status examinations assessing the patient’s reflex, motor and sensory function.

RESULTS: Data are presented for the first 47 patients. At six weeks the neck disability index reduced by 36.1 for the investigational group compared to 34.8 for the fusion group. The pain score had reduced by 8.2 for the investigational group and by 9.9 for the control group. This improvement appeared to be maintained until the 12 month follow-up. In general there appeared to be a slightly better outcome for the investigational group. Both pain score and disability scores improved statistically significantly compared to the pre-operative scores (p< 0.001 all comparisons). Analysis of non inferiority of outcome for the investigational group using ANCOVA with the pre-operative score as the covariate and a non inferiority margin of five points showed statistical significance at six and 12 weeks for Neck disability index. Operative time appeared slightly less (2.3 hours) for the investigational group compared to the fusion group (2.5 hours). Blood loss also appeared higher in the fusion group (165 mls compared to 91 mls). Hospital stay was equivalent (2.8 days and 2.9 days).

DISCUSSION: Anterior cervical discectomy and fusion has a good short term outcome though there is a high incidence of failure at adjacent levels over time. It is hypothesised that the maintenance of motion of a segment will prevent adjacent premature degeneration. It will take long term follow-up studies however to prove this. In the meantime, the justification to insert artificial cervical prostheses rests on being able to prove equivalence of outcome between fusion and prosthesis in the short term. This paper shows that the outcomes appear to be equivalent. Early statistical evidence is available for some of the outcome measures at early post-operative follow-up. Further statistical power will be available when the full 60 cases are available for study and this may give further weight to the hypothesis of equivalence of outcome.

Objective: To assess the safety, clinical stability and capacity to preserve motion in the cervical spine of a newly designed cervical intervertebral disc replacement for patients with degenerative disc disease.

Design: A prospective cohort pilot study.

Subjects: Fifteen patients considered to be at risk of developing adjacent level degenerative changes received the artificial joint. Patients had either radiculopathy and/or myelopathy with radiological evidence of compression.

Outcome Measures: Radiological evidence of stability of the device and preservation of motion at the operated level and adverse events associated with the procedure. Secondary outcome measures were changes in scores on SF-36, Neck Disability Index, European Myelopathy Score and Visual Analogue Pain Scale assessments.

Results: The artificial joint maintained motion at the operated in all patients. The procedure was considered safe to be performed by experienced spine surgeons. The device was stable with no dislocation of components or backing out of screws. Improvements were noted in all of the assessment scores though statistical significance was not achieved.

Conclusions: Cervical intervertebral motion can be maintained with this device which at two years is clinically stable. The long-term influence of this device remains unknown.