Metal-on-metal (MOM) bearings after total hip arthroplasty are known to elevate the serum concentrations of metal ions, raising concerns about the long-term effects. One potential modifier of ion release is the bearing diameter used. Resurfacing MOM bearings have a large surface area available for corrosion compared to the typical bearing size of 28 mm in total hip replacement (THR) but may benefit from improved lubrication and reduced production of corrodible wear debris. The net effect of these two variables on metal ion release is unknown. In this study, we compared the level of ion release in patients after large bearing MOM hip resurfacing arthroplasty with patient after small bearing MOM THR.

We measured the serum cobalt and chromium levels from 22 patients with large bearing diameter MOM hip resurfacing arthroplasty (Cormet 2000 and Birmingham Hip Resurfacing) and compared them to the serum cobalt and chromium levels of 22 patients with small bearing diameter (28 mm) MOM THR (Ultima). Patients were prospectively matched for activity level, body mass and date after surgery at blood sampling. All were at least 6 months after surgery.

We found the median cobalt and chromium levels after hip resurfacing arthroplasty to be 7.6 times normal (median 38 nmol/L, range 14 to 144 nmol/L) and 10.5 times normal (median 53 nmol/L, range 25 to 165 nmol/ L) respectively. This is compared to 4.4 times normal (median 22 nmol/L, range 15 to 87 nmol/L) for cobalt and 3.8 times normal (median 19 nmol/L, range 2 to 58 nmol/L) for chromium after 28 mm MOM THR (p=0.0021 and p< 0.0001).

Conclusion: Large diameter MOM bearings result in greater release of cobalt and chromium ions than do small diameter MOM bearings. This may be of relevance when the potential effects of long-term exposure to elevated these metal ions is considered.

Prior studies have compared the bacterial load observed in laminar flow operating theatres (LFOTs) and standard operating theatres (STOTs) by wound culture and air sampling during surgery. However many organisms responsible for low grade infection after THR are not readily identified on routine culture and may be detectable only by more sensitive techniques such as the poly-merase chain reaction (PCR). This study assessed the wound contamination rate during THRs and compared the results in STOT with that in LFOTs using PCR.

We recruited patients undergoing primary THR for osteoarthritis. Surgery was performed in either STOTs or LFOTs, using identical skin preparation solutions, surgical drapes and operating attire. Specimens of the deep tissue, taken at the beginning and end of surgery, were each immediately separated into two sterile containers, one sent for culture (aerobic, anaerobic and enriched meat broth) and the other frozen at minus 80 degrees Celsius for PCR at a later date.

In each theatre type, 40 specimens from 20 THRs were analysed by both PCR and culture. Using PCR, bacterial DNA was identified on 12 of 40 specimens (30%) from STOTs, of which 3 were taken at the start of surgery and 9 at the end of the surgery, giving a 45% wound contamination rate (9 of 20). Two specimens (5%), both taken at the end of surgery, were positive on enriched culture. In LFOTs, bacterial DNA was identified by PCR on 8 of 40 specimens (20%), of which 2 were taken at the start of surgery and 6 at the end of surgery, giving a 30% wound contamination rate (6 of 20). No specimens were positive on enriched culture.

Wound contamination of primary THR occurs frequently in both STOTs and LFOTs. Although STOTs showed evidence of more frequent wound contamination than LFOTs, with the numbers available, no significant difference was detected. These data remind us the importance of aseptic surgical technique as significant wound contamination can occur despite the use of ultra clean air operating theatres.

Distal tibial fractures may be satisfactorily held in reduction by fine-wire external fixation techniques, avoiding the need for open reduction and internal fixation. However, as the use of external fixation is associated with pin-site infection, extra-articular placement of the wires is recommended. This study assesses the proximal extension of the capsule of the ankle joint in order to provide information on the safety of wire placement for distal tibia fractures.

We recruited 7 patients who were electively scheduled for an MRI ankle investigation with the suspicion of osteochondral defect and/or meniscoid lesion. Patients with a history of ankle fracture or ankle surgery were excluded from the study. Just prior to MRI, the ankle joint was injected with 5 to 15 ml of contrast solution (1 mM dimeglumine gadopentetate). Selected fat-saturated T1-weighted MRI scans with sagittal, coronal and axial views were obtained. The site and proximal extent of the capsular reflection with reference to the anterior joint line were measured.

All contrast-enhanced MRIs of the ankle joint space were well defined and unambiguous. Proximal capsular extensions above the plane of the anterior joint line were noted at the antero-medial and antero-lateral aspect of the joint (mean 8.9 mm, range 4.9 to 13.4 mm) and at the tibia-fibular recess (mean 18.7 mm, range 13.3 to 23.6 mm), areas that are frequently traversed by wire insertion.

Conclusion: This in vivo contrast-enhanced MRI ankle study demonstrates an appreciable capsular extension above the joint line of the ankle. The proximal capsular extensions at the antero-medial and antero-lateral aspect of the joint and at the tibio-fibular recess run the risk of being traversed during fine-wire placement for distal tibia fractures. Surgeons using these techniques should be aware of this anatomy.

Introduction: In the 1970’s, ‘viscosupplementation’ with hyaluronan was proposed as a potential treatment for OA with the idea that it would improve joint lubrication. However, despite studies showing its ability to reduce pain, the fact that the resident time within a joint (48 hours) is much less than its clinical effect (several months) along with pharmacological effects on chondroctyes and synoviocytes has confirmed that injected hyaluronan acts as a pharmaceutical rather than as a lubricant as originally thought. In this regard, the effects of inert synthetic lubricants on arthritic joints have not previously been adequately investigated.

This study examines the effect of injecting an inert synthetic lubricant, perfluoroalkylether (PFAE16350), as a mechanical joint lubricant to prevent the development of osteoarthritis in a surgically induced model of osteoarthritis in the adult guinea pig.

Materials & Methods: Osteoarthritic changes were initiated in the hind knee joint of 12 adult male Dunkin-Hartley guinea-pigs by excision of the medial meniscus and anterior cruciate ligament.

After wound closure, the animals were randomly assigned to 1 of 2 groups: (1) Single intra-articular injection of 1ml synthetic, sterile lubricant (PFAE16350) or (2) Control group with single intra-articular injection of 1ml 0.9% sterile saline.

At 9 weeks after surgery, after sacrifice, knee arthrotomy was performed, the presence of synthetic lubricant noted and the articular cartilages examined for macroscopic evidence of osteoarthritis. These cartilages were then fixed, embedded, sectioned, stained and graded histologically for osteoarthritis according to a modified Mankin scoring system.

Immunohistochemical studies were performed to assess for any inflammatory or cytotoxic effect by the lubricant.

Results: All guinea-pigs remained healthy and mobile throughout the study.

Subjective macroscopic assessment of the medial tibial plateau osteophyte was noted to be larger and the articular surface more roughened in the control cases compared to the lubricated cases. Synthetic lubricant was noted at arthrotomy in all cases where it was injected.

Guinea-pig joints treated with the synthetic lubricant showed a mean modified Mankin score of 3.0 points compared with the guinea-pig joints treated with saline where the median modified Mankin score was 8.5 points (p< 0.001). There was no evidence of an inflammatory or cytotoxic response by immunohistochemical studies.

Discussion: This study has confirmed that inert synthetic perfluoroalkylether lubricants can remain in the articular space for prolonged periods and inhibit the development of osteoarthritis without initiating an inflammatory response. Synthetic lubricants such as PFAE16350 warrant further investigation for potential use in osteoarthritis.

Introduction: Although there is evidence that laminar flow operating theatres (LFOTs) can reduce the incidence of wound infection over standard operating theatres (STOTs) when no routine peri-operative antibiotics were used, the evidence for the use with concurrent parenteral antibiotics is less compelling. A number of prior studies have compared the bacterial load observed in LFOTs and STOTs by wound culture and air sampling during surgery. However many organisms responsible for low grade infection after THR are not readily identified on routine culture and may be detectable only by more sensitive techniques such as the polymerase chain reaction (PCR), a molecular biology test for the presence of bacterial DNA. The purpose of this study was to compare the wound contamination rate during THRs performed in STOT with that in LFOTs using PCR.

Method: Patients undergoing primary THR for osteoarthritis without a history of joint infection were recruited for the study. Surgery was performed in either STOTs or LFOTs, using identical skin preparation solutions, surgical drapes and operating attire. Specimens of the deep tissue, taken at the beginning and end of surgery, were each immediately separated into two sterile containers, one sent for culture (aerobic, anaerobic and enriched meat broth) and the other frozen at minus 80 degrees Celsius for PCR at a later date.

Results: In each theatre type, 40 specimens from 20 THRs were analysed by both PCR and culture (80 specimens and 40 THRs in total).

Using PCR, bacterial DNA was identified on 12 of 40 specimens (30%) from STOTs. Of these 12, three were taken at the start of surgery and nine at the end of the surgery, equivalent to a 45% wound contamination rate (9 of 20). Only two specimens (5%), both taken at the end of surgery, were positive on enriched culture.

In LFOTs, bacterial DNA was identified by PCR on eight of 40 specimens (20%). Of these eight, two were taken at the start of surgery and six at the end of surgery, equivalent to a 30% wound contamination rate (6 of 20). None of the specimens were positive on enriched culture.

Discussions: We concluded that wound contamination of primary THR occurs frequently in both STOTs and LFOTs. Although STOTs showed evidence of more frequent wound contamination than LFOTs, with the numbers available, no significant difference was detected. These data are important in that they confirm that continued vigilance to technique continue to be important as significant wound contamination can occur despite the use of ultra clean air operating theatres.

Introduction: Metal-on-metal (MOM) bearings after total hip arthroplasty are known to elevate the serum concentrations of metal ions, raising concerns about the long term effects. One potential modifier of ion release is the bearing diameter used. Resurfacing MOM bearings have a large surface area available for corrosion compared to the typical bearing size of 28 mm in total hip replacement (THR) but may benefit from improved lubrication and reduced production of corrodible wear debris. The net effect of these two variables on metal ion release is unknown. In this study, we compared the level of ion release in patients after large bearing MOM hip resurfacing arthroplasty with patient after small bearing MOM THR.

Methods: We measured the serum cobalt and chromium levels from 22 patients with large bearing diameter MOM hip resurfacing arthroplasty (Cormet 2000 and Birmingham Hip Resurfacing) and compared them to the serum cobalt and chromium levels of 22 patients with small bearing diameter (28 mm) MOM THR (Ultima). Patients were prospectively matched for activity level, body mass and date after surgery at blood sampling. All were at least 6 months after surgery.

Results: We found the median cobalt and chromium levels after hip resurfacing arthroplasty to be 7.6 times normal (median 38 nmol/L, range 14 to 144 nmol/L) and 10.5 times normal (median 53 nmol/L, range 25 to 165 nmol/L) respectively. This is compared to 4.4 times normal (median 22 nmol/L, range 15 to 87 nmol/L) for cobalt and 3.8 times normal (median 19 nmol/L, range 2 to 58 nmol/L) for chromium after 28 mm MOM THR (p=0.0021 and p< 0.0001).

Discussion: We concluded that large diameter MOM bearings result in greater release of cobalt and chromium ions than do small diameter MOM bearings. This may be of relevance when the potential side-effects of long-term exposure to elevated these metal ions is considered. It is not known to what extent this difference is due to corrosion of the component surfaces or of the wear particles produced.

Aims: Elevated serum cobalt and chromium ion levels associated with carcinogenesis and chromosomal damage in animals has raised concerns that metal-on-metal (MOM) total hip replacement (THR) in humans may produce the same effects over time. Considering that the risks may be related to the level of these ions in the body, this study compared the serum cobalt and chromium ion levels in patients with unilateral versus bilateral 28 mm diameter MOM THR.

Methods: All patients having THR at our institution were prospectively registered on a computerised database. From our database, we identified 108 patients with Ultima (Johnson and Johnson, Leeds) MOM THR with 28 mm bearing made of cobalt-chromium alloy. After patient review in clinic and before blood results were known, patient matching was performed by date after surgery at blood sampling, activity level and body mass. Using these stringent criteria, 11 unilateral THR could be adequately matched with 11 bilateral THR. Blood serum was taken with full anti-contamination protocols and serum analysed via inductively coupled plasma mass spectrometry.

Statistical analysis used the Mann-Whitney U test.

Results: The serum cobalt ion level after unilateral MOM THR was 4.4 times normal (median 22 nmol/L, range 15 to 37 nmol/L) compared to 8.4 times normal (median 42 nmol/L, range 19 to 221 nmol/L) for bilateral MOM THR (p=0.001). The serum chromium ion level after unilateral MOM THR was 3.8 times normal (median 19 nmol/L, range 2 to 35 nmol/L) compared to 10.4 times normal (median 52 nmol/L, range 19 to 287 nmol/L) for bilateral MOM THR (p=0.04).

Conclusions: This study has shown that the serum cobalt and chromium ion levels in patients with bilateral MOM THR are significantly higher than those in patients with unilateral MOM THR. With levels of up to 50 times the upper limit of normal, this finding may be of relevance for the potential development of long-term side effects.

Aims: Identifying low-grade infection in failed total hip replacements (THR) is an important but often difficult task. Recently, there has been interest in the use of molecular biology techniques as potential sensitive tests for low-grade infection by identifying fragments of bacterial DNA within human tissue. Methods: We investigated the ability of a molecular biology technique known as the polymerase chain reaction (PCR) to identify low-grade infection during revision of THR considered to have failed from aseptic causes. We analysed 113 specimens of tissue and synovial fluid from 31 THR revised for aseptic loosening and compared them to 105 control specimens taken during 28 primary THR. All cases were performed in laminar flow theatres. No primary or revision specimen had positive microbiological cultures. No revision specimen had histological evidence suggestive of infection. Results: Using PCR, we identified bacterial DNA in 39 of 85 revision THR tissue specimens (46%) compared to 18 of 84 primary THR specimens (21.4%, p=0.001). Bacterial DNA was identified within the synovial fluid in three specimens taken from 28 revision THR (10.7%) and in two specimens taken from 21 primary THR (9.5%, p=0.36). As multiple specimens were sent per case, 16 of 31 revision THR (52%) and eight of 28 primary THR (29%) were considered to be infected (p=0.072). Conclusions: Our results suggest that many aseptically loose revision THR actually contain bacterial DNA within the peri-prosthetic tissue, but infrequently within the synovial fluid. With an overall specimen contamination rate of 19%, however, PCR has poor specificity for routine diagnostic use in revision THR.

Aims: Cobalt (Co) and chromium (Cr) ion associated carcinogenesis and chromosomal damage in animals has raised concerns that metal-on-metal (MOM) total hip replacement (THR) in humans may produce the same effects over time. Considering that the risks may be related to the level of these ions in the body, this study compared the serum Co and Cr levels in patients with unilateral versus bilateral 28 mm diameter MOM THR. Methods: All patients having THR at our institution were prospectively registered on a computerised database. From our database, 108 Ultima MOM THR with 28 mm CoCrMo bearing were identiþed. After patient review in clinic and before blood results were known, patient matching was performed by date after surgery, activity level and weight. Using these stringent criteria, 11 unilateral THR could be adequately matched with 11 bilateral THR. Blood serum was taken with full anti-contamination protocols and serum analysed via atomic absorption spectrometry. Statistical analysis used the Mann-Whitney U test. Results: The median serum Co level after unilateral MOM THR was 22 nmol (range 15 to 37 nmol) compared to 42 nmol (range 19 to 221 nmol) for bilateral MOM THR (p=0.001). The median serum Cr level after unilateral MOM THR was 19 nmol (range 2 to 35 nmol) compared to 52 nmol (range 19 to 287 nmol) for bilateral MOM THR (p=0.04). Conclusions: This study has shown that the serum Co and Cr levels in patients with bilateral MOM THR are signiþcantly higher than those with unilateral MOM THR. With levels of up to 50 times the upper limit of normal, this þnding may be of relevance for the potential development of long-term side effects.

Lubricated metal-on-metal (MOM) bearing surfaces are not easily separated, unlike ceramic- or metal-on-UHMWPE (COP, MOP), due to interfacial forces and low diametric clearance that provides a ‘suction-fit’. In vivo videofluoroscopic studies have shown that patients with MOP/COP THRs exhibit separation of bearing surfaces by up to 3.1 mm during normal gait and 5.4 mm during active abduction while patients with MOM bearings do not. In this regard, MOM bearings may have similarities to constrained bearings with the potential to lower dislocation rates.

All patients under 70 years old undergoing primary THRs for primary osteoarthritis were prospectively registered on a computer database. From 1993–8, patients were offered a 28 mm COP bearing. After 1998, as part of a clinical trial, a 28 mm MOM bearing was inserted instead. For all cases, we used a metal-backed, uncemented acetabulum allowing a modular 10-degrees posteriorly augmented insert (Duraloc/PFC/Ultima, J& J) and the same cemented femoral stem (Ultima, J& J). The same experienced surgeon performed all operations using the posterior approach. Interfacial forces between bearing surfaces were assessed in vitro with a variable-speed-motor winch (APT) and a load-cell (E375/RDP) by recording peak-retaining-forces of bearing couples during separation with variable impact-distraction velocities. Statistical analysis used the Chi-square and student’s t-test.

We identified 140 COP THRs in 129 patients and 109 MOM THRs in 100 patients. Nine of 140 (6.4%) COP bearings dislocated within 3 months of surgery compared to 1 of 109 (0.9%) in the MOM group (p=0.024). No significant differences were identified between groups when comparing patient and prosthesis factors. In vitro assessment demonstrated that MOM bearing possessed interfacial retaining forces up to 30N more than COP bearing (p< 0.001).

This study demonstrates a significantly lower dislocation rate in THR with MOM bearing compared with COP. A potential explanation is the differential ease of separation that the two lubricated bearing couples possess due to interfacial retaining forces (viscous tension and ionic adhesive forces) exerted by the lubricating fluid.

We made a clinical study of polyethylene wear in 240 hips of 187 patients having primary total hip arthroplasties from 1989 to 1990, using uncemented Osteonics components, with a head size of 26 mm. We excluded cups with anteversion of over 20° and measured linear wear by a new method using a digitiser and special software of our design. Follow-up was from two to five years (mean 4.3).

The mean age at operation was 50.3 years, with more men than women (1.4:1). The mean linear wear per year was 0.15 mm; this did not increase with the longevity of the prosthesis (p = 0.54). In 59 hips showing evidence of osteolysis, the mean linear wear rate was significantly higher at 0.23 mm/year (p < 0.001). The mean linear wear rate also correlated significantly with age at the time of operation (p = 0.008), but we found no significant correlations with body-weight, gender, aetiology of the disease, thickness of polyethylene, or cup position.

Our new method of measurement is time-saving and reproducible. The results confirm the greater rate of linear wear of polyethylene in patients showing osteolysis and in those who are younger.

Six normal cadaver lower limbs were mounted on a specially designed loading apparatus. Wires were used to simulate the five muscle bellies of the quadriceps, the ratio of their tensions having been determined from that of the anatomical cross-sectional areas of the muscles. A three-camera system was used to track the patella during knee movements from flexion to extension. The patellofemoral contact area was determined by pressure-sensitive film. The limb was loaded with and without tension on the wire which simulated the oblique part of the vastus medialis (VMO). Absence of VMO tension caused the patella to displace laterally (4.2 mm) and increased the load on the lateral patellar facet throughout the range of knee motion. When the tension on the wire simulating vastus lateralis was reduced by 40% to simulate the effect of a lateral release procedure, the abnormal kinematics caused by the absent VMO returned to normal.

We reviewed 20 adult patients with spondylolysis and isthmic spondylolisthesis an average of 10.5 years after treatment by anterior spinal fusion. Nineteen patients had excellent or satisfactory results. Ten of the patients were symptom-free at one year, and 15 were asymptomatic at final follow-up. Anterior spinal fusion can produce results comparable to those of posterior fusion with or without decompression. The results tend to improve with time in contrast to the known worsening of late results after posterior decompression without fusion.

Thirteen patients with dystrophic spinal deformities from neurofibromatosis treated by anterior and posterior fusion have been reviewed. The shortest follow-up was five years, the average seven years. Combined fusion produced satisfactory results in patients with a smooth kyphoscoliosis or with scoliosis without kyphosis, but it was unsatisfactory in patients with an angular kyphoscoliosis. Of the five patients with angular kyphoscoliosis, one had a persistent pseudarthrosis after operation and all had progression of the kyphosis despite the treatment. The morbidity rate also was high in this group of patients. Many of the complications were related to soft-tissue manifestations of the disease. It is recommended that very special attention be paid to the dystrophic angular deformity in neurofibromatosis; even anterior and posterior spinal fusion may fail to control its progression.