Modularity in total hip replacement(THR) enables precise recreation of native hip biomechanics. However, there have been concerns about raised metal ion levels with increased number of interfaces. We present the 3 year results of ML taper with Kinectiv technology(MLKT), a modular neck uncemented stem. This system has modular neck options, but has only one [0] head in various diameters. 97 hips in 97 patients with a MLKT stem and Continuum socket were included in this prospective study. Harris hip score, Oxford hip scores (HHS and OHS) and yearly blood Cobalt(Co), Chromium(Cr) and Titanium(Ti) were recorded. The primary end point was revision for any reason. Paired t- test was used to assess improvement in functional scores.Background
Methods
High failure rates have been associated with large diameter metal-on-metal total hip replacements (MoM THR). However there is limited literature describing the outcomes following the revision of MoM THR for adverse local tissue reaction (ALTR). A total of 98 large diameter MoM THRs underwent revision for ALTR at our institution. The data was obtained from the clinical records and included the demographics, intra-operative findings of ALTR and post-operative complications. Any subsequent procedures and re-revision for any reason was analysed in detail. The clinical outcome was measured using functional outcome scores using the Oxford hip score (OHS), Western Ontario and McMaster Universities osteo-arthritis index (WOMAC) score and Short Form (SF12). The mean age of the patients at the time of revision was 58.2 yrs. At a mean follow-up of 3.9 years (1.0 to 8.6) from revision for ALTR, there were 15 hips (15.3 %) with post-operative complications and 8 hips (8 %) requiring re-revision. The Kaplan–Meier five-year survival rate for ALTR revision was 91 % (95% confidence interval 78.9 to 98.0). There were no statistically significant predictors of re-revision. The rate of postoperative dislocation following revision was 9.2% (9 hips). The post-operative functional outcome depends on the intra-operative findings of tissue destruction secondary to ALTR. The short term results following revision of large diameter MoM THR for ALTR are comparable with other reports in the literature. The use of constrained liners reduces the incidence of post-operative dislocation. There is an increased risk of postoperative instability following revision THR for ALTR. Early identification and intervention seems to be the logical approach in the management of patients with ALTR.
The advantages of metal on metal (MOM) hip replacement are decreased wear rate, preservation of bone stock, anatomical restoration and enhanced stability. Large amounts of metal wear particles and metal ions are released which may induce adverse reactions including local soft tissue toxicity, hypersensitivity reactions, bone loss and risk of carcinogenesis. Aseptic loosening can be the result of a peri prosthetic osteolysis generated as a result of a biological response to particulate wear debris. Our aim in this study was to determine whether a steeply inclined acetabular component would give rise to a higher concentration of metal ions. Between April 2003 and June 2006, 22 patients had MOM hip replacement for osteoarthritis by a single Surgeon. There were 12 male and 10 female patients. The average age at the time of surgery was 56 years (Range: 44–69 years). We divided the 22 patients into 2 groups, one group (A) of 11 patients with the acetabular inclination angle more than 50 degrees and the other group (B) of 11 patients with the angle less than 50 degrees. The inclination of the acetabular cup was measured using a standard AP radiograph of the pelvis. The patients had metal ion levels (blood chromium and serum cobalt) measured at an average follow up of 3.2 years (Range 2.4 to 5 years).Introduction
Patients and methods
The advantages of large diameter metal on metal total hip arthroplasty (MoM THA) and hip resurfacing arthroplasty are decreased wear rate, preservation of bone stock, anatomical restoration and enhanced stability. Large amounts of metal wear particles and metal ions are released which may induce adverse reactions including local soft tissue toxicity, hypersensitivity reactions, bone loss and risk of carcinogenesis. Aseptic loosening can be the result of a peri-prosthetic osteolysis generated as a result of a biological response to particulate wear debris. No reports in the literature exist as to whether circulating levels of Chromium (Cr) and Cobalt (Co) decrease upon removal of a symptomatic large diameter MoM implant or whether levels remain high due to the effect of metal ions debris left behind in the soft tissues after revision surgery. Between June 2006 and June 2009 we undertook 44 revision surgeries of both large head MoM THAs (femoral head diameter 38mm) and metal-on-metal hip resurfacings for suspected metallosis. Mean time from original implant to revision was 4 years, 8 months (1yr 4mo–7yr 9mo). The mean follow up evaluation was 2 years and 2 months (1yr 2mo–4 years). Blood samples were taken for whole blood Cr and serum Co according to a recognised protocol and compared with reference levels indicated by the Medicines and Healthcare Regulatory Agency recommendation of less than 7ppb for Cr (130nM/L) and Co (119nM/L).INTRODUCTION
PATIENTS AND METHODS
On hundred and ninety unselected patients, mean age 62(SD12.8) were operated upon by one surgeon, using same approach. HSS improved from 33 to 75 post-operatively, the low figures reflecting a high percentage of Charnley C patients (71%). There was a 5% mortality rate from unrelated causes. Early complications included a 2.97% femoral fracture rate within 4–8 weeks of surgery (analysis showed no relation between implant position, BMI, age or Charnley classification, but there was correlation between high level of satisfaction and early weight bearing). There was one infection and one dislocation. Late complications included 3 periprosthetic fractures, 3 dislocations and 2 aseptic cup failures. However, 30% of patients developed groin pain, increasing stiffness and clunking at 1–2 years following surgery. These patients were investigated with an ultrasound scan. 28 patients (14%) had an effusion and were aspirated. Chrome and cobalt levels in synovial fluid, blood and urine were very high. 13 patients have been revised. 1 showed infection, 10 showed metal allergy and 2 a mixed picture of allergy and foreign body reaction. In our MOM database (762 hips including the current study) a total of 35 patients were revised for similar problems. Two distinct histological finding were observed. Metal allergy occurred independently of cup angle. The implants were well fixed; there was tissue necrosis and histological evidence of ALVAL. There was no infection or metalosis. FB reaction occurred more frequently when the cup was open. The Implants were loose; there was naked eye evidence of metalosis and metallic particles seen on light microscopy. We concluded that Birmingham/Freeman Hybrid had high complication rate without significant functional superiority, and other MoM devises shared similar complication. Both Metal allergy and FB reaction can occur in MOM THR. Ultra sound is a good screening tool in symptomatic patients.
