Metal-on-metal hip resurfacing: correlation between clinical and radiological assessment, metal ions and ultrasound findings

Is there still an indication for the Birmingham Hip Resurfacing in femoral head osteonecrosis?

PURPOSE

Osteonecrosis of the femoral head (ONFH) is a progressive hip disease. Hip resurfacing arthroplasty (HRA) is a preferred surgical procedure among hip arthroplasty performed in young patients. The aim of this study is to show the long-term clinical and radiological results of HRA procedures performed for patients suffering from ONFH.

METHODS

Forty-five patients who underwent hip resurfacing with the diagnosis of femoral head osteonecrosis were included in the study. The Harris Hip Score (HHS) was used for clinical scoring of the patients. The blood chromium, cobalt, white blood cell (WBC) count, and CRP levels of patients were checked. Ultrasonography (USG) was performed for all patients at mid-term control checked for pseudo-tumours. For the radiological evaluation, acetabular inclination, stem shaft angle, prothesis-to-neck ratio, osteolysis zones, and heterotopic ossification were used.

RESULTS

The mean age of the patients was 46.6 ± 9.3 years, and the mean follow-up period was 11.83 ± 2.9 years. The mean HHS was 90.3 ± 12.8 for final follow-up. The mean WBC value was 8.2 109/L, mean CRP value was 6.3 mg/L, mean chromium value was 4.9 µg/L, and mean cobalt value was 1.8 µg/L. Inclination changing 0.2°(p = 0.788), stem shaft angle changing 0.7°(p = 0.424), and neck-to-prosthesis ratio changing 0.01°(p = 0.075). No pseudo-tumours were detected in any patients in USG examination.

CONCLUSION

HRA provides long-term implant survival and excellent clinical outcomes for end-stage ONFH patients with low complication rates.

Radiographic evaluation of hip resurfacing: the role of x-rays in the diagnosis of a problematic resurfaced hip

INTRODUCTION

Hip resurfacing (HRA) requires a new standardised radiographic evaluation protocol. Evaluation of acetabular components is similar to total hip arthroplasty (THA) but femoral components require different criteria. This study evaluates the efficacy of a new femoral zonal system for radiographic HRA assessment in identifying clinical problems.

METHODS

A new proximal femoral zonal system divides implant-cement-bone interfaces at head and neck into 7 DeSmet zones. 611 in situ and 100 revised HRA were assessed for component positioning, borderline findings (reactive lines, cortical thickening, cancellous condensation) or sinister findings (lucent lines, bone resorption, osteolysis). Findings were correlated with gender, size, implant survival, clinical scores, metal ions, and adverse soft tissue reactions (ALTR).

RESULTS

Radiological changes were found in 265 hips (37.3%), 154 sinister (21.7%) and 111 borderline (15.6%). 84% of revisions had sinister findings versus 11.4% of in situ HRA (p < 0.001). The mean number of abnormal acetabular and femoral zones was 3.3 in revised compared to 0.6 in situ HRA (p < 0.001). Sinister findings were associated with female gender, lower clinical scores, smaller sizes or ASR design (all: p < 0.001). Metal ions were higher with sinister (p < 0.001) and borderline (p < 0.01) findings compared to normal radiographs. Pathological findings in ⩾4 zones had a sensitivity of 50% and specificity of 94.2% (AUC = 0.898) in detecting hips with ALTR (odds ratio = 49).

CONCLUSION

In order to accurately evaluate progressive radiographic changes in HRA, specific zones have been established around the femoral component. There was a high correlation between radiographic findings and outcome measures. 84% of problematic hips and 90.4% of proven ALTR had sinister changes.

Higher Prevalence of Mixed or Solid Pseudotumors in Metal-on-Polyethylene Total Hip Arthroplasty Compared With Metal-on-Metal Total Hip Arthroplasty and Resurfacing Hip Arthroplasty

BACKGROUND

Pseudotumors are a common finding in metal-on-metal (MoM) total hip arthroplasty (THA) and resurfacing hip arthroplasty (RHA). However, information on pseudotumors in metal-on-polyethylene (MoP) THA is limited.

METHODS

One hundred eleven patients with 148 hip articulations-30 MoM THA, 47 MoM RHA, and 71 MoP THA-participated in a cross-sectional study at mean 7.1 (range: 0.2-21.5) years postoperatively. Patients were evaluated with metal artifact reducing sequence magnetic resonance imaging, measurements of metal ions, clinical scores of Harris Hip Score, Oxford Hip Score, the Copenhagen Hip and Groin Outcome Score, and conventional radiographs.

RESULTS

Pseudotumors were present in 13 of 30 (43%) MoM THA, 13 of 47 (28%) MoM RHA, and 29 of 71 (41%) MoP THA patients, which was a similar prevalence (P = .10). The prevalence of mixed or solid pseudotumors was significantly higher in patients with MoP THA (n = 10) compared to MoM THA (n = 3) and MoM THA (n = 0), (P = .01). Hips with a mixed or solid pseudotumor had significantly poorer scores of Harris Hip Score (P = .01) and OHS (P = .002) and higher metal ion levels of cobalt (P = .0009) compared to hips without a pseudotumor or with a cystic pseudotumor.

CONCLUSION

Pseudotumors have primarily been associated with MoM hip articulations, but we found a similar pseudotumor prevalence in MoP THA, which is the most common bearing worldwide. Mixed or solid pseudotumors were more often seen in MoP THA compared with MoM hip articulations, and patients with a mixed or solid pseudotumor had poorer clinical scores and higher metal ion levels than patients without a pseudotumor or with a cystic pseudotumor.

Patient Obesity Influences Pelvic Lift During Cup Insertion in Total Hip Arthroplasty Through a Lateral Transgluteal Approach in Supine Position

BACKGROUND

Movement of the pelvis during implantation of total hip arthroplasty (THA) has a major influence on the positioning of the acetabular cup. Strong traction caused by retractors leads to iatrogenic pelvic lift and can thus be partly responsible for cup malpositioning. The objective of this study was to investigate such factors that influence pelvic lift.

METHODS

The dynamic movement of the pelvis was measured during implantation of THA in 67 patients. This was done by measuring the acceleration using the SensorLog app on a smartphone.

RESULTS

At its maximum, the pelvis was lifted by an average of 6.7°. When impacting the press-fit cup, the surgical side was raised by 4.4° compared with the time of skin incision. This lift at the time of cup implantation correlates significantly with the body mass index and the patient's abdominal and pelvic circumference.

CONCLUSION

Every surgeon performing THA must be aware of the pelvic lift during an operation. Especially in patients with a high body mass index, a large abdominal circumference, or a large pelvic circumference, there is an increased risk of malpositioning of the acetabular cup. When impacting the cup, we recommend releasing the traction of the retractor, so that the pelvis can tilt back into its natural position, and thus, the anticipated cup positioning can be implemented as exactly as possible.

Influence of Surgical Approach on Pelvic Lift in Hip Arthroplasty During Cup Insertion

The position of the acetabular cup is a major factor in the long-term outcome of total hip arthroplasty (THA). Malpositioning of the acetabular cup frequently has been reported with the use of a minimally invasive implantation technique. It remains unclear whether the limited visibility or the increased retractor traction and thus tilting of the pelvis during cup implantation is the cause. This study investigated the influence of iatrogenically related pelvic lift using an anterolateral minimally invasive THA technique. In a group of 30 consecutive patients who underwent THA via a minimally invasive anterolateral approach, iatrogenic lifting of the pelvis was measured with a smartphone using a 3-axis accelerometer and compared with patients in a historical age- and sex-matched control group who underwent THA using a transgluteal approach. Postoperatively, the inclination and anteversion of the cup was determined on pelvic radiographs. In the anterolateral group, the pelvis was lifted by a maximum of 6.3° and by an average of 3.9° when the acetabular cup was impacted; no difference was noted compared with the transgluteal group. In contrast, the cups in the anterolateral group showed significantly increased inclination and reduced anteversion. In both techniques, the iatrogenic tilting of the pelvis at the time of cup implantation occurred to a comparable extent. Therefore, the significant differences in postoperative radiographs cannot be attributed to increased retractor traction on exposure of the acetabulum, which means that the limited visibility must be responsible. [Orthopedics. 2017; 40(4):e589-e593.].

Metal-on-Metal Total Hip Arthroplasty Associated with Adverse Local Tissue Reaction and Pseudoaneurysm of the Superior Gluteal Artery: A Case Report and Literature Review

Adverse local tissue reaction (ALTR) and pseudoaneurysm formation are rare but known complications following metal-on-metal hip total hip arthroplasty (THA). We report the first known case in the English literature of a concurrent unilateral ALTR and pseudoaneurysm of the superior gluteal artery in the same patient. Following minimal rise in serum metal ions, an ultrasound of the right hip demonstrated an avascular solid/cystic lesion anterolaterally in keeping with an ALTR. More posterolaterally, a second discrete thick-walled cystic lesion was identified. Doppler interrogation demonstrated a “yin yang” pattern suggestive of a pseudoaneurysm. Magnetic resonance imaging confirmed the presence of an anterolateral periarticular lesion with a second discrete lesion within the gluteus medius. Subsequent computed tomography angiography confirmed the presence of arterial contrast blush within the posterior gluteal lesion adjacent to the superior gluteal artery. The patient remains asymptomatic and is being managed conservatively. We review the imaging characteristics of ALTR and pseudoaneurysm occurring post-THA. When a complex solid/cystic lesion is encountered in a patient with a THA, radiologists must ensure that the lesion is interrogated with color Doppler to confidently distinguish a pseudotumor from a pseudoaneurysm. This information is vital to the surgeon to avoid unexpected hemorrhage if revision joint replacement surgery is being contemplated.