Aims

Metal-on-metal hip resurfacing (MoM-HR) has seen decreased usage due to safety and longevity concerns. Joint registries have highlighted the risks in females, smaller hips, and hip dysplasia. This study aimed to identify if reported risk factors are linked to revision in a long-term follow-up of MoM-HR performed by a non-designer surgeon.

Introduction: Lateral insufficiency fractures following total hip replacements have been reported with the femoral stems positioned in varus, together with osteopenia of the lateral femoral cortex. Any abnormal alignment of the lower limbs, such as genu valgum, will alter the load distribution across the femoral cortices, and repetitive loading during walking will predispose the bones to stress fractures at any stress riser point, such as the tip of a femoral component. Bilateral femoral stress fractures post total hip replacements have not been previously described

Materials and Methods: We present a 55 yr old lady, diagnosed with juvenile idiopathic arthritis aged 5 years, and had undergone bilateral total hip replacements at the age of 29 and 30 years and bilateral knee replacements aged 37 and 42 years. The right hip required revision of the cup 15 years later. The knees were in valgus and the left knee was extremely stiff flexing to just 5 degrees. She presented to us as an emergency with bilateral thigh pain with plain radiographs confirming bilateral peri-prosthetic fractures of the femur at the tip of well fixed femoral components. There had been no history of injury and her hips were functioning well up to this time.

Results: The patient required revision of both hips to long stem un-cemented components, bypassing the fractures, and revision of both knees to stemed seni-constrained implants, thereby correcting the alignment of both lower limbs.

Both fractures healed and the patient is currently pain free and mobile with walking aids.

Discussion: Surgeons must remain aware that when implants are in situ, abnormal alignments will lead to abnormal forces, and stress fractures are likely to occur at any stress riser around the implant. Avoiding mal-alignment will avoid this complication.

Bilateral peri-prosthetic stress fractures following total hip replacements have not been previously reported.

Introduction: Serum inflammatory markers are routinely used as pre assessment investigation before the revision hip surgery. Various investigations are used to aid in diagnosis of infection in the revision prosthetic hip replacement including aspiration, broad range PCR, bone scan and serum interleukin- 6.

Materials and Methods: 256 consecutive revision total hip replacements were assessed for the value of pre operative ESR and c-reactive proteins (CRP) in predicting the deep infections.

All patients were evaluated prior to surgery. The patients with coexisting inflammatory disease or peri-prosthetic fracture were also evaluated.

A hip was diagnosed as infected on the basis of positive intra operative microbiology samples three or more out of five and or histological evidence.

Results: Using the values of ESR > 35 mm/1^st hour and CRP> 10mg/l, the positive predictive value (either /or) was 56% and the negative predictive value was 96%. 14 patients had an underlying inflammatory arthritis and 5 were peri prosthetic fractures. The inflammatory markers tended to be elevated in these patients. Excluding these 19 patients and using the same criteria, the positive predictive value was 65% and the negative predictive value was 97%

Discussion: We conclude that a CRP< 10 mg/l and ESR < 35 mm/1^st hour are very useful in excluding infection (negative predictive value of 97%, excluding peri-prosthetic fractures and inflammatory joint disease), but raised inflammatory markers are less accurate in predicting infection.