title: An unusual case of persistent groin pain after total hip arthroplasty: a case report.
abstract: BACKGROUND
  Arthroplasty is a well-established routine elective surgical procedure in orthopaedics. To a great extent, diagnosis, treatment and post-operative rehabilitation in these patients is standardised. In a busy clinic, surgeons from time to time tend to focus their attention on common causes of joint pain, but it may lead them to overlook sinister but less common pathologies. Here we report a case of a patient with groin pain due to pre-operatively undetected pelvic metastases from a pyeloureteral carcinoma who underwent total hip arthroplasty. There are several case reports which deal with primary or secondary tumours which were either discovered at the time of replacement surgery or developed at the site of prosthesis years after total hip or knee replacement. To the best of our knowledge, this is the first case report in which a metastatic cancer was missed pre-operatively and intra-operatively both by the radiologist and by the orthopaedic surgeon and should be reported so that surgeons are reminded to be careful when dealing with seemingly routine cases.
  
  
  METHODS
  A 79-year-old Caucasian woman presented to the arthroplasty clinic with groin pain. Initial radiographs showed subtle bilateral abnormalities in the pelvis. Neither the radiologist nor the orthopaedic surgeon recognized it. A diagnosis of osteoarthritis of the hip was established, and she underwent total hip arthroplasty. Despite initial improvement, the patient came back with worsening hip pain three months later. Further radiological examination revealed multiple metastatic lesions throughout the pelvis due to a pyeloureteral carcinoma.
  
  
  CONCLUSIONS
  This case report emphasizes the importance of meticulous, unbiased pre-operative assessment of patients and their radiographs, even in so-called routine clinical cases. Often subtle radiological changes are classed as normal, especially if they are bilateral. Further radiological imaging should be recommended in all cases where unexplained clinical features or radiological findings are present.
authors.affiliation: Musculoskeletal Surgery Department, Imperial College, London, UK. Michael.Hirschmann@ksbh.ch.
authors.forename: Praveen
authors.initials: P
authors.lastname: Konala
authors.forename: Thomas K
authors.initials: TK
authors.lastname: Schaefer
authors.forename: Farhad
authors.initials: F
authors.lastname: Iranpour
authors.forename: Niklaus F
authors.initials: NF
authors.lastname: Friederich
authors.forename: Michael T
authors.initials: MT
authors.lastname: Hirschmann