Stand up! Are normal weight-bearing forces sufficient for a 12/14 Morse taper locking in total hip arthroplasty?

BACKGROUND: The aim of this study was to investigate total hip arthroplasty (THA) Morse taper pull-off strengths after impaction prior to cyclical loading compared to cyclical loading alone. The practical relevance of the experiment is to provide a perspective on what may be clinically satisfactory taper assembly given the spectrum of head tapping patterns used by surgeons, as well as compare traditional impaction performed in standard THA with alternate methods of taper engagement such as 'in situ assembly' used in micro-invasive techniques. METHODS: 36 taper constructs utilising a combination of cobalt-chrome alloy and ceramic-titanium alloy junctions were investigated in vitro in wet and dry conditions with cyclical loading of the constructs. Taper disengagement strengths with and without impaction were compared. Secondary investigation of the surface roughness of the heads and tapers was also assessed. RESULTS: An impaction to a wet taper resulted in a greater pull off force compared to a dry taper with a CoCr head and taper combination. Impacting the head and dryness of the taper did not affect pull off forces of a ceramic femoral head on titanium taper. Pulling a head off a taper significantly alters the head surface roughness. CONCLUSION: Impaction of a taper does not provide any benefit over cyclical loading of a taper assembly alone for pull-off strength.

Driving After Microinvasive Total Hip Arthroplasty.

BACKGROUND: Patients undergoing total hip arthroplasty (THA) are often advised to avoid driving for 6 weeks postoperation. This is based on patients having to maintain postoperative hip precautions and studies investigating brake reaction time (BRT) following THA using conventional techniques. The aim of this study was to assess patients' ability to drive in the early postoperative period following microinvasive THA by assessing BRT. METHODS: Hundred consecutive patients undergoing SuperPATH® THA in 2015 who drove automobiles preoperatively were included in this prospective cohort study. BRT was measured preoperatively and at day 1 or 2 postoperation using a driving simulator. A subset of 25 consecutive patients had repeat BRT testing at 2 weeks postoperation. Five BRT measures were taken at each time point. Differences in the patient's mean and best BRT at each time point were assessed using the paired t-test. RESULTS: The study cohort included 50 men and 50 women with mean age 63 years (range 25-86). The mean preoperative BRT was 0.63 s (range 0.43-1.44), with a mean difference of -0.1 s (range -0.57 to 0.33, P < .0001) at day 1 or 2 postoperation. The 2-week mean and best BRTs were also better than paired preoperative readings with a mean improvement of 0.15 s (range -0.78 to -0.004, P < .0001). CONCLUSION: BRT reaches preoperative values by day 2 following microinvasive THA. Patients may be suitable to drive earlier than the previously recommended 6 weeks postoperation.