Hip Innovation Technology Product Information

Reverse HRS Features and Benefits

While the orthopaedic community has advanced hip arthroplasty through the years, there remain 3 consensus complications:

• Dislocation and Instability
• Component Positioning / Placement
• Edge Loading

The Hip Innovation Technology (HIT) Reverse Hip Replacement System (Reverse HRS) provides design features that we believe address these potential hip arthroplasty complications.¹

Dislocation and Instability

Dislocation is one of the most common complications of total hip arthroplasty (THA).² Specifically, dislocations can occur at a rate as high as 10% after primary surgeries and at rates as high as 25% after revision surgeries. Recurrent instability is a difficult problem to overcome despite traditional methods including reorientation of the implants, use of elevated rim liners, removal of sources of impingement, trochanteric advancement, and abductor repair. Surgical stabilization using these traditional methods is unpredictable with success rates of only 60 to 80% depending on the series, etiology of dislocation, and surgical technique used.³

Reverse HRS Solution⁴

The Reverse HRS implant design provides greater range of motion in all planes with enhanced hip stability. This feature provides the following benefits:

• Significantly minimizes risk of dislocation
• Increases stability and ranges of motion

In addition, we believe the Reverse HRS may provide minimal postoperative restrictions and reduce the need for durable medical equipment (abduction pillow, elevated toilet seat, shower chair)

Component Positioning / Placement

A study of 1823 Total Hip Arthroplasty’s (THAs) by Callaghan, et al (2011) found that only 50% of the acetabular cups were properly placed within the “safe zone”, with a tendency toward higher abduction angles and anteverted cups. Factors correlated to malpositioned cups found within this study included surgical approach, low volume (average of 13 THAs per year) and obese patients (BMI > 30).⁵

Reverse HRS Solution⁴

The Reverse HRS allows variability of component placement including higher abduction angles and anteverted cups. The acetabular cup overlaps and articulates with the femoral cup as the hip undergoes flexion-extension, abduction- adduction and internal-external rotation. This forgiving design compensates for suboptimal positioning which may provide the following benefits:

• Maintains range of motion, stability and reduces likelihood of impingement
• Uncouples relationship between component placement, wear and stability

Edge Loading

Edge loading is a chiseling effect that can occur when the ball of the implant presses on the socket edge. Edge loading is associated with acetabular cup malposition and may cause accelerated component wear and increased debris particles that heighten the likelihood of osteolysis and subsequent loosening and failure of the implant.

Reverse HRS Solution⁴

The unique implant design of the Reverse HRS provides optimal surface area contact between the acetabular ball and femoral cup, which may eliminate edge loading. Elimination of edge loading may provide the following benefits:

• Reduces high-contact stresses and decreases wear
• Provides uniform wear and minimizes edge loading
• Minimizes generation of wear debris and concerns related to osteolysis
  
  
  
  

¹ Clinical Literature and data on file.

² Trivellin, G., A. Sandri, et al. (2013). "Ceramic liner fatigue fracture: 3-D CT findings in a late recurrent THA dislocation." Orthopedics 36(1): e101-104.

³ Niimi, R., A. Sudo, et al. (2012). "Failure mechanism of a constrained liner: a case report." Acta Orthop Belg 78(1): 129-133.

⁴ Conclusions based on non-clinical and cadaveric testing are on file with HIT.

⁵ Callaghan, M.C., Jarrett, B., et al. (2011). "Risk Factors for Cup Malpositioning. Quality Improvement Through a Joint Registry at a Tertiary Hospital."
  Clin Orthop Relat Res. 469:319-329.