Intraoperative instability during THA can be addressed by proper restoration of femoral offset. Leg-length equality and acetabular component position are also fundamental considerations in THA for patient satisfaction and prevention of dislocation.4 Patients with spinal deformities and younger, more active patients, create higher demands on implant components needed to improve functional outcomes and avoid dislocation.
Femoral Offset & Leg-length Equality
Patients expectations following total hip replacement have become increasingly more demanding. Return to a pain free lifestyle with no limitations and equal leg lengths are considered the "norm"."
Meeting these expectations is dependent on the approach as well as reestablishment of the patients' native biomechanics. Patients' leg length and offset should not be at the mercy of limited stem options including offset.” Said E. Stolarki, MD “
The MasterLoc stem gives me incredible versatility with three offset options within an 11 mm range. Whether it is avoiding increasing native offset of a valgus DDH neck or matching the most extreme varus offset, the MasterLoc stem allows for recreating that patient's native biomechanics. This reduces trochanteric bursitis in the DDH patient and avoids increasing leg lengthening for stability in those patients with significant offset.”
Acetabular Cup Positioning
“
The Mpact Double Mobility Cup has become an integral part of my hip implant armamentarium to address patients who have a high risk of dislocation.” Said R. Jain, MD, “
The traditional safe zone for acetabular component inclination and anteversion, as proposed by Lewinnek, may need to be reconsidered in some patients.5 For example, patients with stiff hips, limited spinopelvic motion, have the greatest risk for dislocation. It is in these situations that I like to increase my "safe zone" by using the Mpact DM double mobility cup.” “
In these patients, I find the Mpact DM cup to be invaluable. In addition, I find that the high coefficient of friction of the plasma spray coating of the Mpact cup really grabs the acetabulum when implanting, even in these osteoporotic hip fracture patients.”
References:
[1] Kwon MS, et al. Does surgical approach affect total hip arthroplasty dislocation rates? Clin Orthop Relat Res. 2006;447:34–38.
[2] Gwam CU, et al. Current epidemiology of revision total hip arthroplasty in the United States: National Inpatient Sample 2009 to 2013. J Arthroplasty 2017;32:2088e92. https://doi.org/10.1016/j.arth.2017.02.046.
[3] Forde B., et al. Restoring femoral offset is the most important technical factor in preventing total hip arthroplasty dislocation. Journal of Orthopaedics 15 (2018) 131-133
[4] M.M. Innmann et al. Additive influence of hip offset and leg length reconstruction on postoperative improvement in clinical outcome after total hip arthroplasty. The Journal of Arthroplasty 33 (2018) 156-161
[5] Lewinnek GE, et al. Dislocations after total hipreplacement arthroplasties. J Bone Joint Surg Am 1978;60:217-20.
