The Viability of Short Stems in Total Hip Arthroplasty

The purpose of this study is to determine the viability of short femoral stems as an alternative to standard-length stems in total hip arthroplasty.

Porous-coated cementless stems were introduced in the late 1970s, in response to the high incidence of aseptic loosening associated with cemented stems (Judet et al 1978, Kavanagh et al 1989, Lord 1982, Stauffer 1982). The stem's porous surface achieves fixation via bony ingrowth at the endosteum (Engh et al 1987). In an effort to mimic the femur's natural stress distribution, many designs preferentially load the metaphysis (Joshi et al 2000). One such design is the proximally coated titanium tapered wedge, which is widely used today (Pitto et al 2010). Because loading is primarily dictated by bony ingrowth, the proximal porous coating avoids fixation at the diaphysis. The flat, tapered geometry reduces stiffness compared to cylindrical stems, thereby propagating stress to the proximal femur, rather than down the stem's axis (Engh et al 1987, Harvey et al 1999), (Boehm 1998). Further contributing to decreased stiffness is titanium's low elastic modulus, relative to that of cobalt-chromium (Harvey et al 1999, Mulliken et al 1996). Some contend the need for distal fixation in Dorr type C hips due to thin cortical bone at the metaphysis; however, proximally engaging stems have been shown to perform well in these patients (Kelly et al 2007, Reitman et al 2003). If a stem's objective is to load proximally, then perhaps it need not extend into the diaphyseal canal. The emergence of short stems has initiated an alternative means of proximal loading, without the disruption of diaphyseal bone stock. The smaller incisions involved with short stem total hip arthroplasty (THA) reduce damage to muscle and soft tissue (Molli et al 2012). This enables a faster, more complete recovery for the patient, as well as a cosmetically superior result (Sherry et al 2003). Additionally, the preservation of bioavailable bone can be advantageous if a revision surgery is required (Toth et al 2010). Because short stems do not extend into the diaphysis, issues regarding proximal-distal mismatch of the femur are avoided (Patel et al 2013). This eases implantation and reduces the risk of intraoperative fracture (Azzam et al 2010, Cooper & Rodriguez 2010). The risk of intraoperative fracture is further mitigated because short stem THA does not require the use of reamers (Molli et al 2012, Scott et al 1975, Taylor et al 1978). Although the standard-length proximally coated titanium tapered wedge has a successful long-term track record, its design leaves room for improvement (Mallory et al 2001, Marshall et al 2004). Standard length stems cause stress-shielding in Gruen zones 1 and 7, suggesting that the diaphyseal portion of a stem may interfere with proximal loading (Gibbons et al 2001, Schmidt et al 2004). Even proximally coated flat tapered stems are subject to diaphyseal loading (Cooper et al 2011). The Accolade stem has been associated with significant early subsidence, especially in males with Dorr type A hips (Jacobs & Christensen 2009). This suggests that the stem may wedge distally, thereby interfering with osseointegration (White et al 2012). By achieving a purely metaphyseal fit, short stems can prevent excessive bone loss secondary to stress shielding (Gustke 2012). The investigators believe short stems are an equally effective alternative to traditional tapered stems in THA; however, long-term studies are essential to proving their efficacy. Long-term studies of short stems are lacking in current literature. With respect to initial stability and bony ingrowth, short-term data is promising; however, there is still potential for late aseptic failure (Capello et al 2009, Kroell et al 2009, Morales de Cano et al 2013, Schmidutz et al 2012). By conducting a single blinded, prospective, randomized investigation of two stems of varying length with equal metallurgy, coating, and proximal geometry, the investigators can identify the effects of stem length on long-term outcomes.

Veteran's RAND 12 Item Health Survey used to assess health-related quality of life, to estimate disease burden, and to evaluate disease-specific benchmarks. Scores for the Mental Composite Score (MCS) range from 5.2 to 76.3 and are evaluated as a summative T-score with population mean of 50 (Standard Deviation = 10);higher scores indicate improved mental wellness/function as reported by patients.

Assesed pre-operatively, 6 weeks post-operatively, 3 months post-operatively, 6 months post-operatively, 12 months post-operatively, and 2 years post-operatively.

Veteran's RAND 12 Item Health Survey used to assess health-related quality of life, to estimate disease burden, and to evaluate disease-specific benchmarks. Scores for the Physical Composite Score (PCS) range from 6.3 to 71.8 and are evaluated as a summative T-score with population mean of 50 (Standard Deviation = 10);higher scores indicate improved mental wellness/function as reported by patients.

Assessed pre-operatively, 6 weeks post-operatively, 3 months post-operatively, 6 months post-operatively, 12 months post-operatively, and 2 years post-operatively.

Patient-reported outcome (PRO) measures use answers that patients provide to questions to produce numeric values which indicate patients' state of wellbeing or suffering as well as their ability or lack of ability to function. Values are reported as T-scores with a reference population mean of 50 (SD=10); for the Pain Behavior domain higher scores indicate more frequent and severe incidence of pain during daily activities

Pre-operatively, 6 weeks post-operatively, 3 months post-operatively, 6 months post-operatively, 12 months post-operatively, and 2 years post-operatively.

Patient-reported outcome (PRO) measures use answers that patients provide to questions to produce numeric values which indicate patients' state of wellbeing or suffering as well as their ability or lack of ability to function. Values are reported as T-scores with a reference population mean of 50 (SD=10); for the Physical Function domain higher scores indicated improved physical function as reported by the patient

Pre-operatively, 6 weeks post-operatively, 3 months post-operatively, 6 months post-operatively, 12 months post-operatively, and 2 years post-operatively.

Patient-reported outcome (PRO) measures use answers that patients provide to questions to produce numeric values which indicate patients' state of wellbeing or suffering as well as their ability or lack of ability to function. Values are reported as T-scores with a reference population mean of 50 (SD=10); for the Pain Interference domain higher scores indicated greater impact on patient's ability to perform daily activities and social function

Pre-operatively, 6 weeks post-operatively, 3 months post-operatively, 6 months post-operatively, 12 months post-operatively, and 2 years post-operatively.

EBRA (Ein-Bild-Roentgen-Analyse) Femoral Component Analysis (EBRA-FCA) of Implant Subsidence Through 2 Years Post Operative

EBRA-FCA is a commonly employed technique to evaluate implant migration via radiographic measurements taken over the duration of recovery. The mean subsidence values measured in millimeters were recorded for both the short and standard stem cohorts at each of the clinic visits for SOC. Of note, the individual responsible for performing and recording these measurements could not be reached during upload of the final study data and consequently the dispersion values for this measure were not available at the time of publication. The dispersion values for these measures have been recorded as '0' for each time point pending any response from the individual to obtain the original data.

Assessed 6 weeks post-operatively, 6 months post-operatively, 12 months post-operatively, and 2 years post-operatively.

Inclusion Criteria: Must require a total hip arthroplasty. Ages 18-85 years, regardless of gender, ethnicity, or pathology Exclusion Criteria: This study excludes any populations at risk. Minors, as well as any persons unable to consent, will not be eligible.