The use of cemented versus cementless joint prostheses in total hip replacement has undergone exhaustive investigations over the past several decades with researchers seeking to establish guidelines for one approach over the other as having greater benefit for patients. The answer to which is the better option depends on many patient related factors, which influence overall patient outcomes and, in particular, durability. Overall in the United States, cementless primary total hip arthroplasty (THA) is the favored procedure at a rate of 94.2 percent according to the American Joint Replacement Registry.
Suffice it to say both cemented and cementless prostheses have merit. Each has been refined in technique and technology over the years and can be selected on the clinical dynamics of the individual patient. While cementless components are predominant in this country, cemented femoral stems also have clear benefits in specific patient populations.
Dr. H. John Cooper
Dr. Roshan P. Shah
With this in mind, H. John Cooper, MD, and Roshan P. Shah, MD, JD, orthopedic surgeons specializing in adult reconstructive surgery in the Department of Orthopedic Surgery at NewYork-Presbyterian/
Although the cementing process adds technical complexity to total hip arthroplasty, growing evidence supports its use in certain cohorts. As such, it is critical that orthopedic surgeons and investigators have a thorough understanding of the fundamentals and evidence underlying modern cementation techniques.— Study authors, JBJS Reviews
In particular, the article presents an extensive range of research – often with conflicting findings – into the many elements related to cement properties and preparation as well as application and insertion factors to help address the concerns that still surround the use of femoral stem cementation. The reporting encompasses years of investigations that point out the challenges faced early on in cementing techniques and how research continues to inform present-day recommendations. Following are just a few of the conclusions they present based on an extensive literature review.
Cement Viscosity
Viscosity, which is the resistance of cement fluid to flow and deformation, has been the focus of extensive research related to its effect on outcomes following total hip arthroplasty. While current day practices lean toward using medium- and high-viscosity cement, the available evidence does not endorse a unified recommendation. In particular, the study authors caution that the use of high-viscosity cement, which could produce excessive intramedullary pressure, should potentially be avoided in patients at risk for pathologic hip fracture.
Mixing Technique and Porosity
As high porosity can affect the mechanical strength and fatigue life of cement, the technique for mixing polymethylmethacrylate is critical. During the earliest days of arthroplasty, cement was hand-mixed in a bowl, resulting in higher porosity due to air entrapment. Vibration, centrifugation, and vacuum mixing techniques were subsequently introduced to reduce cement porosity and improve mechanical properties, with vacuum mixing now considered the standard approach for cementing femoral stems.
Adding Antibiotics to Cement
Mixing antibiotics into the cement to prevent infection has been a longtime practice dating back to the 1970s, but when first introduced the concept was fraught with a number of cautionary concerns, including effectiveness, toxicity, development of resistance, and impact on mechanical properties. Despite years of rigorous investigations, current research supporting the widespread use of antibiotic-loaded bone cement (ALBC) remains inconclusive. However, there is evidence that encourages a role for ALBC in primary total hip arthroplasty in patients who may be at increased risk for developing perioprosthetic joint infection.
Cement Timing
Overall, the study authors note that cement consistency at the time of stem insertion is a more important variable to consider than timing for insertion as mixing time is only one of many variables, including room temperature and humidity, affecting consistency. Additionally, the stem insertion rate was not found to significantly affect porosity distribution within the cement mantle.
Preparing the Canal
With the goal of improving the cement-bone interlock, preparation of the bone bed has been recommended to begin with broaching, with irrigation and suctioning repeated between broaching to reduce the risk of embolism. Additionally, high-pressure pulse lavage, which can remove intervening blood, fat, and marrow cells, lowers the risk for embolization and bone cement implantation syndrome. This lavage procedure is now a standard clinical practice and is recommended in the American Academy of Orthopaedic Surgeons Toolkit.
Value of a Cement Restrictor
According to the research evaluated by Drs. Cooper and Shah and others, the different types of restrictors available are seen as comparable when standard techniques are followed. Furthermore, non-absorbable restrictors are recommended in routine cases where insertion at the isthmus can be achieved. If more distal placement is preferred, an expandable restrictor can be considered, albeit cautiously.
Cement Thickness
Cement thickness is another subject of intense interest. Cement mantle thickness of 2 to 5 mm is considered appropriate based on results of clinical, laboratory, and autopsy studies, with most surgeons preferring a mantle of <2 mm.
Calling Centralizers into Question
While proximal and distal centralizers are designed to achieve an adequate central stem position within the canal, findings from a number of research studies question their benefit. One study comparing insertion of stems with and without a centralizer did not demonstrate a significant benefit of a centralizer in avoiding coronal malalignment of the stem. Another study noted that a distal centralizer allowed for less variation in the circumferential cement mantle compared with stems inserted without a centralizer. A third study showed that proximal stem centralizers did not provide a benefit in cement penetration and pressurization but did increase the risk of stem malpositioning. These findings cast doubt on the need for a centralizer, and if a centralizer device is used, close attention should be paid to stem positioning without relying on self-correction of a flawed stem alignment.
Importance of Cement Pressurization
During cement pressurization, if higher pressures generally lead to better bone penetration, then sustaining that pressure for a longer duration may inhibit fluid backflow into the canal and avoid jeopardizing the integrity of the cement mantle. A number of studies have assessed pressurizer systems but with varying results. However, the results do indicate that “systems achieving a closer fit to the canal opening allow for longer higher-pressure levels while simultaneously controlling for cement leakage.” Moreover, using a pressurizer during cement application followed by calcar occlusion during stem insertion is recommended to achieve adequate high pressures for longer duration.
In summary, the NewYork-Presbyterian/Columbia faculty, Dr. Cooper and Dr. Shah, and their co-authors note, “Although the cementing process adds technical complexity to total hip arthroplasty, growing evidence supports its use in certain cohorts. As such, it is critical that orthopedic surgeons and investigators have a thorough understanding of the fundamentals and evidence underlying modern cementation techniques.”
