Total Hip Replacement with Use of the French Paradox Cementing Technique for a Shortened Charnley-Kerboull Stem via a...

The "French Paradox" technique, one of the various femoral cementing techniques in total hip replacement, was developed by Marcel Kerboull at Cochin Hospital, Paris, in the 1960s. Its fundamental principles include removal of the cancellous bone, use of a highly polished and collared canal-filling stem, and a straightforward cementation technique. This technique differs from the taper-slip philosophy, which relies on controlled subsidence, and the composite-beam concept, which seeks rigid bonding between stem and cement to act as a single structural unit.

Following patient positioning on the Judet positioning table, a bikini Hueter anterior approach is performed. After implantation of the acetabular component, the femur is exposed with the aid of the positioning table. Femoral preparation begins with the use of an aggressive canal-finder rasp and curet to establish the entry and remove initial cancellous bone. Subsequent preparation is performed with use of either aggressive cutting broaches or flexible reamers, with the objective of removing as much cancellous bone as possible. Following insertion of the cement plug, the femoral canal is thoroughly washed and then dried. A suction drain is then inserted close to the cement plug, and medium-viscoelasticity cement is inserted with use of a regular syringe or a flexible cement gun. Creating negative pressure within the canal helps aspirate any blood that might impede optimal cement interposition. Furthermore, given the canal-filling design of the stem, any small tunnel that exists after drain removal is expected to collapse under pressure. The highly polished stem is then inserted until the collar touches the neck cut.

Alternatives include the taper-slip and composite-beam techniques. The taper-slip technique involves the use of a highly polished stem that subsides slightly within the cement mantle, generating controlled compressive forces to preserve the cement-bone interface. The composite-beam technique involves the use of a matte stem that bonds to the cement mantle, creating a unified structure that resists micromotion and maintains stability.

The French Paradox cementing technique requires the removal of cancellous bone, which becomes weak with aging and cannot effectively carry load. By eliminating this compromised layer, the technique is thought to allow forces to be transmitted directly to the cortical bone. This is the proposed mechanism for reducing the risk of periprosthetic fracture in the elderly population by preventing any subsidence of the stem. Additionally, compared with other cementing techniques, the French Paradox technique is easy, cost-effective, and reproducible. There is no need for a tip centralizer or vacuum cement preparation, and the femoral preparation closely resembles that for a cementless implant, making the technique more intuitive for surgeons already experienced with cementless hip arthroplasty.

El Masri et al. observed that femoral components cemented with use of the French Paradox technique had not subsided at long-term follow-up. Nich et al. and Kerboull et al. also reported >98% survival of Charnley-Kerboull stems at 15 years postoperatively. More recently, a shortened version of the Charnley-Kerboull stem (AMIS-K; Medacta International) was developed after in vitro validation, providing optimal stem length reduction of 12%. Laboudie et al. compared the in vivo migration of the AMIS-K implant and the standard-length Charnley-Kerboull implant in a matched-pair cohort of 50 hips in each group. At 2 years postoperatively, the mean subsidence was 0.65 mm in the AMIS-K group compared with 0.68 mm in the standard Charnley-Kerboull group. In another study of 416 hips in patients >70 years old undergoing primary total hip replacement with the French Paradox technique and AMIS-K implant, Laboudie et al. reported a 0.48% rate of early periperiprosthetic femoral fractures.

Perform the femoral neck cut according to the preoperative plan, as this technique employs a collared stem.Remove cancellous bone thoroughly, particularly in the superomedial region, with use of a curet or flexible reamer.Utilize cutting broaches of increasing size until the trial broach or stem achieves good anteroposterior and rotational stability. The trial broach should provide a press-fit comparable to that of standard cementless techniques, making the procedure more intuitive for surgeons accustomed to cementless designs.Note that a compaction-broaching technique is not considered a French Paradox because it compacts rather than removes cancellous bone. Switching intraoperatively to a cemented stem that mimics the shape of a cementless straight stem (e.g., the CORAIL [DePuy Synthes]) is also not considered a French Paradox.Insert a cement restrictor and perform simple lavage of the medullary canal.Utilize medium-viscoelasticity cement.Insert cement with use of a syringe or cement gun in a straightforward manner.Achieve pressurization via the canal-filling design of the stem.

THR = total hip replacementCK = Charnley-KerboullPFF = periprosthetic femoral fractureCMK = Charnley Marcel KerboullEBRA-FCA = Ein Bild Roentgen Analyse-femoral component analysisTHR = total hip replacementDAA = direct anterior approachCPT = CPT Hip System (Zimmer Biomet)LFCN = lateral femoral cutaneous nerveGT = greater trochanterTFL = tensor fascia latae.