Is there a “best” stapes prosthesis?†
The authors have no funding, financial relationships, or conflicts of interest to disclose.
The surgical approach to otosclerosis has evolved significantly over the decades following Shea's first stapedectomy in 1956. The procedure has progressed from total removal of the stapes footplate, to partial stapedectomy, and now to small fenestra stapedotomy using a microdrill or laser. Likewise, the choice of stapes prosthesis has changed over the years in terms of size, shape, and composition.1 The three most common prosthesis designs are the wire loop, piston, and bucket handle, although there are many variations on each. Piston diameter has ranged from 0.3 to 0.8 mm. Prostheses have been made from a wide array of materials including Teflon, stainless steel, platinum, gold, and more recently a nickel titanium alloy, nitinol.
Recent investigations have focused on the manner in which the prosthesis fixates on the incus. Traditionally, the most common prosthesis used is a piston with a wire loop on the end. This loop is secured to the incus by using a forceps to crimp the wire down around the incus. The crimping of the wire loop is arguably the most critical step in stapes surgery. If done too loosely, the prosthesis may shift and lead to a deterioration in hearing. If crimped too tightly, reduced perfusion may lead to incus erosion and necrosis.
One way around the challenge of crimping is by using a prosthesis design other than the traditional wire-loop piston. The bucket handle prosthesis is one such option. The general design has the lenticular process placed in the bucket, with the handle then flipped over the incus. In one large series, Daniels and colleagues reviewed operative and audiologic records of 1,800 patients (3,600 ears), who underwent bilateral stapedectomy using a Robinson bucket prosthesis.2 Ninety-five percent of patients with otherwise normal anatomy achieved <10 dB air-bone gap (ABG) in both ears, and 98% achieved this result in at least one ear.
Another prosthesis that does not require crimping is the clip model. The clip is inserted by setting it on the long process of the incus and then gently pushing it into position. The clip does not fully encircle the incus, theoretically reducing the risk of strangulation. Tange and Grolmon retrospectively reviewed 126 cases in which 63 patients received a titanium K-piston prosthesis, and 63 patients received a titanium CliP-piston àWengen prosthesis.3 Using ABG closure <10 dB as the final end point, a statistically significant difference in audiologic results between prostheses could not be determined (P = .566).
A different answer to the challenge of crimping can be found in the nitinol-based prosthesis. Nitinol is a nickel-titanium alloy that is heat activated and self-crimping. Several authors report similar hearing outcomes with nitinol. Fayad and colleagues4 reviewed 416 ears, 306 receiving a SMart prosthesis and 110 receiving a self-crimped piston prosthesis. There was no significant difference in rate of gap closure to within 10 dB (78.3% vs. 84.2%, SMart and non-SMart, respectively) or 20 dB (94.2% and 98.0%, SMart and non-SMart, respectively) between the two prostheses.
There are a handful of studies that favor nitinol over manually crimped prostheses. Tenney et al.5 reviewed 94 patients, half receiving a nitinol prosthesis and half receiving a traditional piston prosthesis. A significant difference favoring nitinol was found in immediate postoperative ABG (P = .022) and ABG at least 1 year postoperatively (P = .013).
A systematic review of 13 recent studies, including the two mentioned above, comparing manual crimping to nitinol prostheses, was conducted by Van Rompaey et al.6 Three studies were identified that found a statistically significant improvement in audiologic outcome with nitinol. One studied favored manually crimped prosthesis. The remaining studies could not find a significant difference in outcomes. Because of heterogeneity in reported outcome measures and follow-up period, the data could not be pooled. Thus, superiority of the nitinol prosthesis could not be demonstrated in this review. Furthermore, a recent article described a need for revision stapedectomy in 11% of patients who underwent surgery, with the SMart prosthesis compared to a revision rate of 4% in patients in whom the De La Cruz stapes prosthesis was used.7 The authors comment that the crimping process that occurs with the heat-activated prosthesis likely requires the use of a slightly longer prosthesis than that used with a prosthesis that is crimped manually. The SMart prosthesis was rapidly adapted by many surgeons, so it is not surprising that modifications in the technique would emerge as surgeons began to evaluate their results. Further studies will be required to confirm that using slightly longer SMart prostheses will result in a revision rate analogous to that achieved with other prostheses.
BEST PRACTICE SUMMARY
Long-term follow-up may eventually show some benefit to using a newer stapedectomy prosthesis such as the titanium clip or nitinol prosthesis. However, at this time there is no evidence that one prosthesis design is significantly better than another with regard to postoperative hearing outcomes. An experienced surgeon should be able to achieve good results with whichever prosthesis he or she feels most comfortable using.
LEVEL OF EVIDENCE
This series has one level 3a article, and five level 3b articles.