A Closer Look At An Emerging Fixation Option For The Akin Osteotomy
The original Akin osteotomy for the correction of hallux abducto valgus (HAV) included resection of the medial prominence of the first metatarsal head in combination with a medial based wedge osteotomy of the proximal phalanx of the hallux.1 Subsequently, there have been several modifications to the original procedure in order to address factors such as location, rotation, shortening, dorsiflexion and plantarflexion.2-12
In regard to fixation options, researchers have described different approaches (transverse, oblique) to the orientation of the osteotomy.11
The Akin procedure is rarely indicated alone in the treatment of HAV deformity but surgeons commonly use it in combination with a more proximal procedure in order to address all components of the deformity.13 Surgeons utilize this procedure in the correction of a structural lateral deviation deformity of the hallux due to a high distal articular set angle (DASA) or hallux interphalangeus angle (HIA). Contraindications of this procedure include severe metatarsus primus varus, incongruous and/or severe osteoarthritis of the first metatarsophalangeal joint (MPJ).12
The original procedure described stabilization of the osteotomy via external splinting. Advances in fixation techniques introduced a variety of internal fixation options including: Kirschner wires (single or crossed double); stainless steel wire-loop fixation; and the more rigid options of the screw or staple.14
Let us take a closer look at the use of EasyClip SI™ staple fixation (Memometal Technologies, Inc.), which is a viable option for the fixation of an Akin osteotomy. The advantages of using the EasyClip SI include:
• elastic memory property of the material that allows for constant compressive forces from 5 to 6 kg;
• rigid fixation;
• technical ease of insertion that minimizes surgery time; and
• a low profile that minimizes the chance of irritation to the patient and thus the need of a second surgery for removal of hardware.
A Step-By-Step Guide To The Surgical Technique
Ensure the patient is in a supine position on the operating table. Following IV sedation, local anesthesia (Mayo block) and the application of an ankle tourniquet (if appropriate), proceed to perform the surgical prep and drape of the extremity.
Make a curvilinear skin incision over the dorsomedial aspect of the first MPJ extending from approximately the midshaft of the first metatarsal to approximately the head of the proximal phalanx. Place the incision medial to the extensor hallucis longus (EHL) tendon and follow the contour of the underlying joint alignment. Identify and retract all vital neurovascular structures during dissection and exposure of the osteotomy site.
One would perform the appropriate first metatarsal procedure first. We have typically performed the Akin in combination with an Austin osteotomy (through and through, distal apex V-type osteotomy through the head and distal shaft of the metatarsal) and two-screw fixation.
The surgeon would perform a transversely oriented Akin procedure because it provides a wider surface area of bone on each side of the osteotomy in which to secure the staple. Proceed to perform subperiosteal dissection of the proximal phalanx. Perform an osteotomy with the base medial and the apex proximal. For a proximal Akin, the apex is located at least 5 mm away from the MPJ to ensure preservation of the joint space. Take caution to preserve the lateral cortex to serve as a second point of fixation. “Feather” the osteotomy and reduce until you have achieved good correction and bone apposition.
Proceed to utilize the appropriate double-holed EasyClip SI template/drill guide by centering it dorsally over and ensuring a perpendicular orientation to the hallux proximal phalanx osteotomy site. Use a 2.0 mm drill to pre-drill the pilot holes for the EasyClip SI compression device. After completing each drill hole, use a 2 mm post to maintain and identify each drill hole. Use a depth gauge to measure the length of staple needed and load the appropriately sized staple on the provided forceps. We have most commonly used the EZM 10-10-10 staple, which has a 10 mm staple width and 10 mm staple leg length, for the hallux proximal phalanx.
Use the forceps to preload and diverge the prongs of the staple to allow for insertion. Then insert it into the pre-drilled holes in the hallux with one prong distal and one proximal to the osteotomy site. When you have released the staple from the forceps, the elastic property of the staple allows the prongs to converge to achieve compression across the osteotomy site. Use a tamp to ensure the staple sits flush to the bone.
At this time, one may utilize a C-arm to assess alignment and fixation if desired. Otherwise, surgeons may opt for radiographic evaluation of fixation postoperatively.
Irrigate the wound with sterile normal saline and perform capsular, subcutaneous and skin closure according to your preference. The postoperative course includes immediate weightbearing as tolerated in a surgical shoe. Then one may transition the patient to a sneaker in approximately four weeks.
Facilitating Good Compression, Rigid Fixation And Lower Risks Of Complications
While a limited number of articles have described the complications associated with the Akin procedure, the more commonly discussed and encountered complications include: plantar angulation at the osteotomy site; fracture at the lateral cortical hinge; shortening; under/over correction; and delayed/nonunion.11,13,14 A delayed or nonunion as well as recurrence can result from bone apposition of less than 50 percent. One can maintain bone apposition by diligently performing an accurate osteotomy as well as internal fixation.
The EasyClip SI compression device offers excellent compression and rigid fixation. It offers constant compressive forces that optimize bone apposition and reduce the risk of delayed and nonunion. This staple gives the benefits of screw fixation with relative technical ease of application. Additionally, the EasyClip SI compression device is sleek enough that should the lateral hinge be violated or fracture, application of a second staple would be possible. When using screw fixation, if the lateral cortical hinge is compromised, it can be technically challenging to achieve a second point of fixation.
Another advantage of using this fixation device is the minimal dissection of the soft tissue required for its insertion. One can obtain access to the bone from the dorsum as opposed to the medial aspect. This reduces the need for overzealous retraction and exposure. This subsequently reduces the risks of postoperative complications such as tissue necrosis, wound dehiscence, edema and infection. The dorsal approach also decreases the risk of directly compromising the neurovascular bundle.
Utilizing this method of fixation also affords the surgeon the option to perform a traditional transverse osteotomy of the proximal phalanx. We have found that the transverse osteotomy adequately corrects the deformity with less removal of bone, thus decreasing the shortening of the hallux as long as the cortical hinge remains intact. Optimal orientation of screw fixation should achieve maximal compression across the osteotomy site and increased bone apposition is perpendicular to the osteotomy. Screw fixation technique would be nearly impossible with a transverse Akin (which led to its obliquely oriented variation). Also, due to the nature of the staple, there is less chance for rotation of the bone as opposed to a traditional screw.
In previous years, one of the authors has also utilized wire fixation in the Akin osteotomy. Though this also has a relatively easy method of insertion, other inherent complications can occur with this fixation. It can be difficult to achieve adequate compression of the plantar cortex. We have also found that wire fixation breaks and fails more often than other methods of fixation. This subsequently compromises stability and leads to decreased compression, bone apposition, and can result in delayed unions and nonunions.
To date, we have not seen any failure or breakage of the EasyClip SI staple fixation or other fixation related complication.
The EasyClip SI compression device is a promising alternative for the fixation of standard Akin procedures. This fixation is low profile and provides a constant compressive force of at least 5 to 6 kg without the need for heat activation and in fewer steps than it takes to insert a lag screw. It offers a simple technique of attaining rigid, stable internal fixation that allows for a short learning curve and decreases tourniquet time as well as overall surgical time.
Dr. Ho is a third-year resident in the Department of Podiatric Medicine and Surgery at the Washington Hospital Center in Washington, D.C.
Dr. Rhodes is a third-year resident in the Department of Podiatric Medicine and Surgery at the Washington Hospital Center in Washington, D.C.
Dr. Kominsky is the Director of the Department of Podiatric Medicine and Surgery at the Washington Hospital Center in Washington, D.C. He is a Fellow of the American College of Foot and Ankle Surgeons.
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