STAR and Preoperative Varus Deformity (Part 3)

STAR and Preoperative Varus Deformity Part 3

By Mark E. Easley, M.D.

Case 4:  59-year-old female, formerly very active in recreational sports, with progressively worsening right ankle pain.

Figure 30: (Case 4 Fig 1A-C)

The patient has endstage right ankle arthritis with varus malalignment.  Measurements suggest that she has a relatively small ankle. (A) Bilateral AP weightbearing radiograph. (B) Right AP weightbearing radiograph. (C) Lateral weightbearing radiograph.

Figure 31: (Case 4 Fig 2A,B)

Tibial preparation, after I performed a medial release. (A) AP cutting block was somewhat difficult to position in the coronal plane, but with the variability to the lateral pin placement, I was able to position it in a satisfactory manner.  However, I was relatively close to the medial malleolus. (B) Lateral view with the “angel wing” guide demonstrating the resection level and slope for the tibial cut.

Figure 32: (Case 4 Fig 3A,B)

Talar preparation. (A) The resection level and slope for the talar component was made using the “angel wing” guide on the lateral fluoroscopic image. (B) I was satisfied with the 4-in-1 talar reference guide position also based on the lateral fluoroscopic image.

Figure 33: (Case 4 Fig 4A,B)

I was pleased with the position of the trial tibia and polyethylene with the final talar component in place. (A) AP fluoroscopic view.  Note that the talar crest does is not directly centered over the coronal dimension of the talar dome. Instead, it is centered over the base (most inferior coronal dimensions) of the talar component and therefore, the talus.  I was a little concerned about the medial “notch” created by the pin that is placed to protect the medial malleolus from injury, but not enough to place a prophylactic screw in the medial malleolus. (B) Lateral fluoroscopic view. The talar component and polyethylene are centered well under the tibial shaft axis and tibial trial component.

Figure 34: (Case 4 Fig 5A,B)

Final intraoperative fluoroscopic images. (A) AP view.  I am pleased with the position of the components.  Perhaps the talar component is one size too large in the coronal plane, but the polyethylene keeps it away from the malleoli, albeit based on nonweightbearing fluoroscopic analysis. (B) Lateral view.  The talar component and polyethylene are well centered under the tibial component, again based on nonweightbearing fluoroscopic images.

Figure 35: (Case 4 Fig 6A,B)

Three-month weightbearing followup radiographs. (A) AP view.  The patient complains of medial malleolar tenderness. This corresponds to the medial malleolar stress fracture she has sustained.  Based on this weightbearing film, the talar component now appears wide in the coronal plane.  Also, the talus appears to have translated slightly medially under the tibia, but not enough to create edge-loading. (B) The talar component and polyethylene appear slightly posterior to where they were positioned on the final intraoperative fluoroscopic image, again without obvious edge-loading.

Question:  Why did the medial malleolus fracture in this case?

Answer:  In my opinion, I weakened the medial malleolus in this relatively small ankle with the medial pin placed to protect the malleolus during initial tibial preparation.  While I could have placed a prophylactic screw, I do not think that would have prevented the fracture.  The problem is that I have oversized the talar component.  Traditionally, the thought was that if a bigger talar component was used, greater stability would be imparted to the ankle with preoperative deformity.  In this case, it is actually detrimental. A narrower talar component probably would have provided adequate stability without impinging on the medial malleolus.

Question:  Why did the talar component and polyethylene translate posteriorly?

Answer:  Perhaps the medial release was too aggressive, thereby allowing greater than desired posterior translation in this mobile-bearing prosthesis.  Also, if there is any displacement of the medial malleolar fracture, the talus may be able to translate posteriorly.

Question:  What is the course of action at this point?

Answer:  I have had patients whom I protected from weightbearing, with or without casting, who have spontaneously healed the medial malleolar fracture in a position that allows slightly greater coronal plane dimensions to the ankle mortise so that the impingement by the talar component was eliminated.  However, I have had patients who required internal fixation to stablilize the fracture to allow healing. I have not had to downsize the talar component, but I have avoided overreduction of the medial malleolus.  Remember, the talar component is close to being the proper size since I measured at the time of implantation, based on the talar sizing guide.

Question:  Are there any concerns of an intraoperative or postoperative medial malleolar fracture in a patient who has undergone medial release?

Answer:  I think so, particularly given this case.  I treated this patient nonoperatively for the fracture and she has not healed the fracture despite immobilization and restricted weightbearing.  I am concerned that a medial release devascularizes the medial malleolus, which leads to problems healing a medial malleolar fracture.  With medial release, tension on the medial malleolus is essentially eliminated; however, as in this case, impingement may still lead to fracture.  While I am a proponent of the medial release, I try to avoid an overrelease so that some vascularity to the medial malleolus is preserved, if at all possible.

Case 5:  44-year-old male status post left lateral ankle ligament reconstruction and subsequent supramalleolar lateral closing wedge osteotomy, with persistent pain secondary to end stage ankle arthritis associated with varus malalignment.

Figure 36: (Case 5 Fig 1A,B)

Preoperative weightbearing radiographs. (A) AP view. (B)  Lateral view.

Figure 37: (Case 5 Fig 2A,B)

I performed hardware removal from the distal anterolateral tibia and performed a medial release through the anterior approach.  I used a distraction device medially to maintain initial correction. (A) AP view with external tibial alignment guide properly positioned. (B) Lateral view of the resection level determined based on the “angel wing” guide.

Figure 38: (Case 5 Fig 3A,B)

Talar resection. (A) Lateral intraoperative fluoroscopic view using the “angel wing” guide suggests an appropriate resection level and slope for the initial talar preparation. (B) Following the initial talar cut, the “black plastic” spacer suggested that the tibial cut was in varus. (C) I replaced the external tibial alignment guide in more valgus and recut the tibia, thereby establishing congruent tibial and talar preparations (suggested by the “black plastic” being reinserted to check congruency and the prepared ankle now aligned with the tibial shaft and properly aligned external tibial alignment guide).

Figure 39: (Case 5 Fig 4AC)

Components aligned well. (A) AP view of the final talar component and trial tibial and polyethylene components. (B) Lateral view with the final talar component and trial tibial and polyethylene components. (C) AP view of the final components.

Figure 40: (Case 5 Fig 5A,B)

Six-month followup.  Patient is fully weightbearing, has returned to full activities except recreational sports, and has minimal to no pain. (A) AP weightbearing X-ray. (There appears to be a slight residual varus tendency for the talar and polyethylene components.) (B) Lateral weightbearing X-ray.

Question:  Why is there a slight residual tendency toward varus of the talar and polyethylene components and should I be concerned?

Answer:  These corrections are challenging, particularly when a nonanatomic supramalleolar osteotomy has been performed previously.  I will continue to observe this patient, as this minimal amount of residual deformity may not have any clinical repercussions and may auto-correct as the components “settle” (not subside!) into their final positions.  Intraoperatively, I did not sense that a lateralizing calcaneal osteotomy was warranted. Based on the clinical examination of the patient at six months, the hindfoot alignment is appropriate.

This case did make me think about a medial malleolar osteotomy.  In my reassessment of the preoperative AP radiograph, the intraoperative AP fluoroscopy images, and the followup radiographs, perhaps a distal sliding medial malleolar osteotomy may have retentioned the medial soft tissues more appropriately than a medial release.  In my opinion, he certainly had abundant medial bone to promote healing of a medial malleolar osteotomy.  As I mentioned previously, I am giving stronger consideration to the distal sliding medial malleolar osteotomy, as many of my European colleagues prefer.

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