Faculty Bibliography

BACKGROUND:Obtaining adequate fixation during tibiotalocalcaneal (TTC) arthrodesis may be challenging. Various fixation constructs have been tested biomechanically, but the use of a locking plate has not been reported. We hypothesized that the locking plate with a TTC augmentation screw would provide structural rigidity comparable to that of the intramedullary (IM) nail with a TTC augmentation screw during dorsiflexion testing. MATERIALS AND METHODS/METHODS:Six matched pairs of fresh frozen cadavers underwent TTC arthrodesis. Specimens in each pair were randomized to receive a locking plate or an intramedullary nail. Each specimen had an additional TTC augmentation screw through the calcaneus, talus, and medial tibia. All samples underwent dorsiflexion testing with determination of structural rigidity at the first cycle (initial rigidity) and last cycle (final rigidity) and the torque required to achieve a failure of 10 degrees of dorsiflexion. Statistical analysis was performed using a paired t-test to determine whether any differences were significant (p < 0.05). RESULTS:The locking plate construct showed higher final rigidity (mean +/- standard error of the mean) (27.7 +/- 2.6 N-m/degree versus 17.6 +/- 2.1 N-m/degree, p = 0.01) than the IM nail construct. There were no other differences measured. CONCLUSION/CONCLUSIONS:Rigidity with the the IM nail was inferior to that with locking plate fixation for TTC arthrodesis in one of the four parameters tested. CLINICAL RELEVANCE/CONCLUSIONS:Screw augmented IM nail fixation and augmented locking plate fixation may offer similar rigidity clinically for TTC arthrodesis.

BACKGROUND:We hypothesized that a locking plate would be stronger than a blade plate for tibiotalocalcaneal arthrodesis under dorsiflexion and torsional loading. MATERIALS AND METHODS/METHODS:Nine pairs of matched cadaveric lower extremities were used. BMD was obtained for each specimen. Each received a retrograde augmentation screw and a stainless steel LC-angled blade plate (Synthes, Paoli, PA) or a stainless steel LCP proximal humerus locking plate (Synthes, Paoli, PA). Specimens were cyclically loaded in dorsiflexion to simulate 6 weeks of partial weightbearing and then monotonically loaded to failure. Specimens were removed from the load frame and remounted to simulate fusion. The specimen received an axial load of 720 N and was externally rotated proximal to the construct at 5 degrees/sec to fracture. Data were compared with a Student's t-test. Pearson correlation analysis was used to determine whether bone mineral density was significantly related to measured parameters. Significance was set at p < or = 0.05. RESULTS:The locking plate group had higher initial stiffness, higher dorsiflexion and torsional load to failure, and lower construct deformation than the blade plate group. Bone mineral density was positively correlated with dorsiflexion failure load and torsional failure load in the locking plate construct. CONCLUSION/CONCLUSIONS:Fixation with the locking plate was superior to that with the blade plate. CLINICAL RELEVANCE/CONCLUSIONS:Use of a locking plate may be an effective fixation technique in tibiotalocalcaneal arthrodesis, especially in complex hindfoot reconstructions with bone loss or deformity.

BACKGROUND:Transarticular pin fixation for ankle stabilization has drawbacks, including ankle joint arthrosis. An extraarticular technique could help avoid these problems. We compared stiffness under minimal dorsiflexion loading with transarticular versus extraarticular fixation. METHODS:Cadaveric specimens from ten lower extremity matched pairs were randomized to receive transarticular or extraarticular fixation. For transarticular fixation, axial pins were passed retrograde through the plantar heel, calcaneus, subtalar joint, talar body, and ankle joint. For extraarticular fixation, the first pin was inserted antegrade from the anterior distal tibia to the posterolateral aspect of the calcaneus tuberosity. The second pin was inserted percutaneously antegrade from the distal medial tibial metaphysis to the dorsal navicular, passing anterior to the ankle and dorsal to the talonavicular joint. Each specimen was subjected to 1000 cycles at 5 mm/s to 100 N. After testing, the extraarticular specimens were dissected to establish the distance of the pin from the flexor hallucis longus (FHL) tendon. RESULTS:There was no significant difference in stiffness between the transarticular and the extraarticular group (mean+/-standard error of the mean) (17.93 N/mm+/-1.0 N/mm and 18.61 N/mm+/-1.07 N/mm, respectively). The lateral pin was 4.2+/-1.4 mm (range, 2.5 to 6.0 mm) from the FHL. CONCLUSIONS:Fixation stiffness with extraarticular crossed antegrade pins was not different from that of transarticular fixation and did not disrupt the ankle or the plantar skin. CLINICAL RELEVANCE/CONCLUSIONS:Extraarticular ankle fixation may help avoid the complications found with the joint, cartilage, and plantar skin disruption associated with transarticular fixation.

BACKGROUND:Lag screw fixation commonly is used to treat avulsion fractures of the posterior calcaneal tuberosity, but this method may not offer reliable fixation. This study compared the strength to failure of lag screws compared to lag screw fixation augmented with suture anchors in these fractures. METHODS:The calcanei and Achilles tendons of 12 fresh lower extremity cadaver matched pairs were dissected and removed. An oblique osteotomy was created in the calcaneus, and two 4.0-mm lag screws were placed nearly perpendicular to the plane of the fracture in the dorsal aspect of the calcaneus with 30 degrees of divergence between them. In the contralateral specimen, the same procedure was done, but with two suture anchors placed 1.5 to 2 mm distal to the osteotomy. A zigzag suture technique through the Achilles tendon was used. The specimens were mounted and placed in a load frame for monotonic loading to failure. A paired Student t-test and a Pearson correlation were used to analyze the data (p <or= 0.05). RESULTS:The specimens treated with lag screws alone failed at 251.3 (range 66 to 459) N whereas specimens repaired with lag screws and suture anchors failed at 441.6 (range 274 to 661; p = 0.01 N). CONCLUSIONS:Suture anchor augmentation significantly improved the strength of screw fixation of the calcaneal posterior tuberosity avulsion fractures. CLINICAL RELEVANCE/CONCLUSIONS:The use of suture anchor augmentation as described may improve the reliability of fixation in avulsion fractures of the posterior calcaneal tuberosity.

Efficacy and morbidity of a surgically implanted direct-current bone stimulator were evaluated in 38 patients (40 feet) with fracture nonunion or at high risk for nonunion; 14 of these patients had Charcot (diabetic) neuroarthropathy. Union occurred in 26 (65%) of the 40 feet; complications other than nonunion occurred in 16 feet (40%). Two amputations (5%) were performed in cases of intractable neuritis and deep infection. Of the 6 cases of deep infection (15%), 5 resolved with device removal, and the sixth case required below-knee amputation. Use of a bone stimulator in patients with diabetes may be problematic, but the device did not have any adverse effects in other high-risk patients.

BACKGROUND:This study compared intramedullary (IM) fixation for tibiotalocalcaneal arthrodesis with and without a tibiotalocalcaneal augmentation screw. METHODS:Each specimen in six matched pairs of fresh frozen cadavers underwent tibiotalocalcaneal arthrodesis with an IM nail. One specimen from each pair also received a tibiotalocalcaneal augmentation screw. Initial and final stiffness, load to failure, and construct deformation at failure were calculated with dorsiflexion loading. Bone mineral density of each pair was determined. Statistical analysis was done using a paired Student t-test and a Pearson correlation. RESULTS:Initial and final stiffness and load to failure were significantly higher for the tibiotalocalcaneal screw augmented fixation group as compared with the specimens with no additional screw (initial stiffness, 128.0 versus 78.4 N/mm, p = 0.04; final stiffness, 230.9 versus 164.7 N/mm, p = 0.04; load to failure, 875.5 versus 660.2 N, p = 0.03). There was a significant negative correlation between bone mineral density and average construct deformation in the samples without the added tibiotalocalcaneal screw (r = -0.90, p = 0.02). CONCLUSIONS:In tibiotalocalcaneal arthrodesis with intramedullary nail fixation, a tibiotalocalcaneal augmentation screw provides more stable fixation. CLINICAL RELEVANCE/CONCLUSIONS:Use of an augmentation screw as described in this study may lead to lower complication rates, particularly in patients with osteopenic bone.

The adult acquired flatfoot deformity is characterized by flattening of the medial longitudinal arch with insufficiency of the supporting posteromedial soft tissue structures of the ankle and hindfoot. While the etiology of this deformity can be arthritic or traumatic in nature, it is most commonly associated with posterior tibial tendon dysfunction (PTTD). By one estimate, PTTD affects approximately five million people in the United States. The clinical presentation of adult flatfoot can range from a flexible deformity with normal joint integrity to a rigid, arthritic foot.

Subtalar arthroereisis as an adjunct procedure may hold promise for patients who have mild and more severe variants of posterior tibial tendon dysfunction (PTTD). The biomechanics of the implant function have not been fully elucidated, and questions remain about the best clinical indications for the device. This article reviews the limited existing literature and describes the author's personal experience testing subtalar arthroereisis in the laboratory and using the implant clinically for correction of adult flexible flatfoot.

BACKGROUND:Over the past 20 years, ankle arthrodesis with use of screw augmentation has become a popular technique to gain fusion of the arthritic ankle. The objective of this cadaver study was to identify the risks to local neurovascular structures using standard operative practices for percutaneous guide pin placement. METHODS:Nine fresh frozen cadaver limbs were used. A guide pin from the Synthes (Paoli, PA) 7.3-mm cannulated set was placed percutaneously into the distal posterolateral leg with the ankle held in neutral position. A layered dissection was then performed from the skin to tibia. Neurovascular injury and distance of the guide pin from the sural and tibial nerves were noted. RESULTS:The guide pin did not touch the sural or tibial nerves in any specimens. With this technique, the mean distance of the pin from the sural nerve and tibial nerve at the closest point was 0.9 mm and 6.5 mm, respectively. CONCLUSIONS:In placement of a percutaneous screw, care should be taken to start the posterolateral guide pin placement more lateral or closer to the fibula at this level in the leg to avoid injury to the sural nerve. Additionally, the tibial nerve is potentially an at risk structure if percutaneous pin insertion crosses medial to the coronal plane midline. CLINICAL RELEVANCE/CONCLUSIONS:The use of percutaneous screw placement is safe and effective with minimal risk to local neurovascular structures if standard operative technique is followed.