Kinematic Analysis of Sequential Partial-Midfoot Arthrodesis in Simulated Gait Cadaver Model.

BACKGROUND: Primary tarsometatarsal (TMT) arthrodesis is gaining popularity in the surgical treatment of Lisfranc injuries. However, few studies have evaluated biomechanical effects of TMT arthrodesis. The purpose of this study was to compare the kinematics of joints adjacent to the midfoot during simulations of stance before and after sequential arthrodesis of the first, second, and third TMT joints. METHODS: Ten midtibia cadaveric specimens were loaded on a 6-degree-of-freedom robotic gait simulator. Motion capture cameras were used to collect joint kinematics throughout simulations of the stance phase. Simulations were performed for the intact and sequential arthrodesis conditions of the first, second, and third TMT joints. The sagittal, coronal, and transverse plane rotational kinematics of the intact condition were compared to kinematics after each sequential arthrodesis condition. RESULTS: Sequential arthrodesis of the first and second TMT joints had no significant effect on ankle, subtalar, talonavicular, and first metatarsophalangeal joint motion during simulated stance when compared to the intact condition. In contrast, inclusion of the third TMT joint into the sequential arthrodesis significantly increased subtalar inversion (P = .032) in late stance and increased range of motion values in the ankle and subtalar joints by 2.1 degrees (P = .009) and 2.8 degrees (P = .014), respectively. CONCLUSION: Sequential primary arthrodesis induced changes to ankle and adjacent joint kinematics during stance phase simulations, although not until the third TMT joint was included into the primary arthrodesis. The significant changes to kinematics due to arthrodesis of the first, second, and third TMT joints were small. CLINICAL RELEVANCE: The minimal changes in sagittal, coronal, and transverse plane rotational kinematics support the positive clinical outcomes reported in the literature for primary partial arthrodesis of Lisfranc injuries. The inclusion of the third TMT joint should be done judiciously.

The use of polyvinyl alcohol hydrogel implants in the lesser metatarsal heads. Is it safely doable? A cadaveric study.

BACKGROUND: The use of synthetic polyvinyl alcohol hydrogel (PVAH) implants for treatment of lesser toe metatarsophalangeal joint (MTPJ) arthritis is promising and currently limited by the size of implants available. The primary objective of this cadaveric study was to investigate the maximum drilling size and largest PVAH implant dimension that could be safely introduced while still preserving an intact bone rim of the lesser metatarsal heads. METHODS: Height and width of all lesser metatarsals were measured on CT and during anatomic dissection. Sequential reaming of the second to fourth metatarsals was performed. Maximum reaming size, largest implant inserted, and failure of the metatarsal head were recorded. Metatarsal head sizes were compared and a multiple regression analysis evaluated measurements that influenced maximum drilling and implant size. RESULTS: CT and anatomical measurements demonstrated significant correlation (ICC range, 0.-0.85). Mean values for height and width of the metatarsal heads were respectively: second (14.9 mm and 9.9 mm), third (14.8 mm and 8.8 mm), fourth (14.0 mm and 8.7 mm) and fifth (12.3 mm and 9.3 mm). All the second, third and fourth metatarsal heads could be safely drilled up to 7.5 mm, preserving an intact bone rim. At 80% of the time, the heads could be safely drilled up to 8.0 mm. Height of the metatarsal heads was the only factor to significantly influence the size of maximum reaming and implant introduced. In respectively 20%, 40% and 50% of the second, third, and fourth metatarsal heads, neither 8 mm nor 10 mm PVAH implants could be used. CONCLUSIONS: Our cadaveric study found that the even though the majority of the lesser metatarsal heads could be safely drilled up to 8 mm, the smallest PVAH implant size currently available in most countries (8 mm) could be inserted in most of the second, but only in about half of the third and fourth metatarsal heads. The remaining bone rim around inserted implants was considerably thin, usually measuring less than 1 mm. In order to optimize the use PVAH in lesser metatarsal heads, smaller implant options are needed.

The success rate of first metatarsophalangeal joint lateral soft tissue release through a medial transarticular approach: A cadaveric study.

BACKGROUND: The objective of this study was to evaluate the success rate of first metatarsophalangeal joint (MTPJ) lateral soft tissue release through a medial transarticular approach. METHODS: Ten cadaveric specimens were used (6 females/4 males, mean age, 73.4years). Lateral release was performed through a 4cm medial approach using a number 15 blade. Surgical aim was to release four specific structures: lateral capsule, lateral collateral ligament (LCL), adductor hallucis tendon (AHT) and lateral metatarsosesamoid suspensory ligament (LMSL). Once completed, a dissection of the first intermetatarsal space was performed. Success rate was graded in accordance to the number of structures successfully released: 0% (no structures), 25% (1/4), 50% (2/4), 75% (3/4) and 100% (4/4). Inadvertent injuries to other soft tissue structures were recorded. RESULTS: The success rate for lateral soft tissue release was 100% in 7 cadaveric specimens, and respectively 75%, 50% and 25% in the other 3 specimens. The LCL was successfully released in all specimens. The lateral joint capsule, AHT and LMSL were released in 80% of the specimens. Chondral damage to the first metatarsal head, unintended release of the conjoined tendon and lateral head of the flexor hallucis brevis (FHB) occurred respectively in 40%, 50% and 20% of the specimens. CONCLUSIONS: Our cadaveric study demonstrated high success rate in the release of specific lateral soft tissue structures of the first MTPJ through a medial transarticular approach. Inadvertent release of the lateral head of the FHB, conjoined tendon and iatrogenic chondral damage of the first metatarsal head are complications to be considered. LEVEL OF EVIDENCE: Cadaveric study - Level V.

Soft Tissue Structures at Risk With Percutaneous Posterior to Anterior Screw Fixation of the Talar Neck.

BACKGROUND: Fractures of the talar neck and body can be fixed with percutaneously placed screws directed from anterior to posterior or posterior to anterior. The latter has been found to be biomechanically and anatomically superior. Percutaneous guidewire and screw placement poses anatomic risks for posterolateral and posteromedial neurovascular and tendinous structures. The objective of this study was to determine the injury rate to local neurovascular and tendinous structures using this technique in a cadaveric model. In addition, we aimed to determine the number of attempts at passing the guidewires required to achieve acceptable placement of 2 parallel screws. METHODS: Eleven fresh frozen cadaver limbs were used. Two 2.0-mm guidewires were placed under fluoroscopic guidance, posterior to anterior centered within the talus. The number of attempts required was recorded. A layered dissection was then performed to identify injury to any local anatomic structure. The shortest distance between the closest guidewire and the soft tissue structures was measured. RESULTS: The mean total number of guidewires passed to obtain optimal placement of 2 parallel screws was 2.9 ± 0.7. Direct contact between the guidewire and the sural nerve was seen in 100% of the specimens, with the nerve impaled by the guidewire in 3 of 11 (27.2%) cases. The peroneal tendons were impaled in 1 of 11 (9%) specimens and the Achilles tendon was in contact with the guidewire in 8 of the 11 (72.7%) specimens, and impaled at its most lateral border with the guidewire in 2 specimens (18.2%). CONCLUSION: The placement of posterior to anterior percutaneous screws for talar neck fixation is technically demanding, and multiple guidewires are needed. Our cadaveric study showed that important tendinous and neurovascular structures were in proximity with the guidewires and that the sural nerve was injured in 100% of the cases. CLINICAL RELEVANCE: Given the risk of injury to these structures, we recommend a formal posterolateral incision for proper visualization and retraction of the anatomic structures at risk.