Tohoku University · Materials Science
Professor Kei Hayashi's research lab specializes in experimental orthopedic biomechanics and regenerative tissue engineering, with a primary focus on the thermal modification of joint capsular tissues for treating joint instability. The lab investigates the effects of controlled thermal energy—using lasers or radiofrequency devices—on the structural, mechanical, and biological properties of collagen-rich connective tissues, particularly in the shoulder and stifle joints. Key research directions include understanding the histological and ultrastructural changes in capsular tissue following thermal treatment, evaluating the resulting tissue shrinkage and mechanical recovery, and exploring the potential of thermal capsulorrhaphy as a minimally invasive surgical intervention. The lab also examines the pathophysiology of cranial cruciate ligament disease in dogs, emphasizing the role of chronic inflammation and tissue remodeling in ligament failure.
Figures are computed from collected data and may differ slightly.
The purpose of this study was to evaluate the effect of temperature on shrinkage and the histologic properties of glenohumeral joint capsular tissue. Six fresh-frozen cadaveric shoulders were used for this study. Seven joint capsule specimens were taken from different regions from each glenohumeral joint and assigned to one of seven treatment groups (37 degrees, 55 degrees, 60 degrees, 65 degrees, 70 degrees, 75 degrees, 80 degrees C) using a randomized block design. Specimens were placed in a t
Cruciate disease is a common cause of chronic lameness in dogs. Midsubstance rupture of the cranial cruciate ligament (CCL) arises from progressive pathological failure, often under conditions of normal loading in adult dogs with CCL instability. A high risk of rupture is associated with inflammation of the synovium and adaptive or degenerative changes in the cells and matrix of the CCL. In contrast, CCL rupture in puppies is usually associated with traumatic injury and avulsion of the CCL from
This study was designed to evaluate the effect of laser energy at nonablative levels on the ultrastructure of joint capsular collagen. The femoropatellar joint capsules of six mature New Zealand white rabbits were harvested immediately after death. Specimens were divided into three treatment groups (5, 10, and 15 watts) and one control group. Laser energy was applied using a holmium: YAG laser. Transmission electron microscopy showed significant ultrastructural alterations in collagenous archite
To evaluate the effect of laser energy at nonablative levels on the mechanical properties of joint capsular tissues, we tested the femoropatellar joint capsules of 12 mature New Zealand White rabbits. Specimens were divided into three treatment groups (5, 10, and 15 watts) and one control group. All specimens were first nondestructively mechanically tested to determine stiffness and viscoelastic properties and then treated with laser energy or served as a control. Shrinkage was recorded and mech
The cellular and ECM changes in ruptured CCL that we have described appear to result from the cumulative effects of remodeling and adaptation to mechanical loading and microinjury. Treatment of early cruciate disease in dogs will need to inhibit or reverse these progressive changes to CCL tissue, which are directly associated with partial or complete structural failure of the CCL under conditions of normal activity.
Thermal capsulorrhaphy is a new treatment modality for shoulder instability, where the joint capsular tissue is heated and reduced in length by laser or radiofrequency energy to regain joint stability. Experimental studies have shown that (1) joint capsular tissue can be modified significantly (shortened) by thermal energy at the temperature range of 70 degrees to 80 degrees C; (2) thermal energy causes immediate deleterious effects such as loss of the mechanical properties, collagen denaturatio
The purpose of this study was to evaluate the effect of laser energy at nonablative levels on joint capsular histologic and biochemical properties in an in vitro rabbit model. The medial and lateral portions of the femoropatellar joint capsule from both stifles of 12 mature New Zealand White rabbits were used. Specimens were divided into three treatment groups (5 watts, 10 watts, and 15 watt) and one control group using a randomized block design. Specimens were placed in a 37 degrees bath of lac
Glenohumeral joint capsule obtained from 42 patients who had undergone an arthroscopic laser-assisted capsular shift procedure was evaluated histologically. A total of 53 samples from the anterior inferior glenohumeral ligament of the joint capsule were collected before and at various times after the procedure (range, 0 to 38 months). Despite glenohumeral instability, joint capsule of the patients before the procedure showed no significant histologic lesions. Laser treatment significantly altere
This study illustrates the short-term in vivo tissue response to nonablative laser treatment, where acellular hyalinized regions of collagen are infiltrated by fibroblasts that have used the treated collagen as the framework for migration and secretion of new collagen matrix in order for tissue repair to proceed.
We have studied the effects of doping on the high-temperature thermoelectric properties of the delafossite-type oxide CuCrO2. The single or double doping of divalent cations for Cr3+ ions was carried out to introduce hole carriers. For the first step, we measured the electrical conductivity σ and Seebeck coefficient S of single-doped samples, and calculated the power factor P=σS2. Mg-, Zn-, Ca-, Ni-, and Co-doped samples showed a higher power factor than CuCrO2, while the Fe-, V-, and Mn-doped s
The purpose of this study was to understand the mechanism responsible for joint capsule shrinkage after nonablative laser application in an in-vitro sheep model. Femoropatellar joint capsular tissue specimens harvested from 20 adult sheep were treated with one of three power settings of a holmium:yttrium-aluminum-garnet laser or served as a control. Laser treatment significantly shortened the tissue and decreased tissue stiffness in all three laser groups, whereas failure strength was not altere
CCA combined with TDL may improve the outcome of chylothorax in dogs.
The study compared the effects of laser and monopolar radiofrequency energy on thermal and architectural properties of joint capsular tissue in an in vitro ovine model. Sheep glenohumeral joint capsular specimens were treated with laser (5, 10, 15 W) or radiofrequency energy (55 degrees, 65 degrees, 75 degrees C) (n = six per group). Energy application caused significant tissue shrinkage and decreased surface area in all laser and radiofrequency treatment groups. Tissue thickness significantly i
The purpose of this study was to evaluate the effect of nonablative laser energy on mechanical, histologic, ultrastructural, and biochemical properties of joint capsular tissue in an in vivo sheep model. Femoropatellar joint capsule was treated with the holmium:yttrium-aluminum-garnet laser via an arthroscope, and tissues were harvested immediately after surgery, or at 3, 7, 14, 30, 60, 90, and 180 days after surgery (n = 8/group). Laser treatment caused significant decreases in tissue stiffness
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