Joint distraction force changes the three-dimensional articulation of the femur and tibia in total knee arthroplasty: a cadaveric study.

PURPOSE: The purpose of this study was to test the hypotheses that the joint distraction force changes the three-dimensional articulation between the femur and the tibia and that the presence of posterior cruciate ligament (PCL) affects the three-dimensional articulation during joint gap evaluation in total knee arthroplasty (TKA). METHODS: Cruciate-retaining TKA procedures were performed on 6 cadaveric knees using a navigation system. The joint center gap and varus ligament balance were measured using Offset Repo-Tensor® with the knee at 90° of flexion before and after PCL resection for joint distraction forces of 89, 178, and 266 N. The three-dimensional location of the tibia relative to the femur and the axial rotational angle of the tibia were also assessed. RESULTS: Regardless of PCL resection, the joint center gap became larger (p = 0.002, p = 0.020) and varus ligament balance became more varus (p = 0.002, p = 0.002) with increasing joint distraction force, whereas the tibia was more internally rotated (p = 0.015, p = 0.009) and more anteriorly located (p = 0.004, p = 0.009). The tibia was more internally rotated (p = 0.015) and more posteriorly located (p = 0.026) after PCL resection than before resection. CONCLUSIONS: Joint distraction force changed three-dimensional articulation regardless of PCL preservation. PCL function was revealed as a factor restraining both tibial posterior translation and internal rotation. Surgeons should recognize that joint gap evaluation using a tensor device is subject to three-dimensional changes depending on the magnitude of the joint distraction force.

The medial constrained insert restores native knee rotational kinematics after bicruciate-retaining total knee arthroplasty.

PURPOSE: The aim of this study was to test the hypothesis that the medial constrained insert would reproduce the native knee kinematics after bicruciate-retaining (BCR) total knee arthroplasty (TKA). METHODS: Using an image-free navigation system in six fresh-frozen whole-body cadavers, the rotation angle of the tibia at minimum flexion, at 10° intervals from 0° to 130° flexion, and at maximum flexion during manual passive knee flexion was assessed. The data was collected in native knees, in BCR TKA using a normal flat insert (BCR-XP), and in BCR TKA using a more constrained insert in the medial side (BCR-AS). The differences in the rotation angle of the tibia were statistically evaluated. RESULTS: The rotation angles of the tibia in BCR-XP were significantly different from those of the native knees both in the early flexion phase (p = 0.002 at minimum knee flexion, p = 0.002 at 0°, p = 0.041 at 10°, p = 0.009 at 20°, p = 0.026 at 30°) and in the late flexion phase (p = 0.015 at 130°, p = 0.015 at maximum knee flexion), whereas the rotational angles of the tibia in BCR-AS were similar to those of the native knee. CONCLUSION: This study shows that the rotational kinematics of the native knee is reproduced after BCR TKA with the medial constrained insert. Surgeons and implant designers should be aware that constraint of the medial side in BCR TKA is a crucial factor for restoration of native kinematics which may lead to better clinical outcome.

Direction and location of the nutrient artery to the fifth metatarsal at risk in osteotomy for bunionette.

BACKGROUND: The aims of this study were to identify the artery feeding the fifth metatarsal and determine how bunionette osteotomy could injure this vessel. METHODS: The nutrient artery entering the fifth metatarsal was investigated in 10 adult cadaveric lower limbs by barium injection and enhanced computed tomography. RESULTS: The nutrient artery entered the medial aspect of the fifth metatarsal around the junction of the middle and proximal thirds obliquely from a distal direction (mean angle 36°) in the coronal plane in all cases; in the axial plane, the point of entry and direction of the artery was medial-plantar (mean angle 49°). CONCLUSIONS: This report revealed direction and location of the nutrient artery entering the fifth metatarsal.

Incidence of reoperation and wound dehiscence in patients treated for peroneal tendon dislocations: comparison between osteotomy versus soft tissue procedures.

PURPOSES: There is a lack of substantial clinical evidence endorsing the clinical outcomes of osteotomy for peroneal tendon dislocations. The aim of this study was to compare the post-operative reoperation rates following osteotomy techniques and soft tissues procedures using large database in order to investigate the efficacy of bony techniques. METHODS: Patients who underwent osteotomy and soft tissue procedures for peroneal tendon dislocations were identified and subsequently analysed using the United Healthcare Orthopedic and the Medicare datasets (PearlDiver Patient Record Database, PearlDiver Technologies Inc., Fort Wayne, IN). The investigated period was from 2005 to 2012. The annual incidence, gender distribution, and incidences of reoperation and wound dehiscence following primary operative procedures were determined in these cohorts. RESULTS: Of 6122 patients who received operative treatment for peroneal tendon dislocations, 1416 patients (23.1%) received the osteotomy technique, while 4706 (76.9%) were treated with the soft tissue techniques. The incidence of these operative procedures did not change significantly over the time periods of each database. In both databases, reoperation rates were 2.8% (40/1416) for osteotomy patients and 3.4% (158/4706) for soft tissue repair patients, with no statistical difference (2.8 vs. 3.4%. odds ratio 0.8, 95% confidence interval [CI] 0.6-1.2, [n.s.]) between them. Based on both databases, wound dehiscence occurred in 2.6% (37/1416) of the osteotomy patients and 2.3% (110/4706) of soft tissue repair patients with no statistical difference (2.6 vs. 2.3%, odds ratio 1.1, 95% CI 0.8-1.6, [n.s.]) between the groups. CONCLUSION: The results of this study show that osteotomy techniques were frequently performed for patients with peroneal tendon dislocations. Nevertheless, osteotomy techniques for peroneal tendon dislocations are not associated with a lower risk of reoperation. In conclusion, soft tissue procedures offer a satisfactory method of treating peroneal tendon dislocations without any additional risk of reoperation when compared to osteotomy techniques that have potentially greater complication rates. LEVEL OF EVIDENCE: III.

Native rotational knee kinematics is restored after lateral UKA but not after medial UKA.

PURPOSE: The aim of this study was to compare the intraoperative kinematics of medial and lateral unicompartmental knee arthroplasty (UKA) with those of the native knee using a navigation system. METHODS: Six fresh-frozen cadaveric knees were included in the study. Medial UKA was performed in all right knees and lateral UKA was performed in all left knees. All UKA procedures were performed with a computerised navigation system. The tibial internal rotation angle and coronal alignment of the mechanical axis during passive knee flexion were assessed as rotational and varus/valgus kinematics before and after surgery using the navigation system. RESULTS: The rotation angles of the tibia in the early flexion phase of medial UKA were significantly larger than those of native knees (p = 0.008 at minimum knee flexion, p = 0.008 at 0° knee flexion). The rotational kinematics of lateral UKA was similar to those of the native knees throughout knee flexion. There were no significant differences in varus/valgus kinematics between native and UKA knees. CONCLUSION: The rotational kinematics of the native knee was not restored after medial UKA but was preserved after lateral UKA. There were no significant differences in the varus/valgus kinematics after either medial or lateral UKA when compared with those of the native knees. Thus, the geometry of the medial tibial articular surface is a determinant of the ability to restore the rotational kinematics of the native knee. Surgeons and implant designers should be aware that the anatomical medial articular geometry is an important factor in restoration of the native knee kinematics after knee arthroplasty.

Anatomic Study of Anterior and Posterior Ankle Portal Sites for Ankle Arthroscopy in Plantarflexion and Dorsiflexion: A Cadaveric Study in the Japanese Population.

Arthroscopy is an important and minimally invasive diagnostic and therapeutic tool. However, the risk of injury to the neurovascular structures around the portals exists during arthroscopy of the ankle. In the present study, we measured the distance between each portal and the adjacent neurovascular structures with the foot in plantarflexion and dorsiflexion in the Japanese population. Standard anterolateral (AL), anteromedial, posterolateral (PL), and posteromedial portal positions were identified in 6 fresh adult cadaveric feet. The skin was dissected from the underlying tissue to visualize the adjacent neurovascular structures as noninvasively as possible. The superficial peroneal nerve was the structure closest to an anterior (i.e., AL) portal (3.2 ± 4.2 and 8.3 ± 3.9 mm in plantarflexion and 5.2 ± 4.3 and 10.8 ± 4.1 mm in dorsiflexion), followed by the saphenous nerve and great saphenous vein (SpV). The distance from the superficial peroneal nerve to the AL portal and from the saphenous nerve and great SpV to the anteromedial portal increased significantly with dorsiflexion and decreased significantly with plantarflexion. The sural nerve was the structure closest to the posterior (i.e., PL) portal (10.4 ± 4.8 mm in plantarflexion and 8.5 ± 3.9 mm in dorsiflexion), followed by the lesser SpV. The distance from the sural nerve, saphenous nerve, and lesser SpV to the PL portal and from flexor hallucis longus, posterior tibial artery, and tibial nerve to the posteromedial portal increased significantly in plantarflexion and decreased significantly in dorsiflexion. These findings could help to prevent damage to the neurovascular structures during ankle arthroscopy.

Symptomatic Os Intercuneiform: A Case Report.

We encountered a case of an accessory bone in the foot in the distal portion of the tarsal navicular and the proximal portion of the intermediate cuneiform, namely an os intercuneiform. The patient presented with a history of pain on the dorsal aspect of the left foot, with tenderness and swelling. Perioperative findings revealed a synfibrotic connection between the accessory bone and the navicular and intermediate cuneiform. After unsuccessful conservative treatment, the accessory bone was excised, leading to postoperative symptomatic relief.

Location and direction of the nutrient artery to the first metatarsal at risk in osteotomy for hallux valgus.

BACKGROUND: Osteotomy for hallux valgus interrupts intraosseous blood supply to the first metatarsal, presumably causing non-union, delayed union, or osteonecrosis of the head of the first metatarsal. We investigated the first metatarsal nutrient artery, arising from the first dorsal metatarsal artery, and identified aspects of surgical technique contributing to nutrient artery injury. METHODS: Enhanced computed tomography scans of 8 feet of 8 fresh cadavers were assessed. Barium was injected through the external iliac artery; location and direction of the first metatarsal nutrient artery was recorded. RESULTS: Mostly, the nutrient artery entered the first metatarsal at the distal third or junction of the middle and distal thirds obliquely from a proximal direction coronally; entry point and direction varied axially. Saw blade overpenetration alone or with extensive capsular stripping might damage the artery. CONCLUSIONS: Location and direction of the first metatarsal nutrient artery was established.

Total calcanectomy for metastasis of renal cell carcinoma in the calcaneus: A case report.

We present a rare case of metastasis of renal cell carcinoma to the calcaneus in a 59-year-old man who presented with pain and inability to bear weight on the left foot 3 years after right nephrectomy for renal cell carcinoma. He successfully underwent en bloc resection of his right calcaneus with a limb salvage procedure, total calcanectomy without bony reconstruction. Histological findings identified the lesion as a metastasis originating from a renal cell carcinoma. Recent follow-up examination showed no recurrence. To the best of our knowledge, this is the first reported case to be treated with total calcanectomy for renal cell carcinoma metastasis.

Use of the arthroereisis screw with tendoscopic delivered platelet-rich plasma for early stage adult acquired flatfoot deformity.

PURPOSE: Early stage adult acquired flatfoot deformity (AAFD) is traditionally treated with osteotomy and tendon transfer. Despite a high success rate, the long recovery time and associated morbidity are not sufficient. This study aims to evaluate the functional and radiological outcomes following the use of the arthroereisis screw with tendoscopic delivered PRP for early stage AAFD. METHODS: Patients with stage IIa AAFD who underwent the use of the arthroereisis screw with tendoscopic delivered PRP with a minimum follow-up time of 24 months were retrospectively evaluated. Clinical outcomes for pain were evaluated with the Foot and Ankle Outcomes Score (FAOS) and Visual Analog Score (VAS). Radiographic deformity correction was assessed using weight-bearing imaging. RESULTS: Thirteen patients (13 feet) with mean follow-up of 29.5 months were included. The mean age was 37.3 years (range, 28-65 years). FAOS-reported symptoms, pain, daily activities, sports activities, and quality of life significantly improved from 52.1, 42.6, 57.6, 35.7, and 15.4 pre-operatively to 78.5, 68.2, 83.3, 65.0, and 49.6 post-operatively, respectively (p < 0.05). Statistically significant radiographic improvements (lateral talus first metatarsal angle, calcaneal pitch, and cuneiform to ground distance) were also observed between the pre- and post-operative images. CONCLUSIONS: This study elucidates the successful implementation of a less invasive approach to stage IIa AAFD. Through the use of a subtalar arthroereisis screw, PTT tendoscopy, and PRP injection, clinical and radiographic outcomes were improved.

Morphology of the Incisura Fibularis at the Distal Tibiofibular Syndesmosis in the Japanese Population.

The morphology of the distal tibiofibular syndesmosis can determine the pathology and mechanism of syndesmotic injury. The present study assessed measurements obtained from computed tomography (CT) images of the normal distal tibiofibular syndesmosis in Japanese subjects. CT scans of 120 right feet with a normal distal tibiofibular syndesmosis obtained from January 2009 to December 2016 were retrospectively assessed at the level 10 mm proximal to the tibial plafond. The incisura fibularis was considered concave when its depth was ≥4 mm and shallow when its depth was <4 mm. The depth of the incisura fibularis, anterior tibiofibular distance (TFD), posterior TFD, and longitudinal/transverse length of the distal fibula were measured. The incisura fibularis was concave in 64.2% of the feet and shallow in 35.8%. The mean anterior TFD was 2.2 ± 0.8 mm (2.4 ± 0.8 mm in males; 2.1 ± 0.8 mm in females; 2.1 ± 0.8 mm for concave; 2.2 ± 0.9 mm for shallow). The mean posterior TFD was 5.9 ± 1.6 mm (6.7 ± 2.1 in males; 5.7 ± 1.3 mm in females; 5.5 ± 1.3 mm for concave; 6.5 ± 1.9 mm for shallow). The mean longitudinal/transverse length of the distal fibula at the level of the syndesmosis was 1.2 mm (1.3 mm in males; 1.2 mm in females; 1.1 mm for concave; 1.3 mm for shallow). The mean posterior TFD was significantly greater than the mean anterior TFD and was also significantly greater in males than in females. Significant differences were found in the body mass index, posterior TFD, and longitudinal/transverse length of the distal fibula according to whether the incisura fibularis was concave or shallow. The present study has provided measurements of the normal tibiofibular syndesmosis in the Japanese population. These data suggest that the morphology of the syndesmosis varies, especially with respect to whether the incisura fibularis is concave or shallow.

Republication of "Mucous Cyst at the Interphalangeal Joint of the First Toe Caused by Contact Pressure With the Second Toe due to Hallux Valgus: A Case Report".

A 77-year-old woman presented with a mucous cyst on the lateral aspect of the interphalangeal joint of the first toe caused by contact pressure with the second toe from hallux valgus. She complained of discomfort and discharge from the left first toe for approximately 4 months. Physical examination showed the second toe pressing strongly against the first toe due to hallux valgus and discharge from the skin on the lateral aspect of the interphalangeal joint of the first toe. Magnetic resonance imaging showed a cystic lesion at the same level. The patient underwent a modified scarf osteotomy of the first metatarsal for hallux valgus to resolve the contact pressure between the toes-considered the cause of the mucous cyst-and resection of mucous cyst. Forefoot weight bearing was allowed 6 weeks after surgery. As of 1 year after surgery, she has had no recurrence of the cyst. The score on the Japanese Society for Surgery of the Foot hallux metatarsophalangeal-interphalangeal scale improved from 59/100 points to 92/100. This outcome suggests that hallux valgus correction should be considered when a mucous cyst is associated with contact pressure due to a hallux valgus deformity. To the best of our knowledge, there are no previous reports of a mucous cyst caused by contact pressure between the first toe and second toe due to hallux valgus.

Republication of "Gelatinous Transformation of Bone Marrow in the Calcaneus, Diagnosed by Open Bone Biopsy in a Patient With Anorexia Nervosa: A Case Report".

Gelatinous transformation of bone marrow (GTBM) is a complication of various diseases, one of which is anorexia nervosa (AN). We describe a rare case of a 20-year-old man who presented to our clinic with a 3-month history of heel pain without trauma. At presentation, he was noted to have a low body mass index (BMI) of 16.2 kg/m2 and pancytopenia. On magnetic resonance imaging, the left calcaneus showed low intensity on T1-weighted and high intensity on T2-weighted images. Open biopsy was done because we suspected that the lesion was either a lymphoproliferative tumor or a trabecular-type bone metastatic tumor. However, tissue histology of bone samples showed atrophy of fat cells with deposition of gelatinous material and a decreased hematopoietic cell population. Therefore, we made a diagnosis of GTBM, most likely caused by AN. We started treatment with nutritional support, and 6 months later, the hematological parameters returned to normal and BMI improved to 19.4 kg/m2. He was able to return to work and had no left heel pain. This case indicates that foot and ankle surgeons need to be aware of this rare pathology, although it might be difficult to diagnose without biopsy. To our knowledge, very few descriptions of GTBM in the calcaneus have been reported to date.

Staged external fixation for chronic fracture-dislocation of the proximal interphalangeal joint: outcomes of patients with a minimum 2-year follow-up.

PURPOSE: To introduce a new surgical strategy for chronic fracture-dislocations of the proximal interphalangeal (PIP) joint with 2-staged external fixation. We also assessed the results of this method in all of our patients with at least 2 years of follow-up. METHODS: We used the procedure in 6 cases. For the first step, we applied mini external fixators for 1 week before surgery to apply traction to the PIP joint with sufficient force to stretch the dislocated joint components. The second procedure was surgical release of the PIP joint and an attempt at percutaneous reduction and fixation. This was not possible in 4 cases, and we performed an open reduction and corrective osteotomy. Postoperative early rehabilitation was achieved under controlled movement using an external fixator that allowed PIP joint flexion and extension. RESULTS: At long-term follow-up (mean, 3.5 y), the range of movement of PIP joints had increased by 76°, and that of distal interphalangeal joints by 35°. Osteochondral remodeling likely occurred not only while the joint was protected with the dynamic external fixator during a 12-week period (range, 8-14 wk), but also after removal. CONCLUSIONS: Preoperative traction softens the PIP joint, facilitating both surgery and rehabilitation. Postoperative early exercise with controlled movement, while maintaining concentric reduction with the external fixator, may accelerate osteochondral repair of the injured PIP joint.

Flexor tenotomy for mallet toe with penetration of the middle phalanx head by dual-component intramedullary implant following proximal interphalangeal arthrodesis.

INTRODUCTION: There is a risk of mallet toe following proximal interphalangeal (PIP) joint fusion for hammertoe. Here we describe a rare case of penetration of the dorsal aspect of the middle phalanx head by the distal portion of a dual-component intramedullary implant during progression of mallet toe that was treated with flexor tenotomy. PRESENTATION OF CASE: A 59-year-old man underwent uneventful arthrodesis of the third PIP using a dual-component intramedullary implant and presented 6 months later with progressive mallet toe and swelling, pain, and ulceration over the distal interphalangeal joint of the third toe. Imaging showed that the distal portion of the implant had penetrated the dorsal aspect of the middle phalanx head. A longitudinal incision was made over the dorsum of the middle and proximal phalanges of the third toe and the implant was removed. A plantar incision was made at the metatarsophalangeal joint and the flexor tendon was cut to correct the mallet toe deformity. One year later, correction was satisfactory with an acceptable functional outcome and good pain relief. DISCUSSION: We successfully treated a man with penetration of the dorsal border of the middle phalanx head in the third toe by the distal portion of a dual-component intramedullary implant as a result of mallet toe that developed following PIP arthrodesis, by removing the implant and performing flexor tenotomy. CONCLUSION: Addition of flexor tenotomy should be considered when performing PIP arthrodesis in a patient with risk factors for severe mallet toe.

Relationship Between the Lateral Plantar Artery and the Retrograde Intramedullary Nail During Tibiotalar and Subtalar Arthrodesis: A Fresh Cadaveric Study.

BACKGROUND: Tibiotalocalcaneal (TTC) arthrodesis with retrograde intramedullary nailing has become established. Iatrogenic injury to the vasculature (eg, lateral plantar artery [LPA] pseudoaneurysm) during insertion of the nail has been reported. The aim of this study was to identify the safe zone that avoids injury to the LPA during TTC arthrodesis. METHODS: The retrograde lateral curved nail entry point should be in line with the midpoint of the tibial medullary canal and the lateral column of the calcaneus. Enhanced 3-dimensional computed tomography scans of 26 fresh cadaveric feet were assessed. The closest distance between the LPA and the edge of the nail entry point was measured in the plantar view. RESULTS: The closest mean distance between the LPA and the edge of the nail entry point was 6.7 mm for all 26 feet, 12.8 mm for 3 feet (11.5%) in which the LPA did not cross the medial wall of the calcaneus, 8.1 mm for 9 (34.1%) in which the point where the LPA crossed the medial wall of the calcaneus was anterior to the center of the nail entry point, and 4.2 mm for 14 (53.8%) feet in which this point was posterior to the center of the nail entry point. CONCLUSIONS: Care should be taken to avoid the LPA during reaming at the nail entry point, especially when the point where the LPA crosses the medial wall of the calcaneus is posterior to the center of the nail entry point. LEVELS OF EVIDENCE: IV, cadaveric study.

Examination of Safe Zone to Avoid Injury of the Lateral Plantar Artery During Calcaneal Osteotomy: A Fresh Cadaveric Study.

BACKGROUND: Calcaneal osteotomy are used to treat various pathologies in the correction of hindfoot deformities. But lateral plantar artery (LPA) pseudoaneurysms have been reported following calcaneal osteotomy, and LPA pseudoaneurysms may be at risk for rupture. Although the vascular structures in close proximity to calcaneal osteotomies have variable courses and branching patterns, there is little information on safe zone for LPA during calcaneal osteotomy. The aims of this study were to identify the safety zone to avoid the LPA injury during calcaneal osteotomy. METHODS: Enhanced computed tomography scans of 25 fresh cadaveric feet (male, n = 13; female, n = 12; mean age 79.0 years at the time of death) were assessed. The specimens were injected with barium via the external iliac artery. Line A is the landmark line and extends from the posterosuperior aspect of the calcaneal tuberosity to the plantar fascia origin, and the perpendicular distance between the LPA and line A at its closest point was measured on sagittal images. RESULTS: The average perpendicular distance between the LPA and line A at its closest point was 15.2 ± 2.9 mm. In 2 cases (8.0 %), the perpendicular distance between the LPA and line A at its closest point was very close, approximately 9 mm. In 18 of 25 feet (72.0%), the point where perpendicular distance from the line A to LPA is the closest was the bifurcation of one of the medial calcaneal branches from LPA, and in 7 feet in 25 feet (28.0%) feet the point where perpendicular distance from the line A to LPA is the closest was the trifurcation of LPA, medial plantar artery, and one of the medial calcaneal branches. CONCLUSIONS: Calcaneal osteotomy approximately more than 9 mm from the line A could injure the LPA in overpenetration into the medial aspect of tcalcaneal osteotomy. Completion of the osteotomy on the medial side should be performed with caution to avoid iatrogenic injury of the LPA. LEVELS OF EVIDENCE:: Level IV, Cadaveric study.

Implications of Dorsalis Pedis Artery Anatomical Variants for Dorsal Midfoot Surgery.

BACKGROUND: The dorsalis pedis artery (DPA) usually branches into the arcuate artery (AA) from its lateral side which in turn crosses the bases of the lateral four metatarsals. The DPA then passes into the first interosseous space, where it divides into the first metatarsal artery and the deep plantar artery. In this study, we aimed to determine the extent of variation in the DPA and the distance between the AA and the tarsometatarsal (TMT) joint with the aim of reducing the risk of vascular complications arising from dorsal midfoot surgery. METHODS: In 29 fresh cadaveric feet, we examined the course of the DPA and the distance between the AA and the TMT joint on computed tomography images with barium sulfate contrast. RESULTS: The DPA was observed to have a standard course in 11 of the 29 cases (37.9%) but did not give rise to the AA and lateral tarsal artery or branches of the plantar arterial arch supplying to the second to fourth metatarsal spaces in 10 of 29 cases (34.5%). The mean closest distance from the TMT joint to the AA at the second, third, and fourth metatarsal level in the sagittal plane was 11.4, 14.6, and 17.1 mm, respectively. CONCLUSION: We found substantial variation in the arterial anatomy of the DPA system across the dorsal midfoot. CLINICAL RELEVANCE: The risk of pseudoaneurysm and frank arterial disruption may be mitigated if the surgeon is aware of the variations of the course of the DPA when performing dorsal midfoot surgery.

Influence of the glenoid baseplate position on the direction and length of the superior and inferior locking screws.

Introduction : Superior screw insertion in reverse shoulder arthroplasty (RSA) carries the potential risk of suprascapular injury. The purpose of this study was to evaluate how the baseplate position affects the superior screw position and length in RSA. Methods : Three-dimensional (3D) computer simulation models of RSA were established using computed tomography data of baseplates with superior and inferior screws and 3D scapular models from 10 fresh cadavers. Superior screw position, the distance from the superior screw hole to the suprascapular notch, and the screw lengths were measured and compared among various baseplate positions with two inferior tilts (0 and 10 degrees) and three rotational patterns (11-5, 12-6, and 1-7 o'clock in the right shoulder). Results : For the 1-7 o'clock / inferior tilt 0 degrees baseplate, the superior screw located anterior to the SS notch in all shoulders, the distance to the SS notch was the longest (12.8 mm), and the inferior screw length was the shortest (23.1 mm). Conclusion : Although there is a concern of a short inferior screw length, initial fixation using a baseplate with 1-7 o'clock rotation and an inferior tilt of 0 degrees appears preferable for SS nerve injury prevention during superior screw insertion. J. Med. Invest. 69 : 185-190, August, 2022.

Temporary Kirschner wire fixation of the first metatarsophalangeal joint before osteotomy for hallux valgus.

INTRODUCTION: Numerous operative procedures have been described for correction of hallux valgus, including distal step-cut osteotomy such as the Mitchell osteotomy. However, overcorrection can occur due to technical problems with the initial metatarsal osteotomy. Here, we describe a modified Mitchell osteotomy with a novel method, the temporary Kirschner wire fixation of the first metatarsophalangeal joint (TeKFiM) method (Tonogai method), that can be used before osteotomy for hallux valgus to avoid incongruency and overcorrection. OPERATIVE TECHNIQUE: A skin incision and Y-shaped capsulotomy are performed and the medial exostosis is excised. Lateral capsule release is done if the first metatarsophalangeal (MTP) joint cannot be reduced manually. Next, a Kirschner wire (K-wire) is inserted subcutaneously through the medial side of the first proximal phalanx to the lateral side of the first metatarsal to preserve the correct congruency of the first MTP joint during surgery. To correct pronation of the distal fragment, step-off transverse cuts are made in the distal fragment, as described by Mitchell, reaching one-second to two-thirds of the transverse diameter of the neck from the plantar medial side. After the osteotomies are completed, the lateral spike of the proximal fragment is flattened. The distal fragment is displaced laterally and slightly plantarward, and the pronation deformity of the distal fragment is corrected by inserting a K-wire to act as a joystick. The osteotomy site is stabilized using two Herbert-type screws. After removal of the K-wire, the operation is completed by closing the medial capsule of the first MTP joint and the skin. A plantar cast is applied for 2 weeks, followed by a special heel brace for 4-6 weeks. Sutures are removed 2 weeks after surgery. Patients are allowed to start weightbearing gradually as tolerated from 2 weeks after surgery. DISCUSSION: After osteotomy, it is difficult to maintain the correct congruency of the first MTP joint due to instability of the distal fragment. The TeKFiM method (Tonogai method) reliably maintains this congruency during surgery. Also, by using a K-wire as a joystick to fix the joint in correct congruency, the first toe is rotated and pronation is corrected by supinating the distal fragment. The K-wire also serves as a landmark for determining how far the distal fragment is shifted plantarward. CONCLUSIONS: We have developed a modified Mitchell osteotomy with the novel TeKFiM method (Tonogai method) before osteotomy for hallux valgus to avoid incongruency and overcorrection. This method also provides a landmark to correct pronation and plantarward shifting.