Is the lateral jack-knife position responsible for cases of transient neurapraxia?

OBJECTIVE: The lateral jack-knife position is often used during transpsoas surgery to improve access to the spine. Postoperative neurological signs and symptoms are very common after such procedures, and the mechanism is not adequately understood. The objective of this study is to assess if the lateral jack-knife position alone can cause neurapraxia. This study compares neurological status at baseline and after positioning in the 25° right lateral jack-knife (RLJK) and the right lateral decubitus (RLD) position. METHODS: Fifty healthy volunteers, ages 21 to 35, were randomly assigned to one of 2 groups: Group A (RLD) and Group B (RLJK). Motor and sensory testing was performed prior to positioning. Subjects were placed in the RLD or RLJK position, according to group assignment, for 60 minutes. Motor testing was performed immediately after this 60-minute period and again 60 minutes thereafter. Sensory testing was performed immediately after the 60-minute period and every 15 minutes thereafter, for a total of 5 times. Motor testing was performed by a physical therapist who was blinded to group assignment. A follow-up call was made 7 days after the positioning sessions. RESULTS: Motor deficits were observed in the nondependent lower limb in 100% of the subjects in Group B, and no motor deficits were seen in Group A. Statistically significant differences (p < 0.05) were found between the 2 groups with respect to the performance on the 10-repetition maximum test immediately immediately and 60 minutes after positioning. Subjects in Group B had a 10%-70% (average 34.8%) decrease in knee extension strength and 20%-80% (average 43%) decrease in hip flexion strength in the nondependent limb. Sensory abnormalities were observed in the nondependent lower limb in 98% of the subjects in Group B. Thirty-six percent of the Group B subjects still exhibited sensory deficits after the 60-minute recovery period. No symptoms were reported by any subject during the follow-up calls 7 days after positioning. CONCLUSIONS: Twenty-five degrees of right lateral jack-knife positioning for 60 minutes results in neurapraxia of the nondependent lower extremity. Our results support the hypothesis that jack-knife positioning alone can cause postoperative neurological symptoms.

Retroperitoneal oblique corridor to the L2-S1 intervertebral discs: an MRI study.

OBJECT The purpose of this study was to analyze MR images of the lumbar spine and document: 1) the oblique corridor at each lumbar disc level between the psoas muscle and the great vessels, and 2) oblique access to the L5-S1 disc space. Access to the lumbar spine without disruption of the psoas muscle could translate into decreased frequency of postoperative neurological complications observed after a transpsoas approach. The authors investigated the retroperitoneal oblique corridor of L2-S1 as a means of surgical access to the intervertebral discs. This oblique approach avoids the psoas muscle and is a safe and potentially superior alternative to the lateral transpsoas approach used by many surgeons. METHODS One hundred thirty-three MRI studies performed between May 4, 2012, and February 27, 2013, were randomly selected from the authors' database. Thirty-three MR images were excluded due to technical issues or altered lumbar anatomy due to previous spine surgery. The oblique corridor was defined as the distance between the left lateral border of the aorta (or iliac artery) and the anterior medial border of the psoas. The L5-S1 oblique corridor was defined transversely from the midsagittal line of the inferior endplate of L-5 to the medial border of the left common iliac vessel (axial view) and vertically to the first vascular structure that crossed midline (sagittal view). RESULTS The oblique corridor measurements to the L2-5 discs have the following mean distances: L2-3 = 16.04 mm, L3-4 = 14.21 mm, and L4-5 = 10.28 mm. The L5-S1 corridor mean distance was 10 mm between midline and left common iliac vessel, and 10.13 mm from the first midline vessel to the inferior endplate of L-5. The bifurcation of the aorta and confluence of the vena cava were also analyzed in this study. The aortic bifurcation was found at the L-3 vertebral body in 2% of the MR images, at the L3-4 disc in 5%, at the L-4 vertebral body in 43%, at the L4-5 disc in 11%, and at the L-5 vertebral body in 9%. The confluence of the iliac veins was found at lower levels: 45% at the L-4 level, 19.39% at the L4-5 intervertebral disc, and 34% at the L-5 vertebral body. CONCLUSIONS An oblique corridor of access to the L2-5 discs was found in 90% of the MR images (99% access to L2-3, 100% access to L3-4, and 91% access to L4-5). Access to the L5-S1 disc was also established in 69% of the MR images analyzed. The lower the confluence of iliac veins, the less probable it was that access to the L5-S1 intervertebral disc space was observed. These findings support the use of lumbar MRI as a tool to predetermine the presence of an oblique corridor for access to the L2-S1 intervertebral disc spaces prior to lumbar spine surgery.

Retroperitoneal oblique corridor to the L2-S1 intervertebral discs in the lateral position: an anatomic study.

OBJECT: Access to the intervertebral discs from L2-S1 in one surgical position can be challenging. The transpsoas minimally invasive surgical (MIS) approach is preferred by many surgeons, but this approach poses potential risk to neural structures of the lumbar plexus as they course through the psoas. The lumbar plexus and iliac crest often restrict the L4-5 disc access, and the L5-S1 level has not been a viable option from a direct lateral approach. The purpose of the present study was to investigate an MIS oblique corridor to the L2-S1 intervertebral disc space in cadaveric specimens while keeping the specimens in a lateral decubitus position with minimal disruption of the psoas and lumbar plexus. METHODS: Twenty fresh-frozen full-torso cadaveric specimens were dissected, and an oblique anatomical corridor to access the L2-S1 discs was examined. Measurements were taken in a static state and with mild retraction of the psoas. The access corridor was defined at L2-5 as the left lateral border of the aorta (or iliac artery) and the anterior medial border of the psoas. The L5-S1 corridor of access was defined transversely from the midsagittal line of the inferior endplate of L-5 to the medial border of the left common iliac vessel and vertically to the first vascular structure that crosses midline. RESULTS: The mean access corridor diameters in the static state and with mild psoas retraction, respectively, were as follows: at L2-3, 18.60 mm and 25.50 mm; at L3-4, 19.25 mm and 27.05 mm; and at L4-5, 15.00 mm and 24.45 mm. The L5-S1 corridor mean values were 14.75 mm transversely, from midline to the left common iliac vessel and 23.85 mm from the inferior endplate of L-5 cephalad to the first midline vessel. CONCLUSIONS: The oblique corridor allows access to the L2-S1 discs while keeping the patient in a lateral decubitus position without a break in the table. Minimal psoas retraction without significant tendon disruption allowed for a generous corridor to the disc space. The L5-S1 disc space can be accessed from an oblique angle consistently with gentle retraction of the iliac vessels. This study supports the potential of an MIS oblique retroperitoneal approach to the L2-S1 discs.

Can triggered electromyography be used to evaluate pedicle screw placement in hydroxyapatite-coated screws: an electrical examination.

OBJECTIVES: To assess if hydroxyapatite (HA)-coated titanium pedicle screws exhibit the same electroconductive characteristics as non-HA-coated screws. METHODS: Resistance measurements were obtained from a random sampling of 10 HA-coated pedicle screws and 10 non-HA-coated screws, and surgical conditions simulated. Surface resistivity measurements were taken for each screw to determine voltage drop over its entire length. RESULTS: The non-HA-coated screws tested showed low resistive properties and proved to be an ideal conductor of electrical current. The resistive properties associated with the HA-coated pedicle screws were found to be similar to those of commonly used insulators removing the effectiveness of triggered electromyographic responses. CONCLUSIONS: Based on test results, these data suggest that the resistance value of the HA-coated screw is large enough to prevent modern Intra-Operative Monitoring (IOM) equipment from delivering the necessary current through the shank of the screw to create a diagnostic electromyographic response. Any response that would be produced would be because of shunting of electric current from the non-coated head of the screw into adjacent tissue and not through the shank of the screw. These study results suggest that HA-coated screws cannot be stimulated to assist in determining the accuracy of pedicle screw placement.

Revision total hip arthroplasty without bone graft of high-grade acetabular defects.

Mixed results have been reported with bulk and cancellous bone graft to fill defects during acetabular revision arthroplasty. Jumbo cups have been used to maximize host bone contact, and if adequate initial stability can be achieved, this approach may provide a superior long-term outcome. We retrospectively reviewed a consecutive series of 107 acetabular revisions performed using jumbo cups without bone graft. Bone defects were assessed using a validated radiographic classification system that yielded 64 hips with significant bone defects for inclusion. Mean change in American Academy of Orthopaedic Surgeons lower extremity core and pain scores and in Short Form-12 scores showed increases of 22.01, 37.52, and 17.08 points, respectively. Postoperative radiographs consistently demonstrated host bone ingrowth into the jumbo acetabular shells, except for 3 failures. Careful incremental reaming up to a size that optimizes host bone support and contact may eliminate the need for bone graft in most acetabular revision arthroplasties.

Bilateral symptomatic snapping biceps femoris tendon due to fibular exostosis.

We present an unusual case of an athletic 17-year-old male cyclist with bilateral chronic dislocating biceps femoris tendons. On flexion of the knee, the biceps tendon subluxed over a large exostosis, creating a snapping sound. Snapping of tendons is common around the hip, ankles, shoulder, and elbow, but rare at the knee. When it does occur, snapping about the knee can be due to discoid meniscus, rheumatoid nodules, synovial plicae, iliotibial band syndrome, congenital snapping knee, and snapping tendons. Research revealed only 5 previous cases due to subluxation of the biceps femoris tendon. The case we present is the only one due to an exostosis, as well as the only one that required bilateral surgical repair. The patient presented when his pain became significant enough to interfere with his ability to continue competitive cycling.

Rare case of upper arm compartment syndrome following biceps tendon rupture.

We present a case of upper arm compartment syndrome following a biceps tendon rupture in a 77-year old man on warfarin sodium. Compartment syndrome is common in the forearm and leg, but rare in the upper arm with only a handful of cases reported in the literature. Our patient's anticoagulated state predisposed him to the development of compartment syndrome. To the best of our knowledge there has been only one other case reported in the literature of upper arm compartment syndrome following biceps tendon rupture in a patient on warfarin sodium. Compartment syndrome of the upper arm is a rare occurrence. Previous cases have occurred due to malposition of blood pressure cuffs, injections, venepuncture, trauma, tourniquets, shoulder dislocation, surgical complication, subatmospheric pressure induced, biceps rupture, and triceps rupture. The fascia of the upper arm is relatively thinner and more distensible than the fascia of the leg or forearm. This creates more room for the compartment to swell before pressures builds up to a significant level. Thus, a significantly increased amount of pressure needs to build up before compartment syndrome will occur in the upper arm. Once the diagnosis was formed, the patient was treated with emergent fasciotomy and evacuation of hematoma. After a prolonged hospital stay, the patient was released with minor neurological deficits. At final follow-up, the patient was neurovascularly intact with no complaints of numbness or tingling, and he had regained full motor function throughout.

Subtrochanteric fracture in a patient with trabecular metal osteonecrosis intervention implant.

We present an unreported case of a sixty-four year old woman who suffered a subtrochanteric fracture of the femur four weeks after implantation of a trabecular metal osteonecrosis intervention implant for osteonecrosis of the femoral head. Traditional treatments for femoral head avascular necrosis include observation, core decompression, bone grafting, vascularized fibular grafting, osteotomy, hemiarthroplasty and total hip arthroplasty. With the recent development of trabecular metal, a new implant system has been developed using the properties of trabecular metal for treatment of osteonecrosis. Trabecular metal is a relatively new and unique material that physically and mechanically more closely resembles bone than any other prosthesis. Its use in osteonecrosis of the femoral head has shown promising results with few if any short term complications. To the best of our knowledge, besides normal progression of the disease, no major complications of this implant system have been reported. This article presents the first reported case of a subtrochanteric fracture of the femur following implantation of a trabecular metal osteonecrosis implant.