Imaging diagnosis of lumbar foraminal stenosis in the fifth lumbar nerve root: reliability and reproducibility of T1-weighted three-dimensional lumbar MRI.

BACKGROUND: Various magnetic resonance imaging (MRI) techniques have been reported in detection of lumbar foraminal stenosis (LFS), especially for T2-weighted three-dimensional MRI (3D-MRI) describing the shape of nerve roots. The detection of LFS in the fifth lumbar nerve root (L5 root), however, is still less reliable compared to other lumbar nerve roots. Then we have been using T1-weighted 3D-MRI aiming to depict the shape of, and also pathology affecting the L5 root. The aim of this study is to evaluate our T1-weighted 3D-MRI in diagnosing LFS of the L5 root. METHODS: This retrospective study included 24 patients with intracanal stenosis (ICS) at L4-5, and 30 patients with LFS at L5-S causing unilateral L5 root lesion. The pre-operative T1-weighted 3D-MRI aiming bilateral L5 nerve roots of each patient were blinded and reviewed twice by five spine surgeons, independently. The image evaluation was performed in two conditions: (I) the symptomatic side was judged in 30 patients of LFS patients, and (II) the symptomatic side or the absence of LFS was judged in images of all the 54 patients including LFS and ICS patients. The correct-answer-rate, sensitivity and specificity of the imaging study were calculated. Also, the intra- and interobserver agreement of the imaging study by five spine surgeons were evaluated by the kappa (κ) statistics. RESULTS: For conditions (I) and (II) above, the mean correct-answer-rate was 92.3% and 69.8%, respectively. The sensitivity and specificity of the imaging study was 72.6% and 66.3%, respectively. The average of intraobserver κ-value of five examiners was 0.874 and 0.708, and the average of interobserver κ-value was 0.837 and 0.578, respectively. CONCLUSIONS: As well as previously reported T2-weighted 3D-MRI, our T1-weighted 3D-MRI was found to be reliable in diagnosing LFS of the L5 root.

Comparison between single and double suture passing techniques in the suture bridge rotator cuff repair with a 2-mm tape: A simulation study using a three-dimensional finite element method.

BACKGROUND: Suture bridge repair has been widely used as one of the standard procedures in the arthroscopic rotator cuff repair. We compared the intratendinous stress distribution between single and double suture passing techniques in the suture bridge repair using a 2-mm tape and clarified the roles of tensioning in this procedure. METHODS: A board-like model of the supraspinatus tendon and humeral head was used in order to standardize conditions and exclude the influence of anatomical variations between individuals. Reattachment of the supraspinatus tendon to the bone was simulated using both single and double suture passing techniques for the suture bridge repair using a 2-mm tape. A tensile load was applied to the medial end of the tendon, and the stress distribution pattern was observed. Elastic analysis enabled comparison of the von Mises equivalent and maximum principal stresses between the single and double suture passing techniques. The tape configuration was subsequently translated 1 mm toward the insertion points of lateral anchors to simulate the tensioning maneuver. RESULTS: Although the distribution pattern of both the equivalent and the maximum principal stresses was similar for both models, areas with a high stress concentration were smaller in the single suture passing model than those in the double suture passing model. The equivalent stress concentrated within the tendon beneath the tapes as well as in the area between the crossing tapes and the lateral end of the tendon, whereas the maximum principal stress concentrated medial to the sites of suture penetration. CONCLUSIONS: Single suture passing technique can reduce the extent of intratendinous stress concentration compared with double suture passing technique, which might be beneficial to reduce the incidence of type 2 retear after suture bridge repair of rotator cuff tendon using a 2-mm tape.

Lumbosacral Transitional Vertebrae Cause Spinal Level Misconception in Surgeries for Degenerative Lumbar Spine Disorders.

Human lumbar spine usually consists of five vertebrae; however, some individuals have vertebral anomalies with four or six lumbar vertebrae because of sacralized fifth lumbar vertebra (L5 sacralization) or lumbarized first sacral vertebra (S1 lumbarization), respectively. These vertebral anomalies are called lumbosacral transitional vertebra (LSTV). Although LSTV is an asymptomatic anomaly, it is known to cause misconception in spinal counts and in spinal level at lumbar spinal surgery. The purpose of this study is to evaluate how LSTV affects the diagnosis and surgeries in lumbar spine disorders. In 550 consecutive patients who underwent lumbar spinal surgeries, a whole-spine X-ray was taken on admission to assess the true number of lumbar vertebrae. We assessed the coherence between the neurological level diagnosis and the level of spinal canal stenosis on imaging studies before and after the recognition of LSTV to clarify how recognition of LSTV affected pre-operative surgical planning. Out of 550 patients, LSTV was found in 71 (12.9%) patients: 37 cases with L5 sacralization and 34 cases with S1 lumbarization. The number of vertebrae was miscounted at the outpatient department (OPD) in 38 cases (54%): 10 L5-sacralization cases and 28 S1-lumbarization cases. Moreover, surgical spinal levels were altered from the original surgical plans at OPD in 11 cases (15%; 3 L5-sacralization and 8 S1-lumbarization cases), after recognizing the true spinal counts by the whole spine X-ray. To avoid errors in spinal level diagnosis, we should recognize the possibility of LSTV that could be assessed by a whole spine X-ray.

Tight medial knot tying may increase retearing risk after transosseous equivalent repair of rotator cuff tendon.

BACKGROUND: Retearing mechanism after transosseous equivalent (TOE) rotator cuff repair has not been fully clarified yet. OBJECTIVE: The purposes of this study were to compare the stress distribution pattern in the tendon stump between knotted and knotless TOE repair and to investigate the role of suture tension applied during medial knot tying using a 3-dimensional finite element (3D-FE) method. METHODS: Both knotted and knotless TOE repairs were simulated on the 3D-FE human rotator cuff tear model. Elastic analysis was performed to compare the stress distribution pattern inside the tendon between the two models. The amount of compressive load applied to the medial-row sutures was then changed as 0, 20, 40, 60, 80, and 100 N in the knotted model. RESULTS: Knotted model demonstrated more distinct stress concentration inside the tendon around medial-row sutures than the knotless model. Mean von Mises equivalent stress in this area in the 0, 20, 40, 60, 80, and 100 N models was 0.26, 0.35, 0.50, 0.70, 1.11, and 1.14 MPa, respectively. CONCLUSIONS: In the knotted TOE repair, tight medial knot tying might cause a high stress concentration around medial knots, which may constitute one of the pathogenetic factors of postoperative retearing at this site.

Comparison of fixation properties between coil-type and screw-type anchors for rotator cuff repair: A virtual pullout testing using 3-dimensional finite element method.

BACKGROUND: Pullout of inserted anchor constitutes one of the pathomechanisms of re-tearing after rotator cuff repair. The purpose of the present study was to investigate the fixation properties of suture anchors using 3-dimensional finite element method. METHODS: The computer models of three types of anchors (TwinFix Ti, HEALICOIL PK and HEALICOIL RG) were inserted into the isotropic cube model that simulated cancellous bone. In the virtual pullout testing, a tensile load (500 N) along the long axis of the inserted anchor was applied to the site of suture thread attachment to simulate a traction force. The distribution of von Mises equivalent stress, the failure patterns of elements inside the cube and the anchor displacement were compared among the three anchors. RESULTS: In TwinFix Ti, the highest stress concentration was seen around the anchor threads close to the surface of the cube, which caused element failure at this site. On the other hand, both HEALICOIL PK and HEALICOIL RG demonstrated a high stress concentration as well as element failure around the anchor tip. Comparing the anchor displacement, HEALICOIL RG showed the smallest displacement among the three anchors. The tensile loads that required a 0.1-mm displacement for TwinFix Ti, HEALICOIL PK and HEALICOIL RG were 400 N, 370 N, and greater than 500 N, respectively. CONCLUSIONS: The bony structures close to the footprint surface may be damaged during surgery due to preparation for the bony bed as well as the insertion of anchors. Thus, we assumed that HEALICOIL RG represented the best initial fixation properties among the three anchors tested. Virtual pullout testing using 3-dimensional finite element method could reveal the detailed biomechanical characteristics of each suture anchor, which would be important for shoulder surgeons to improve the clinical outcomes of rotator cuff repair.

Elderly-onset degenerative "lumbar spondylotic myelopathy" in a patient with a low-placed spinal cord successfully treated by laminotomy: a case report.

The authors report a rare case of elderly-onset "lumbar spondylotic myelopathy" occurred on a low-placed spinal cord compressed at multiple levels with thickened ligamenta flava. A posterior decompression surgery could alleviate neurological symptoms successfully instead of untethering of the spinal cord, a widely accepted surgery for tethered cord.