Ryuichi Gejo

Serial changes in trunk muscle performance after posterior lumbar surgery.

STUDY DESIGN Serial changes in trunk muscle performance were prospectively studied in 20 patients who underwent posterior lumbar surgery. OBJECTIVE To evaluate the influence of back muscle injury on postoperative trunk muscle performance and low back pain, to clarify the significance of minimization of back muscle injury during surgery. SUMMARY OF BACKGROUND DATA The current investigators have reported examination of iatrogenic back muscle injury in an animal model and in humans. However, definite impairment caused by such back muscle injury has not been clarified. METHODS The patients were divided into a short-retraction-time group (< 80 minutes; n = 12) and a long-retraction-time group (> or = 80 minutes; n = 8). Before surgery and 3 and 6 months after surgery, the degree of back muscle injury was estimated by magnetic resonance imaging, and trunk muscle strength was measured. In addition, the incidence and severity of low back pain were serially analyzed. RESULTS Back muscle injury was directly related to the muscle retraction time during surgery. The damage to the multifidus muscle was more severe, and the recovery of extensor muscle strength was delayed in the long-retraction-time group. In addition, the incidence of postoperative low back pain was significantly higher in the long-retraction-time group. CONCLUSIONS Postoperative trunk muscle performance is dependent on the muscle retraction time. Thus, it is beneficial to shorten the retraction time to minimize back muscle injury and subsequent postoperative low back pain.

Axial symptoms after en bloc cervical laminoplasty.

Eighty-two patients were evaluated after cervical laminoplasty to explore measures that could minimize future postoperative axial complaints. Patients were divided into two groups: Group A--severe postoperative axial symptoms, and Group B--mild axial complaints. Japanese Orthopaedic Association outcomes scores were similar for the two groups. Radiologic studies demonstrated greater restriction of range of motion in Group A patients who had undergone longer and more extensive surgical procedures.

Preventive measures of back muscle injury after posterior lumbar spine surgery in rats.

Study Design. Postoperative back muscle injury was studied in rats. Postoperative findings were compared among three groups: 2‐hour continuous back muscle retraction, 5‐minute retraction release after 1 hour of retraction, and 5‐minute release at every 40 minutes of retraction. Objective. To determine whether intermittent release of the retractor during surgery is effective to prevent severe muscle injury. Summary of Background Data. In surgery performed on the extremities using a tourniquet, intermittent reperfusion intervals can permit extended tourniquet application when the operation is prolonged. However, there have been no specific studies on the effects of intermittent retraction release for postoperative back muscle injury. Methods. The back muscle of rats was retracted using a self‐retaining retractor for 2 hours. The 36 rats were divided equally into the following three groups: Group 1, 2 hours of continuous retraction; Group 2, two 1‐hour retractions interposed with a 5‐minute retraction release; and Group 3, three 40‐minute retractions interposed with a 5‐minute retraction release. In each group, the multifidus muscle was histologically analyzed at 48 hours, 1 week, and 6 weeks after surgery. The muscles were stained by a variety of histochemical methods. The level of serum CPK‐MM isoenzyme was measured 48 hours after surgery. Results. Postoperative back muscle degeneration was the most severe in Group 1. The concentration of CPK‐MM in Group 1 was significantly higher than that in Groups 2 and 3. One week after surgery, the lesser diameter of regenerated fibers in Group 1 was smaller than that in Groups 2 and 3. The incidence of neurogenic muscle damage was the highest in Group 1. Conclusions. During posterior lumbar spine surgery, 5‐minute retraction release after 1 hour or after 40 minutes of retraction was effective in preventing severe back muscle injury after surgery.

Surgical outcome of cervical expansive laminoplasty in patients with diabetes mellitus.

STUDY DESIGN The results from cervical laminoplasty in 18 patients with diabetes mellitus were compared with results from the same procedure in 34 nondiabetic patients matched for age, gender, and disease. OBJECTIVE To analyze the effects of diabetes mellitus on the surgical outcome after cervical laminoplasty. SUMMARY OF BACKGROUND DATA There have been no reports on the results of cervical laminoplasty patients with diabetes. METHODS A retrospective analysis of 18 patients with diabetes mellitus who underwent cervical laminoplasty and 34 nondiabetic patients who underwent the same surgical procedure was undertaken. The postoperative score, intra- and postoperative findings, complications, and radiologic factors were compared between the two groups. In the group with diabetes, the correlation between the recovery rate of the Japanese Orthopedic Association score and the factors indicating the severity of diabetes was assessed. RESULTS There was no statistical difference between the total Japanese Orthopedic Association scores of the two groups. However, the group with diabetes mellitus showed a poor recovery of sensory function of the lower extremities. Three patients in the group with diabetes had superficial wound complication after surgery. In contrast, none of the patients in the control group had a wound problem. Furthermore, a negative correlation was observed between the recovery rate and the preoperative HbA1 level in the group with diabetes. CONCLUSIONS Although patients with diabetes mellitus who had cervical myelopathy experienced benefits from cervical laminoplasty similar to those of nondiabetic patients, the patients with diabetes were more likely to have wound complication. Furthermore, the negative correlation between the recovery rate and the preoperative HbA1 value might suggest that long-term diabetes control of more than 2 to 3 months before surgery at least is recommended for a favorable surgical outcome.

Magnetic resonance imaging and histologic evidence of postoperative back muscle injury in rats.

Study Design. Postoperative back muscle injury was evaluated in rats by magnetic resonance imaging and histologic analyses. Objective. To compare the magnetic resonance imaging manifestation of back muscle injury with the histologic findings in rats and to subsequently clarify the histopathologic appearance of the high intensity regions on T2-weighted images in human postoperative back muscles. Summary of Background Data. In a previous study, it was found that the signal intensity on T2-weighted images of the postoperative back muscles was increased in patients who had postsurgical lumbar muscle impairment, especially in those with a prolonged surgery duration. However, the specific histopathologic changes that cause the high signal intensity on T2-weighted images remain unclear. Methods. Rats were divided into three groups: sham operation group, 1-hour retraction group, and 2-hour retraction group. Magnetic resonance imaging and histology of the multifidus muscles were examined before surgery and at 2, 7, and 21 days after surgery. Results. T2-weighted imaging was more useful than T1-weighted imaging to estimate back muscle injury. The high signal intensity of the multifidus muscles on T2-weighted images remained 21 days after surgery only in the 2-hour retraction group. Histologically, the regeneration of the multifidus muscles was complete at 21 days after surgery in the 1-hour retraction group, but the regenerated muscle fibers in the 2-hour retraction group had a small diameter, and the extracellular fluid space remained large. Conclusion. The high signal intensity on T2-weighted images of the postoperative multifidus muscles in the regenerative phase may be due to an increased extracellular space and incomplete muscle fiber regeneration.

Biomechanical effects of patellar positioning on intraoperative knee joint gap measurement in total knee arthroplasty

BACKGROUND Balancing both the lateral/medial and extension/flexion joint gaps is a prerequisite for soft tissue balance in total knee arthroplasty. The purpose of this study was to quantify the effects of patellar positioning and quadriceps load during total knee arthroplasty on knee joint gap measurements. METHODS Eight fresh-frozen cadaveric knees ranging in age from 65 to 85 years old were used. Using a medial parapatellar approach, posterior cruciate ligament sacrificing total knee arthroplasty was performed. The specimens were mounted on a custom knee testing system that allowed the femur to be locked in position for knee extension or flexion. Patellar positions of eversion, reduction, and following repair of the arthrotomy were examined. The influence of quadriceps muscle load was investigated by varying the quadriceps load from 0 to 125N. The lateral and medial joint gaps, represented by the distance from the implanted femoral component surface to the cut tibia surface, were measured with 100N tibial distraction force using a 3D digitizer in both extension (0 degrees ) and flexion (90 degrees ). FINDINGS Both the medial and lateral joint gaps with patella eversion were significantly smaller than those with patellar reduction and arthrotomy repair (extension: all quadriceps loads, P<0.0002; flexion: quadriceps loads less than 75N, P<0.0002). In patella eversion, quadriceps loading decreased the lateral joint gap more than the medial joint gap in both extension and flexion; however, the effect was greater in knee flexion with significant differences seen at all quadriceps loads, whereas in extension significant differences were only seen for quadriceps loading of 75N and greater. Patella eversion also caused a lateral-posterior shift and external rotation of the tibia compared to the other conditions (P<0.005). With patella reduction and repair of the arthrotomy lower quadriceps loading decreased the extension gap significantly more than the flexion gap (P<0.01). Following repair of the arthrotomy higher quadriceps loading significantly decreased the flexion gap more than the extension gap (P<0.04). INTERPRETATION The patellar positioning and quadriceps muscle loading in total knee arthroplasty have a strong influence on intraoperative joint gap measurements.

Effects of Kneeling on Tibiofemoral Contact Pressure and Area in Posterior Cruciate-Retaining and Posterior Cruciate-Sacrificing Total Knee Arthroplasty

The objective of this study was to measure the effect of kneeling on tibiofemoral contact following cruciate-retaining and posterior-stabilized total knee arthroplasty. Five cadaveric knees were tested on a custom testing system that allowed physiologic muscle loading. Three forces were used to simulate nonkneeling, double-stance kneeling, and single-stance kneeling at flexion angles of 90°, 105°, 120°, and 135°. Tibiofemoral contact areas and pressures were measured using the Tekscan (South Boston, MA) system. Kneeling increased contact areas and pressures in both designs with variable significance (P < .05). Moving from double- to single-stance kneeling increased pressures in the cruciate-retaining group but decreased pressures in the posterior-stabilized group (P < .05). Chronic, repetitive kneeling after total knee arthroplasty may increase polyethylene wear due to increased contact areas and pressures.

Effects on tibiofemoral biomechanics from kneeling.

BACKGROUND Repetitive kneeling in certain occupations, hobbies and cultures is associated with tibiofemoral joint osteoarthritis. The biomechanics of kneeling is therefore of interest. This cadaveric study investigated tibiofemoral joint contact areas, pressures, and kinematics in response to kneeling. METHODS Five human cadaveric knees were subjected to simulated kneeling at flexion angles of 90°, 105°, 120°, and 135°. Different anterior forces were applied to the knee to simulate crouching (no force), double stance kneeling (339N of force), and single stance kneeling (678N of force). Tibiofemoral joint kinematics, contact areas, and pressures were measured. FINDINGS Kneeling produced tibial posterior translation and external rotation. Posterior translation was significantly less at 90° than at higher flexion angles (P<0.05). Posterior translation and external rotation were significantly greater moving from crouching to double stance kneeling when compared to moving from double to single stance kneeling (P<0.05). Double and single stance kneeling increased contact areas and pressures significantly when compared to crouching (P<0.05). Pressures also increased significantly moving from double to single stance kneeling (P<0.05). INTERPRETATION Kneeling produces less tibial posterior translation at 90° than at higher flexion angles primarily due to posterior cruciate ligament biomechanics. Tibial external rotation results from posterior cruciate ligament biomechanics and differences between medial and lateral compartment anatomy. Different anatomical constraints allow significantly less posterior translation and external rotation moving from double to single stance kneeling is a result of increased pressure with kneeling likely contributes to the development of tibiofemoral osteoarthritis, and single stance kneeling may be more deleterious than double stance kneeling.

Serial Changes of Herniated Intervertebral Discs After Posterior Lumbar Discectomy: The Relation Between Magnetic Resonance Imaging of the Postoperative Intervertebral Discs and Clinical Outcome

To evaluate the relation between the morphologic changes of postoperative intervertebral discs and the clinical outcome after posterior lumbar discectomy, the size of the bulging disc was analyzed prospectively on serial follow-up magnetic resonance images in 26 randomly selected patients. The bulging of postoperative intervertebral discs involved three patterns of reduction: early reduction (n = 15), gradual reduction (n = 6), and late reduction (n = 5). There was a significant difference in the serial changes of subjective symptoms and neurologic function among the three patterns. A late reduction of postoperative disc bulging could cause late recovery of subjective symptoms and neurologic disturbance.

Femoral Anterior Tangent Line of the Osteoarthritic Knee for Determining Rotational Alignment of the Femoral Component in Total Knee Arthroplasty

Several reference axes have been used to establish femoral rotational alignment during total knee arthroplasty. The current study examined the configuration of the anterior surface of the femur immediately proximal to the trochlea as an alternative rotational landmark. An analysis of computed tomographic images of 150 knees with osteoarthritis indicated that the configuration of the surface is mostly flat or slightly depressed, and the line tangential to the surface (femoral anterior tangent line; FAT line) was consistently determined to be 12.2° ± 3.6° internally rotated to the transepicondylar axis. This value was relatively constant and as reliable as the femoral anteroposterior axis for determining rotational alignment. In addition, the FAT line was not affected by the degree of the varus-valgus deformity of the osteoarthritic knees.