Impact of bone density and integrated screw configuration on standalone anterior lumbar interbody construct strength.

Background: In anterior lumbar interbody fusion (ALIF), the use of integrated screws is attractive to surgeons because of the ease of implantation and no additional profile. However, the number and length of screws necessary for safe and stable implantation in various bone densities is not yet fully understood. The current study aims to determine how important both length and number of screws are for stability of ALIFs. Methods: Three bone models with densities of 10, 15, and 20 pounds per cubic foot (PCF) were chosen as surrogates. These were instrumented using the Z-Link lumbar interbody system with either 2, 3, or 4 integrated 4.5 × 20 mm screws or 4.5 × 25 mm screws (Zavation, LLC, Flowood, MS). The bone surrogates were tested with loading conditions resulting in spine extension to measure construct stiffness and peak force. Results: The failure load of the construct was influenced by the length of screws (p=.01) and density of the bone surrogate (p<.01). There was no difference in failure load between using 2 screws and 3 screws (p=.32) or when using four 20 mm screws versus three 25 mm screws (p=.295). Conclusion: In our study, both bone density and length of screws significantly affected the construct's load to failure. In certain cases where a greater number of screws are unable to be implanted, the same stability can potentially be conferred with use of longer screws. Future clinical studies should be performed to test these biomechanical results.

Earlier Return to Light Duty Is Associated With Successful Return to Full Duty of Workers' Compensation Patients Treated With Shoulder Arthroscopic Surgery.

Purpose: To evaluate Workers' Compensation (WC) patients who underwent arthroscopic shoulder surgery for workplace shoulder injuries and to determine whether there was an association between earlier return to light duty and earlier return to full duty. Methods: After receiving institutional review board approval, we performed a retrospective chart review of all WC patients treated with shoulder arthroscopic surgery by 2 senior authors between 2011 and 2018. The patients were divided into 2 groups: Group 1 went back to light-duty work within the first 100 days after surgery, whereas group 2 performed light-duty work after 100 days or performed no light-duty work. The primary outcomes included the length of time from surgery to light-duty work and the length of time from surgery to return to the full-duty work level. Results: A total of 59 patients met the inclusion criteria. There was a moderate correlation between the number of days at which the patients were released to light duty and the days they were able to be released to full duty (r = 0.35). In group 1 (light duty ≤ 100 days), 18 patients (75%) went back to full duty, whereas only 16 patients (46%) in group 2 were able to return to full-duty work (P = .025). Conclusions: Earlier return to light duty is associated with earlier return to full duty after shoulder arthroscopic surgery in patients with a Workers' Compensation claim. Additionally, WC patients who returned to early light duty in the first 100 days postoperatively had a higher rate of return to full duty than did patients who did not return to early light duty. Level of Evidence: Level III, case-control study.

Nitinol Memory Rods Versus Titanium Rods: A Biomechanical Comparison of Posterior Spinal Instrumentation in a Synthetic Corpectomy Model.

STUDY DESIGN: Biomechanical investigation. OBJECTIVE: To compare the biomechanical performance of nitinol memory metal rods and titanium rods when used as posterior spinal instrumentation in a synthetic model. METHODS: Biomechanical testing was performed using ultra-high-molecular-weight polyethylene blocks. Nineteen spinal constructs were created to allow comparison of 5.5-mm nitinol rods with 5.5-mm titanium rods. Static compression and rotational testing were performed on an Instron 8874 and Instron 4202 at 37°C to simulate body temperature. RESULTS: The average titanium construct stiffness under static compression or bending was 47.2 ± 9.1 N/mm while nitinol's stiffness averaged 48.9 ± 12.4 N/mm (P = .83). During axial rotation testing, the nitinol rod system showed no torsional stiffness difference from the titanium system: 0.95 ± 0.03 Nm/deg versus 0.96 ± 0.17 Nm/deg, respectively (P = 0.91). There was a statistically significant difference between the average torsional yield point for the titanium constructs (14.4 ± 1.6 Nm/deg) and nitinol constructs (21.3 ± 0.8 Nm/deg) (P = .004). The torsional toughness of the nitinol constructs was also statistically greater than the titanium rods: 473 GN/m3 versus 784 GN/m3 (P = .0006). There was no statistically significant difference between the nitinol group sustaining a higher number of fatigue cycles until failure and the titanium group (181 660 cycles vs 64 104 cycles, respectively, P = .22). CONCLUSIONS: This study provides biomechanical evidence that nitinol rods used in a posterior construct are comparable to titanium rods with regard to compression and have increased torsional failure load and torsional toughness. While nitinol trended toward superior fatigue resistance, there was no significant difference in nitinol versus titanium construct fatigue resistance.

Open versus minimally invasive sacroiliac joint fusion: a multi-center comparison of perioperative measures and clinical outcomes.

BACKGROUND: Sacroiliac (SI) joint pain is an under diagnosed source of low back pain due in part to lack of visible pathology on radiographs and symptoms mimicking other back-related disorders. Open SI joint fusion has been performed since the 1920s. This technique has fallen out of favor with the introduction of minimally invasive options. To date there has been no direct comparison between open and MIS SI joint fusion. METHODS: We conducted a multi-center, retrospective comparative cohort study of patients who underwent SI joint fusion using either an open surgical (OS) technique using a combination of screws and cages or a minimally invasive surgical (MIS) technique with a series of titanium plasma spray (TPS) coated triangular implants. Operative measures including surgical operating time, length of hospitalization and estimated blood loss (EBL) were collected along with demographics and medical history, surgical complications, and 12- and 24-month pain scores. Improvements in pain were compared after matching for age and gender and controlling for a history of lumbar spine fusion using repeated measures analysis of variance. RESULTS: Data were available for 263 patients treated by 7 surgeons; 149 patients treated with OS and 114 treated with MIS SI joint fusion. Compared to OS patients, MIS patients were on average 10 years older (mean age 57 vs. 46) and 69% of all patients were female. MIS operative measures of EBL, operating time and length of hospitalization were significantly lower than open surgery (p < 0.001). Pain relief, measured as change from baseline to 12 months in VAS pain rating, was 3.5 points lower in the MIS vs. OS group (-6.2 vs. -2.7 points, p < 0.001). When matched for age, gender and a history of prior lumbar spinal fusion, postoperative pain scores were on average 3.0 points (95% CI 2.1 - 4.0) lower in MIS vs. OS (rANOVA p < 0.001). CONCLUSIONS: In this multi-center comparative study, patients who underwent either OS or MIS SI joint fusion showed postoperative improvements in pain score. Compared to OS patients, patients who underwent MIS SI joint fusion had significantly greater pain relief and more favorable perioperative surgical measures.

A comparison of the torsional stiffness of the lumbar spine in flexion and extension.

OBJECTIVE: The main mechanism of injury to the spine is torsion especially when coupled with compression. In this study, the in vitro torsional stiffness of the lumbar spine segments is compared in flexion and extension positions by cyclic and failure testing. METHODS: Fifteen lumbar spines were sectioned from fresh cadavers into 15 L2/3 and 15 L45 motion segments. Each vertebral segment was then potted superiorly and inferiorly in polymethylmethacrylate, effectively creating a bone-disk-bone construct. The potted spinal segments were mounted in a mechanical testing system, preloaded in compression to 300 N, and axially rotated to 3 degrees in both directions at a load rate of 1 degrees /s. This was done over 3 cycles for each motion segment in the flexion and extension positions. Each specimen was then tested to torsional failure in either flexion or extension. Stiffness, torque, and energy were determined from cyclic and failure testing. RESULTS: The results showed that in all cases of cyclic testing, the higher segment extension resulted in higher torsional stiffness. In relative extension, the lumbar specimens were stiffer, generated higher torque values, and generally absorbed more energy than the relative flexion condition. There were no differences found in loading direction or failure testing. CONCLUSIONS: Increasing the effective torsional stiffness of the lumbar spine in extension could provide a protective mechanism against interverbral disk injury. Restoration of segmental extension through increasing the lumbar lordosis may decrease the strain and reinjury of the joints, which can help reduce the extent of pain in the lumbar spine.

Surgical management of primary and metastatic sarcoma of the mobile spine.

OBJECT: Sarcomas of the spine are a challenging problem due to their frequent and extensive involvement of multiple spinal segments and high recurrence rates. Gross-total resection to negative margins, with preservation of neurological function and palliation of pain, is the surgical goal and may be achieved using either intralesional resection or en bloc excision. The authors report outcomes of surgery for primary and metastatic sarcomas of the mobile spine in a large patient series. METHODS: A retrospective review of patients undergoing resection for sarcomas of the mobile spine between 1993 and 2005 was undertaken. Sarcomas were classified by histology study results and as either primary or metastatic. Details of the surgical approach, levels of involvement, and operative complications were recorded. Outcome measures included neurological function, palliation of pain, local recurrence, and overall survival. RESULTS: Eighty patients underwent 110 resections of either primary or metastatic sarcomas of the mobile spine. Twenty-nine lesions were primary sarcomas (36%) and 51 were metastatic sarcomas (64%). Intralesional resections were performed in 98 surgeries (89%) and en bloc resections were performed in 12 (11%). Median survival from surgery for all patients was 20.6 months. Median survival for patients with a primary sarcoma of the spine was 40.2 months and was 17.3 months for patients with a metastatic sarcoma. Predictors of improved survival included a chondrosarcoma histological type and a better preoperative functional status, whereas osteosarcoma and a high-grade tumor were negative influences on survival. Multivariate analysis showed that only a high-grade tumor was an independent predictor of shorter overall survival. American Spinal Injury Association scale grades were maintained or improved in 97% of patients postoperatively, and there was a significant decrease in pain scores postoperatively. No significant differences in survival or local recurrence rates between intralesional or en bloc resections for either primary or metastatic spine sarcomas were found. CONCLUSIONS: Surgery for primary or metastatic sarcoma of the spine is associated with an improvement in neurological function and palliation of pain. The results of this study show a significant difference in patient survival for primary versus metastatic spine sarcomas. The results do not show a statistically significant benefit in survival or local recurrence rates for en bloc versus intralesional resections for either metastatic or primary sarcomas of the spine, but this may be due to the small number of patients undergoing en bloc resections.

The prevalence of wrong level surgery among spine surgeons.

STUDY DESIGN: A questionnaire study. OBJECTIVE: To evaluate the prevalence of wrong level surgery among spine surgeons and their use of preventive measures to avoid its occurrence. SUMMARY OF BACKGROUND DATA: Wrong site surgery fails to improve the patient's symptoms and has medical, emotional, social, and legal implications. Organizations such as the North American Spine Society and the Joint Commission on Accreditation of Healthcare Organizations have established guidelines to prevent wrong site surgery. Spine surgeons' compliance with these guidelines and the prevalence of wrong-level spine surgery have not been investigated previously. METHODS: All members of the American Academy of Neurologic Surgeons (n = 3505) were sent an anonymous, 30-question survey with a self-addressed stamped envelope. RESULTS: A total of 415 (12%) surgeons responded. Sixty-four surgeons (15%) reported that, at least once, they had prepared the incorrect spine level, but noticed the mistake before making the incision. Two hundred seven (50%) reported that they had done 1 or more wrong level surgeries during their career. From an estimated 1,300,000 spine procedures, 418 wrong level spine operations had been performed, with a prevalence of 1 in 3110 procedures. The majority of the incorrect level procedures were performed on the lumbar region (71%), followed by the cervical (21%), and the thoracic (8%) regions. One wrong level surgery led to permanent disability, and 73 cases resulted in legal action or monetary settlement to the patient (17%). CONCLUSION: There is a high prevalence of wrong level surgery among spine surgeons; 1 of every 2 spine surgeons may perform a wrong level surgery during his or her career. Although all spine surgeons surveyed report using at least 1 preventive action, the following measures are highly recommended but inconsistently adopted: direct preoperative communication with the patient by the surgeon, marking of the intended site, and the use of intraoperative verification radiograph.

Clinical results of revision shoulder arthroplasty for glenoid component loosening.

We retrospectively reviewed 32 patients who underwent glenoid revision surgery after total shoulder arthroplasty to compare the results of revision total shoulder arthroplasty with those of revision hemiarthroplasty and to identify factors associated with poor results after revision shoulder arthroplasty for glenoid component loosening. Results were reviewed at a mean follow-up of 4 years (range, 2-8 years). Glenoid reimplantation resulted in significant pain relief (P < .0001), improvement in American Shoulder and Elbow Surgeons (ASES) score (P < .02), and external rotation (24 degrees to 44 degrees , P < .004). Revision to a hemiarthroplasty also resulted in significant pain relief (P < .01) and improvement in ASES score (P < .05). For the treatment of glenoid loosening without glenohumeral instability, both reimplantation of a glenoid component and revision to a hemiarthroplasty improved function, satisfaction, and level of pain. Reimplantation of a new glenoid component offered greater improvements in pain (P < .008) and external rotation (increase of 20 degrees versus 3 degrees , P < .03) compared with hemiarthroplasty. For patients with preoperative glenohumeral instability, revision surgery did not improve motion, function, or pain significantly. Risk factors associated with a poor outcome after revision arthroplasty included persistent glenohumeral instability, rotator cuff tears, and malunion of the greater tuberosity.

Surgical management of spinal mesenchymal tumors.

Primary and metastatic spinal mesenchymal tumors are uncommon lesions. Surgical management of these tumors remains a challenge. En bloc wide resection provides the best chance for local tumor control and long-term survival. However, limitations to this technique include technical considerations (including neurovascular anatomy), patient selection, and tumor histology. Intralesional resection provides good neurologic outcomes, but local recurrence rates are high. Postoperative adjuvant chemotherapy with or without radiation may help to delay recurrence and improve outcomes. We present three cases of our surgical experience with spinal mesenchymal tumors for illustrative purposes.

Combination of hook plate and tibial pro-fibular screw fixation of osteoporotic fractures: a clinical evaluation of operative strategy.

BACKGROUND: Internal fixation of osteoporotic ankle fractures is technically difficult and may fail because of unreliable purchase. This study was undertaken to determine if a combination of a hook plate and tibial pro-fibular screws can provide secure fixation until fracture union. METHODS: Thirty-one patients between the ages of 55 and 90 years had open reduction and internal fixation of ankle fractures between April, 2001, and April, 2003. Sixteen patients with an average age of 71.4 years had ankle fracture fixation with a combination of hook plate and tibial pro-fibular screws for the distal fibular fracture, and 15 patients with an average age of 71.9 years had fixation of their ankle fractures with standard fixation technique using AO/ASIF principles but no tibial pro-fibular screws. All patients were followed with clinical and radiologic assessment at 2 weeks, 6 weeks, and 12 weeks postoperatively. At an average of 15.8 months after injury, patients also completed a mailed questionnaire with the Olerud-Molander ankle score and the AOFAS ankle-hindfoot score for preoperative and postoperative status. RESULTS: All patients who had tibial pro-fibular screw fixation had fracture union without hardware failure or complications. In the standard fixation group two patients had wound breakdown and one had a valgus malunion with screw pull out. The AOFAS and Olerud-Molander scores for the standard open reduction and internal fixation were 57.3 and 82.8 before injury and 37 and 43.8 postoperatively, respectively. The AOFAS and Olerud-Molander scores for the hook plate and tibial pro-fibular fixation group were 55.9 and 81.3 before injury and 42.4 and 50.3 postoperatively, respectively. CONCLUSIONS: The combination of hook plate and tibial pro-fibular screws in osteoporotic ankle fractures in a series of patients has not been reported before. This novel technique provides stable fixation for osteoporotic ankle fractures in elderly patients until union is achieved with good clinical scores.