Temperature changes during cortical bone drilling with a newly designed step drill and an internally cooled drill

Purpose

Bone drilling causes an increase in bone temperature, and a temperature above 47°C is critical because it causes thermal bone necrosis. Thermal osteonecrosis is common with the drill diameter of ≥4.5 mm without cooling. The aim of this study was to determine the increase of bone temperature during drilling using newly contructed two-step and internally cooled drills.

Methods

An experiment was set up according to a central composite design. An internally cooled drill (3.4 mm and 4.5 mm) and a two-step drill (2.5/3.4 and 3.4/4.5 mm) were used in combination with feed rates of (0.02, 0.04, 0.10, 0.16 and 0.18 mm/rev) and cutting speeds (1.18, 10.68, 33.61, 56.55 and 66.05 m/min) with and without cooling with water of 24°C. Bone temperatures were measured with thermocouples. Drilling was performed on pig diaphyses with a three-axis mini milling machine.

Results

Bone temperatures in all combinations of parameters with internal cooling were below the critical 47°C (p = 0.05). The highest temperatures were detected using a 4.5-mm drill (40.5°C). A statistically significant effect other than cooling was found with the drill diameter and feed. A drill diameter of 3.4 mm with internal cooling developed a maximum temperature of 38.5°C and without cooling 46.3°C. For the same conditions a drill with diameter of 4.5 mm reached temperatures of 40.5°C and 55.7°C, respectively. The effect of feed rate is inversely proportional to the increase in bone temperature. With the feed rate 0.16 mm/rev, temperature was below critical even using the 4.5-mm drill (46.4°C, p = 0.05). Using the 3.4-mm drill all temperatures were below critical (46.2°C, p = 0.05). The two-step drill compared to a standard drill with the same diameter did not show statistical differences in maximum bone temperatures for all combinations of parameters (p = 0.05).

Conclusions

A two-step drill does not have any advantages over a standard twist drill of the same diameter. An internally cooled drill causes a significantly smaller increase of bone temperature during drilling with water of 24°C. An internally cooled drill is currently the ''ideal'' drill for traumatology/orthopaedics because it produces the smallest increase in bone drilling temperature. If internal cooling is used the regulation of other drilling parameters is of no importance.     

Fatigue performance of angle-stable tibial nail interlocking screws

Purpose

Tibial nail interlocking screw failure often occurs during delayed fracture consolidation or at early weight bearing of nailed unstable fractures, in general when high implant stress could not be reduced by other means. Is there a biomechanical improvement in long-term performance of angle stable locking screws compared to conventional locking screws for distal locking of intramedullary tibial nails?

Methods

Surrogate bones of human tibiae were cut in the distal third and distal locking of the 10 mm intramedullary tibial nail was performed with either two angle stable locking screws or two conventional locking screws in the mediolateral plane. Six specimens per group were mechanically tested under quasi-static and cyclic axial loading with constantly increasing force.

Results

Angle stable locking screw constructs exhibited significantly higher stiffness values (7,809 N/mm ± 647, mean ± SD) than conventional locking screw constructs (6,614 N/mm ± 859, p = 0.025). Angle stable locking screw constructs provided a longer fatigue life, expressed in a significantly higher number of cycles to failure (187,200 ± 18,100) compared to conventional locking screw constructs (128,700 ± 7,000, p = 0.004).

Conclusion

Fatigue performance of locking screws can be ameliorated by the use of angle stable locking screws, being especially important if the nail acts as load carrier and an improved stability during fracture healing is needed.     

Etanercept treatment enhances clinical and neuroelectrophysiological recovery in partial spinal cord injury

Purpose

To investigate the effect of an anti-TNF-α agent (etanercept) on recovery processes in a partial spinal cord injury (SCI) model using clinical and electrophysiological tests.

Methods

Twenty-four New Zealand rabbits were divided into three groups: group 1 [SCI + 2 ml saline intramuscular (i.m.), n = 8], group 2 (SCI + 2.5 mg/kg etanercept, i.m., 2–4 h after SCI, n = 8) and group 3 (SCI + 2.5 mg/kg etanercept, i.m., 12–24 h after SCI, n = 8). Rabbits were evaluated before SCI, immediately after SCI, 1 week after, and 2 weeks after SCI, clinically by Tarlov scale and electrophysiologically by SEP.

Results

Tarlov scores of groups 2 and 3 were significantly better than group 1, 2 weeks after SCI. SEP recovery was significantly better in groups 2 and 3 than group 1, 2 weeks after SCI.

Conclusions

These results show that blocking TNF-α mediated inflammation pathway by an anti-TNF-α agent enhances clinical and electrophysiological recovery processes in partial SCI model.     

Factors associated with the success of the Rigo System Chêneau brace in treating mild to moderate adolescent idiopathic scoliosis

Background

Adolescent idiopathic scoliosis (AIS) is the most prevalent spine deformity within the pediatric population. Orthosis is the mainstay of conservative treatment for mild to moderate AIS. The Rigo System Chêneau (RSC) brace is a custom-made thoracolumbar sacral orthosis (TLSO) based on a three-dimensional correction concept. The purpose of this study was to identify factors that could predict the therapeutic success/failure of the RSC brace.

Materials and methods

A retrospective cohort study was performed on all consecutive patients according to the Scoliosis Research Society (SRS) criteria for the success of conservative treatment. Participants had a 2-year follow-up beyond the termination of brace treatment. All patients were treated with the RSC orthotic device.

Results

Ninety-three patients met the inclusion criteria. At treatment onset, their average age was 12.9 years, average Cobb angle 31.97°, Risser score 1.07, and the mean angle of thoracic rotation (ATR) was 10.2°. The mean brace treatment period was 36 months. Treatment was successful in 83.8 % of these patients (n = 79). The average final Cobb angle was 28.97°, Risser score 4.88, and ATR 8.09°. The pre-treatment factors associated with the success of applying the RSC brace were a high Risser score [odds ratio (OR) = 2.97, 95 % confidence interval [CI] 1.18–7.44; p = 0.02), a low Cobb angle (OR = 0.92, 95 % CI 0.85–0.99; p = 0.02), and low ATR (OR = 0.86, 95 % CI 0.75–0.99; p = 0.04).

Conclusions

The treatment of mild to moderate AIS with the RSC brace provides excellent clinical results. Its added benefit is enabling a three-dimensional correction of a three-dimensional deformity. Pre-treatment high Risser score, low Cobb angles, and low ATRs are associated with treatment success.

Level of evidence

Retrospective analysis, Level III.     

Late infections after dynamic stabilization of the lumbar spine with Dynesys

Introduction

Dynamic stabilization of the spine was developed as an alternative to rigid fusion in chronic back pain to reduce the risk of adjacent segment degeneration. Dynamic neutralization system (Dynesys, Zimmer CH) is one of the most popular systems available, but some midterm studies show revision rates as high as 30 %. Some late infectious complications in our patients prompted us to review them systematically. Propionibacterium recently has been shown to cause subtle infections of prosthetic material.

Materials and methods

Here, we report on a consecutive series of 50 Dynesys implants. In a median follow-up of 51 months (range 0–91), we identified 12 infectious and 11 non-infectious complications necessitating reoperation or removal of the implant in 17 patients.

Results

Material infections occurred after a median of 52 months (2–77) and were due to Propionibacterium alone (n = 4) or in combination (n = 3) in seven out of 11 patients. Clinical presentation combines new or increasing pain associated with signs of screw loosening on conventional X-rays; however, as many as 73.5 % of patients present some degree of screw loosening without being at all symptomatic of infection.

Conclusion

The high rate of late infections with low-grade germs and the frequency of screw loosening signs made us suspect a lack of integration at the bone-screw interface. Surgeons should be suspicious if the patient presents a combination of new or increasing pain and signs of screw loosening, and aggressive revision is recommended in these cases.     

The anatomic study of clival screw fixation for the craniovertebral region

Purpose

To study the anatomic parameters related to clival screw and establish reference data concerning the craniovertebral fixation technique.

Methods

Morphometric measurement of the clivus and the surrounding anatomic structures were obtained on 41 dry bone specimens. Then, 2-D CT reconstruction of the craniovertebral region of 30 patients (19 men and 11 women, ranging in age from 20–64 years with an average age of 38.8 years) were performed to measure the safety range for a 3.5-mm screw placement. Nine entry points were evaluated. Finally, one male fresh cadaver specimen (age 46 years) was dissected to observe the craniovertebral region.

Results

The clivus faces the basilar artery, the V ~ XII cranial nerves, the pons, and ventral medulla oblongata at its intracranial surface. The longitudinal diameter of extracranial clivus was 25.87 ± 2.64 mm. The narrowest diameter of the clivus was 12.84 ± 1.08 mm, the distance between the left and right hypoglossal canal was 32.70 ± 2.09 mm at its widest part. The distance between the left and right structures, the maximum value was 49.31 ± 4.16 mm at carotid canal, the minimum value was 16.54 ± 2.04 mm at the occipital condyle. The measurement of clival screws placement simulation via 2-D CT reconstruction images shows the maximum upper insertion angle of three components the optimal entry points, the candidate points, the limit entry points was 130.19°, 125.23° and 85.72°, and the total mean screw length was 7.57, 10.13 and 15.6 mm at the vertical entry angle, respectively.

Conclusions

Clival screw placement is a viable option for craniovertebral fixation. There is a safe scope for the screw length and angle of the screw placement. And, these parameters obtained in the present study will be helpful for anyone contemplating the use of clival screw fixation.     

Outcomes of surgical intervention for cervical spondylotic myelopathy accompanying local kyphosis (comparison between laminoplasty alone and posterior reconstruction surgery using the screw-rod system)

Purpose

The surgical strategy for cervical spondylotic myelopathy (CSM) accompanying local kyphosis is controversial. The purpose of the present study was to compare and evaluate the outcomes of two types of surgery for CSM accompanying local kyphosis: (1) laminoplasty alone (LP) and (2) posterior reconstruction surgery (PR) in which we corrected the local kyphosis using a pedicle screw or lateral mass screw.

Methods

Sixty patients who presented with local kyphosis exceeding 5° were enrolled. LP and PR were each performed on a group of 30 of these patients; 30 CSM patients without local kyphosis, who had undergone LP, were used as controls. The follow-up period was 2 years or longer. Preoperative local kyphosis angles in LP and PR were 8.3° ± 4.4° and 8.8° ± 5.7°, respectively. Preoperative C2–7 angles in LP, PR and controls were −1.7° ± 9.6°, −0.4° ± 7.2° and −12.0° ± 5.6°, respectively. The recovery rate of the JOA score, local kyphosis angle and C2–7 angle at post-op and follow-up were compared between the groups.

Results

The recovery rate of the JOA score in the LP group (32.6 %) was significantly worse than that in the PR group (44.5 %) and that of controls (53.8 %). Local kyphosis angles in the PR and LP groups at follow-up were 4.0° ± 8.6° and 8.0° ± 6.0°, respectively. However, although the C2–7 angle at follow-up was improved to −11.1° ± 12.7° in PR, and maintained at −11.6° ± 6.2° in controls, it deteriorated to 0.5° ± 12.7° in LP.

Conclusions

The present study is the first to compare the outcomes between LP alone and PR for CSM accompanying local kyphosis. It revealed that PR resulted in a better clinical outcome than did LP alone. This result may be due to reduction of local kyphosis, stabilization of the unstable segment, and/or the maintenance of C2–7 angle until follow-up in the PR group.     

Pullout strength of all suture anchors in the repair of rotator cuff tears: a biomechanical study

Purpose

We evaluated the biomechanical strength of two all suture anchors (ASA) of reduced diameter (1.4 mm) and compared them with the standard screw anchor (SA) with larger diameter (5.5 mm) used in rotator cuff tears.

Methods

We conducted 30 uniaxial vertical pullout tests using Material Testing System Instron 5566A until failure of the anchorage defined as rupture of the threads or anchor or detachment of the anchor. Anchor fixation was on tuberosities of fresh bovine humerus bone. ASAs were spaced four millimetres apart and were compared with a control SA implanted on the same greater tubercle at two centimetres. The tests were all performed at room temperature in a dry environment. Tensile loads (10 mm/min) were applied parallel to the axis of insertion. A preloading of 10 N was used to overcome loading artifacts of the test sample at the beginning of the test.

Results

Student’s t test showed no statistically significant difference between anchors in terms of load to failure (ASA: force 265.06 ± 87.25 N versus SA : 325.35 ± 113.46 N; p = 0.09) and mean elongation at rupture (ASA : 23 ± 7 mm versus SA : 21 ± 6 mm; p = 0.46).

Conclusions

In vitro, this experimental study showed no statistically significant difference in pullout strength and displacement between ASA and SA at a chosen level of significance (p < 0.05).     

Quantifying subtle but persistent peri-spine inflammation in vivo to submicron cobalt–chromium alloy particles

Purpose

We evaluated the consequences of cobalt–chromium alloy (CoCr) wear debris challenge in the peri-spine region to determine the inflammation and toxicity associated with submicron particulates of CoCr-alloy and nickel on the peri-spine.

Methods

The lumbar epidural spaces of (n = 50) New Zealand white rabbits were challenged with: 2.5 mg CoCr, 5.0 mg CoCr, 10.0 mg CoCr, a positive control (20.0 mg of nickel) and a negative control (ISOVUE-M-300). The CoCr-alloy and Ni particles had a mean diameter of 0.2 and 0.6 μm, respectively. Five rabbits per dose group were studied at 12 and 24 weeks. Local and distant tissues were analyzed histologically and quantitatively analyzed immunohistochemically (TNF-α and IL-6).

Results

Histologically, wear particles were observed in all animals. There was no evidence of toxicity or local irritation noted during macroscopic observations in any CoCr-dosed animals. However, Ni-treated control animals experienced bilateral hind leg paralysis and were euthanized at Day 2. Histopathology of the Ni particle-treated group revealed severe neuropathy. Quantitative immunohistochemistry demonstrated a CoCr-alloy dose-dependent increase in cytokines (IL-6, TNF-α, p < 0.05) at 12 and 24 weeks.

Conclusions

Subtle peri-spine inflammation associated with CoCr-alloy implant particles was dose dependent and persistent. Neuropathy can be induced by highly reactive Ni particles. This suggests peri-spine challenge with CoCr-alloy implant debris (e.g., TDA) is consistent with past reports using titanium alloy particles, i.e., mild persistent inflammation.     

Radiographic quantification of dynamic hip screw migration

Purpose

This study aimed to propose a technique to quantify dynamic hip screw (DHS®) migration on serial anteroposterior (AP) radiographs by accounting for femoral rotation and flexion.

Methods

Femoral rotation and flexion were estimated using radiographic projections of the DHS® plate thickness and length, respectively. The method accuracy was evaluated using a synthetic femur fixed with a DHS® and positioned at pre-defined rotation and flexion settings. Standardised measurements of DHS® migration were trigonometrically adjusted for femoral rotation and flexion, and compared with unadjusted estimates in 34 patients.

Results

The mean difference between the estimated and true femoral rotation and flexion values was 1.3° (95 % CI 0.9–1.7°) and −3.0° (95 % CI – 4.2° to −1.9°), respectively. Adjusted measurements of DHS® migration were significantly larger than unadjusted measurements (p = 0.045).

Conclusion

The presented method allows quantification of DHS® migration with adequate bias correction due to femoral rotation and flexion.

Electronic supplementary material

The online version of this article (doi:10.1007/s00264-013-2146-4) contains supplementary material, which is available to authorised users.     

Sprengel’s shoulder treated by the Woodward procedure: analysis of factors affecting functional and cosmetic outcome

Purpose

To report the functional and cosmetic results of cases with Sprengel’s shoulder who underwent the Woodward procedure.

Materials and methods

Twelve children were operated at a mean age of 5.58 years and reviewed at an average follow up of 31.83 months.

Results

The mean preoperative Cavendish grade for cosmetic evaluation was 3.17, which decreased to 1.25 postoperatively (statistically significant, p < 0.0005, Wilcoxon signed-rank test). Similarly, the range of abduction at the shoulder increased from a mean of 115.83° preoperatively to 153.33° at final review (p < 0.0005). Age had a negative correlation with both functional improvement (r = −0.55, Spearman correlation coefficient) and cosmetic improvement (r = −0.11), although the latter suggested a very weak association, if any. Cavendish grade improvement and increase in abduction had a strong positive association (r = 0.713). However, there was no correlation between the increase in abduction and lowering of the scapula achieved (r = 0.131). The presence of an omovertebral bar did not affect the final functional outcome, nor did the presence of associated congenital anomalies.

Conclusion

The Woodward procedure is a reliable method for obtaining uniformly predictable results in Sprengel’s shoulder. The surgery should be performed at a younger age in order to optimise the functional outcome.     

Tracked Ultrasound Snapshots in Percutaneous Pedicle Screw Placement Navigation: A Feasibility Study

Background

Computerized navigation improves the accuracy of minimally invasive pedicle screw placement during spine surgery. Such navigation, however, exposes both the patient and the staff to radiation during surgery. To avoid intraoperative exposure to radiation, tracked ultrasound snapshots—ultrasound image frames coupled with corresponding spatial positions—could be used to map preoperatively defined screw plans into the intraoperative coordinate frame. The feasibility of such an approach, however, has not yet been investigated.

Questions/purposes

Are there vertebral landmarks that can be identified using tracked ultrasound snapshots? Can tracked ultrasound snapshots allow preoperative pedicle screw plans to be accurately mapped—compared with CT-derived pedicle screw plans—into the intraoperative coordinate frame in a simulated setting?

Methods

Ultrasound visibility of registration landmarks was checked on volunteers and phantoms. An ultrasound machine with integrated electromagnetic tracking was used for tracked ultrasound acquisition. Registration was performed using 3D Slicer open-source software (www.slicer.org). Two artificial lumbar spine phantoms were used to evaluate registration accuracy of pedicle screw plans using tracked ultrasound snapshots. Registration accuracy was determined by comparing the ultrasound-derived plans with the CT-derived plans.

Results

The four articular processes proved to be identifiable using tracked ultrasound snapshots. Pedicle screw plans were registered to the intraoperative coordinate system using landmarks. The registrations were sufficiently accurate in that none of the registered screw plans intersected the pedicle walls. Registered screw plan positions had an error less than 1.28 ± 1.37 mm (average ± SD) in each direction and an angle difference less than 1.92° ± 1.95° around each axis relative to the CT-derived positions.

Conclusions

Registration landmarks could be located using tracked ultrasound snapshots and permitted accurate mapping of pedicle screw plans to the intraoperative coordinate frame in a simulated setting.

Clinical Relevance

Tracked ultrasound may allow accurate computer-navigated pedicle screw placement while avoiding ionizing radiation in the operating room; however, further studies that compare this approach with other navigation techniques are needed to confirm the practical use of this new approach.     

Radiological assessment of cervical lateral mass screw angulations in Asian patients

Background:

Various lateral mass screw fixation methods have been described in the literature with various levels of safety in relation to the anterior neurovascular structures. This study was designed to radiologically determine the minimum lateral angulations of the screw to avoid penetration of the vertebral artery canalusing three of the most common techniques: Roy-Camille, An, and Magerl.

Materials and Methods:

Sixty normal cervical CT scans were reviewed. A minimum lateral angulation of a 3.5 mm lateral mass screw which was required to avoid penetration of the vertebral artery canal at each level of vertebra were measured.

Results:

The mean lateral angulations of the lateral mass screws (with 95% confidence interval) to avoid vertebral artery canal penetration, in relation to the starting point at the midpoint (Roy-Camille), 1 mm medial (An), and 2 mm medial (Magerl) to the midpoint of lateral mass were 6.8° (range, 6.3–7.4°), 10.3° (range, 9.8–10.8°), and 14.1° (range, 13.6–14.6°) at C3 vertebrae; 6.8° (range, 6.2–7.5°), 10.7° (range, 10.0–11.5°), and 14.1° (range, 13.4–14.8°) at C4 vertebrae; 6.6° (range, 6.0–7.2°), 10.1° (range, 9.3–10.8°), and 13.5° (range, 12.8–14.3°) at C5 vertebrae and 7.6° (range, 6.9–8.3°), 10.9° (range, 10.3–11.6°), and 14.3° (range, 13.7–15.0°) at C6 vertebrae. The recommended lateral angulations for Roy-Camille, Magerl, and An are 10°, 25°,and 30°, respectively. Statistically, there is a higher risk of vertebral foramen violation with the Roy-Camille technique at C3, C4 and C6 levels, P < 0.05.

Conclusions:

Magerl and An techniques have a wide margin of safety. Caution should be practised with Roy-Camille''s technique at C3, C4, and C6 levels to avoid vertebral vessels injury in Asian population.     

Changes in the cross-sectional area of deep posterior extensor muscles of the cervical spine after anterior decompression and fusion: 10-year follow-up study using MRI

Purpose

To evaluate changes in the transverse area of deep posterior muscles of the cervical spine 10 years after anterior cervical decompression and fusion (ACDF), in comparison with healthy volunteers.

Methods

Thirty-one patients (22 males, 9 females, mean age at follow-up 59.3 years, mean follow-up 12.1 years) who had undergone preoperative MRI and non-instrumented ACDF within levels C3-4 to C5-6 were enrolled. 32 asymptomatic volunteers (17 males, 15 females; mean age, 54.7 years; mean follow-up, 11.7 years) who underwent MRI between 1993 and 1996 served as controls. Follow-up MRI was performed on both patients and control subjects, and the cross-sectional areas of deep posterior muscles were measured digitally at levels C3-4, 4-5, and 5-6.

Results

The mean total cross-sectional area in the ACDF and control groups was 4,693.6 ± 1,140.9 and 4,825.8 ± 1,048.2 mm² in the first MR study (P = 0.63), and 4,616.7 ± 1,086.0 and 5,036.7 ± 1,105.6 mm² at follow-up (P = 0.13). The total cross-sectional area in the ACDF group slightly decreased, while that in the control group increased (−77.1 ± 889.7 vs. 210.9 ± 622.0 mm², P = 0.14). The mean change in the cross-sectional area had no significant correlation with clinical symptoms, including neck pain or JOA score.

Conclusions

ACDF patients did not show a marked decrease in the cross-sectional area of the deep posterior cervical muscles, but as compared with control subjects there was a slight decrease. A decrease in the cross-sectional area of these muscles after ACDF may not result in the axial symptoms as seen in patients treated by posterior surgery.     

Subclinical bilateral involvement of the hip in patients with slipped capital femoral epiphysis—a multicentre study

Purpose

This study was conducted to assess the posterior inclination of the contralateral femoral epiphysis in patients with unilateral slipped capital femoral epiphysis (SCFE).

Methods

The posterior sloping angle (PSA) was measured using lateral radiographs in 67 patients with a unilateral SCFE and in 41 age-matched normal controls. A symptomatic epiphyseal slip was defined as the development of SCFE.

Results

The contralateral PSA in SCFE patients was more widely distributed and significantly larger compared to controls (15.0° vs. 9.0°, p < 0.0001). Forty-seven hips (70.1 %) had a PSA of greater than 12.8°, which was +2SD of the control hips. Of the 65 hips excluding the two cases with prophylactic pinning, 11 hips (16.9 %) eventually developed a contralateral SCFE during adolescence and their PSA at the initial visit was significantly larger compared to patients without a contralateral SCFE (18.0° vs. 14.3°, p < 0.005) with a cutoff value of 19°.

Conclusions

These findings suggested the possibility of bilateral hip involvement in SCFE patients. Hips with greater degrees of PSA (> 19°) are likely to become symptomatic.     

Refractory osteitis condensans ilii: Outcome of a novel mini-invasive surgical approach

Purpose

Osteitis condensans Ilii (OCI) is an orthopaedic mystery until now and the refractory type poses a great challenge in its management. Surgical resection and sacroiliac arthrodesis are major procedures with no guarantee of success for an unknown disease entity with a normal sacroiliac joint. The aim of this retrospective study was to evaluate results of a novel mini-invasive surgical approach for the refractory type after failure of conservative management.

Materials and Methods

Fourteen females were included with an average age 35.5 ± 5.8 years. Nine cases were multiparous and five were nulliparous. The pathology was bilateral in all cases; however, seven cases suffered bilateral symptoms, while seven cases had only unilateral complaints. Preoperative computed tomography was mandatory. All cases had three to five percutaneous iliac core decompressions through a cannulated drill bit. The Bath ankylosing spondylitis functional index (BASFI) was used for functional outcome evaluation.

Results

The mean follow up was 23.3 ± 4.1 months. The mean BASFI improved from 3.7 ± 0.6 preoperatively to 1.3 ± 0.2 during follow up (P = <0.001). There was a significant improvement with the four drillings over five decompression drillings (P = 0.011). Sacral side sclerosis was associated significantly (P = 0.009) with less improvement. No relapse or substantial complications were encountered.

Conclusions

This novel approach can be of great benefit for refractory OCI cases with almost no added morbidity or complications. It has advantages of the mini-invasive techniques in addition to sparing the physiological functions of the affected sacroiliac joints.     

Supplemental S1 fixation for type C pelvic ring injuries: biomechanical study of a long iliosacral versus a transsacral screw

Background

A single iliosacral screw placed into the S1 vertebral body has been shown to be clinically unreliable for certain type C pelvic ring injuries. Insertion of a second supplemental iliosacral screw into the S1 or S2 vertebral body has been widely used. However, clinical fixation failures have been reported using this technique, and a supplemental long iliosacral or transsacral screw has been used. The purpose of this study was to compare the biomechanical effect of a supplemental S1 long iliosacral screw versus a transsacral screw in an unstable type C vertically oriented sacral fracture model.

Materials and methods

A type C pelvic ring injury was created in ten osteopenic/osteoporotic cadaver pelves by performing vertical osteotomies through zone 2 of the sacrum and the ipsilateral pubic rami. The sacrum was reduced maintaining a 2-mm fracture gap to simulate a closed-reduction model. All specimens were fixed using one 7.0-mm iliosacral screw into the S1 body. A supplemental long iliosacral screw was placed into the S1 body in five specimens. A supplemental transsacral S1 screw was placed in the other five. Each pelvis underwent 100,000 cycles at 250 N, followed by loading to failure. Vertical displacements at 25,000, 50,000, 75,000, and 100,000 cycles and failure force were recorded.

Results

Vertical displacement increased significantly (p < 0.05) within each group with each increase in the number of cycles. However, there was no statistically significant difference between groups in displacement or load to failure.

Conclusions

Although intuitively a transsacral screw may seem to be better than a long iliosacral screw in conveying additional stability to an unstable sacral fracture fixation construct, we were not able to identify any biomechanical advantage of one method over the other.

Level of evidence

Does not apply—biomechanical study.     

Cams and Pincer Impingement Are Distinct, Not Mixed: The Acetabular Pathomorphology of Femoroacetabular Impingement

Background

Many impinging hips are said to have a mix of features of femoral cam and an overcovered acetabulum causing pincer impingement. Correction of such a mixed picture by reduction of the cam lesion and the acetabular rim is the suggested treatment.

Questions/purposes

We therefore asked two questions: (1) Is the acetabulum in cam impingement easily distinguishable from the pincer acetabulum, or is there a group with features of both types of impingement? (2) Is version or depth of socket better able to distinguish cam from pincer impingement?

Methods

We analyzed the morphologic features of the acetabulum and rim profile of 20 normal, healthy hips, 20 with cams and 20 with pincers on CT. Pelvises were digitized, orientated to the best-fit acetabular plane, and a rim profile was plotted.

Results

Cam hips were shallower than normal hips, which in turn were shallower than pincer hips (84° ± 5° versus 87° ± 4° versus 96° ± 5°, respectively). The rim planes of cam, normal, and pincer hips had similar version (23°, 24°, 25°), but females were 4° more anteverted than males.

Conclusions

We concluded cam and pincer hips are distinct pathoanatomic entities. Cam hips are slightly shallower than normal, whereas pincers are deeper.

Clinical Relevance

Before performing surgery for cam-type femoroacetabular impingement, surgeons should consider measuring the acetabular depth. The cam acetabulum is shallower than normal and may be rendered pathologically shallow by acetabular rim resection leading to early joint failure.     

The locking attachment plate for proximal fixation of periprosthetic femur fractures-a biomechanical comparison of two techniques

Purpose

Mechanical properties of a locking attachment plate construct (LAP-LCP), allowing bicortical screw placement laterally to the prosthesis stem, are compared to a cerclage-LCP construct.

Methods

Eight right synthetic femora with implanted uncemented hip endoprosthesis were cut distally and fixed with LCP, monocortical locking screws and either LAP (n = 4) or cerclage (n = 4). Cyclic testing was performed with monotonically increasing sinusoidal load until failure. Relative movements at the plate–femur interface were registered by motion tracking. Statistical differences were detected by unpaired t-test and general linear model repeated measures.

Results

Stiffness of the LAP-LCP was significantly higher at the beginning (875.4 N/mm ± 29.8) and after 5000 cycles (1213.0 N/mm ± 101.1) compared to the cerclage-LCP (644.96 N/mm ± 50.1 and 851.9 N/mm ± 81.9), with p = 0.013. Relative movements for AP-bending (B) and axial translation (T) of the LAP-LCP at the beginning (0.07° ± 0.02, 0.20 mm ± 0.08), after 500 cycles (0.16° ± 0.10, 0.26 mm ± 0.07) and after 5000 cycles (0.26° ± 0.11, 0.31 mm ± 0.07) differed significantly from the cerclage-LCP (beg.: 0.26° ± 0.04, 0.28 mm ± 0.05; 500 cyc: 0.47° ± 0.03, 0.53 mm ± 0.07; 5000 cyc.: 0.63° ± 0.18, 0.79 mm ± 0.13), with B: p = 0.02, T: p = 0.04. Relative movements for medial bending were not significantly different between the two constructs. Cycles to failure (criterion 1 mm axial translation) differed significantly between LAP-LCP (19,519 ± 1,758) and cerclage-LCP (11,265 ± 2,472), with p = 0.035.

Conclusions

Biomechanically, the LAP-LCP construct improves proximal fixation of periprosthetic fractures compared to the cerclage-LCP construct.     

Muscle spasticity associated with reduced whole-leg perfusion in persons with spinal cord injury

Objective

To determine the association between peripheral blood flow and spasticity in individuals with spinal cord injury (SCI).

Design

A cross-sectional study with measurements of muscle spasticity and whole-limb blood flow in individuals with SCI.

Setting

University of Texas at Austin and Brain & Spine Recovery Center, Austin, TX, USA.

Participants

Eighteen individuals (14 males and 4 females) with SCI were classified into high (N = 7), low (N = 6), and no (N = 5) spasticity groups according to the spasticity levels determined by the modified Ashworth scale scores.

Interventions

Whole-limb blood flow was measured in the femoral and brachial arteries using Doppler ultrasound and was normalized to lean limb mass obtained with dual-energy X-ray absorptiometry.

Outcome measures

Limb blood flow and muscle spasticity.

Results

Age, time post-SCI, and the American Spinal Injury Association impairment scale motor and sensory scores were not different among groups with different muscle spasticity. Femoral artery blood flow normalized to lean leg mass was different (P = 0.001) across the three spasticity groups (high 78.9 ± 16.7, low 98.3 ± 39.8, no 142.5 ± 24.3 ml/minute/kg). Total leg muscle spasticity scores were significantly and negatively correlated with femoral artery blood flow (r = −0.59, P < 0.01). There was no significant difference in brachial artery blood flow among the groups.

Conclusions

Whole-leg blood flow was lower in individuals with greater spasticity scores. These results suggest that a reduction in lower-limb perfusion may play a role, at least in part, in the pathogenesis leading to muscle spasticity after SCI.