Does the type of surgical approach affect the clinical outcome of total knee arthroplasty?

BACKGROUND: The aim of the study was to investigate the issue of medial midvastus (MMV) vs. medial parapatellar (MPP) approaches in total knee arthroplasty (TKA). It was hypothesized that the two surgical approaches would produce significantly different results with respect to patient-reported knee score outcome (hypothesis 1), short-term postoperative range of motion (ROM) (hypothesis 2), long-term postoperative ROM (hypothesis 3) and prosthesis survival (hypothesis 4). METHODS: A retrospective comparative study design was applied. Data sets were obtained from the state arthroplasty registry. The Western Ontario and McMaster Universities osteoarthritis index (WOMAC) data were analyzed from preoperative and 1 year postoperatively. The ROM data were analyzed for the time points preoperative, postoperative days 4 and 10 and 1 year. RESULTS: Available were 627 cases (407 MMV vs. 220 MPP) and 1 year postoperatively there were no significant differences between groups regarding the WOMAC scores (hypothesis 1). Early postoperatively on days 4 and 10 after TKA there were no differences between groups (p = 0.305 and p = 0.383, respectively, hypothesis 2). Likewise, ROM did not significantly differ between the groups 1 year after TKA (p = 0.338, hypothesis 3). The 5­year prosthesis survival did not differ between the groups and showed 94.46% (95% confidence interval, CI 90.69-96.73%) in the MMV group and 94.33% (95% CI 89.96-96.83%) in the MPP group (p = 0.664, hypothesis 4). CONCLUSION: Both surgical approaches produce equivalent clinical results in terms of early postoperative ROM, late postoperative ROM and 1­year WOMAC. The same prosthesis survival rates can be expected.

The direct anterior approach: treating periprosthetic joint infection of the hip using two-stage revision arthroplasty.

BACKGROUND: Either one- or two-stage revision arthroplasties can be used for the treatment of chronic periprosthetic joint infection (PJI) after total hip arthroplasty (THA). We report our results following two-stage revision surgery performed through the direct anterior approach (DAA) interval using a custom-made articulating spacer. METHODS: Between 2009 and 2014, 49 patients (49 consecutive procedures) had surgery through either a DAA or extended DAA approach. Each patient received perioperative intravenous administration of antibiotics. A custom-made spacer was implanted after explanting cup and stem and following extensive debridement. Broad-spectrum antibiotics were administered during the immediate perioperative period and then adjusted according to the infecting organism. Complication rates and eradication rates were observed. WOMAC patient assessments were administered preoperatively and one-year postoperatively. RESULTS: Of the 49 study patients, five had a recurrence of the infection after the second-stage revision, five had a proximal periprosthetic fracture during the first stage procedure and one patient had a transient femoral nerve palsy that resolved fully within the first postoperative year. 30 different microorganisms were identified on intraoperative specimens. The average time between first and second stage procedure was 65.7 days (range 21-132 days). Eradication of infection was defined as healed wound without fistula, no drainage, no recurrence of the infection, no subsequent surgical intervention for persistent or perioperative infection after second stage revision and no long-term (> 6 months) antimicrobial suppression therapy. Eradication rate of infection in our study was 89.8%. Postoperative WOMAC scores improved significantly CONCLUSION: The preliminary clinical results for the custom-made spacer technique implanted through the DAA are promising. Therefore, we believe the DAA can be used safely as a standard operative approach for two-stage revision procedures.

Extension of the Direct Anterior Approach for the Treatment of Periprosthetic Femoral Fractures.

BACKGROUND: Periprosthetic femoral fractures (PFFs) after total hip arthroplasty are devastating complications often resulting in functional limitations and increased mortality. The use of the direct anterior approach (DAA) is becoming more popular, and the number of revisions done through this interval is increasing. The DAA interval can be expanded to treat PFFs. This retrospective case series assessed outcomes of PFF patients treated with the extension of the DAA interval. METHODS: The study contained 40 patients (40 hips). Mean patient age was 74.3 years (range, 55.1-92.2 years). Mean follow-up time was 50.4 months (range, 20-98.2 months). Fractures were classified as Vancouver B2 (n = 36) and B3 (n = 4). RESULTS: Median cut-to-close time was 152 minutes (interquartile range: 80-279). There were five complications (12.5%): 2 deaths, 1 transient femoral nerve palsy, 1 fissure distal to the stem, and 1 hematoma. CONCLUSION: Expansion of the DAA interval to treat PFF showed similar results compared with other surgical approaches in terms of mortality, complications, fracture healing, and dislocation rate. These results indicate that femoral revision for PFF in the DAA interval is a safe and reliable procedure compared with other surgical approaches for the treatment of Vancouver B2 and B3 periprosthetic fractures.

Fusion rate and clinical outcome in anterior lumbar interbody fusion with beta-tricalcium phosphate and bone marrow aspirate as a bone graft substitute. A prospective clinical study in fifty patients.

PURPOSE: Bone graft substitutes have been successfully used in posterolateral lumbar fusion, anterior cervical fusion and animal studies. This study has been conducted to assess the safety and efficacy of ß-tricalcium phosphate (ß-TCP) in instrumented anterior lumbar interbody fusion (ALIF) procedure. METHODS: In a prospective clinical study, ALIF cages were prefilled with ß-TCP and additionally fixated with posterior pedicle screw. Computed tomography (CT) and X-rays were performed one year after surgery. Fusion was assessed and functional status was evaluated before and one year after surgery. RESULTS: X-ray evaluation showed a definite fusion in 85.48 % of treated levels. CT assessment showed anterior and posterior intersegemental bone bridging in 77.78 % of treated levels. CONCLUSIONS: The X-ray fusion rate presented is comparable with those published for ALIF procedures with bone graft. Fusion rates ß-TCP are similar to autologous bone. ALIF with ß-TCP and additional posterior fixation is a safe and effective procedure.

Comparison of two- and three-dimensional measurement of the Cobb angle in scoliosis.

PURPOSE: The Cobb angle as an objective measure is used to determine the progression of deformity, and is the basis in the planning of conservative and surgical treatment. However, studies have shown that the Cobb angle has two limitations: an inter- and intraobserver variability of the measurement is approximately 3-5 degrees, and high variability regarding the definition of the end vertebra. Scoliosis is a three-dimensional (3D) pathology, and 3D pathologies cannot be completely assessed by two-dimensional (2D) methods, like 2D radiography. The objective of this study was to determine the intraobserver and interobserver reliability of end vertebra definition and Cobb angle measurement using X-rays and 3D computer tomography (CT) reconstructions in scoliotic spines. METHODS: To assess interoberver variation the Cobb angle and the end vertebra were assessed by five observers in 55 patients using X-rays and 3D CT reconstructions. Definition of end vertebra and measurement of the Cobb angle was repeated two times with a three-week interval. Intraclass correlation coefficients (ICC) were used to determine the interobserver and intraobserver reliabilities. 95% prediction limits were provided for measurement errors. RESULTS: Intraclass correlation coefficient (ICC) showed excellent reliability for both methods. The measured Cobb angle was on average 9.2 degrees larger in the 3D CT group (72.8°, range 30-144) than on 2D radiography (63.6°, range 24-152). CONCLUSIONS: In scoliosis treatment it is very essential to determine the curve magnitude, which is larger in a 3D measurement compared to 2D radiography.

The extent of environmental and body contamination through aerosols by hydro-surgical debridement in the lumbar spine.

INTRODUCTION: Surgical site infections occur in 1-6% of spinal surgeries. Effective treatment includes early diagnosis, parenteral antibiotics and early surgical debridement of the wound surface. MATERIALS AND METHODS: On a human cadaver, we executed a complete hydro-surgery debridement including a full surgical setup such as draping. The irrigation fluid was artificially contaminated with Staphylococcus aureus (ATCC 6538). Surveillance cultures were used to detect environmental and body contamination of the surgical team. RESULTS: For both test setups, environmental contamination was observed in an area of 6 × 8 m. Both test setups caused contamination of all personnel present during the procedure and of the whole operating theatre. However, the concentration of contamination for the surgical staff and the environment was lower when an additional disposable draping device was used. CONCLUSIONS: The study showed that during hydro-surgery debridement, contaminated aerosols spread over the whole surgical room and contaminate the theatre and all personnel.

Cartilage degeneration and not age influences the health-related quality of life outcome after partial meniscectomy.

PURPOSE: The purpose of this study is to investigate whether inconsistently reported factors influence the health-related quality of life (HRQOL) outcome of partial meniscectomy. METHOD: Short Form 36 (SF-36) data on 216 patients were retrospectively analysed for the influence of the factors age, gender and degree of cartilage degeneration. Mixed linear models were applied for univariate and multivariate analyses. RESULTS: All SF-36 scales, including the psychosocial scales, showed a significant improvement from pre- to post-operative (p < 0.001). The factor 'degree of cartilage degeneration' was found to significantly influence post-surgical improvement of the SF-36 'physical component summary' score. Patients with mild cartilage degeneration benefited significantly more from surgery than did patients with advanced cartilage degeneration (p = 0.011). Older patients had significantly lower scores on each subscale, but showed no significant age-time interaction, that is, no association was seen between age and the degree of improvement. No effect was determined for the variable gender. CONCLUSIONS: The findings of the current study can be interpreted to show that arthroscopic partial meniscectomy significantly improves HRQOL, even in mental or psychosocial dimensions of HRQOL. Not age but the degree of cartilage degeneration influences the HRQOL gain that can be expected. The factor gender has no effect on HRQOL. The findings of our study influence our daily routine, in that we take the degree of cartilage degeneration and not age as predictive value for the success to be anticipated from the procedure. Concerning the preoperative consenting, it is important to mention that advanced cartilage degeneration is a predictor of a less favourable outcome. LEVEL OF EVIDENCE: IV.

Driving reaction time before and after anterior cervical fusion for disc herniation: a preliminary study.

PURPOSE: Reduced driving reaction time (DRT) has already been studied in context with lumbar disc surgeries. Data on whether cervical spine pathologies impair driving abilities are still lacking. In addition, no return-to-driving recommendations after anterior cervical fusion procedures have been published. Therefore, we assessed DRT before and after anterior cervical discectomy and fusion. METHODS: We performed a prospective study with 12 patients (mean age 47.2 years; female 7, male 5). DRT as well as arm and neck pain were evaluated before surgery, on the day before discharge from hospital and at the 4-6-week follow-up examinations. 31 healthy subjects were tested for DRT as a control group. RESULTS: All patients showed significant improvement in DRT in the longitudinal course (p < 0.05). DRT was 601 ms (median, IQR: 63) before surgery, which was reduced to 580 ms (median, IQR: 112) on the day before discharge from hospital and to 532 ms (median, IQR: 48) at follow-up examination. Control subjects had a driving reaction time of 487 ms (median, IQR: 116), which differed significantly from that of patients at all three testing times (p < 0.05). VAS for arm and neck pain showed significant improvement (p < 0.05). CONCLUSION: The present results show a positive effect of anterior cervical discectomy and fusion on driving safety. Based on our data we state that it appears to be safe to resume driving after discharge from hospital. However, patients scheduled to undergo anterior cervical discectomy and fusion should be informed about increased DRT as compared to healthy individuals.

The use of beta-tricalcium phosphate and bone marrow aspirate as a bone graft substitute in posterior lumbar interbody fusion.

PURPOSE: Due to the disadvantages of iliac crest bone and the poor bone quality of autograft gained from decompression surgery, alternative filling materials for posterior lumbar interbody fusion cages have been developed. ß-Tricalcium phosphate is widely used in cages. However, data regarding the fusion rate of ß-TCP assessed by computer tomography are currently not available. MATERIALS: A prospective clinical trial involving 34 patients (56.7 years) was performed: 26 patients were treated with single-level, five patients double-level and three patients triple-level PLIF filled with ß-TCP and bone marrow aspirate perfusion, and additional posterior pedicle screw fixation. Fusion was assessed by CT and X-rays 1 year after surgery using a validated fusion scale published previously. Functional status was evaluated with the visual analogue scale and the Oswestry Disability Index before and 1 year after surgery. RESULTS: Forty-five levels in 34 patients were evaluated by CT and X-ray with a follow-up period of at least 1 year. Clinically, the average ODI and VAS for leg and back scores improved significantly (P < 0.001). CT assessment revealed solid fusion in 12 levels (26.67%) and indeterminate fusion in 15 levels (34.09%). Inadequate fusion (non-union) was detected in 17 levels (38.63%). CONCLUSION: The technique of PLIF using ß-TCP yielded a good clinical outcome 1 year after surgery, however, a high rate of pseudoarthrosis was found in this series therefore, we do not recommend ß-TCP as a bone graft substitute using the PLIF technique.

Surgical procedure and initial radiographic results of a new augmentation technique for vertebral compression fractures.

PURPOSE: Recently, a new minimally invasive technique called 'vertebral body stenting' (VBS) was introduced for the treatment of osteoporotic vertebral fractures. The technique was developed to prevent the loss of reduction after deflation of the balloon and to reduce the complication rate associated with cement leakage. METHODS: The amount of kyphosis correction, improvement of vertebral body height and quantitative cement leakage rate by applying CT-based quantitative volumetry after VBS were measured in 27 patients (55 vertebra) and compared with a control group (29 patients, 61 vertebrae), which was treated with conventional vertebroplasty. RESULTS: After VBS, a significant improvement was seen in vertebral height, compared to conventional vertebroplasty. The mean improvement in segmental kyphosis and vertebral kyphosis were 5.8° (p < 0.05) and 3.5° (p < 0.05), respectively. In the VBS group, the mean injected volume of cement per vertebral body was 7.33 cm(3) (3.34-10.19 cm(3)). The average amount of cement outside the vertebrae was 0.28 cm(3) (0.01-1.64 cm(3)), which was 1.36% of the applied total cement volume. In the vertebroplasty group, the applied mean volume of the cement per level was 2.7 cm(3) (1-5.8 cm(3)) and the average amount of cement outside the vertebrae was 0.15 cm(3) (0.01-1.8 cm(3)), which was 11.5% (0.2-60%) of the applied total volume of cement. CONCLUSION: The frequency of cement leakage after VBS was 25.5% compared to 42.1% in the vertebroplasty group. VBS led to a significant decrease in the leakage rate compared with conventional vertebroplasty.

Footprint mismatch in total cervical disc arthroplasty.

PURPOSE: Cervical disc arthroplasty has become a commonplace surgery for the treatment of cervical radiculopathy and myelopathy. Most manufacturers derive their implant dimensions from early published cadaver studies. Ideal footprint match of the prosthesis is essential for good surgical outcome. METHODS: We measured the dimensions of cervical vertebrae from computed tomography (CT) scans and to assess the accuracy of match achieved with the most common cervical disc prostheses [Bryan (Medtronic), Prestige LP (Medtronic), Discover (DePuy) Prodisc-C (Synthes)]. A total of 192 endplates in 24 patients (56.3 years) were assessed. The anterior-posterior and mediolateral diameters of the superior and inferior endplates were measured with a digital measuring system. RESULTS: Overall, 53.5 % of the largest device footprints were smaller in the anterior-posterior diameter and 51.1 % in the mediolateral diameter were smaller than cervical endplate diameters. For levels C5/C6 and C6/C7 an inappropriate size match was noted in 61.9 % as calculated from the anteroposterior diameter. Mismatch at the center mediolateral diameter was noted in 56.8 %. Of the endplates in the current study up to 58.1 % of C5/C6 and C6/C7, and up to 45.3 % of C3/C4 and C4/C5 were larger than the most frequently implanted cervical disc devices. CONCLUSION: Surgeons and manufacturers should be aware of the size mismatch in currently available cervical disc prostheses, which may endanger the safety and efficacy of the procedure. Undersizing the prosthetic device may lead to subsidence, loosening, heterotopic ossification and biomechanical failure caused by an incorrect center of rotation and load distribution, affecting the facet joints.

Treatment of periprosthetic femoral fractures following total hip arthroplasty: results of an online survey of the European Hip Society.

BACKGROUND: Periprosthetic femoral fractures (PPF) are a devastating complication after total hip arthroplasty (THA). Both trauma and adult reconstruction surgeons or combined teams treat these fractures following management algorithms. The aim of this study is to investigate the current treatment of PPF by members of the European Hip Society (EHS). METHODS: An online survey of the members of the European Hip Society (EHS) was conducted. 20 cases of periprosthetic fracture were presented and surgeons were asked to answer questions regarding classification, treatment and postoperative treatment protocol. RESULTS: A total of 132 (130 male; 2 female) EHS members responded. Mean years in surgical practice was 18.8 (min. 1 year; max. 50 years). The preferred surgical method was combined open reduction and internal fixation (ORIF) (30.3%) for AG fractures, ORIF with cables (30.4%) for AL fractures, combined ORIF (cable and plate) for B1 fractures (49.2%), stem revision with cables for B2 fractures (73.1%), stem revision with cables for B3 (55.9%) fractures and combined ORIF (cable and plate: 55.5%) for C fractures. Surprisingly, 10.8% suggested various stem revision techniques for B1 and 17.4% for C fractures. Strong variations were observed regarding postoperative weight-bearing protocol. CONCLUSIONS: A strong consensus was found for the choice of conservative or surgical treatment of the different PPF types according to the Vancouver Classification. Various stem revision techniques were the preferred surgical techniques for Vancouver B2 (91.2%) and B3 (88.6%) fractures. However, for postoperative weight-bearing, when the ORIF technique was used, a significant variation of protocols was found.

Driving reaction time before and after surgery for lumbar disc herniation in patients with radiculopathy.

PURPOSE: Although patients scheduled to undergo lumbar disc surgery often ask when they are allowed to drive a motor vehicle again, there are no published recommendations on this subject. METHODS: We conducted a prospective study in 46 consecutive patients (mean age 48.9 years) to determine driving reaction time (DRT) before and after surgery in patients with lumbar disc herniation. Of the patients 23 had left-side radiculopathy and 23 right-side radiculopathy. Driving reaction time as well as back and leg pain were evaluated preoperatively, on the day of discharge from hospital and at the 5-week follow-up examination (FU). 31 healthy subjects were tested as controls. RESULTS: Significant improvement in DRT was seen for both patient samples (p < 0.05). For patients with a right-side radiculopathy preoperative DRT was 664 ms (median, IQR: 241), which was reduced to 605 ms (median, IQR: 189) immediately postoperatively and to 593 ms (median, IQR: 115) at FU. For patients with a left-side radiculopathy DRT was 675 ms (median, IQR: 247) preoperatively, 638 ms (median, IQR: 242) postoperatively and 619 ms (median, IQR: 162) at FU. Pain was moderately correlated to DRT. Control subjects had a driving reaction time of 487 (median, IQR: 116), which differed significantly from patients at all three testing times (p < 0.001). CONCLUSION: Our data indicate a positive effect of the surgery on driving ability. Therefore, we would suggest that for both patient samples it is safe to continue driving after hospital discharge. However, patients have to be informed about increased DRT caused by radiculopathy already before surgery.

An intraoperative assessment of bacterial contamination on surgical helmets and gloves during arthroplasty surgeries.

INTRODUCTION: Infection is a devasting complication after primary and revision arthroplasty. Therefore, identifying potential sources of infection can help to reduce infection rates. The aim of this study was to identify the impact and potential risk of contamination for glows and surgical helmets during arthroplasty procedures. METHODS: Surveillance cultures were used to detect contamination of the glow interface during the surgery and the surgical helmets immediately at the end of the surgery. The cultures were taken from 49 arthroplasty procedures from the surgeon as well as the assisting surgeon. RESULTS: In total, 196 cultures were taken. 31 (15.8%) of them showed a contamination. 12 (13.5%) of 98 cultures taken from the surgical helmets were positive, while 18 (18.3%) of 96 cultures taken from the gloves showed a contamination. DISCUSSION: The study showed that during arthroplasty procedures, surgical helmets and gloves were frequently contaminated with bacteria. In 20 of 49 (40.8%) arthroplasty surgeries, either the surgical helmet or the gloves showed a contamination. Surgeons should be aware that they might be a source for infection during arthroplasty surgeries.

Inter- and intraobserver reliability assessment of computed tomographic 3D measurement of pedicles in scoliosis and size matching with pedicle screws.

BACKGROUND: In patients with scoliosis, the morphology of the pedicles differs from those in normal spines. Preoperative three-dimensional information of these complex anatomic situations means a great advantage for the surgeon in order to assess which pedicles can be instrumented safely avoiding screw misplacement and for the decisions in choosing the appropriate screw size. The objective of this study was to measure pedicle dimensions in scoliotic spines on three-dimensional computed tomographic (CT) scans and to determine the intra- and interobserver reliability of the method. Additionally, the pedicles that cannot be instrumented safely by available screws were identified. METHODS: All pedicles from T1 to L5 in 30 patients with scoliosis were measured by two independent observers. The pedicle width, height and length were assessed for two times with a 3-week interval. Intraclass correlation coefficients were used to determine the intra- and interobserver reliabilities. The diameters of the pedicles were matched with the dimensions of the smallest available pedicle screws of scoliosis implant systems. RESULTS: The intrarater reliability was strong in 60% of the parameters and moderate in 40%. The interrater reliability was strong in all parameters but in pedicle length. The concave-sided pedicles in the curve revealed to be smaller compared to the convex-sided ones. The highest percentage of size mismatch was found in levels T7 (31%) and T8 (33%). CONCLUSIONS: Measurement of pedicle dimensions on three-dimensional CT scans is a reliable but time-consuming procedure to assess pedicle dimensions. CT measuring should be reserved for special cases, where the anatomic situation remains unclear despite X-ray. In scoliotic spines, one-third of the mid-thoracic pedicles cannot be instrumented safely with pedicle screws.

Brake reaction time before and after surgery for patients with sequestrectomy versus conventional microdiscectomy.

The aim of this study was to compare the effects of sequestrectomy versus conventional microdiscectomy on breaking response time (BRT) for lumbar disc herniation (LDH). BRT is the key factor for return to drive recommendations after surgery. A prospective clinical study was conducted. Patients aged 25-65 years who underwent surgery for lumbar disc herniation and held a valid motorcar driving license were recruited in a single institution. The patients were assessed before surgery, immediately after the surgery and at the follow up examination 30 days post-surgery. BRT was measured using a driving simulator, a visual analogue scale (VAS) was used for pain assessment. BRT values were compared with BRT values of a healthy control group. In patients treated with microdiscectomy BRT reduced from 749 (±223) msec before surgery to 649 (±223) msec immediately after the surgery. In the sequestrectomy group BRT reduced from 852 (±561) msec before surgery to 693 (±173) msec immediately after the surgery. BRT at follow up was 610 (±145) msec for patients treated with microdiscectomy and 630 (±98) msec for patients operated with sequestrectomy. BRT for healthy controls was 487 (±116) msec. Pain improved significantly for both patient samples. Sequestrectomy and microdiscectomy were associated with similar effects on pain and BRT after surgery. There was no statistically significant difference between BRT of both patient samples at 30 days follow up examination. Both surgical techniques showed a positive effect on BRT. No statistically significant difference between sequestrectomy and microdiscectomy on BRT could be found.

Braking reaction time before and after surgery for patients with recurrent lumbar disc herniation.

OBJECTIVE: The positive effect of primary lumbar disc surgery on braking reaction time (BRT) has already been shown. The authors investigated the effect of recurrent lumbar disc herniation surgery on BRT. METHODS: Twenty-four patients (mean age 49.9 years) were investigated for BRT 1 day before surgery, postoperatively before hospital discharge, and 4 to 5 weeks after surgery. Thirty-one healthy subjects served as a control group. RESULTS: Significant improvement of BRT following surgery was found in all patients (p < 0.05). For patients with right-sided recurrent disc herniation, median BRT was 736 msec before surgery, 685 msec immediately postoperatively, and 662 msec at follow-up. For patients with left-sided recurrent disc herniation, median BRT was 674 msec preoperatively, 585 msec postoperatively, and 578 msec at follow-up. Control subjects had a median BRT of 487, which differed significantly from the patient BRTs at all 3 test times (p < 0.05). CONCLUSIONS: A significant reduction in BRT in patients with recurrent disc herniation was found following lumbar disc revision surgery, indicating a positive impact of surgery. Due to the improvement in BRT observed immediately after surgery, we conclude that it is appropriate to recommend that patients keep driving after being discharged from the hospital.

Two-year gait analysis controls of the minimally invasive total hip arthroplasty by the direct anterior approach.

BACKGROUND: The purpose of the study was to determine the long-term functional outcome of two hip approaches by gait analysis. Patients were selected by prospective randomization, and operated on either by the anterolateral approach or by a minimally invasive direct anterior approach. METHODS: 33 patients (17 anterolateral approach; 16 direct anterior approach) were analyzed using a Vicon 870 system. Gait analysis was performed two years after total hip arthroplasty. Temporo-spatial and kinematic variables were obtained. FINDINGS: On chest and pelvic kinematics, no patient group demonstrated significant differences. The time-distance parameters showed significant differences with the anterior approach in cadence and stride time. INTERPRETATION: The study indicates that the direct anterior approach exerts positive effects compared with the anterolateral approach two years after surgery. The muscle-sparing concept of direct anterior approach results in significant differences in gait compared to the anterolateral approach 2 years after surgery.

The Influence of Liquids on the Mechanical Properties of Allografts in Bone Impaction Grafting.

Allografts are used to compensate for bone defects resulting from revision surgery, tumor surgery, and reconstructive bone surgery. Although it is well known that the reduction of fat content of allografts increases mechanical properties, the content of liquids with a known grain size distribution has not been assessed so far. The aim of the study was to compare the mechanical properties of dried allografts (DA) with allografts mixed with a saline solution (ASS) and with allografts mixed with blood (AB) having a similar grain size distribution. Fresh-frozen morselized bone chips were cleaned chemically, sieved, and reassembled in specific portions with a known grain size distribution. A uniaxial compression was used to assess the yield limit, initial density, density at yield limit, and flowability of the three groups before and after compaction with a fall hammer apparatus. No statistically significant difference could be found for the yield limit between DA and ASS (p = 0.339) and between ASS and AB (p = 0.554). DA showed a statistically significant higher yield limit than AB (p = 0.022). Excluding the effect of the grain size distribution on the mechanical properties, it was shown that allografts have a lower yield limit when lipids are present. The liquid content of allografts seems to play an inferior role as no statistically significant difference could be found between DA and ASS. It is suggested, in accordance with other studies, to chemically clean allografts before implantation to reduce the contamination risk and the fat content.

Driving reaction time before and after surgery for disc herniation in patients with preoperative paresis.

BACKGROUND CONTEXT: The effect of many types of surgeries on driving reaction time (DRT) has been reported. Although lumbar disc herniation is one of the most common spinal diseases, the effect on DRT has not been investigated. PURPOSE: To assess the effect of left- and right-sided pareses caused by lumbar disc herniation on DRT before and after surgery. STUDY DESIGN: Controlled prospective clinical trial. PATIENT SAMPLE: Patients undergoing disc surgery. OUTCOME MEASURES: Impact of paresis caused by lumbar disc herniation and disc surgery on DRT. METHODS: Forty-two consecutive patients (mean age, 50.3 years) were tested for DRT 1 day before surgery, postoperatively before hospital discharge, and 5 weeks after surgery. Visual analogue scale (VAS) for back and leg pain as well as pain medication and patients' driving frequency were recorded. RESULTS: Significant improvement of DRT after surgery was seen in patients with left- and right-sided pareses (p<.005). For the right-sided paresis group, the preoperative DRT was 761 ms (median, interquartile range [IQR]: 490), 711 ms (median, IQR: 210) immediately postoperatively, and 645 ms (median, IQR: 150) at follow-up (FU). For the left-sided paresis group, DRT was 651 ms (median, IQR: 270) preoperatively, 592 ms (median, IQR: 260) postoperatively, and 569 ms (median, IQR: 140) at FU. Significant differences between right- and left-sided pareses were identified preoperatively and at FU testing (p<.005). No correlation was found between VAS for leg or back pain and DRT. Historical control subjects had a DRT of 487 (median, IQR: 116), which differed significantly at all three test times (p<.001). CONCLUSIONS: A significant reduction in DRT in patients with right- and left-sided pareses was found after surgery, indicating a positive effect of surgery. The improvement in DRT seen immediately postoperatively and the lack of a generally accepted threshold for DRT would suggest that for both patient samples, it is safe to continue driving after hospital discharge. However, patients should be informed accordingly.