Complete Eradication of Biofilm From Orthopedic Materials.

BACKGROUND: Interest exists in finding alternatives to current management strategies in periprosthetic joint infections, which typically include a 2-stage revision with placement of an antibiotic spacer and delayed placement of a new implant. We studied the efficacy of autoclaving, ultrasonication, and mechanical scrubbing for sterilization and biofilm eradication on infected cobalt-chrome discs. METHODS: Strains of Staphylococcus aureus MRSA252 or Staphylococcus epidermidis RP62A were grown on the discs. For each strain, discs were divided into 5 groups (5 discs each) and exposed to several sterilization and biofilm eradication treatments: (1) autoclave, (2) autoclave + sonication, (3) autoclave + saline scrub, (4) autoclave + 4% chlorhexidine (CHC) scrub, and (5) autoclave + sonication + CHC scrub. Sterilization and biofilm eradication were quantified with crystal violet assays and scanning electron microscopy. RESULTS: Relative to nontreated controls, autoclaving alone reduced biofilm load by 33.9% and 54.7% for MRSA252 and RP62A strains, respectively. Biofilm removal was maximized with the combined treatment of autoclaving and CHC scrub for MRSA252 (100%) and RP62A (99.5%). The addition of sonication between autoclaving and CHC scrubbing resulted in no statistically significant improvement in biofilm removal. High-resolution scanning electron microscopy revealed no cells or biofilm for this combined treatment. CONCLUSION: Using 2 commonly encountered bacterial strains in periprosthetic joint infection, infected cobalt-chrome discs were sterilized and eradicated of residual biofilm with a combination of autoclaving and CHC scrubbing.

Glenoid baseplate fixation using hybrid configurations of locked and unlocked peripheral screws.

BACKGROUND: The use of peripheral locked screws has reduced glenoid baseplate failure rates in reverse shoulder arthroplasty. However, situations may arise when one or more non-locked screws may be preferred. We aimed to determine if different combinations of locked and non-locked screws significantly alter acute glenoid baseplate fixation in a laboratory setting. MATERIALS AND METHODS: Twenty-eight polyurethane trabecular bone surrogates were instrumented with a center screw-type glenoid baseplate and fixated with various combinations of peripheral locked and non-locked screws (1-, 2-, 3- and 4-locked con). Each construct was tested through a 55° arc of abduction motion generating compressive and shear forces across the glenosphere. Baseplate micromotion (µm) was recorded throughout 10,000 cycles for each model. RESULTS: All constructs survived 10,000 cycles of loading without catastrophic failure. One test construct in the 1-locked fixation group exhibited a measured micromotion >150 µm (177.6 µm). At baseline (p > 0.662) and following 10,000 cycles (p > 0.665), no differences were observed in baseplate micromotion for screw combinations that included one, two, three and four peripheral locked screws. The maximum difference in measured micromotion between the extremes of groups (1-locked and 4-locked) was 29 µm. CONCLUSIONS: Hybrid peripheral screw fixation using combinations of locked and non-locked screws provides secure glenoid baseplate fixation using a polyurethane bone substitute model. Using a glenosphere with a 10-mm lateralized center of rotation, hybrid baseplate fixation maintains micromotion below the necessary threshold for bony ingrowth. LEVEL OF EVIDENCE: N/A/, basic science investigation.

Evaluation of Factors Affecting Acute Postoperative Pain Levels After Arthroscopic Rotator Cuff Repair.

PURPOSE: To evaluate multiple preoperative and operative factors that may be predictive of and correlate with acute postoperative pain levels after arthroscopic rotator cuff repair. METHODS: One hundred eighty-one patients underwent arthroscopic rotator cuff surgery along with subacromial decompression and met the inclusion criteria for this study. Postoperative visual analog scale (VAS) scores were obtained on postoperative days 1, 7, and 90. Multivariate linear regression analysis was used to correlate postoperative VAS scores with multiple independent factors, including preoperative subjective pain tolerance, preoperative VAS score, preoperative narcotic use, sex, smoking status, number of suture anchors used, tear size, single- or double-row repair, and patient age. RESULTS: Preoperative subjective pain tolerance, notably those patients rating themselves as having an extremely high pain tolerance, was the most significant predictor of high VAS pain scores on both postoperative day 1 (P = .0001) and postoperative day 7 (P < .0001). Preoperative narcotic use was also significantly predictive (P = .010) of high pain scores on postoperative day 1 and day 7 (P = .019), along with nonsmokers (P = .008) and younger patients (P = .006) being predictive on day 7. There were no patient factors that were predictive of VAS scores 3 months postoperatively (P = .567). CONCLUSIONS: Preoperative subjective pain tolerance, notably those patients rating themselves as having an extremely high pain tolerance, was the strongest factor predicting high acute pain levels after arthroscopic rotator cuff surgery. Preoperative narcotic use, smokers, and younger patients were also predictive of higher pain levels during the first postoperative week. LEVEL OF EVIDENCE: Level IV, prognostic case series.

Partial rotator cuff repair and biceps tenotomy for the treatment of patients with massive cuff tears and retained overhead elevation: midterm outcomes with a minimum 5 years of follow-up.

BACKGROUND: A subset of patients with massive irreparable rotator cuff tears present with retained overhead elevation and pain as their primary complaint. Our aim was to evaluate the outcomes of partial arthroscopic rotator cuff repair with biceps tenotomy and to report the failure rate of this procedure for patients with >5 years of follow-up. METHODS: Thirty-four patients underwent partial rotator cuff repair and biceps tenotomy for treatment of a massive rotator cuff tear. Patients had preoperative active forward elevation >120° and no radiographic evidence of glenohumeral arthritis. Patients were followed up clinically and radiographically, and 28 patients had a minimum of 5 years of follow-up. Failure was defined as an American Shoulder and Elbow Surgeons score of <70, loss of active elevation >90°, or revision to reverse shoulder arthroplasty during the study period. RESULTS: Patients demonstrated improvements in average preoperative to postoperative American Shoulder and Elbow Surgeons scores (46.6 to 79.3 [P < .001]) and Simple Shoulder Test scores (5.7 to 9.1 [P < .001]) along with decrease in visual analog scale for pain scores (6.9 to 1.9 [P < .001]). No significant change in forward elevation (168° to 154° [P = .07]), external rotation (38° to 39° [P = 1.0]), or internal rotation (84% to 80% [P = 1.0]) was identified; 36% of patients had progression of the Hamada stage. The failure rate was 29%; 75% of patients were satisfied with their index procedure. CONCLUSION: Partial rotator cuff repair and biceps tenotomy for patients with massive irreparable rotator cuff tears with retained overhead elevation and pain as the primary complaint produced reasonable outcomes at midterm follow-up of at least 5 years.

Intubation Biomechanics: Laryngoscope Force and Cervical Spine Motion during Intubation in Cadavers-Cadavers versus Patients, the Effect of Repeated Intubations, and the Effect of Type II Odontoid Fracture on C1-C2 Motion.

BACKGROUND: The aims of this study are to characterize (1) the cadaver intubation biomechanics, including the effect of repeated intubations, and (2) the relation between intubation force and the motion of an injured cervical segment. METHODS: Fourteen cadavers were serially intubated using force-sensing Macintosh and Airtraq laryngoscopes in random order, with simultaneous cervical spine motion recorded with lateral fluoroscopy. Motion of the C1-C2 segment was measured in the intact and injured state (type II odontoid fracture). Injured C1-C2 motion was proportionately corrected for changes in intubation forces that occurred with repeated intubations. RESULTS: Cadaver intubation biomechanics were comparable with those of patients in all parameters other than C2-C5 extension. In cadavers, intubation force (set 2/set 1 force ratio = 0.61; 95% CI, 0.46 to 0.81; P = 0.002) and Oc-C5 extension (set 2 - set 1 difference = -6.1 degrees; 95% CI, -11.4 to -0.9; P = 0.025) decreased with repeated intubations. In cadavers, C1-C2 extension did not differ (1) between intact and injured states; or (2) in the injured state, between laryngoscopes (with and without force correction). With force correction, in the injured state, C1-C2 subluxation was greater with the Airtraq (mean difference 2.8 mm; 95% CI, 0.7 to 4.9 mm; P = 0.004). CONCLUSIONS: With limitations, cadavers may be clinically relevant models of intubation biomechanics and cervical spine motion. In the setting of a type II odontoid fracture, C1-C2 motion during intubation with either the Macintosh or the Airtraq does not appear to greatly exceed physiologic values or to have a high likelihood of hyperextension or direct cord compression.

Peripheral Quantitative Computed Tomography Predicts Humeral Diaphysis Torsional Mechanical Properties With Good Short-Term Precision.

Peripheral quantitative computed tomography (pQCT) is a popular tool for noninvasively estimating bone mechanical properties. Previous studies have demonstrated that pQCT provides precise estimates that are good predictors of actual bone mechanical properties at popular distal imaging sites (tibia and radius). The predictive ability and precision of pQCT at more proximal sites remain unknown. The aim of the present study was to explore the predictive ability and short-term precision of pQCT estimates of mechanical properties of the midshaft humerus, a site gaining popularity for exploring the skeletal benefits of exercise. Predictive ability was determined ex vivo by assessing the ability of pQCT-derived estimates of torsional mechanical properties in cadaver humeri (density-weighted polar moment of inertia [I(P)] and polar strength-strain index [SSI(P)]) to predict actual torsional properties. Short-term precision was assessed in vivo by performing 6 repeat pQCT scans at the level of the midshaft humerus in 30 young, healthy individuals (degrees of freedom = 150), with repeat scans performed by the same and different testers and on the same and different days to explore the influences of different testers and time between repeat scans on precision errors. IP and SSI(P) both independently predicted at least 90% of the variance in ex vivo midshaft humerus mechanical properties in cadaveric bones. Overall values for relative precision error (root mean squared coefficients of variation) for in vivo measures of IP and SSI(P) at the midshaft humerus were <1.5% and were not influenced by pQCT assessments being performed by different testers or on different days. These data indicate that pQCT provides very good prediction of midshaft humerus mechanical properties with good short-term precision, with measures being robust against the influences of different testers and time between repeat scans.

A Mechanical Evaluation of Zone II Flexor Tendon Repair Using a Knotless Barbed Suture Versus a Traditional Braided Suture.

PURPOSE: To determine repair site bulk, gliding resistance, work of flexion, and 1-mm gap formation force in zone II flexor tendon lacerations repaired with knotless barbed or traditional braided suture. METHODS: Transverse zone II lacerations of the flexor digitorum profundus (FDP) tendon were created in 36 digits from 6 matched human cadaveric pairs. Repair was performed with 2-0 barbed suture (n = 18) or 3-0 polyethylene braided suture (n = 18). Pre- and postrepair cross-sectional area was measured followed by quantification of gliding resistance and work of flexion during cyclic flexion-extension loading at 10 mm/min. Thereafter, the repaired tendons were loaded to failure. The force at 1 mm of gap formation was recorded. RESULTS: Repaired FDP tendon cross-sectional area increased significantly from intact, with no difference noted between suture types. Gliding resistance and work of flexion were significantly higher for both suture repairs; however, we identified no significant differences in either nondestructive biomechanical parameters between repair types. Average 1-mm gap formation force with the knotless barbed suture (52 N) was greater than that of the traditional braided suture (43 N). CONCLUSIONS: We identified no significant advantage in using knotless barbed suture for zone II FDP repair in our primary, nondestructive mechanical outcomes in this in vitro study. CLINICAL RELEVANCE: In vivo studies may be warranted to determine if one suture method has an advantage with respect to the parameters tested at 4, 6, and 12 plus weeks postrepair and the degree of adhesion formation. The combined laboratory and clinical data, in additional to cost considerations, may better define the role of barbed knotless suture for zone II flexor tendon repair.

Glenoid subchondral bone density distribution in male total shoulder arthroplasty subjects with eccentric and concentric wear.

BACKGROUND: Glenoid component loosening in total shoulder arthroplasty may be prevented by component placement on a congruent and adequate bony surface. Glenoid subchondral bone density (SBD) variability may be correlated with this concept. This study analyzed the 3-dimensional distribution of glenoid SBD in total shoulder arthroplasty patients with osteoarthritis. MATERIALS AND METHODS: Three-dimensional computed tomography osteoabsorptiometry (CT-OAM) was performed in 42 men (21 with eccentric and 21 with concentric wear patterns) with glenohumeral arthritis. Glenoid SBD was measured from the joint surface based on 5 clinically relevant topographic zones. The correlation of the wear pattern with the SBD distribution was investigated. RESULTS: The glenoid subarticular layers could be separated into distinct regions: calcified cartilage (≤ 1.5 mm), subchondral plate (2-4.5 mm) and cancellous bone (≥ 5 mm). There were significant differences in SBD among these layers within and between patients with concentric and eccentric wear patterns. In concentric glenoids, the SBD distribution was homogeneous, with greater mineralization in the central zone, 1,749.1 ± 162.3 Hounsfield units (HU) (at 2.5 mm), compared with the posterior, anterior, and superior zones (P < .001). In the eccentric group, the SBD distribution was inhomogeneous. Mineralization was greatest in the posterior zone, 1,739.0 ± 172.6 HU (at 2.5 mm), followed by the inferior zone, 1,722.1 ± 186.6 HU (at 3 mm). CONCLUSION: This study represents the first study using CT-OAM to evaluate the 3-dimensional SBD distribution of the glenoid vault for different arthritic wear patterns. The study findings indicate that the SBD distribution is dependent on (1) depth from the articular surface, (2) topographic zone, and (3) wear pattern. CT-OAM may be an effective tool to assist in preoperative planning for shoulder arthroplasty.

The effects of glenoid wear patterns on patients with osteoarthritis in total shoulder arthroplasty: an assessment of outcomes and value.

BACKGROUND: Despite the success of total shoulder arthroplasty (TSA), concerns remain about the longevity of the implant, in particular, glenoid component survivorship. The purpose of this study was to determine whether preoperative glenoid wear patterns affect clinical outcomes and value in patients undergoing TSA. METHODS: A comparative cohort study was conducted of 309 patients with a total of 344 TSA procedures, performed for primary glenohumeral osteoarthritis. Computed tomography scans were obtained in all patients, with preoperative glenoid wear pattern characterized as either concentric (n = 196; follow-up time, 49.2 months) or eccentric (n = 148; follow-up time, 52.3 months) according to a modified Levine classification. A clinical, radiographic, and economic assessment was performed between the 2 wear patterns. RESULTS: There was no significant difference in American Shoulder and Elbow Surgeons (ASES) score in the concentric group (80.8 ± 20.8) compared with the eccentric group (77.6 ± 21.2) at final follow-up (P = .159). Range of motion and final visual analog scale for pain score were similar between the 2 groups. Radiographic evidence of gross glenoid loosening was significantly lower in the concentric group [11 of 195 (5.6%)] compared with the eccentric group [18 of 147 (12.2%)] (P = .030). Revision rates were similar between the concentric group [4 of 195 (2.0%)] and the eccentric group [3 of 147 (2.0%)]. A value assessment also showed no significant difference between the concentric and eccentric groups [concentric 26.1 vs. eccentric 25.5 (ΔASES score/$10,000 hospital cost) (P = .479)]. CONCLUSIONS: Similar clinical results and value can be expected with both concentric and eccentric glenoid wear patterns in TSA. Concerns arise, however, as the eccentric group demonstrated a more than 2-fold increased rate of glenoid component loosening compared with the concentric group.

The effect of glenoid bone loss on reverse shoulder arthroplasty baseplate fixation.

BACKGROUND: Glenoid bone loss is commonly observed during primary and revision reverse shoulder arthroplasty. Glenoid baseplates are often implanted with incomplete glenoid bone support. The purpose of this study was to evaluate the glenoid component fixation of the glenoid baseplate with variable amounts of incomplete coverage. METHODS: Twenty-eight polyurethane trabecular bone surrogates were instrumented with the same center screw-type glenoid baseplate with 4 peripheral 5.0-mm locking screws in a glenoid bone loss model consisting of 25%, 50%, 75%, and 100% coverage. Each construct was tested through a 55° arc of motion with both compressive and shear forces across the glenosphere. Baseplate micromotion was recorded throughout 10,000 cycles for each model. RESULTS: There was no significant difference in baseline micromotion between the 4 experimental groups (P = .099). In the 25% baseplate coverage group, 3 of 7 exhibited micromotion above the 150-µm threshold (624.5, 469.1, and 712.1 µm) during cyclic loading. After 10,000 cycles of loading, the 25% coverage group exhibited significantly more micromotion than the 50% (P = .049), 75% (P = .026), and 100% (P = .040) coverage groups. There was no significant difference between the 100%, 75%, and 50% coverage groups (P = 1.00). CONCLUSIONS: Glenoid baseplate fixation in the setting of glenoid bone loss is no different when 50%, 75%, or 100% of the baseplate is supported by glenoid bone. Bone loss resulting in only 25% coverage results in significantly greater micromotion, often above the 150-µm threshold.

Outcome and value of reverse shoulder arthroplasty for treatment of glenohumeral osteoarthritis: a matched cohort.

BACKGROUND: Total shoulder arthroplasty (TSA) is commonly used to treat glenohumeral osteoarthritis (GHOA) with an intact rotator cuff. Recently, reverse shoulder arthroplasty (RSA) has been used for GHOA patients who are elderly or have eccentric glenoid wear. We evaluated patients with GHOA scheduled to have TSA but who were changed to RSA because of intraoperative difficulties with the glenoid component or instability and compared them with a cohort that underwent TSA to determine if the groups had similar outcomes. METHODS: We identified 24 consecutive GHOA patients who underwent RSA and matched them to 96 patients who underwent TSA. Glenoid wear and rotator cuff musculature were assessed with preoperative computed tomography scans. Direct hospital costs of the procedure were collected. RESULTS: Postoperative American Shoulder and Elbow Surgeons score, Simple Shoulder Test score, and range of motion were similar between the 2 groups. Five TSA patients had radiographic glenoid loosening, whereas no RSA patients did. Neither group required a revision. One RSA patient required surgery for treatment of a periprosthetic fracture. RSA was $7274 more costly than TSA, related mainly to implant cost. CONCLUSIONS: Patients with GHOA who were converted intraoperatively to RSA because of improper seating of the glenoid trial or persistent posterior subluxation had outcomes comparable to those of a similar group of patients in whom TSA was performed. At midterm follow-up, TSA is associated with lower cost than RSA. The higher rate of radiographic loosening in the TSA group warrants longer follow-up to assess revision costs. In cases in which a TSA cannot be performed with confidence, RSA is a reasonable alternative.

Glenosphere dissociation after reverse shoulder arthroplasty.

BACKGROUND: Reverse shoulder arthroplasty (RSA) is gaining popularity for the treatment of debilitating shoulder disorders. Despite marked improvements in patient satisfaction and function, the RSA complication rate is high. Glenosphere dissociation has been reported and may result from multiple mechanisms. However, few RSA retrieval studies exist. METHODS: We reviewed our RSA database and identified patients with glenosphere dissociation between 1999 and 2013. Prosthesis type, glenosphere size, and contributing factors to dissociation were noted. Five retrieved implants were available for analysis, and evidence of wear or corrosion on the Morse taper was documented. Further, we biomechanically investigated improper Morse taper engagement that may occur intraoperatively as a potential cause of acute dissociation. RESULTS: Thirteen patients with glenosphere dissociation were identified (0.5 months to 7 years postoperatively). Glenosphere size distribution was as follows: 32 mm (n = 1), 36 mm (n = 4), 40 mm (n = 6), and 44 mm (n = 2). Incidence of dissociation was correlated to glenosphere size (P < .001). Taper damage was limited to fretting wear, and there was minimal evidence of taper corrosion. Biomechanically, improper taper engagement reduced the torsional capacity of the glenosphere-baseplate interface by 60% from 19.2 ± 1.0 N-m to 7.5 ± 1.5 N-m. CONCLUSION: We identified several mechanisms contributing to glenosphere dissociation after RSA, including trauma and improper taper engagement. Limited evidence of corrosive wear on the taper interface was identified. Although it is rare, the incidence of glenosphere dissociation was higher when 40- and 44-mm glenospheres were implanted compared with smaller glenospheres (32 and 36 mm), probably because of the larger exposed surface area for potential impingement.

Intubation biomechanics: laryngoscope force and cervical spine motion during intubation with Macintosh and Airtraq laryngoscopes.

INTRODUCTION: Laryngoscopy and endotracheal intubation in the presence of cervical spine instability may put patients at risk of cervical cord injury. Nevertheless, the biomechanics of intubation (cervical spine motion as a function of applied force) have not been characterized. This study characterized and compared the relationship between laryngoscope force and cervical spine motion using two laryngoscopes hypothesized to differ in force. METHODS: Fourteen adults undergoing elective surgery were intubated twice (Macintosh, Airtraq). During each intubation, laryngoscope force, cervical spine motion, and glottic view were recorded. Force and motion were referenced to a preintubation baseline (stage 1) and were characterized at three stages: stage 2 (laryngoscope introduction); stage 3 (best glottic view); and stage 4 (endotracheal tube in trachea). RESULTS: Maximal force and motion occurred at stage 3 and differed between the Macintosh and Airtraq: (1) force: 48.8 ± 15.8 versus 10.4 ± 2.8 N, respectively, P = 0.0001; (2) occiput-C5 extension: 29.5 ± 8.5 versus 19.1 ± 8.7 degrees, respectively, P = 0.0023. Between stages 2 and 3, the motion/force ratio differed between Macintosh and Airtraq: 0.5 ± 0.2 versus 2.0 ± 1.4 degrees/N, respectively; P = 0.0006. DISCUSSION: The relationship between laryngoscope force and cervical spine motion is: (1) nonlinear and (2) differs between laryngoscopes. Differences between laryngoscopes in motion/force relationships are likely due to: (1) laryngoscope-specific cervical extension needed for intubation, (2) laryngoscope-specific airway displacement/deformation needed for intubation, and (3) cervical spine and airway tissue viscoelastic properties. Cervical spine motion during endotracheal intubation is not directly proportional to force. Low-force laryngoscopes cannot be assumed to result in proportionally low cervical spine motion.

An in vivo ovine model of bone tissue alterations in simulated microgravity conditions.

Microgravity and its inherent reduction in body-weight associated mechanical loading encountered during spaceflight have been shown to produce deleterious effects on important human physiological processes. Rodent hindlimb unloading is the most widely-used ground-based microgravity model. Unfortunately, results from these studies are difficult to translate to the human condition due to major anatomic and physiologic differences between the two species such as bone microarchitecture and healing rates. The use of translatable ovine models to investigate orthopedic-related conditions has become increasingly popular due to similarities in size and skeletal architecture of the two species. Thus, a new translational model of simulated microgravity was developed using common external fixation techniques to shield the metatarsal bone of the ovine hindlimb during normal daily activity over an 8 week period. Bone mineral density, quantified via dual-energy X-ray absorptiometry, decreased 29.0% (p < 0.001) in the treated metatarsi. Post-sacrifice biomechanical evaluation revealed reduced bending modulus (-25.8%, p < 0.05) and failure load (-27.8%, p < 0.001) following the microgravity treatment. Microcomputed tomography and histology revealed reduced bone volume (-35.9%, p < 0.01), trabecular thickness (-30.9%, p < 0.01), trabecular number (-22.5%, p < 0.05), bone formation rate (-57.7%, p < 0.01), and osteoblast number (-52.5%, p < 0.001), as well as increased osteoclast number (269.1%, p < 0.001) in the treated metatarsi of the microgravity group. No significant alterations occurred for any outcome parameter in the Sham Surgery Group. These data indicate that the external fixation technique utilized in this model was able to effectively unload the metatarsus and induce significant radiographic, biomechanical, and histomorphometric alterations that are known to be induced by spaceflight. Further, these findings demonstrate that the physiologic mechanisms driving bone remodeling in sheep and humans during prolonged periods of unloading (specifically increased osteoclast activity) are more similar than previously utilized models, allowing more comprehensive investigations of microgravity-related bone remodeling as it relates to human spaceflight.

Indirect decompression of lumbar stenosis with transpsoas interbody cages and percutaneous posterior instrumentation.

BACKGROUND: The minimally invasive lateral transpsoas retroperitoneal approach to address lumbar stenosis offers advantages to traditional approaches, including sparing of the AP annulus and longitudinal ligament and less risk to the peritoneal contents and retroperitoneal vascular structures. Few studies have presented longitudinal measures of radiographic indirect decompression and relief of pain and restoration of function using the lateral approach to spine fusion. QUESTION/PURPOSES: We determined (1) whether radiographic measures suggestive of decompression were achieved after surgery and maintained 1 year after surgery, (2) whether the intervention resulted in sustained improvements in patient-reported outcomes scores 1 year after surgery, and (3) the frequency of pseudarthrosis on CT scans at 1 year after surgery in patients with moderate or severe lumbar stenosis treated with the approach. METHODS: Between 2008 and 2012, 158 patients were surgically treated to alleviate symptoms associated with degenerative lumbar stenosis, of whom 60 (38%) were treated with lateral lumbar interbody fusion. Of these 60 patients, 36 (60%) received CT scans preoperatively and at 1-year postoperatively and were available for radiographic analysis. Of the 60 treated patients, 16 (27%) were lost to followup before 12 months, leaving the records of 44 patients available for review of patient-reported improvements in pain and return to function. Radiographic increases in disc height, foraminal area, and canal area were measured by one observer on CT scans postoperatively and at 1 year and compared to preoperative values. Patient-reported scores, including VAS pain score and Oswestry Disability Index (ODI), were collected preoperatively and at 3 and 12 months postoperatively. RESULTS: Increases in disc height (67%, p < 0.001), foraminal area (24%-31%, p < 0.001), and canal area (7%, p = 0.011) measured immediately postoperatively were sustained at 1-year followup. VAS pain score and ODI both improved (p < 0.001) at 3 months and were maintained at 1 year. No pseudarthroses were noted radiographically. CONCLUSIONS: The lateral transpsoas approach to interbody fusion is capable of sustaining indirect decompression of the neural structures and resolving preoperative claudication and radiculopathy. A larger series of patients with longer followup should be studied to substantiate these early clinical results. LEVEL OF EVIDENCE: Level IV, therapeutic study. See Instructions for Authors for a complete description of levels of evidence.

Are quadrilateral surface buttress plates comparable to traditional forms of transverse acetabular fracture fixation?

BACKGROUND: Several construct options exist for transverse acetabular fracture fixation. Accepted techniques use a combination of column plates and lag screws. Quadrilateral surface buttress plates have been introduced as potential fixation options, but as a result of their novelty, biomechanical data regarding their stabilizing effects are nonexistent. Therefore, we aimed to determine if this fixation method confers similar stability to traditional forms of fixation. QUESTIONS/PURPOSES: We biomechanically compared two acetabular fixation plates with quadrilateral surface buttressing with traditional forms of fixation using lag screws and column plates. METHODS: Thirty-five synthetic hemipelves with a transverse transtectal acetabular fracture were allocated to one of five groups: anterior column plate+posterior column lag screw, posterior column plate+anterior column lag screw, anterior and posterior column lag screws only, infrapectineal plate+anterior column plate, and suprapectineal plate alone. Specimens were loaded for 1500 cycles up to 2.5x body weight and stiffness was calculated. Thereafter, constructs were destructively loaded and failure loads were recorded. RESULTS: After 1500 cycles, final stiffness was not different with the numbers available between the infrapectineal (568±43 N/mm) and suprapectineal groups (602±87 N/mm, p=0.988). Both quadrilateral plates were significantly stiffer than the posterior column buttress plate with supplemental lag screw fixation group (311±99 N/mm, p<0.006). No difference in stiffness was identified with the numbers available between the quadrilateral surface plating groups and the lag screw group (423±219 N/mm, p>0.223). The infrapectineal group failed at the highest loads (5.4±0.6 kN) and this was significant relative to the suprapectineal (4.4±0.3 kN; p=0.023), lag screw (2.9±0.8 kN; p<0.001), and anterior buttress plate with posterior column lag screw (4.0±0.6 kN; p=0.001) groups. CONCLUSIONS: Quadrilateral surface buttress plates spanning the posterior and anterior columns are biomechanically comparable and, in some cases, superior to traditional forms of fixation in this synthetic hemipelvis model. CLINICAL RELEVANCE: Quadrilateral surface buttress plates may present a viable alternative for the treatment of transtectal transverse acetabular fractures. Clinical studies are required to fully define the use of this new form of fixation for such fractures when accessed through the anterior intrapelvic approach.

A cadaveric radiographic analysis on the effect of extreme lateral interbody fusion cage placement with supplementary internal fixation on indirect spine decompression.

STUDY DESIGN: Cadaveric Biomechanical and Radiographic Analysis. OBJECTIVE: The purpose of this study was to quantify the changes in intervertebral height and lateral and central recess areas afforded by lateral interbody fusion cages with 2 supplemental forms of internal fixation in cadaveric specimens. BACKGROUND DATA: When conservative treatment for symptomatic lumbar stenosis fails, traditional intervention has been direct posterior decompression. The minimally invasive, lateral transpsoas approach may be a viable alternative to direct decompression by providing restoration of the foraminal and intervertebral dimensions, yet few reports have examined the anatomic and radiographic changes that occur using this technique. METHODS: Computed tomography (CT) scans were taken of 18 intact lumbar (L1-S1) cadaveric specimens under a 400 N preload. Intervertebral height, foraminal areas, and canal area were measured at L3-L4 and L4-L5. Thereafter, the cadaveric specimens were instrumented with lateral cages placed in the central or posterior third of the disk space at L3-L4 and L4-L5 and either (1) lateral plate (n=9) or (2) bilateral posterior pedicle screw fixation (n=9). All constructs were again subjected to a 400 N preload, postinstrumentation CT scans were taken, and changes in intervertebral height and lateral and central recess areas were calculated. RESULTS: There was no effect of cage placement on any radiographic metric of indirect decompression for either fusion construct. In the lateral plate and pedicle screw groups, respectively, significant increases in average posterior disk height (30.9%, 60.1%), average right (35.3%, 61.5%) and left foraminal area (48.3%, 57.8%), and average canal area (32.3%, 33.3%) were observed. Pedicle screw instrumentation afforded a significantly greater increase in average posterior disk height and foraminal area compared with the lateral plate group, though there was no difference in the average increase in canal area afforded by either form of fixation. CONCLUSIONS: The radiographic results reported here using a cadaveric model add validity to the underlying rationale described for the minimally invasive lateral approach technique. Increases in disk height, foraminal and canal areas were not dependent on cage positioning within the disk space. As intraoperative placement of a cage in the central portion of the disk is an easier and safer technique, our results suggest that central placement may be preferable in a clinical setting.

Osteoporosis and shoulder osteoarthritis: incidence, risk factors, and surgical implications.

BACKGROUND: Patients with osteoarthritis undergoing shoulder arthroplasty may suffer from osteoporosis. The purpose of this study was to determine whether computed tomography (CT)-derived Hounsfield unit (HU) measurements correlate with bone mineral density (BMD) and whether these data could predict implant size and fixation choice. MATERIALS AND METHODS: The study analyzed preoperative dual energy x-ray absorptiometry and shoulder CT scans for 230 patients who underwent total shoulder arthroplasty. Hip BMD and T scores and HU attenuation in the humerus were correlated. HU cutoff values were developed to aid in differentiating patients whose BMD values were within normal reference ranges from patients with osteopenia or osteoporosis. Risk factors associated with low BMD were correlated, and the effect of BMD on humeral stem size, and fixation method was investigated. RESULTS: Significant correlations between HU and hip BMD and T score were identified (P < .001). HU value ranges were identified that may alert the surgeon of metabolic bone disease. Significant correlation (P < 0.05) was found between low BMD and certain osteoporosis risk factors. Age at time of surgery was a predictor of cemented stem fixation (P = .024). Patients with a lower BMD were statistically more likely to receive a larger-diameter humeral stem (P = .016). CONCLUSIONS: Orthopedic surgeons may be able to use data obtained from shoulder CT scans to predict the need for larger stem size or cement fixation during shoulder arthroplasty. In combination with the risk factor profile, these data may be useful in predicting the need for an osteoporosis workup and treatment. LEVEL OF EVIDENCE: Level III, Study of Nonconsecutive Patients, Diagnostic Study.

Reverse shoulder arthroplasty components and surgical techniques that restore glenohumeral motion.

BACKGROUND: Modifications in reverse shoulder arthroplasty (RSA) have been made with the intent of maximizing motion, although there is little objective evidence outlining their benefit. This study investigated the RSA component combinations that impart the greatest effect on impingement-free glenohumeral motion. METHODS: A previously validated virtual shoulder model was implanted with RSA components that varied by humeral implant type (inset/onset), glenosphere diameter (30, 36, and 42 mm), glenosphere placement (inferior/neutral), glenosphere center-of-rotation offset (0, 5, and 10 mm), humeral neck-shaft angle (130° and 150°), and humeral offset (zero, five, and ten mm). Motion was simulated in all technique combinations until the point of impingement in abduction, flexion/extension (F/E), and internal/external rotation (IR/ER). Regression analysis was used to rank combinations based on motion. RESULTS: Of 216 possible study combinations, 126 constructs (58%) demonstrated no arm-at-side impingement and were included for analysis. Models with the largest motion in abduction, F/E, and IR/ER, respectively, were inset-42-inferior-10-150-zero (107°), inset-36-inferior-10-130-five (146°), and inset-42-inferior-10-130-ten (121°). Humeral neck-shaft angle, glenosphere center-of-rotation offset, glenosphere placement, and glenosphere diameter had a significant effect on motion in all planes tested. Of these variables, humeral neck-shaft angle was most predictive of a change in abduction and F/E motion, whereas glenosphere placement was most predictive of a change in IR/ER motion. CONCLUSION: Higher glenosphere center-of-rotation offsets led to an increase in motion in all planes. To maximize motion in abduction, a valgus humeral component should be selected; to maximize F/E, a varus humeral component should be selected; and, to maximize IR/ER, the glenosphere should be placed inferiorly.

Quantifying massive allograft healing of the canine femur in vivo and ex vivo: a pilot study.

BACKGROUND: Allograft integration in segmental osseous defects is unpredictable. Imaging techniques have not been applied to investigate angiogenesis and bone formation during allograft healing in a large-animal model. QUESTIONS/PURPOSES: We used dynamic contrast-enhanced (DCE)-MRI and cone beam (CB)-CT to quantify vascularity and bone volume in a canine femoral allograft model and determined their relationship with biomechanical testing and histomorphometry. METHODS: Femoral ostectomy was performed in three dogs and reconstructed with a 5-cm allograft and compression plate. At 0.5, 3, and 6 months, we performed DCE-MRI to quantify vascular permeability (Ktrans) and perfused fraction and CB-CT to quantify bone volume. We also performed posteuthanasia torsional testing and dynamic histomorphometry of the grafted and nonoperated femurs. RESULTS: DCE-MRI confirmed the avascular nature of allograft healing (perfused fraction, 2.08%-3.25%). CB-CT demonstrated new bone formation at 3 months (26.2, 3.7, and 2.2 cm(3)) at the graft-host junctions, which remodeled down at 6 months (14.0, 2.2, and 2.0 cm(3)). The increased bone volume in one subject was confirmed with elevated Ktrans (0.22) at 3 months. CB-CT-identified remodeled bone at 6 months was corroborated by histomorphometry. Allografted femurs recovered only 40% of their strength at 6 months. CONCLUSIONS: CB-CT and DCE-MRI can discriminate differences in angiogenesis and bone formation in the canine allograft model, which has potential to detect a small (32%) drug or device effect on biomechanical healing with only five animals per group.