Joseph Nguyen

Reduced cortical bone compositional heterogeneity with bisphosphonate treatment in postmenopausal women with intertrochanteric and subtrochanteric fractures.

Reduction of bone turnover with bisphosphonate treatment alters bone mineral and matrix properties. Our objective was to investigate the effect of bisphosphonate treatment on bone tissue properties near fragility fracture sites in the proximal femur in postmenopausal women with osteoporosis. The mineral and collagen properties of corticocancellous biopsies from the proximal femur were compared in bisphosphonate‐naive (−BIS, n = 20) and bisphosphonate‐treated (+BIS, n = 20, duration 7 ± 5 years) patients with intertrochanteric (IT) and subtrochanteric (ST) fractures using Fourier transform infrared imaging (FTIRI). The mean values of the FTIRI parameter distributions were similar across groups, but the widths of the parameter distributions tended to be reduced in the +BIS group relative to the −BIS group. Specifically, the widths of the cortical collagen maturity and crystallinity were reduced in the +BIS group relative to those of the −BIS group by 28% (+BIS 0.45 ± 0.18 versus −BIS 0.63 ± 0.28, p = 0.03) and 17% (+BIS 0.087 ± 0.012 versus −BIS 0.104 ± 0.036, p = 0.05), respectively. When the tissue properties were examined as a function of fracture morphology within the +BIS group, the FTIR parameters were generally similar regardless of fracture morphology. However, the cortical mineral:matrix ratio was 8% greater in tissue from patients with atypical ST fractures (n = 6) than that of patients with typical (IT or spiral ST) fractures (n = 14) (Atypical 5.6 ± 0.3 versus Typical 5.2 ± 0.5, p = 0.03). Thus, although the mean values of the FTIR properties were similar in both groups, the tissue in bisphosphonate‐treated patients had a more uniform composition than that of bisphosphonate‐naive patients. The observed reductions in mineral and matrix heterogeneity may diminish tissue‐level toughening mechanisms.

Risk factors for postoperative infection following posterior lumbar instrumented arthrodesis.

BACKGROUND Surgical site infection in the spine is a serious postoperative complication. Factors such as posterior surgical approach, arthrodesis, use of spinal instrumentation, age, obesity, diabetes, tobacco use, operating-room environment, and estimated blood loss are well established in the literature to affect the risk of infection. The goal of this study was to analyze and identify independent risk factors for surgical site infection among spine patients undergoing posterior lumbar instrumented arthrodesis. METHODS The medical records of 3218 patients who underwent posterior lumbar instrumented arthrodesis from January 2000 to December 2006 were reviewed to identify those who developed a postoperative infection (eighty-four patients; 2.6%). The size of this single-institution patient group allowed construction of a multivariate logistic regression model to evaluate the independent associations of potential risk factors for surgical site infection in the spine. RESULTS In the final regression model, obesity, estimated intraoperative blood loss, ten or more people in the operating room, a dural tear, history of diabetes, chronic obstructive pulmonary disease, coronary heart disease, and osteoporosis were critical risk factors for the onset of spinal surgical site infection. Obesity and a history of chronic obstructive pulmonary disease were the strongest risk factors for postoperative spinal infection after adjusting for all other variables. The most common pathogen was methicillin-resistant Staphylococcus aureus with a prevalence of 34.5%. This study established a single institution infection rate for posterior lumbar instrumented arthrodesis at 2.6%. CONCLUSIONS This analysis confirms previously demonstrated risk factors for postoperative infection while reporting on new potential independent risk factors of osteoporosis, chronic obstructive pulmonary disease, and dural tears in the setting of posterior lumbar instrumented arthrodesis. Areas of new research can focus on the roles these novel factors may play in the pathogenesis of surgical site infections in the spine.

Hypovitaminosis D in patients scheduled to undergo orthopaedic surgery: a single-center analysis.

BACKGROUND Vitamin D is essential for optimal bone health and muscle function. An alarmingly high rate of vitamin-D deficiency in the general population has been reported recently. The purpose of the present study was to characterize the extent of low serum levels of vitamin D among orthopaedic surgery patients. METHODS We performed a retrospective chart review of 723 patients who were scheduled for orthopaedic surgery between January 2007 and March 2008. Preoperative serum 25-hydroxyvitamin D (25[OH]D) levels were measured. The prevalence of normal (≥32 ng/mL), insufficient (<32 ng/mL), and deficient (<20 ng/mL) vitamin-D levels was determined. Logistic regression was used to assess risk factors for insufficient (<32 ng/mL) 25(OH)D levels. RESULTS Overall, 43% of all patients had insufficient serum vitamin-D levels, and, of these, 40% had deficient levels. Among the orthopaedic services, the highest rates of low serum vitamin-D levels were seen in the trauma and sports services, in which the rates of abnormal (insufficient and deficient) vitamin-D levels were 66% and 52%, respectively. The lowest rate of abnormal vitamin-D levels was seen in the metabolic bone disease service. Patients between the ages of fifty-one and seventy years were 35% less likely to have low vitamin-D levels than patients between the ages of eighteen and fifty years (p = 0.018). The prevalence of low vitamin-D levels was significantly higher in men (p = 0.006). Individuals with darker skin tones (blacks and Hispanics) were 5.5 times more likely to have low vitamin-D levels when compared with those with lighter skin tones (whites and Asians) (p < 0.001). CONCLUSIONS The prevalence of low serum levels of vitamin D among patients undergoing orthopaedic surgery is very common. Given the importance of vitamin D in musculoskeletal health, such low levels may negatively impact patient outcomes.

Obesity increases the risk of recurrent herniated nucleus pulposus after lumbar microdiscectomy

BACKGROUND CONTEXT Recurrent herniation of the nucleus pulposus (HNP) frequently causes poor outcomes after lumbar discectomy. The relationship between obesity and recurrent HNP has not previously been reported. PURPOSE The purpose of this study was to investigate the association of obesity with recurrent HNP after lumbar microdiscectomy. STUDY DESIGN Retrospective Cohort. PATIENT SAMPLE We reviewed all cases of one- or two-level lumbar microdiscectomy from L2-S1 performed by a single surgeon with a minimum follow-up of 6 months. OUTCOME MEASURES The primary clinical outcomes were evidence of recurrent HNP on magnetic resonance imaging (MRI) and need for repeat surgery. METHODS All patients with recurrent radicular pain or new neurological deficits underwent a postoperative MRI scan. Recurrent HNP was defined as a HNP at the same side and same level as the index procedure. RESULTS Seventy-five patients were included in the study. The average body mass index (BMI) was 27.6+/-4.6. Thirty-two patients received an MRI scan. The time from operation to repeat MRI scan varied widely (3 days to 15 months). Eight patients (10.7%) had recurrent HNP. Four patients had persistent symptoms requiring reoperation (5.3%). The mean BMI of patients with recurrent HNP was significantly higher than that of those without recurrence (33.6+/-5.1 vs. 26.9+/-3.9, p<.001). In univariate analysis, obese patients (BMI >or=30) were 12 times more likely to have recurrent HNP than nonobese patients (odds ratio [OR]: 12.46, 95% confidence interval [CI]: 2.25-69.90). Obese patients were 30 times more likely to require reoperation (OR: 32.81, 95% CI: 1.67-642.70). Age, sex, smoking, and being a manual laborer were not significantly associated with recurrent HNP. A logistic regression analysis supported the findings of the univariate analysis. In a survival analysis using a Cox proportional hazards model, the hazard ratio of recurrent HNP for obese patients was 17 (OR: 17.08, 95% CI: 2.85-102.30, p=.002). CONCLUSIONS Obesity was a strong and independent predictor of recurrent HNP after lumbar microdiscectomy. Surgeons should incorporate weight loss counseling into their preoperative discussions with patients.

Clinical and MRI outcomes after platelet-rich plasma treatment for knee osteoarthritis.

The purpose of this study was to investigate whether platelet-rich plasma therapy for early knee osteoarthritis is associated with good clinical outcomes and a change in magnetic resonance imaging (MRI) structural appearances. The design was a prospective cohort study following patients 1 year after platelet-rich plasma therapy for knee osteoarthritis. Twenty-two patients were treated with platelet-rich plasma for early osteoarthritis, confirmed with a baseline MRI. Inclusion criteria were Kellgren grade 0-II with knee pain in patients aged 30 to 70 years. All the patients received a 6-mL platelet-rich plasma injection using the Cascade system. Fifteen subjects underwent clinical assessments at baseline, 1 week, and 1, 3, 6, and 12 months, and MRIs at 1 year. Pain scores significantly decreased, whereas functional and clinical scores increased at 6 months and 1 year from baseline. Qualitative MRIs demonstrated no change per compartment in at least 73% of cases at 1 year.

Functional Outcomes and Patient Satisfaction After Fasciotomy for Chronic Exertional Compartment Syndrome

Background: Patients with chronic exertional compartment syndrome who have failed nonoperative treatment are evaluated with pre-exertion and postexertion compartment pressure testing and may be treated with fasciotomy. Failure rates of up to 20% have been reported and may be related to factors such as age, sex, postexertion compartment pressures, compartment(s) released, and duration of symptoms. Hypothesis: Higher preoperative postexertion compartment pressures are correlated with higher success and patient satisfaction rates after fasciotomy. Study Design: Cohort study; Level of evidence, 3. Methods: From 1999 to 2008, patients with clinical symptoms of chronic exertional compartment syndrome with failed nonoperative management underwent standardized pre-exertion and postexertion compartment pressure measurements. Patients were then offered continued nonoperative treatment or referral to an orthopaedic surgeon for compartment release. Patients with a minimum 2-year follow-up were given a telephone questionnaire describing their pretreatment and posttreatment conditions including quality and duration of symptoms, analog pain scale, symptomatic and functional responses to treatment, and satisfaction with treatment. Medical records and operative reports were reviewed. Results: The mean follow-up period for the nonoperative treatment group (n = 27) was 5.6 years (range, 2.1-10.6) and for the operative group (n = 73) was 5.2 years (range, 2.0-11.3). The operative group had a higher success rate (81%) compared with the nonoperative group (41%) (P < .001), and the operative group had a higher patient satisfaction rate (81%) compared with the nonoperative group (56%) (P = .011). There was no significant correlation between compartment pressures and patient outcomes. Patients with combined anterior and lateral compartment releases had an increased failure rate compared with isolated anterior release (31% vs 0%, respectively; P = .035). Surgical patients who were post-college had a lower satisfaction rate (66%) compared with high school (89%) and college patients (94%) (P = .017). Conclusion: High school and college patients (age <23 years) and isolated anterior compartment release (compared with anterior/lateral release) were factors associated with improved subjective function and satisfaction after fasciotomy. We recommend the avoidance of lateral release unless symptoms or postexertion compartment pressures are clearly indicative of lateral compartment involvement.

Abnormal tibiofemoral contact stress and its association with altered kinematics after center-center anterior cruciate ligament reconstruction: an in vitro study.

Background: Abnormal tibiofemoral contact stress and aberrant kinematics may influence the progression of osteoarthritis in the anterior cruciate ligament (ACL)–deficient and the ACL-reconstructed knee. However, relationships between contact stress and kinematics after ACL reconstruction are poorly understood. Therefore, we posed the following research questions: (1) How do ACL deficiency and reconstruction affect the kinematics of and contact stress in the tibiofemoral joint? (2) What kinematic differences are associated with abnormal contact stress after ACL reconstruction? Hypothesis: Center-center ACL reconstruction will not restore knee kinematics and contact stress. Correlations will exist between abnormal contact stress and aberrant kinematics after ACL reconstruction. Study Design: Controlled laboratory study. Methods: Clinical tests of anterior and rotational stability were simulated on 11 cadaveric knees using an industrial robot. Tests were conducted with the ACL intact, sectioned, and after single-bundle ACL reconstruction using a quadrupled hamstring autograft with tunnels drilled through the center of the native footprints. Kinematics were recorded during the tests. Contact stress was continuously recorded from a stress transducer fixed to the tibial plateau, and mean contact stress was calculated regionally. Results: ACL deficiency resulted in increased mean contact stress in the posterior sectors of the medial and lateral compartments under anterior and rotational loads, respectively. Reconstruction reduced stress in these locations; however, contact stress abnormalities remained. On average, kinematics were overconstrained after ACL reconstruction (≤1.8 mm and ≤2.6° in all directions). However, combinations of overconstrained and underconstrained motions in abduction/adduction and medial-lateral translation in response to combined moments, and anterior-posterior translation, medial-lateral translation, and axial rotation in response to an anterior load were associated with abnormal mean contact stress. Conclusion: ACL reconstruction reduces high stresses generated in the posterior compartment of the ACL-deficient knee. Abnormal contact stress after ACL reconstruction is related to multiplanar variations in knee kinematics. Clinical Relevance: Clinical measures of multiplanar kinematics may help to better characterize the quality of ACL reconstruction. Such measures may help identify patients at increased risk of long-term joint degeneration following this surgery.

Preoperative three-dimensional CT predicts intraoperative findings in hip arthroscopy.

BackgroundCurrently, plain radiographs and MRI are the standard imaging modalities used for diagnosing femoroacetabular impingement (FAI) and preoperative planning for arthroscopic treatment of FAI. The value of three-dimensional (3D) CT for these purposes is unclear.Questions/purposesWe therefore determined the reliability of CT assessment of FAI and whether CT findings of hip disease predict arthroscopic findings.MethodsWe retrospectively assessed the preoperative CT scans of 118 patients who underwent primary hip arthroscopy. Intraoperative findings, including size of the cam lesion, presence of an acetabular labral articular disruption lesion, and one of four types of labral tear were recorded and compared with the retrospectively read CT findings.ResultsAgreement analysis between CT and intraoperative detection of FAI yielded kappa values of 0.48 for cam lesions and 0.16 for pincer lesions. Increasing values for the CT-based alpha angle correlated with increasing severity of arthroscopically assessed acetabular labral articular disruption grade. Each pattern of FAI predicted a specific labral tear type.ConclusionsOur data suggest CT has moderate value in predicting mechanically based labral tear patterns, although better parameters for assessment of pincer lesions are needed. Diagnostic assessment of patients with suspected FAI may be improved with use of 3D CT.Level of EvidenceLevel III, diagnostic study. See the Guidelines for Authors for a complete description of levels of evidence.

Autologous Osteochondral Transplantation of the Talus Partially Restores Contact Mechanics of the Ankle Joint

Background: Autologous osteochondral transplantation procedures provide hyaline cartilage to the site of cartilage repair. It remains unknown whether these procedures restore native contact mechanics of the ankle joint. Purpose: This study was undertaken to characterize the regional and local contact mechanics after autologous osteochondral transplantation of the talus. Study Design: Controlled laboratory study. Methods: Ten fresh-frozen cadaveric lower limb specimens were used for this study. Specimens were loaded using a 6 degrees of freedom robotic arm with 4.5 N·m of inversion and a 300-N axial compressive load in a neutral plantar/dorsiflexion. An osteochondral defect was created at the centromedial aspect of the talar dome and an autologous osteochondral graft from the ipsilateral knee was subsequently transplanted to the defect site. Regional contact mechanics were analyzed across the talar dome as a function of the defect and repair conditions and compared with those in the intact ankle. Local contact mechanics at the peripheral rim of the defect and at the graft site were also analyzed and compared with the intact condition. A 3-dimensional laser scanning system was used to determine the graft height differences relative to the native talus. Results: The creation of an osteochondral defect caused a significant decrease in force, mean pressure, and peak pressure on the medial region of the talus (P = .037). Implanting an osteochondral graft restored the force, mean pressure, and peak pressure on the medial region of the talus to intact levels (P = .05). The anterior portion of the graft carried less force, while mean and peak pressures were decreased relative to intact (P = .05). The mean difference in graft height relative to the surrounding host cartilage for the overall population was −0.2 ± 0.3 mm (range, −1.00 to 0.40 mm). Under these conditions, there was no correlation between height and pressure when the graft was sunken, flush, or proud. Conclusion/Clinical Relevance: Placement of the osteochondral graft in the most congruent position possible partially restored contact mechanics of the ankle joint. Persistent deficits in contact mechanics may be due to additional factors besides graft congruence, including structural differences in the donor cartilage when compared with the native tissue.

Abnormal Tibiofemoral Contact Stress and Its Association With Altered Kinematics After Center-Center Anterior Cruciate Ligament Reconstruction

Background: Abnormal tibiofemoral contact stress and aberrant kinematics may influence the progression of osteoarthritis in the anterior cruciate ligament (ACL)–deficient and the ACL-reconstructed knee. However, relationships between contact stress and kinematics after ACL reconstruction are poorly understood. Therefore, we posed the following research questions: (1) How do ACL deficiency and reconstruction affect the kinematics of and contact stress in the tibiofemoral joint? (2) What kinematic differences are associated with abnormal contact stress after ACL reconstruction? Hypothesis: Center-center ACL reconstruction will not restore knee kinematics and contact stress. Correlations will exist between abnormal contact stress and aberrant kinematics after ACL reconstruction. Study Design: Controlled laboratory study. Methods: Clinical tests of anterior and rotational stability were simulated on 11 cadaveric knees using an industrial robot. Tests were conducted with the ACL intact, sectioned, and after single-bundle ACL reconstruction using a quadrupled hamstring autograft with tunnels drilled through the center of the native footprints. Kinematics were recorded during the tests. Contact stress was continuously recorded from a stress transducer fixed to the tibial plateau, and mean contact stress was calculated regionally. Results: ACL deficiency resulted in increased mean contact stress in the posterior sectors of the medial and lateral compartments under anterior and rotational loads, respectively. Reconstruction reduced stress in these locations; however, contact stress abnormalities remained. On average, kinematics were overconstrained after ACL reconstruction (≤1.8 mm and ≤2.6° in all directions). However, combinations of overconstrained and underconstrained motions in abduction/adduction and medial-lateral translation in response to combined moments, and anterior-posterior translation, medial-lateral translation, and axial rotation in response to an anterior load were associated with abnormal mean contact stress. Conclusion: ACL reconstruction reduces high stresses generated in the posterior compartment of the ACL-deficient knee. Abnormal contact stress after ACL reconstruction is related to multiplanar variations in knee kinematics. Clinical Relevance: Clinical measures of multiplanar kinematics may help to better characterize the quality of ACL reconstruction. Such measures may help identify patients at increased risk of long-term joint degeneration following this surgery.