Thomas H. Wuerz

Feasibility of using orthogonal fluoroscopic images to measure in vivo joint kinematics

Accurately determining in vivo knee kinematics is still a challenge in biomedical engineering. This paper presents an imaging technique using two orthogonal images to measure 6 degree-of-freedom (DOF) knee kinematics during weight-bearing flexion. Using this technique, orthogonal images of the knee were captured using a 3-D fluoroscope at different flexion angles during weight-bearing flexion. The two orthogonal images uniquely characterized the knee position at the specific flexion angle. A virtual fluoroscope was then created in solid modeling software and was used to reproduce the relative positions of the orthogonal images and X-ray sources of the 3-D fluoroscope during the actual imaging procedure. Two virtual cameras in the software were used to represent the X-ray sources. The 3-D computer model of the knee was then introduced into the virtual fluoroscope and was projected onto the orthogonal images by the two virtual cameras. By matching the projections of the knee model to the orthogonal images of the knee obtained during weight-bearing flexion, the knee kinematics in 6 DOF were determined. Using regularly shaped objects with known positions and orientations, this technique was shown to have an accuracy of 0.1 mm and 0.1 deg in determining the positions and orientations of the objects, respectively.

The Effect of Age on the Outcomes of Arthroscopic Repair of Type II Superior Labral Anterior and Posterior Lesions

Background The majority of clinical outcome studies of type II superior labral anterior and posterior (SLAP) repair assess patients younger than age 40. Biceps tenotomy or tenodesis is often recommended for patients older than age 40 with superior labrum-biceps complex injury. Hypothesis There is no difference in patient clinical outcomes comparing arthroscopic type II SLAP repair in patients younger or older than age 40. Study Design Cohort study; Level of evidence, 3. Methods Fifty-two patients stratified to groups younger than age 40 (21 patients; average age, 32.9 years) and older than age 40 (31 patients; average age, 55.1 years) were identified at a minimum 2-year follow-up (average, 28 months) after type II SLAP repair by a single surgeon using suture anchors. Outcome scores included American Shoulder and Elbow Society scores (ASES), Short Form-12 scores, Simple Shoulder Test scores, and visual analog pain scale. Results At follow-up, there was no statistical difference in visual analog pain scale (P = .16), ASES scores (P = .07), Simple Shoulder Test scores (P =.41), Short Form-12 testing, or range of motion testing. Patients older than age 40 noted their shoulder to be 87% of normal; 26 of 31 (84%) were satisfied to completely satisfied, and 28 of 31 (90%) would have the surgery again. Patients younger than 40 noted their shoulder to be approximately 89% of normal; 20 of 21 (95%) were satisfied to completely satisfied, and 18 of 21 (86%) would have the same procedure performed again. Conclusion Our findings support that arthroscopic treatment of isolated type II SLAP repair using suture anchors can yield good to excellent results in patients older and younger than age 40. We found no statistically significant difference in patient outcome scores, satisfaction levels, or willingness to have the same procedure again when comparing arthroscopic SLAP repair in patients younger or older than age 40.

The Surgical Apgar Score in hip and knee arthroplasty

BackgroundA 10-point Surgical Apgar Score, based on patients’ estimated blood loss, lowest heart rate, and lowest mean arterial pressure during surgery, was developed to rate patients’ outcomes in general and vascular surgery but has not been tested for patients having orthopaedic surgery.Questions/purposesFor patients undergoing hip and knee arthroplasties, we asked (1) whether the score provides accurate risk stratification for major postoperative complications, and (2) whether it captures intraoperative variables contributing to postoperative risk based on the three parameters independent of preoperative risk.Patients and MethodsWe retrospectively reviewed the electronic records for all 3511 patients who underwent a hip or knee arthroplasty from March 2003 to August 2006 and extracted data to calculate a Surgical Apgar Score. We evaluated the relationship between scores and likelihood of major postoperative in-hospital complications and assessed its discrimination and calibration.ResultsComplication rates increased monotonically as the score decreased. Even after controlling for preoperative risk, each 1-point decrease in the score was associated with a 34.0% increase (95% confidence interval, 0.66–0.84) in the odds of a complication. The overall discriminatory performance of the score was a c-statistic of 0.61. Seventy-six percent of all major complications occurred in patients classified as low risk with scores of 7 or greater.ConclusionsFor patients undergoing hip and knee arthroplasties, the score captures important intraoperative information regarding risk of complications and contributes additional information to preoperative risk, but on its own is insufficient to provide comprehensive postoperative risk stratification for arthroplasties.Level of EvidenceLevel II, prognostic study. See Guidelines for Authors for a complete description of levels of evidence.

Labral Reconstruction With Iliotibial Band Autografts and Semitendinosus Allografts Improves Hip Joint Contact Area and Contact Pressure

Background: Labral reconstruction using iliotibial band (ITB) autografts and semitendinosus (Semi-T) allografts has recently been described in cases of labral deficiency. Purpose/Hypothesis: To characterize the joint biomechanics with a labrum-intact, labrum-deficient, and labrum-reconstructed acetabulum in a hip cadaveric model. The hypothesis was that labral resection would decrease contact area, increase contact pressure, and increase peak force, while subsequent labral reconstruction with ITB autografts or Semi-T allografts would restore these values toward the native intact labral state. Study Design: Controlled laboratory study. Methods: Ten fresh-frozen human cadaveric hips were analyzed utilizing thin-film piezoresistive load sensors to measure contact area, contact pressure, and peak force (1) with the native intact labrum, (2) after segmental labral resection, and (3) after graft labral reconstruction with either ITB autografts or Semi-T allografts. Each specimen was examined at 20° of extension and 60° of flexion. Statistical analysis was conducted through 1-way analysis of variance with post hoc Games-Howell tests. Results: For the ITB group, labral resection significantly decreased contact area (at 20°: 73.2% ± 5.38%, P = .0010; at 60°: 78.5% ± 6.93%, P = .0063) and increased contact pressure (at 20°: 106.7% ± 4.15%, P = .0387; at 60°: 103.9% ± 1.15%, P = .0428). In addition, ITB reconstruction improved contact area (at 20°: 87.2% ± 12.3%, P = .0130; at 60°: 90.5% ± 8.81%, P = .0079) and contact pressure (at 20°: 98.5% ± 5.71%, P = .0476; at 60°: 96.6% ± 1.13%, P = .0056) from the resected state. Contact pressure at 60° of flexion was significantly lower compared with the native labrum (P = .0420). For the Semi-T group, labral resection significantly decreased contact area (at 20°: 68.1% ± 12.57%, P = .0002; at 60°: 67.5% ± 6.70%, P = .0002) and increased contact pressure (at 20°: 105.3% ± 3.73%, P = .0304; at 60°: 106.8% ± 4.04%, P = .0231). Semi-T reconstruction improved contact area (at 20°: 87.9% ± 7.95%, P = .0087; at 60°: 92.9% ± 13.2%, P = .0014) and contact pressure (at 20°: 97.1% ± 3.18%, P = .0017; at 60°: 97.4% ± 4.39%, P = .0027) from the resected state. Comparative analysis demonstrated no statistically significant differences between either graft reconstruction in relation to contact area, contact pressure, or peak force. Conclusion: Segmental anterosuperior labral resection results in significantly decreased contact areas and increased contact pressures, while labral reconstruction partially restores time-zero acetabular contact areas and pressures as compared with the resected state. Although labral reconstruction improved the measured biomechanical properties as compared with the resected state, some of these properties remained significantly different compared with the native intact labrum. Clinical Relevance: Labral reconstruction appears to improve femoroacetabular joint biomechanics as compared with the labrum-resected state; these improved biomechanics may translate into increased joint function clinically.

Labral Reconstruction with Iliotibial Band Autograft and Semitendinosus Allograft Improves Hip Joint Contact Area and Contact Pressure: An In-Vitro Analysis

Objectives: Labral reconstruction using iliotibial band (ITB) autograft and semitendinosus (Semi-T) allograft have recently been described in cases of labral deficiency. The current study seeks to understand the biomechanical effects of an intact labrum, segmental labral resection, and labral reconstruction on joint contact area, contact pressure, and peak force. Methods: Ten fresh-frozen human cadaver hips were analyzed utilizing thin-film piezoresistive load sensors to measure contact area, contact pressure, and peak force 1) with the native intact labrum, 2) after segmental labral resection and 3) after graft labral reconstruction with either ITB autograft or Semi-T allograft. Each specimen was examined at 20° extension and 60° flexion. Statistical analysis was conducted through one-way ANOVA with post-hoc Games-Howell tests. Results: For the ITB group, labral resection significantly decreased contact area (20°: 73.2%±5.38, P=0.0010; 60°: 78.5%±6.93, P=0.0063) and increased contact pressures (20°: 106.7%±4.15, P=0.0387; 60°: 103.9%±1.15, P=0.0428). ITB reconstruction improved contact area (20°: 87.2%±12.3, P=0.0130; 60°: 90.5%±8.81, P=0.0079) and contact pressures (20°: 98.5%±5.71, P=0.0476; 60°: 96.6%±1.13, P=0.0056) from the resected state. Contact pressure at 60° flexion was significantly lower compared to the native labrum (P = 0.0420). For the Semi-T group, labral resection significantly decreased contact area (20°: 68.1±12.57, P=0.0002; 60°: 67.5%±6.70, P=0.0002) and increased contact pressures (20°: 105.3%±3.73, P=0.0304; 60°: 106.8%±4.04, P=0.0231). Semi-T reconstruction improved contact area (20°: 87.9%±7.95, P=0.0087; 60°: 92.9%±13.2, P=0.0014) and contact pressures (20°: 97.1%±3.18, P=0.0017; 60°: 97.4%±4.39, P=0.0027) from the resected state. Comparative analysis demonstrated no statistically significant differences between either graft reconstruction in relation to contact area, contact pressure, or peak forces. (Figure 1). Conclusion: Segmental anterosuperior labral resection results in significantly decreased contact area and increased contact pressures, while labral reconstruction partially restores time-zero acetabular contact areas and pressures as compared to the resected state. Although labral reconstruction improved the measured biomechanical properties as compared to the resected state, some of these properties remained significantly different compared to the native intact labrum.

Pediatric physeal ankle fracture.

Ankle fracture is the second most common fracture type in children, and physeal injury is a particular concern. Growing children have open physes that are relatively weak compared with surrounding bone and ligaments, and traumatic injuries can cause physeal damage and fracture. Tenderness to palpation over the physis can aid in the clinical diagnosis of ankle fracture. Swelling, bruising, and deformity may be identified, as well. Plain radiographs are excellent for initial evaluation, but CT may be required to determine displacement and to aid in surgical planning, particularly in the setting of intra‐articular fractures. The Salter‐Harris classification is the most widely used system to determine appropriate management and assess long‐term prognosis. Complications of physeal injury include shortening and/or angular deformity. Tillaux and triplane fractures occur in the 18‐month transitional period preceding physeal closure, which typically occurs at age 14 years in girls and age 16 years in boys. Management is determined by the amount of growth remaining, with the intent of maintaining optimum function while limiting the risk of physeal damage and joint incongruity.

A Nomogram to Predict Major Complications After Hip and Knee Arthroplasty

We aimed to develop a nomogram for risk stratification of major postoperative complications in hip and knee arthroplasty based on preoperative and intraoperative variables, and assessed whether this tool would have better predictive performance compared to the Surgical Apgar Score (SAS). Logistic regression analysis was performed to develop a nomogram. Discrimination and calibration were assessed. Net reclassification improvement (NRI) was used to compare to the SAS. All variables were found to be statistically significant predictors of post-operative complications except race and lowest heart rate. The concordance index was 0.76 with good calibration. Compared to the SAS, the NRI was 71.5% overall. We developed a clinical prediction tool, the Morbidity and Mortality Acute Predictor for arthroplasty (arthro-MAP) that might be useful for postoperative risk stratification.

The Natural History of Femoroacetabular Impingement

Femoroacetabular impingement (FAI) is a clinical syndrome resulting from abnormal hip joint morphology and is a common cause of hip pain in young adults. FAI has been posited as a precursor to hip osteoarthritis (OA); however, conflicting evidence exists and the true natural history of the disease is unclear. The purpose of this article is to review the current understanding of how FAI damages the hip joint by highlighting its pathomechanics and etiology. We then review the current evidence relating FAI to OA. Lastly, we will discuss the potential of hip preservation surgery to alter the natural history of FAI, reduce the risk of developing OA and the need for future arthroplasty.

Management of patellofemoral chondral injuries.

Treatment of patellofemoral chondral defects is fraught with difficulty because of the generally inferior outcomes and significant biomechanical complexity of the joint. Noyes and Barber-Westin38 performed a systematic review of large (>4 cm2) patellofemoral ACI (11 studies), PFA (5 studies), and osteochondral allografting (2 studies) in patients younger than 50 years. Respectively, failures or poor outcomes were noted in 8% to 60% after ACI, 22% after PFA, and 53% after osteochondral allograft treatment. As noted in the outcome reviews earlier, unacceptable complication and reoperation rates were reported from all 3 procedures, and it was concluded that each operation had unpredictable results for this patient demographic. This study highlights the importance of strict indications and working to address all concomitant diseases to decrease revision rate. Outcomes are most predictable in young patients with low BMI and unipolar defects lower than 4 cm2.

Sonographic Prevalence of Groin Hernias and Adductor Tendinopathy in Patients With Femoroacetabular Impingement

Background: Femoroacetabular impingement (FAI) is a common debilitating condition that is associated with groin pain and limitation in young and active patients. Besides FAI, various disorders such as hernias, adductor tendinopathy, athletic pubalgia, lumbar spine affections, and others can cause similar symptoms. Purpose: To determine the prevalence of inguinal and/or femoral herniation and adductor insertion tendinopathy using dynamic ultrasound in a cohort of patients with radiographic evidence of FAI. Study Design: Case series; Level of evidence, 4. Methods: This retrospective study consisted of 74 patients (36 female and 38 male; mean age, 29 years; 83 symptomatic hips) with groin pain and radiographic evidence of FAI. In addition to the usual diagnostic algorithm, all patients underwent a dynamic ultrasound examination for signs of groin herniation and tendinopathy of the proximal insertion of the adductors. Results: Evidence of groin herniation was found in 34 hips (41%). There were 27 inguinal (6 female, 21 male) and 10 femoral (9 female, 1 male) hernias. In 3 cases, inguinal and femoral herniation was coexistent. Overall, 5 patients underwent subsequent hernia repair. Patients with groin herniation were significantly older than those without (33 vs 27 years, respectively; P = .01). There were no significant differences for any of the radiographic or clinical parameters. Tendinopathy of the proximal adductor insertion was detected in 19 cases (23%; 11 female, 8 male). Tendinopathy was coexistent with groin herniation in 8 of the 19 cases. There were no significant differences for any of the radiographic or clinical parameters between patients with or without tendinopathy. Patients with a negative diagnostic hip injection result were more likely to have a concomitant groin hernia than those with a positive injection result (80% vs 27%, respectively). Overall, 38 hips underwent FAI surgery with satisfactory outcomes in terms of score values and subjective improvement. Conclusion: The results demonstrate that groin herniation and adductor insertion tendinopathy coexist frequently in patients with FAI. Although the clinical effect is yet unclear, 5 patients underwent hernia repair. Dynamic ultrasound is a useful tool to detect such pathological abnormalities. Diagnostic hip injections can be helpful to differentiate between the sources of pain.